[r fortney] trilobite eyewitness to evolution(bookzz org)

TRILOBITE!

TRILOBITE! Eyewitness to Evolution BY

Richard Fortey

ALFRED

A.

KNOPF

New York

2000

THIS

IS

PUBLISHED

A

BORZOI

BOOK

BY

ALFRED

A.

KNOPF

C o p y r i g h t © 2 0 0 0 by Richard Fortey All rights reserved u n d e r International a n d P a n - A m e r i c a n C o p y r i g h t C o n v e n t i o n s . P u b l i s h e d in the U n i t e d States by Alfred A. K n o p f , a division of R a n d o m H o u s e , Inc., N e w York. Distributed by R a n d o m H o u s e , Inc., N e w York. www.aaknopf.com Originally p u b l i s h e d in Great Britain by H a r p e r C o l l i n s Publishers, L o n d o n .

K n o p f , B o r z o i B o o k s , a n d the c o l o p h o n are registered t r a d e m a r k s o f R a n d o m H o u s e , Inc. Library of C o n g r e s s C a t a l o g i n g - i n - P u b l i c a t i o n Data Fortey, Richard A. T r i l o b i t e ! : e y e w i t n e s s to evolution / by Richard Fortey. — 1 s t A m e r i c a n ed. p.

cm.

I n c l u d e s index.

ISBN 0 - 3 7 5 - 4 0 6 2 5 - 5

1. Trilobites.

I. Title.

QE821.F67 2 0 0 0 565'.39—dc2i

00-034908

M a n u f a c t u r e d in the United States of A m e r i c a First A m e r i c a n Edition

For my mother

Contents

List of Illustrations

ix

List of Plates

xi

Preface

xiii

I Discovery

3

II Shells

27

III Legs

52

IV Crystal Eyes

84

V Exploding Trilobites VI M u s e u m VII VIII

120 146

A Matter of Life and Death Possible Worlds

159 190

IX Time

218

X Eyes to See

255

Acknowledgements

267

Suggestions for Further Reading

269

Index

271

vii

Illustrations

Drawing of the giant trilobite Paradoxides by Philip Lake.

23

The anatomy of a trilobite.

Spines recovered from trilobites from the Ordovician of

31

Virginia by Professor Whittington.

"Flatfish"

figured

in Philosophical

40

Transactions of the Royal

Society by Dr. Lhwyd (1679).

48

Fantasy trilobite from J. S. Shroeter (1774).

54

Charles Doolittle Walcott.

Walcott's first attempt to show the limbs of the trilobite

59

Ceraurus.

62

Modern reconstruction of the branched limb of Triarthrus.

Professor Beecher's reconstruction of Triarthrus from the

62

underside, showing branched limbs and antennae.

67

Legs of Phacops.

72

The workings of a trilobite's eye.

97

Trilobite eyes.

Clarkson and Levi-Setti's illustration of the workings

105

of the highly refractive bowl inside the lens of Phacops.

109

Reconstruction of the giant-eyed Opipeuter.

112

Free-swimming Parabarrandia.

116

Olenellus.

127

Anomalocaris as reproduced in Stephen J. Gould's Wonderful Life.

139

Place of trilobites in the emergence of animals in the early Cambrian era.

142

ix

Illustrations

Tray of trilobites from the vast collection in the Natural History Museum. Photographed by Catherine Eldridge.

Horseshoe crab Limulus, now regarded as the closest

148

living relative of the trilobites.

Rudolf Kaufmann.

158 167

Smallest trilobite, Acanthopleurella.

176

Ken M c N a m a r a ' s time shifts diagram.

180

Head and tail of Mucronaspis.

184

Gerastos, Ditomopyge and an enroled Symphysurus.

188

Early Ordovician world, as revealed by the trilobites.

201

Ogyginus.

204

Ordovician G o n d w a n a from a polar projection.

210

Trilobite moult, Paradoxides.

222

Joachim Barrande.

223

Growth of Cambrian trilobite Sao hirsuta.

Electron micrographs of protaspis larvae of Cybelurus.

225 227

Ontogeny of Shumardia.

Sir James Stubblefield en route to Shetland and Orkney.

232 234

Trilobite tracks.

235

Paralbertella bosworthi.

239

Elrathia and the tail of Drepanura.

243

Dicranurus.

244

A trident-bearing trilobite, as yet unnamed.

262

Spiny trilobite Kettneraspis.

264

x

Plates

SECTION

ONE

1. Dr. Lhwyd's "flatfish," now known as Ogygiocarella debuchii.

2. Silicified trilobite headshields.

3.

Bumastus.

4. Radiaspis, a fantastically spiny trilobite from the Devonian rocks of Morocco.

5. Dalmanites, one of the first trilobites to be discovered.

6. X-ray of Phacops.

7. Olenoides serratus from the Cambrian Burgess Shale.

8. Hypertnecaspis, showing small headshield and long thorax.

9. "Graveyard"

of

Leptoplastides.

10. Olenellus, one of the oldest trilobites from the Lower Cambrian rocks.

11. Tiny, blind Agnostus pisiformis.

12. The elegant Isotelus from the Ordovician of N e w York State.

13. Blind, medallion-like trilobite Trinucleus fimbriatus.

14. Head of trilobite Protolloydolithus, related to Trinucleus.

15. Giant-eyed trilobite Pricyclopyge.

16. Silurian trilobite Calymene, from Gotland, Sweden.

17. Antique gold brooch with Calymene as the centrepiece.

18. Lateral view of perfectly preserved enroled Phacops.

SECTION

19.

TWO

Crotalocephalus.

20. Acanthopyge, a trilobite the size of a crab. xi

Plates 21. Thysanopeltis,

a

relative

of

Scutellum.

22. Cluster of five Cyphaspis.

23. Griffithides, from Carboniferous rocks of Indiana.

24.

23.

Paraharpes.

Cnemidopyge, a close relative of Ampyx.

26. Three blind trilobites, Conocoryphe.

27. A strawberry-headed trilobite of the Silurian period, Balizoma

variolaris.

28. Pagetia, a diminutive, flea-sized trilobite.

29. Selenopeltis, with enormously elongated genal spines.

30. Moulted, cast-off exoskeleton of Leonaspis.

31. Sao hirsuta from the Cambrian of Bohemia.

32. A plate from Barrande's magnificent work on the trilobites of Bohemia.

33. A piece of Cambrian "swallow stones" from Shandong, China.

34. Fantastically spiny trilobite Comura, from the Devonian of Morocco.

References in the text to figures refer to images reproduced the plate sections.

xii

Preface

I have been enthralled by trilobites for more than thirty years.

This book is both my homage to them, and an attempt to convey to others something of the pleasure that their study has given to me. In the process, something of the scientific method may be revealed. My last book was a biography of all life, from bacterium to mankind, in which the trilobites were passed over in a page or two. N o w I have the chance to turn the focus the other way and to allow my favourite animals to tell their stories in the detail they deserve. Even so, I am as conscious of what I have had to leave out as of what I have been able to include. History can never be told completely, and three hundred million years of history is bound to be more of a precis than a narrative. I wish to persuade the reader of the excitement of recreating vanished worlds, and of seeing ancient seas through the eyes of the trilobites. This is not an academic study, rather, it is an incitement to discovery.

London,

xiii

October

1999

TRILOBITE!

I

Discovery

Out of season, the bar of the C o b w e b Inn at Boscastle is everything a pub should be. There is a low, heavily-beamed ceiling hung with antique bottles, and a plain floor which is a jigsaw of flagstones. Photographs of the local women's darts team hang on the wall, alongside framed, faded newspaper cuttings which record in print the several virtues of the inn. A log fire gives out rather more heat than is needed. There is no music save the low buzz of rich vernacular; in November, no Londoner ventures to the North Cornwall coast. The C o b w e b is a slightly scruffy, comfortable old place, where you can talk if you need to, but if you feel like saying nothing you can just watch the flames in the hearth, and nobody will think you odd if a smile plays on your lips. It takes an effort of will to leave the dark, comfortable, nourishing w o m b of the inn, and emerge, blinking, into the bright world outside; but leave I must, because I have to find Beeny Cliff before the light fades.

It can be dangerous out on the cliffs after nightfall.

Boscastle is tucked into a cleft on the wild northern coast of the long peninsula that completes south-west England, and it is built around a narrow harbour where the River Valency cuts down to the sea. It is an ancient place, where the cosmetics of the tourist trade—Witchcraft M u s e u m and knick-knack 3

T R I L O B I T E !

shops—have not quite succeeded in smothering a character that was born of slate and hardship. At one time the town comprised almost nothing but inns serving miners and seamen, of which the C o b w e b is a survivor, and you can still imagine a dozen different signs advertising their wares all along the crooked street that leads to the haven. The houses are former inns, prettified with features that fail to disguise their boozy origins. The rough local stone gives the buildings their character. Even the Witchcraft M u s e u m is a cottage with an ancient roof that sags crazily under the weight of Cornish slates. On this day the harbour is almost deserted, and I can imagine the place as it must have looked when the poet and novelist Thomas Hardy visited it as a young man, more than a century ago.

I leave the town on the northern side of the harbour where the path zig-zags up the side of the steep valley. There are gorse bushes which even at this time of year cheerfully wave sprigs of yellow pea flowers. Small birds secretively flit across the path—a wren and some stonechats—as if inviting me onwards. From up here I can see piers guarding the long, narrow harbour entrance, barriers that were already ancient when the first Elizabeth was on the throne. A cold breeze makes me wish I had put on an extra sweater, but I have luckily caught an interval between showers. Suddenly, I climb high enough to see the sea. This is one of those days when the furthest horizon is obscured in mist, as if the sea went on for ever. It is not stormy weather, but I can hear the growl of the surf smashing against cliffs, which weave in and out to the south, one after another, sheer to the sea. A white surf-line marks the junction: With

its

And

cliff side

long sea

lashings

clashings

as Hardy described this coast. The cliffs are dark, almost black, while the sea is strangely heavy, wrinkled like a pachy4

Discovery

derm, so that only the lazily shifting white line of breakers serves to animate the prospect. The town in its secret valley has quite slipped from view; the solitude is absolute. I shelter from the breeze behind a wall, which is overgrown with rounded tussocks of sea campion and thrift. It is constructed mostly from blocks of slate; curiously, the slate slabs are placed vertically, so that they look like books set on their edges, pages towards you. I am accustomed to different, horizontally-built stone walls around Oxford. The pattern is broken by occasional piers incorporating angular blocks of white, coarse-looking vein quartz. The artisans w h o built these walls knew their rocks. Slates stacked vertical will let the rainwater (and there is plenty in Cornwall) drain rapidly away, parallel to the way the rock naturally splits. Rubbly quartz is indifferent to all weathers and makes for obstinate pillars. Both rock types are now decorated with a leafy, frilly form of green lichen, which softens every stony outline in such a d a m p climate.

N o w that I study the cliffs I can see that they, too, are made of the same black slates. This is why they seem so forbidding, so stern and dark. In places they are beetling (a word which only seems to apply to brows and cliffs) with teetering overhangs, fissured, and with obviously dangerous crags. These cliffs are a hymn to vertigo: "haggard cliffs, of every ugly altitude . . . " I pay careful attention to the narrow and slippery path; there has been a lot of rain recently, and one foolish step might have serious consequences. Tumbledown stone walls indicate that fields formerly extended very close to the top of the sheer edge, but now there is only a steep grassy slope between the walker and the airy heights where razorbills and fulmars wheel on the wind. The few, stunted trees on the slopes lean away from the fall as if their branches stretched in horror from the tumbling edge.

By the time I reach the top of Pentargon Bay I have some feeling for the geology. The dark rocks displayed on the inaccessible cliffs have surely suffered in a great vice of Earth 5

T R I L O B I T E !

movements, for they are tilted and crimped. No strata follow a straight line, instead they take off on a convoluted journey of their own. On the far side of the bay I can see a fissure that extends vertically from cliff edge to sea, which has been excavated by the elements over millennia. This is certainly a fault—a great fracture through the black rocks—a dislocation which must have once m a d e the Earth shudder and tremble.

Faults are the visible signatures of earthquakes, sealed for eternity in the rocks. The whole coast must have been gripped by a mighty upheaval causing the strata to crack and buckle.

The evidence of a prehistoric paroxysm of the crust is imprinted on these heights.

Look harder, and evidence of tectonism is everywhere. Not far from the fault a stream follows a narrow valley which has been excavated along another plane of weakness in the rocks.

Where the stream reaches the sea its valley is cut off abruptly at the cliff, and the brook suddenly plunges into a waterfall two hundred feet above the sea, where it is whipped up by the breeze into spray. Near the water-line there are caves and smaller crevices which have been excavated by the probing sea. Even on such a calm day I can hear the suck and cough of waves assaulting the slates, picking out the weakest spots where folds have cracked the strata, marking each small fault with a chasm or a hole. From time to time a wave rushes into a cave compressing the air within it—which then recoils with a report. It makes a sound like distant cannon fire, an irregular salvo fired in an orogenic war. Imagine the battery on a stormy day. N o w it is possible to comprehend how thousands of years of erosion have eventually isolated stacks and islands, like Meachard off Boscastle harbour. In time, these outposts of land will be worn quite away and returned to the sea. I can identify white quartz in the matrix of the gloomy cliffs, as clearly as scribblings of chalk on a blackboard. There is even a patch where the quartz trace shows the strata to have been folded over completely—turned upside down. I can only speculate on the massive forces which have treated solid rock 6

Discovery

with such disdain. Thicker masses of quartz are aligned along the faults. Squeezed from the rock like serum from a wound, it congeals in the cracks. This must have been the source of those large lumps in the stone walls. Elsewhere, it fills in voids in stressed rock like some kind of mad spaghetti. Ultimately, though, quartz is tougher than slate, and survives as pebbles long after the country rock has been eroded away. I would be willing to wager that some of the rounded pebbles on inaccessible Pentargon beach far below me are made of quartz. They will outlast these cliffs, a n d — w h o knows?—maybe they will outlast the human species.

The sooty shales and slates were once soft muds—sediments—which accumulated deep beneath the sea. Time has transformed them: hardened them, elevated them hundreds of feet above present sea level, and folded them. But how much time?

Where I am standing now, close to the edge, there is a notice

in

red

letters:

Caution!

Cliffs

are

liable

to

cracking.

Take

extra care. And it's true. A stack of shale is teetering outwards into the void. It is hard to escape a shiver of apprehension as you imagine the block tumbling over and over to smash to pieces far below. The next haven up the coast is called Crackington, the name encapsulating the precariousness induced by erosion.

I have a geological memoir for the Boscastle area tucked into my jacket pocket. From the geological m a p which sketches out the pattern of the outcrops of the rocks I can see something of the tectonic agony which is so patent in the cliffs: rock formations twist and turn over the mapped ground, which is criss-crossed by faults. I can identify exactly where I am standing, on the outcrop of the Boscastle Formation; in the dry language of science the slates are described as early Carboniferous (what in the US would be called Mississippian). This corner of the world has an extremely ancient origin, older than m a m m a l s , older even than dinosaurs. These black slates would already have carried their contorted signa7

T R I L O B I T E !

ture as a guarantee of antiquity when Tyrannosaurus was king of the hill. W h e n they were first laid down there were only tree ferns and cockroaches and cumbrous amphibians on land. Can there be a better place to reflect upon the vastness of geological time?

The erosion which I can both see and hear is ineffably slow.

I could stand here all my life and notice little difference to the cliffs. Maybe a chasm excavated along a fault might seem subtly darker as its girth increased after an exceptional storm.

Perhaps a rock fall would leave a scar cleared of campion and grass. But I am certain that when Thomas Hardy stood on this spot he would have gazed upon a comparable scene; my eyes now see what his once saw. To be sure, the vegetation would have changed, but the geological signature of the cliffs would have been legible in much the same way. H o w can we conceive of the time needed to wear away these cliffs to nothing, to convert all the massed slates into fine silt, quartz veins into pebbles—at first angular, then worn by the constant shuffling of the sea rounder and rounder, until they acquire the contours and colours of a hen's egg? Millennia are irrelevant, species come and go, and still the cliffs stand obstinate against the inroads of time. Yet given enough time even this rampart that seems to stand so unflinchingly against the surf will be reduced to nothing, and the flagstones on the floor of the Cobw e b Inn will return to sediment, joining all the other works of M a n , committed once again to the great cycle of change.

Rocks are eroded to sediment: sediment is hardened to rock; rock is elevated above sea level by movements of the Earth, transformed by tectonics; and, thus raised, is once more subject to the assault of the elements. This is the great wheel of the Earth. If Gustav Mahler had taken the geological view, Das Lied

von

der

Erde

(The

Song

of the

Earth)

would

have been

a cycle of erosion and reconstruction endlessly reiterated, enough to try the patience even of those w h o admire the most mantric of symphonies.

Cornwall once formed part of a vast mountain chain. It 8

Discovery

marked one end of the Hercynides, which snaked through Europe just as the Alps do today in the south. The patent folding of the rocks was the result of the slates being trapped in a great tectonic vice that showed no mercy. Rocks buckled, in an attempt to accommodate forces that were irresistible. Every tiny ruckle in the wall of Pentargon Bay is the legacy of suffering under a rule of tectonics so mighty that no mere rock could stand against the imperative of crustal stress. W h e n the rocks were folded, structure was piled upon structure until mountains resulted. Clever geologists from the University of Exeter, like E. B. Selwood, have spent years trying to unpick the buckling. They have interpreted this stretch of coast not as merely folded, but as divided into great slices of crust which have slid over and past one another. Squeezed rocks could not absorb the forces by contortion alone, and were compelled to fracture. To attain equilibrium, vast broken slabs of rock larger than a parish slid away from the centre of the forces at a low angle, like the twisted thorn branches leaning away from the reach of the sea wind. Under the sole of these sliding masses weaker rocks were folded over and over, crumpled like a pack of playing cards in the hands of a ruined gambler. Every crack that was opened up, as the country was ground beneath the tectonic wheel, would be filled with vein quartz. Now, the eroded remains of these mountains lay before me. The lichencovered stone walls were fabricated from the relics of ancient Alps. The farmer who orientated the slaty slabs with such care was conniving with tectonic forces of which he probably knew nothing.

Not many miles to the south, near Bodmin, a granite tor rises above the general plain. It is reminiscent of some stepped Mayan pyramid, not least in scale, but is entirely natural. The strange pile of enormous blocks is what remains behind when granite is weathered over many thousands of years. Even granite eventually succumbs to the onslaught of the elements, rain and wind and frost. But granite endures longer than shale, as I was to see in St. Juliot's churchyard, not far away.

9

T R I L O B I T E !

Granite, too, is part of the narrative of the vanished mountain chain, although its source was utterly different from the shales of the Cornish cliffs. It was crystallized from a liquid magma, hot and invasive, within the deep heart of the former chain.

Look now: you can see big crystals of felspar, and maybe the sparkle of mica. These crystals tell the story of how a mountain chain drives crumpled rocks so deep into the Earth's crust that they melt, and brew a buoyant, hot broth of liquid minerals, which once more rises through the crust to crystallize and solidify as granite batholiths and plutons. Granite lies at depth beneath the Cornish peninsula, reaching to the surface under the boggy stretches of Dartmoor and Bodmin.

At the moment of their formation, some of the crystals set in motion radioactive clocks. Precise modern instruments can now assess the ticking of geological time as it is recorded by decaying radioactive isotopes of uranium or potassium (and several other elements besides) contained in the substance of the crystals. This method provides the answer to that difficult question: how much time has passed? The decay rate is known: it is only a matter of exact measurement and careful calculation to obtain the date of the mineral's formation. If the Bodmin granites were intruded into the folded rocks, then it follows that the granites must postdate the folding. The crystals act almost like eyes that let us see into the past, to calibrate it, to fix it in our vision. So if the crystal age of the granite was 300 million years, it fixes our cliffs as older still—the black slates must have already been folded before the granites were intruded.

As to the soft muds which were eventually hardened and distorted into the black slates, they were deposited on a Carboniferous sea-floor, as long as 340 million years ago. Time hardened them, tectonics twisted them, granites punished them with plutonic heat, long before they came to form the cliffs which now make sites for the inaccessible nests of fulmars and kittiwakes. But messages can be passed on from that ancient sea: messages in the shape of fossils. When the sea10

Discovery

floor was young, shells of m a n y kinds of animals lay littered among the muds and sands, just as clam shells can be found stranded on a beach today. These were mostly ordinary, small creatures, snails and brachiopods and the like. Their shells became incorporated into the sediment as more fine m u d rained down upon them: m u d originated from the erosion of an ancient landmass, which itself was the product of a previous cycle of Earth history. This is how the story of the world turns and turns again. With the passage of time—much more time—the shells were still there as the muds became deeply buried, and then hardened into shales when water was driven out. Perhaps the substance of the shells was augmented by a subtle infiltration of minerals at this time. Their original colours were leached away, a time-change that bleached shells of brightness, converting them to fossil-colour: they became stony simulacra of once-living creatures.

Their journey had only just begun. The Carboniferous sea in which animals once flourished and left their shelly tokens was consumed in the engine of plate tectonics. Rocks and fossils alike—the accumulated legacy of the sea—were passengers on a great journey. M a n y of the fossils were doomed to obliteration. They might be dragged to the centre of the growing Hercynian chain, fated to be squeezed or baked beyond recognition. They might be dissolved away. They might be chopped into pieces as the rocks carrying them recrystallized.

Mountains grew over south-west England, great slabs of country were shrugged sideways in the melee. Granites insinuated themselves into the depths. As soon as the mountains were born, they were destined to die by erosion, so, most likely of all, the fossils could be worn away to an impalpable mash that was already on a journey to the next Earth cycle. We must marvel at the fossil survivors, their chutzpah in the face of the orogenic enemy.

Sealed in the aftermath of tectonics, the fossils still had to survive all that followed: the rendering of a mountain chain once more into the sea. Through more than 200 million years 11

T R I L O B I T E !

the Hercynian relic was ground down to its roots. It is certain that the granites reached the surface at a time when dinosaurs were still lumbering over the Weald and western Europe, for curious and distinctive minerals derived from these granites are found for the first time in rocks laid down in Cretaceous times, about 100 million years ago. Like a geological striptease, veils of rock were stripped slowly away to ever more fundamental levels within the ancient chain. Eventually it was stripped naked to its interior, and the show was over.

What I was looking at in Pentargon Cliff was one of the inner veils, preserved from obliteration, with its strata still crumpled like discarded chiffon.

What fossils might survive in the dark slates? What miracles of endurance might they record, what cheating of the laws of chance? H o w could a wanderer along this slippery path high above the everlasting sea truly comprehend what is meant by the vastness of geological time, even though the evidence is everywhere displayed? Looking down on Boscastle I could almost capture the historical past—I could " s e e " it as one might episodes from half-remembered movies. It is not difficult to paint a mental picture of Hardy on this path. Or to envisage, more than a century ago, filthy slate miners tottering off to the inn of their choice, with the gentry nearby spry in traps; or to conjure up a bustling Tudor port with heavyrigged ships sheltering from the wildness of the sea in the safe haven, talk of the Armada in the inns, costumes out of Holbein; I can even visualize an Iron Age farmer's tilth and husbandry, and the discomfort of a November day like this in a simple, smoke-filled dwelling. My vision is full of details rooted in shared humanity, set in bric-a-brac drawn from memory plausibly arranged. But to quantify the geological time required for the formation of Cornwall I need to multiply time a thousand-fold, and then perhaps nearly a thousand times again. I am as accustomed to writing figures in millions (of years) as is a Swiss banker (in dollars), yet the lines of zeros do not translate in proportion. Just as the average working 12

Discovery

man can understand exactly the purchasing power of fifty bucks, and fifty thousand is probably comprehensible, 500,000,000 has an approximate feel to it—surely, it's a fortune, but what does it mean? A lottery win of 5 million is a lot, but then, so is 22 million. We reel away from such vertiginous figures, we can envisage a huge pile of money, notes piled on notes, but we cannot comprehend its true magnitude. If our intention is to see so far into a past of many millions we shall need to develop a special w a y of seeing, a spyglass trained on former worlds. We will need to cultivate an indifference to magnitude, so that a million years becomes not, after all, such a long stretch of time. We will need to read rocks and cliffs as if they were books, and not shudder at the heights.

I have passed the steep side of Pentargon Cliff. Some kind soul has carved steps to ease the climb, but even so I am out of breath by the time the path levels off. It now follows a course along the middle of a steep, grassy slope, and is very slippery.

There is a curious sense of suspension; the sea is far below, but the slope conceals the vast cliffs which I k n o w must be there. I can still hear the sea clearly enough: there is an irregular bang! bang! as waves punish a sea cave along the invisible surf-line, but the great height I have now reached feels almost illusory, as if I were ambling along some unspecified stratum floating between sea and sky. I have reached Beeny Cliff, and I am grateful that the light has not yet started to weaken. A few drops of rain hit me hard in the neck. A flock of gulls suddenly rises up from beyond the cliff edge, buoyed by the updraught and mewling hysterically. The end of my walk makes me turn up my collar, and shiver.

Beeny Cliff is the scene of a terrifying episode in Hardy's novel A Pair of Blue Eyes. Stephen Knight follows the same path that I had just completed, in the company of Elfride, the first of Hardy's complex, closely-observed w o m e n heroines.

Knight is a man of scientific bent. Perhaps seeking to display his knowledge—or maybe just to satisfy his curiosity—he attempts to demonstrate the contrariwise circulation of the air 13

T R I L O B I T E !

GEOLOGICAL

TIME

Era

SCALE

FOR

Period

TRILOBITES

Age Ma 250

Permian 290 Carboniferous Upper Palaeozoic

354 Devonian

PALAEOZOIC + + + + + + +

417 Silurian 443 Ordovician

Lower Palaeozoic

491 Cambrian

545 Precambrian (Vendian)

currents up the face of the cliff: "an inverted cascade . . . as perfect as Niagara Falls—but rising instead of falling, and air instead of water." He leaps on to the slope below the path, and his hat is caught by the counter-current; in a foolish attempt to retrieve it he slips down the appalling incline. He ends up dangling desperately at the edge of the cliff-face itself; Hardy describes the black slates with some precision. Here it is that Knight comes face to face with the subject of this book.

By one of those familiar conjunctions of things wherewith the inanimate world baits the mind of man when he pauses in moments of suspense, opposite Knight's

Discovery

eyes was an imbedded fossil, standing forth in low relief from the rock. It was a creature with eyes. The eyes, dead and turned to stone, were even now regarding him. It was one of the early crustaceans called Trilobites. Separated by millions of years in their lives, Knight and this underling seem to have met in their place of death. It was the single instance within reach of anything that had been alive and had had a body to save, as he himself had now.

In this bleak spot, where I was gazing out towards the precipice between the wrinkled sea below and the darkening sky above, trilobites made a brief appearance in English literature. The path above Beeny Cliff was where two paths of my own life—trilobites and writing—uniquely intersected. I felt compelled to visit the place; and I was not disappointed. The eyes of the trilobite, "turned to stone," provided the image I needed to guide the reader through this book, which will try to see the world through the eyes of fossils as a means to animate the past. Equally, I was intrigued by the difference between the novelist's truth, which has nothing to do with testability and everything to do with the impact of the work on the mind and emotions, and scientific truth, which has everything to do with testability, but also with the emotions of discovery—many of them the stuff of novels.

So to what extent was Hardy telling the truth? Hardy was writing his novel originally as a serial—he needed to keep his readers enthralled, episode by episode. Knight's predicament was a cliffhanger in the most literal sense. H o w can you have more suspense than to leave your character exactly suspended? The trilobite eyes provided a focus for Knight's nearnemesis; while h u m a n eyes—blue ones—provided both the title and emotional motor for the novel. The critic Pamela Dalziel has noticed how the plot twists upon " s p y i n g " of one kind or another. The book is soaked with the implications of sight.

15

T R I L O B I T E !

I was interested to see how closely Hardy had observed the setting for his cliff-hanging episode. Scholars have identified the location from m a n y details from his early life. While he was still employed as an architect restoring St. Juliot's Church in 1870, he met his future wife, Emma Gifford, who was the sister-in-law of the Rector. Locations in the area are rather thinly disguised, and it evidently lies well to the west of the rest of Hardy's Wessex. A Pair of Blue Eyes included more autobiographical elements than his other novels, and perhaps for that reason evidently remained dear to his heart (he rewrote parts of it m a n y years later). The height of the cliff itself is rather pedantically described, even as poor Knight flounders, surely indicating that the young writer had gazetteers open, and a sharpened pencil in front of him as he catalogued its statistics: "proved by actual measurement not to be a foot less than six hundred and fifty [feet] . . . three times the height of Flamborough, a hundred feet higher than Beachy Head .. . thrice as high as the Lizard" (and there is more in this vein). But what left me in no doubt at all about the site was the walk I had taken, which was duplicated exactly by the characters in the novel. Hardy had observed what was evidently the same waterfall plunging to obscurity that I had seen at Pentargon Bay, "running over the precipice it was dispersed in spray before it was half way down, and falling like rain upon projecting ledges made minute grassy meadows of them." He described the threatening cliffs, with their "horrid personality" at the same point as I had seen them on my walk.

In m a n y respects passages in the novel could be described as reportage: he could recognize both quartz and slate, he recounted physical features in order along the path, he knew some geology and meteorology. While Knight clung to the cliff face his mind raced back through geological time—a series of tableaux of the past succeeded one another in his desperate mind all the way back to the ancient time of the trilobites. It is not a bad account, scientifically speaking, of the

16

Discovery

succession of life through geological time as conceived about i860.

But now we reach a point at which fiction and description take off along different paths; perhaps the fascination of the novel lies in these deviations. W h y did Hardy refer to Beeny Cliff as The Cliff with No N a m e ? The hamlet of Beeny is clearly named on old maps and he was usually adept at nearsynonyms—Camelton for Camelford, Dundagel for Tintagel.

I believe that " N o N a m e " adds to the horror and mystery of the place. The same point was appreciated by Sergio Leone: in his brooding spaghetti westerns " T h e Man with No N a m e , " played by Clint Eastwood, was the anti-hero. Naming is the first way we domesticate our surroundings; we would expect the highest cliff along the coast to have a name. Anonymity is horror. When a series of murders are committed terror is at its worst while the perpetrator is still unknown: a case of nameless dread. The fabricator of fiction k n e w this; this is where artifice comes in. Hardy liked facts, but he knew also when to suspend them. The trilobite itself is a convenient fiction. The Carboniferous rocks on this part of the Cornish coast have yielded no trilobites. The rocks are of the right age, so there is no theoretical objection to finding trilobites there. Fossils are very rare from such tectonically tortured rocks. Enough have been found—precursors of ammonites, clams, microscopic fossils—to establish the geological age, but trilobites are not among them. I would be absolutely delighted to receive a trilobite from a collector lucky enough to h a m m e r one out of these unpromising strata; it would be of appreciable scientific importance. Hardy placed the fossil in the right geological setting, but the finding of a trilobite is an invention. He needed the trilobite to stare out Stephen Knight. As readers of fiction we relish his use of this particular fossil, "but a low type of animal existence," as heightening the drama of the situation. It matters not a jot that the occurrence is fictional, even though the rest of Hardy's account is an almost photographic reproduc-

17

T R I L O B I T E !

tion of a real scene. A scientist would be appalled if one of his colleagues invented such an occurrence, for science trades on the truth—nothing but the objective fact. The truth of the artist can recombine the facts of the world in the service of creation, but the scientist has a different duty, to discover the truth lying behind the facade of appearance. Both processes may be equally imaginative.

As for Mr. Knight, he escaped his predicament thanks to a rope, but a rope desperately manufactured from Elfride's undergarments. It is a turning point in the novel, symbolizing a change in the relationship between a flawed man and an unusual woman. And we are not compelled to wonder whether such an episode was fact or not, because it is woven into the fabric of a novel.

I left Beeny Cliff by climbing up the steep steps to Fire Beacon Point, a wild bluff commanding views of the whole Hercynian coast. It m a y have acquired its name as one of numerous beacons on which fires were lit to warn of the approach of an armada. Now, there is only a bench at the top dedicated to the m e m o r y of Paul C. Heard, but I thanked Mr. Heard's relatives for the chance to rest and regain my breath. I turned inland, following an old, walled track. I wanted to see the parish church of St. Juliot on which Hardy had worked. It is perfectly set on a sheltered hillside, and behind it a track leads out directly across fields upon which sheep graze unhurriedly. Despite the setting, there is something depressingly foursquare and Victorian about St. Juliot's—possibly the fault of Hardy's restoration—including a rather dumpy tower with unnecessary castellation. It is as if the site deserved something m u c h more distinguished to live up to its associations. After all, Hardy wrote that " m u c h of my life claims the spot as its key." Surely it is an ancient holy place, which the church fails adequately to honour. In the graveyard there are several "Jollows"—possibly a bastardized version of the name Juliot—the kind of family that must have grown out of

18

Discovery the local soil as surely as wind-blown gorse. Inside the church there is a notice informing the visitor that most of the church plate has already been stolen. There was nothing to induce me to linger.

But as I left I saw the Celtic crosses, more ancient than the church itself. Close by the gate one crudely shaped column as high as a man stands sentinel; its apex is sculpted into a disc, and you might expect to find some sort of face hewn upon it, but instead there is a schematic cross. Unlike the slatey gravestones, these upright crosses are m a d e from granite. They will endure w h e n all the inscribed memorials to Jollows have crumbled into the same soil that long since claimed their bones. The granite was derived from one of the igneous intrusions into the bowels of the Hercynian mountain range.

M a y b e the blocks were derived from Bodmin or Dartmoor, but whatever the source their hewers knew about permanence. Each monument acknowledges the vast span of geological time, the durability of stone compared with a human lifetime. Each is a symbol of the crossing of h u m a n intention with tectonic history—the same history that placed Hardy's plausible but fictional trilobite into Beeny Cliff. The discoidal apex of the cross is like an eyepiece with a view clear back to the age of the tree ferns and lungfishes. This, after all, m a y have been what I wanted to discover on a chilly N o v e m b e r day in Boscastle. I felt a curious elation, even as the icy raindrops began to refresh the lichens that alone could derive sustenance from incorruptible granite—set solid ever since trilobites had patrolled the shallows of a vanished ocean.

If you can have love at first sight, then I fell in love with trilobites at the age of fourteen.

The peninsula of St. David's forms the south-western promontory of South Wales, extending westwards like a miniature version of the Cornish peninsula where Hardy, too,

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encountered love. Like Cornwall, it is a region of spectacular and ancient cliffs, while inland the scenery is flat and characterless. There are little coves here, too, with names like Solva and Abercastle, formerly wild and remote fishing villages, but now spruce with whitewash over the rough stone. But the cliffs are as wild as ever they were, and displaying rock folds as convoluted as anything in Cornwall. A walk along the coastal path parades one rock formation after another, delineated by contrasts in colour and texture: here massive yellow or purple sandstones plunge like naked ribs into the churning foam, there a group of contorted dark shales zig-zag up the cliffs like some sort of berserk concertina. In Caerfai Bay there are bright red shales, looking improbably pert in a world of dun geology. All of these rocks are still more ancient than their Cornish counterparts. They date from the Cambrian period, the oldest of the shales having been laid down as muds beneath the sea something like 545 million years before the present. This is getting back to the beginning of things, to a time before there were any plants on land, to a time before any kind of backboned animal existed. Yet there were already trilobites to witness this nascent world. These trilobites were 200 million years older than Thomas Hardy's invented fossil (or, I should say, its real equivalents)—a span a hundred times longer than Man's brief tenancy of this planet. This was the time I explored with a coal h a m m e r at a period of my life when my voice had just turned unreliably falsetto and baritone by turns. While others discovered girls, I discovered trilobites.

I had marked the presence of fossils on a local map. They were described as the oldest fossils in the British Isles. What could be more irresistible? There was something extraordinarily exciting about tapping into a vein of such prehistory. The top dressing of the landscape of h u m a n tenancy was stripped away to reveal some deeper reality, layer after layer of geological time unpeeled in my imagination. While my long-suffering mother knitted or read, I beat the rocks at Nine Wells and 20

Discovery

Porth-y-rhaw.* These were places where the rocks were accessible by foot and could be broken by sheer effort. I did not even have a proper geological hammer. The fever of discovery was upon me. I learned how to break the hard rock so that it split in the same direction as the former sea floor—this w a y I was more likely to retrieve something recognizable. It was clear that tectonic forces had tipped the strata vertically. I had to scrabble to dislodge reasonable-sized blocks for breakage. I ignored the sharp pieces of gorse that speared the backs of my hands. Time had made the rock both hard and brittle: it seemed to want to break anywhere but in the right direction.

On the broken surfaces there were scraps and fragments of what might, or might not have been the remains of past life: black patches, a little shinier than the rest of the rock. Then, at last, I found a trilobite. The rock simply parted around the animal, like some sort of revelation. The truth is that the fossil itself had rendered the rock weaker: it was predisposed to reveal itself, almost as if it desired disclosure. I was left holding two pieces of rock: in my left hand the positive impression of the creature itself (known as the part); in my right hand the negative mould which had once comprised its other half (the counterpart); the two together snuggling up to survive the vicissitudes of millions of years of entombment. There was a brownish stain on the fossil, but to me it was no disfigurement—surely what I held was the textbook come alive. Drawings and photographs could not compare with the joy of actually touching a find which seemed, in the egotistical glow of boyhood, dedicated to yourself alone. This was my first discovery of the animals that would change my life. The long thin eyes of the trilobite regarded me and I returned the gaze. More compelling than any pair of blue eyes, there was a shiver of recognition across 500 million years.

I would one day learn that the trilobite had a name, Para*Both these sites are now legally protected from hammering, although they were not at the time of my schoolboy excursions.

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doxides. W h e n we first exchanged glances I knew nothing of classification or nomenclature, and it did not matter to me: there was plenty of time to learn more. What I held was a specimen that fitted comfortably into the palm of my hand. It was clearly divided along its length into three lobes—a convex central portion and to each side of it identical, but slightly flattened, areas. These were the lobes implied by the n a m e — trilobite. The whole animal seemed to bulge towards one end. I knew, by some principle which I could not articulate, that the wider end was the head of the animal. And of course upon this head there were the eyes. Despite the unfamiliar conformation of the fossil, I knew that eyes must always belong on heads. So despite the exoticism of the fossil there was already a c o m m o n bond between me and the trilobite—we both had our heads screwed on the right way. I could see that the body was subdivided into a number of little divisions—or segments, as I would learn to call them. Then there were cracks running across the body. These had nothing to do with the original structure of the animal, rather they were testimony to the long journey through geological time that the Cambrian creature had travelled before it fell apart under my hammer blow. They were joints in the fabric of the rock itself, the scars of an adventure that might have seen the trilobite eroded into oblivion or obliterated in the vice of a thousand tectonic accidents.

This book grew out of that first encounter. I want to invest the trilobite with all the glamour of the dinosaur and twice its endurance. I want you to see the world through the eyes of trilobites, to help you to make a journey back through hundreds of millions of years. I will show that Hardy's description of the trilobite as "but a low type of animal existence" was hardly just, but that his placing the animal at the centre of a drama of life and death might have been nearer the mark.

This will be an unabashedly trilobito-centric view of the world.

For trilobites have been witnesses to great events. Stephen 22

A drawing of the giant trilobite Paradoxides by Philip Lake published in 1935, from the same Middle C a m b r i a n rocks in western Wales that yielded the first specimen to my schoolboy hammer. For a photograph of Paradoxides, see p. 222.

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Knight might have read from the trilobite's stony eyes that the predicament of a mere individual meant nothing. They have seen continents move, mountain chains elevated and eroded to their granite cores, they have survived ice ages and massive volcanic eruptions. No living thing can disengage itself from the biosphere, and trilobites followed the same pattern: their history was also shaped by the events they witnessed. When strangers express their surprise that it is possible to devote a lifetime to studying extinct " b u g s " I remind them of how much has happened in the last few thousand years and invite them to imagine what it is to be a historian of dozens of millions of years. We are doomed to know so little, like fishermen trying to understand an entire ocean by throwing in a few baited handlines. And if anyone wonders how it is possible to invest such devotion in a group of organisms which died out long ago as a result of who-knows-what inadequacies, there is an obvious answer. Trilobites survived for a total of three hundred million years, almost the whole duration of the Palaeozoic era: w h o are we johnny-come-latelies to label them as either "primitive" or "unsuccessful"? Men have so far survived half a per cent as long.

There are accounts of scientific research that present the story of discovery as a series of glittering prizes that must be won by the most muscular intellect; this is science as a version of trial-by-combat. Or else scientific research is contained in a metaphor of a journey into uncharted territory, as expressed

by Robert Louis Stevenson (in Pulvis et umbra): "science carries us into realms of speculation, where there is no habitable city for the mind of m a n . " It is certainly true that there are races to be first in science and that a few massive minds venturing into "realms of speculation" command the most attention—and they deserve it. Such models of scientific progress are typified by mathematicians and physicists, beautifully elaborated by Karl Popper in Conjectures and Refutations.

Nonetheless, as a description of much of scientific endeavour, both the combative and the adventurous-speculative views

Discovery

are flawed. Many scientists—perhaps most of them—are a curious species for w h o m the pleasure of finding out is at least as important as the size of the goal. He or she is often a cooperative creature, comfortable with the happy exercise of innate ability, and if a m o m e n t o u s discovery comes it may arrive unexpectedly, like an unanticipated legacy. The unique property of the scientific endeavour is that so many of the regular footsoldiers contribute to the victory. Unlike a poetaster whose burblings are destined for true oblivion while the creations of a Keats survive, even a minor scientist might well make a permanent contribution to a famous campaign—an uncelebrated private w h o did not die in vain.

Even the most singular fields of scientific inquiry relate in subtle or unexpected ways to larger questions. We shall see that an apparently self-contained and esoteric occupation like the study of trilobites has contributed to mighty debates about the origin of new species, or the nature of major features of evolution, or the distribution of the ancient continents.

Those who started with a deep desire to k n o w more about the details of life habits of vanished animals—out of sheer curiosity—may suddenly realize that the detailed knowledge they have accrued relates to something different and more general: something as grand as the structure of an ancient ocean or the arrival of an asteroid on Earth.

I believe that a more accurate image for the way m u c h of science works might be a series of interconnecting paths. Each one has its own interests and delights; sometimes we k n o w where a path leads, on others we are taken by surprise by twists and turns. And where there are intersections with other paths there can be unanticipated new directions which may lead to wholly unexpected views. Like Stephen and Elf ride on the path above The Cliff with No N a m e there may be a crucial conjunction of circumstances which changes everything, and something as small and ancient as a trilobite may be the catalyst for the transformation.

This book will follow a few of the paths that led me from 25

T R I L O B I T E !

that first schoolboy find. In pursuit of trilobites I shall visit remarkable places and spend time with remarkable people.

Knowledge has been hard won, and there are heroes whose names are known only to me and a few of my friends, who deserve wider recognition. There are stories of personal tragedies which have influenced this tale of trilobites. Discovery isn't a simple matter of "onwards and upwards." It is imbued with all the tawdry and magnificent stuff of human lives. The story of that small part of science which is important to me will illustrate the way this defining human activity works better than some other accounts of greater endeavours: like relativity or the first few nanoseconds of the universe.

Sometimes, a miniature gives a better likeness than a grandiose portrait.

C o m e and see the world as it once was through the crystal eyes of the trilobite. We shall find out how trilobites tell us the pattern of evolution, and how it can be read from the rocks.

We shall discover how faith in trilobites not merely moves mountains but shifts whole continents. We shall see how castoff shells can be re-animated into living animals. We shall understand something of the origins of the richness of the animal kingdom. Through trilobites, we shall take possession of the geological past.

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II

Shells

In 1698 Dr. Lhwyd wrote to his correspondent Martin Lister about the fossils to be found in the limestones around the South Wales town of Llandeilo: "the 15th [of August] whereof we found great plenty must doubtless be referred to the sceleton of some Fiat-Fish." L h w y d ' s "flatfish" were, of course, trilobites.

When my children were young they used to play a game with sea shells. Holding a large whelk to one ear they contrived to " h e a r " the sea: the distant crashing of waves on the shore, or the insistent whistling of a gentle sea breeze. Later they understood that the conch merely amplified the murmuring of the air around them, but they never forgot the leap of imagination that joined shell to sea.

Palaeontology is all about listening to what fossil shells have to say. We have to pay attention to shells, because hard skeletons made of durable minerals are almost always what fossilizes. With rare exceptions, the soft anatomy eludes us.

Body tissues are food for predators, or for the agents of decay.

W h o has not picked up a crab shell on a beach, and let it go with a cry of disgust, startled by the pong of putrefacation?

Bacteria are everywhere, greedy to decompose, voracious for those organic molecules manufactured with vital energy 27

T R I L O B I T E !

during life—and then yielding up that energy again to a host of tiny diners, a few thousandths of a millimetre long.

"Too, too solid flesh" does indeed melt. What remains behind—shells and bones—has little to sustain the ubiquitous bacteria. Trilobite shells are like those of a dozen or more other kinds of marine animals, being sculpted from the hard mineral calcite. Crab shells are composed of calcite, so are those of clams. If trilobites had not carried their hard shells they would have been effectively invisible to us, for they would have left virtually no trace of their former existence. Had the seas teemed with them as thick as oats in porridge we would have remained ignorant of their rich diversity. Fossil shells are the cast-offs of life, the tough bits, the inedible residue. That which was of least interest to other living animals in life is, ironically, just what generates the interest of both the scholar and the geologist once it has been transformed by time into a fossil. To begin to understand trilobites it is necessary to know about their shells.

Even the shell of a trilobite loses something on death.

Colour is the most transient of properties. We know that sealife today is a symphony of hues: colours flashed as warning, colours subtly employed in disguise, colours seemingly just for sheer exuberance. It is likely that the seas hundreds of millions of years ago were just as polychromic. Yet colour is the first property to bleed away in the fossilization process. The fossil world is a pallid world, which only imagination can revivify. The colours of the dark trilobites I saw in western Wales were the colours of the rocks that entombed them, with no indication of the appearance of the original animals. We can colour them up as we fancy.

I learned trilobite shell anatomy as a student. The terms that I heard empowered me, allowed me to place these strange animals within a field of comprehension. It was curious how learning to call the head of the trilobite the cephalon seemed to admit me into the special world of the trilobite lover. Cephalos

28

Shells

is the Greek for " h e a d " so really we are just replacing one head by another. All trilobites, I learned, were divided into three portions not just along their length—the tri-lobes—but also crossways. As I had instinctively recognized from my first trilobite at St. David's, the cephalon was the front portion, the part that looked at m e . At the other end was the tail, which I must learn to call the pygidium—a Greek word again.

The adoption of classical language is not to be wondered at, for in the early days of natural history Latin was still the chief m e d i u m of communication between scientists of different nationalities. Classics was the sine qua non of the educated classes, the lingua franca, and not just dropped into any sentence to impress the reader with the learning of the writer (see sine qua non, above, but not lingua franca, which isn't Latin).

Botanists are still obliged to write a shorthand Latin description of every new species (although this m a y be about to change), something zoologists have not had to worry about for a hundred years. But classical terms for bits of anatomy, whether of an animal or a plant, are more enduring. Medical students curse them even as they commit them to memory, laymen puzzle over them. They serve as a continuous link all the way back to the time of William Harvey and his unscrambling of the circulation of the blood; the terms last while the concepts around them change. This conservatism serves a useful function in retaining a language in which specialists can converse precisely. The first task of the tiro is to master words. The sign that the beginner has joined the hidden club of experts is when he can trade technical descriptions with confidence. There is more to it than that, because the applying the right word is also a guarantee of recognition. The more closely a natural object is anatomized the closer you have to look, and the more terms have to be mastered. Latin or Greek, it matters not, what is important is that a technical term is a shorthand for learning. Nomenclature is a preface to understanding.

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T R I L O B I T E !

So I observed that between cephalon and pygidium there was the thorax. It is a familiar enough word, even if its use in the human context is quite different. This portion of the trilobite was the longest part—at least in those trilobites I studied first. It was further divided into a number of s e g m e n t s — thoracic segments. (At the height of Steven Spielberg's fame I toyed with the idea of a movie to restore trilobites to the dramatic centre in the history of life that they deserve. Perhaps a crazed palaeontologist reanimates them from the dead using some appropriate hocus pocus until they rampage unbridled through N e w York, savaging scantily clad beauties, and knocking down buildings . . . that sort of thing. It was to be called Thoracic Park.)

Each thoracic segment was jointed, and connected by a weak hinge to the one in front and the one behind. Segments form a linked system, rather like railway carriages in a line.

They are all more or less similar, and connected together by a coupling. If we had tried to snap the fresh trilobite in two it is almost certain that it would have snapped between segments.

It is the same principle that makes us divide a lobster shell at the back of the head. The lack of comparable segments is what makes a tortoise so impregnable—but also so inflexible. A tortoise trundles along, lurching over obstacles, and often dies if it happens to tumble on to its back. There is nothing more ineffectual than a tortoise foolishly waving its legs in the air in a doomed attempt to right itself. Not so a segmented animal.

W h e n an obstacle is encountered the segments can shift relative to one another to allow flexibility: they are articulated, hinged, jointed. The movement between segments is dictated by the laws of mechanics: this is w h y iron plated, alien bugs in science fiction movies look both mechanical and convincing.

Segments really are all about the articulation of armature.

Even when stranded on their backs segmented animals can wriggle upright. To the trilobite a certain vulnerability was the price of flexibility, and a price worth paying. The trilobite

30

Shells

Pygidium (tail) T h e a n a t o m y of a trilobite: a few technical terms, labelled here on Calymene, allow us to describe almost any trilobite.

could move over obstacles, flex and turn, like a train that needed no tracks on which to run.

Looking closer at the tail—or pygidium—it is clear that this, too, included a few segments, but instead of being free to articulate they are fused together, forming a shield. In some trilobites the pygidium is longer than the head, and includes many segments; in others it is minute. Later I would learn why these differences might be useful to the animal. Both thorax and pygidium had an obviously convex central p o r t i o n — the middle lobe of the trilobite—which, in a rare display of nomenclatural simplicity, is called the axis. Furrows divide the axis from the lateral, or pleural, parts. So now I had heard the names to distinguish the three lobes of the trilobite: the axial lobe and the flanking pleural lobes. Each thoracic segment had a pleura on either side. In my first ever trilobite these pleurae had spiny tips, so I knew that if I had picked up the living animal it would have felt spiky in my hand, with that particular kind of unpleasant prickliness that one gets with handling a langoustine.

3i

T R I L O B I T E !

As for the trilobite head that first attracted my attention when I cleaved open the dark Cambrian shale of St. David's, that, too, showed an inflated axial part—the axis of the thorax carried on and widened forwards into a swollen, and prominent, median portion. " T h i s , " our professor said, "is the most important and characteristic part of the trilobite—the glabella." No familiar ring to this word, it just had to be learned. It had the small advantage of rhyming with " u m b r e l l a " — a n d undergraduates are fond of such aidesmemoires, even if they are harder to remember than the original thing to be memorized. The glabella was traversed by furrows that suggested that there was more than one segment in the cephalon, just as in the thorax and pygidium. However, the segments must have been fused together to make the head end an altogether more robust contraption than the thorax, and more like the pygidium in this respect. To either side of the glabella are the eyes, and—believe it or not—they are just known as eyes. By using such a simple word we acknowledge our realization of the connection between the student observing and the object studied. Hardy's "eyes, dead and turned to stone" looked across millions of years with a stare of genuine recognition of like for like.

So in just eight technical terms—cephalon, thorax, pygidium, segment, axis, pleura, glabella, eyes—it is possible to begin to embrace the form of these strange animals. To be able to name the parts introduces a certain familiarity. Further, to be competent to recognize the glabella for what it is means that it does not take long to see that one trilobite has a glabella which is quite different from that of another. With language comes discrimination. And it is true that every item named is capable of varying mightily from one species to another: there are those with large eyes and small, those with long thoraces and short, wide or narrow pygidia. I was soon to learn that there were thousands of different species of trilobites and, in the end, I was to become a namer of new names myself.

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Shells

For now, though, trilobites were hardly more than the jettisoned husks of once-living animals. Listening to the message of the shells was like trying to hear the sounds of a far-off sea, more remote than childhood. I had begun to acquire a language to describe what I might be hearing. The reader will need to be equipped with the same short list of terms in order to follow the rest of the tale of the trilobite: it is not so difficult to memorize them. The inventory of trilobite parts that I first learned were the same bits of anatomy that the original discoverers of these fossils had recognized as long ago as the eighteenth century. These pioneers were puzzled as well as excited by trilobites: they gave them names like Agnostus and Paradoxides, which surely reveal the problems they had with their interpretation. There is even a Cambrian species called Paradoxides paradoxissimus, which might be translated from the Latin as "the most paradoxical p a r a d o x " — m o r e paradoxical than which it is not possible to get.

These early observers soon realized that the shells prised from the rock were only carapaces, rather than the whole animal. The trilobite they knew was only the back of a complicated organism. The shell was nothing more or less than a shield which covered its upper side—the part which is most exposed to a hostile world. A shield protects. In old literature it is quite common to find the cephalon referred to as the headshield—and the pygidium as the tailshield—and these descriptions are still entirely appropriate. Tough calcite m a d e the trilobite less vulnerable on its dorsal side, while its underside, the ventral side, was the sheltered underbelly where lay the soft anatomy that is so rarely preserved. The trilobite seems almost pathetically unprotected on its lower side, for the shell stopped abruptly after being "tucked u n d e r " the edge of the trilobite in a narrow shelf, or selvage, known as the doublure. Beyond the doublure there is only a cavity, an absence of evidence. This is quite different from the tortoise, where the underside is sealed by a bone shield called the

33

T R I L O B I T E !

plastron—making it into a veritable tank. The trilobite is half a tank. There is no living creature exactly comparable, although if you turn a woodlouse (or slater) on its back, where their little legs kick and struggle is the equivalent of the trilobite's body underneath. For m a n y years what lay beyond the doublure of the trilobite was a mystery—the trilobite was like a paten without the bread at Eucharist, a vessel lacking its full significance. You will learn h o w the mystery of legs was solved in the next chapter.

I acquired my first trilobite facts from lecturers and professors. W h e n I was a student it w a s possible to assimilate most of the basic elements from textbooks, if you wished, and nowadays we can s u m m o n massive inventories of information from the web, but it still makes a difference to learn directly from a real scholar. This experience reaches back to a time when the oral tradition was the only way of teaching— when the young received wisdom as a favour from the elders.

In China, despite the Cultural Revolution, this reverence for the wisdom of the aged endures. W h e n I was in Nanjing in 1 9 8 3 , 1 was taken to see the grave of Professor Grabau, a western palaeontologist w h o almost singlehandedly introduced modern geological principles into China in the early years of the twentieth century: he was, so I was told, "a great teacher."

The Chinese compliment is such an important one that it is represented by a special ideogram. It was a simple grave, but obviously regularly and lovingly tended. I was once briefly favoured with the status of "great teacher" myself: I received a letter from a far eastern student w h o had evidently learned his English from Rudyard Kipling and Rider Haggard. "Oh Great Palaeontologist!" it began, " m a y I sit at your feet?"

Those w h o k n o w my feet might regard this as unwise, but I was touched by the faith evinced in the oral tradition.

My o w n guru was Professor Harry B. Whittington. He is the doyen of trilobites, the head—the cephalon—of the tribe.

He would teach me to hear the messages of the shells. Somehow, I had managed to convert an infatuation into a career.

34

Shells

I learned my trade on the frozen ground of Spitsbergen beyond the Arctic Circle at 8 o 째 North, with the Valhallfonna icecap defining the skyline and an iceberg-clogged sea before me. An amazing variety of n e w trilobites was discovered in Ordovician (470 million year-old) limestones on the northern part of Spitsbergen, and I was lucky enough to be there when they were found. I collected rock beds exposed along the shore one by one in the appropriate order, so as to turn the stony pages of the trilobite diaries in sequence, tap-taptapping my w a y through my o w n little piece of geological time (a mere 10 million years or so). Mostly this consisted of bashing hard rocks with a geological hammer, until they were in small pieces on which fragments of trilobite could be seen.

Hardened criminals used to be required to do the same thing before it was banned as inhumane. I loved it. All discomfort in the harsh climate was set aside in the inspiriting warmth of discovery. You never knew what the next h a m m e r blow might bring, and occasionally there was something astonishing. The collections were arranged logically, the oldest specimens from the lowest rock beds exposed were carefully labelled and wrapped first, then progressively younger collections, and all were shipped back to the Sedgwick M u s e u m in Cambridge, to which I eventually returned.

I lived in the Sedgwick M u s e u m for nearly three years, happy as Larry. At that time research students shared offices in the attic of the dowdy m u s e u m , a nineteenth-century mock-Gothic building on Downing Street, which still houses the Department of Earth Sciences. I drove my room-mate John Bursnall mad with my trilobite obsession. He ran away to the States as soon as he could, while I continued to learn the m e s sages of the trilobite shells.

Most of the information about trilobites was buried. The first task I had to complete was to excavate the specimens from their rocky matrix, and I spent months doing just this.

My original "lucky break" at St. David's was unusual because the trilobite split out more or less complete: this does not hap35

T R I L O B I T E !

pen often. Usually you might see the top of the glabella, or maybe an eye; you just have to grind away the rock that surrounds the animal to excavate the hidden truth, and that is done later in the warmth of the laboratory. It is a skilful business, and you acquire the skill at the expense of heartbreak.

Little mechanical percussion needles are a standard t o o l — they make an insistent buzzing noise like that of an enraged wasp—but one slip and you gouge a terrible wound across the face of the trilobite you've grown attached to. You rely on the fact that the rock has natural tendency to split a r o u n d — rather than across—a fossil. Sometimes you get it wrong and a lump of your precious find flies across the room, leaving you grovelling on the floor with a magnifying glass looking for the detached fragment. Some days I would spend hours with a dissecting needle peering through a microscope and flicking off minuscule bits of matrix to reveal the beast beneath. John Bursnall used to accuse me of carving out fossils to my own design.

The best needles were those used to play the old 78 rpm gramophone records, which were already a rare commodity in the early 1970s. My fellow student Phil Lane and I used to hunt junk shops for these sharpenable, but hard, steel needles.

If we found a cache we could purchase it for a few pence, to the mystification of the shopkeeper. "Can I interest you in some old records to go with the needles?" he would say. " N o thanks, just the needles," we replied, heading speedily for the door and trying not to look as though we intended to use them for experiments with drugs.

It was soon evident that most of my trilobites were only parts of the animal. Whole ones like my first lucky find are actually rather rare. The carapace of the animal often fell to pieces after it died, like a suit of armour breaking along its joints. Whole animals do not hang together for long. The tailshield is rather robust—an isolated pygidium is often the first thing you find when you split open a piece of rock.

The most fugitive part is the thorax, which disarticulates into 36

Shells

its separate segments, which are then broken or dispersed.

The cephalic shield also frequently breaks into several pieces.

A middle part carrying the glabella makes up one of these fragments. It is called the cranidium. Either side of the cranidium is flanked by a free cheek, or librigena—left and right, and mirror images of one another. Many trilobites carry a prominent spine at the edge of each free cheek which form spiky hind corners to the head—these are genal spines. The eye surface is attached to the free cheek in most trilobites: indeed, the cephalon is designed to split into three or more pieces—including cheeks and cranidium. The free cheeks are separated from the cranidium by special planes of weakness—suture lines.

These facial sutures were an aid to the animal during moulting. The eye surface was probably the most vulnerable part of the trilobite, and difficult to moult successfully. By splitting the headshield along sutures which run fore and aft, and include the eye surface at about mid-length, it was possible to shed the eye surface before moulting the rest of the carapace.

This speeded up the whole business and reduced the time the animal spent in the "soft shell" state. The cheeks were liberated first, and independently from the rest of the animal, and hence were "free." The fixed cheeks remained behind, next to the glabella on the cranidium.

So the average trilobite yielded a considerable number of bits and pieces as they fell apart: cheeks, thoracic segments, cranidium, pygidium. And because they moulted several times as they grew during their lifetime, casting their old shells and growing new ones just as crabs and lobsters do today, it is obvious that a large trilobite would have to shed a succession of its earlier coats as it gradually reached its mature size. All of those earlier pieces were potential fossils— trilobites were veritable fossil factories.

But this is where the problems come in. If you only have the pieces then your first job is to reconstruct the trilobite as it was in life. It is like having to do a jigsaw puzzle of uncertain design. Worse still, if you have a dozen or more species of 37

T R I L O B I T E !

trilobite jumbled together and all of them fragmentary it becomes more like doing a dozen jigsaw puzzles simultaneously without having a colour picture on the cover of the box.

While I was learning my trade, I became adept at matching little pieces. There were clues. The shape of a suture edge on a free cheek should match that on the corresponding cranidium.

Then my predecessors had described occasional whole animals in their publications, and once I had recognized the cephalon, say, as belonging to a particular type of trilobite I could consult these illustrations for a search image of the appropriate matching pygidium. Quite soon my office was a jumble of broken bits of rocks, and needles, and old monographs, all coated in fine, limy dust. I still work in an identical office today. Tidy people's eyes go all peculiar when they come into it. I have a special small padded seat for them to collapse into.

It was fascinating work, more like that of an archaeologist gluing together potsherds than anything to do with whitecoated science. From time to time Harry Whittington would appear and m a k e encouraging remarks, or put me right when I had placed the wrong head and tail together. He was the gentlest of supervisors, surely better described by the American term the P h D "advisor." His advice was always welcome.

He had written the papers and monographs that I most frequently thumbed, and nowadays my personal copies have lost their covers and become dog-eared through years of use.

Harry Whittington has probably added more to our detailed knowledge of trilobites than anyone else. In the 1950s he discovered some remarkably preserved shells. In the Edinburg Limestone, an Ordovician limestone which can be found in a few roadside exposures in Virginia, the trilobite shells have been replaced in almost perfect detail by the hard mineral silica. Since the matrix of the rock is made of limestone it can be rendered into solution by throwing blocks into dilute hydrochloric acid. The limestone is often rather dark in colour, and when you place the piece into the acid it fizzes vio38

Shells

lently, like an Alka-Seltzer. Gradually it settles down to a regular bubbling—more like soda water. Then you notice that little ridges are starting to project from the lumps of rock—these morsels are not dissolving. They are silica trilobites being etched out of the rock. W h e n the process is complete the fine mud and muck can be washed away through a sieve, and what remains is pure trilobite.

This is like suddenly having the living shells at your disposal—handfuls of them. It is as if you have been transported back in time through more than 400 million years and given the freedom of an Ordovician beach. You can turn the pieces of trilobite upside down and look at the underside of the shell for the first time. You can inspect the doublure. What might take weeks to prepare manually from the rocky matrix, can be etched out incomparably well in a matter of days. The larger pieces can be picked up with fine tweezers, the tiny ones with a moist paintbrush and transferred to slides. What you discover is a pile of different free cheeks, pygidia, cranidia, and thoracic segments, a matted palaeontological bonanza. Then they all have to be picked apart under the microscope and matched together, as one might sort with excited anticipation through a spectacular box of bric-a-brac picked up at a jumble sale.

What Harry Whittington's preparations revealed was the fantastical sculpture of some of these trilobites. Spines and prickles—indeed, prickles on top of other prickles—were all picked out perfectly by the silica replication. Even the most careful preparator could never do justice to this thorny magnificence. Some of these trilobites were hairier with spines than any hedgehog. They covered the head, sprouted off every thoracic segment—often splaying off the edge like a defensive comb of slender rapiers—and continued on to the pygidium, where one pair might continue backwards beyond the rest of the animal and sprout subsidiary protuberances.

Surely these were animals as idiosyncratic as any seahorse or spider crab? Even more remarkable was the preservation of 39

A m a z i n g spines recovered from the perfectly silicified (see p.

38) trilobites from the Ordovician of Virginia. This is a cranidium (top right), p y g i d i u m (bottom) and free cheek (top left) of a trilobite related to Odontopleura called Apianurus. Even s o m e of the spines have spines! Such minute details are almost impossible to excavate manually. (Courtesy H. B. Whittington.)

Shells

diminutive organs on the surface of the animals. It was possible to see that the tips of m a n y of the spines carried tiny perforations. In life, maybe, even tinier sensory hairs emerged from the minute holes, sensitive monitors of their ancient marine world, quivering to the scents and vibrations of the time.

Other trilobites had a surface covered with ridges as complex as a fingerprint, swirling in concentric arcs, exuberant as a Jackson Pollock painting. Others again were covered in tubercles, little round lumps that made the surface of the shells look as if dusted with dewdrops. Then there were those that instead of having any projections had the surface of the shell dotted with tiny pits. One trilobite we shall learn more about was surrounded by a kind of perforated sled forming a fringe around the whole of the cephalon. All these were identified and pieced together by Harry Whittington when he sluiced out his acid vats, washing away the millions of years of entombment from the shells as he poured away the Ordovician muds that had once buried them.

There are some other shelly pieces left behind on the sieve that did not fit into the now familiar inventory of head, thorax or pygidium. Most noticeable are a variety of oval plates surrounded by rims, usually with a pair of long projections at one end. It is known from the study of complete trilobites that this plate fitted on the underside of the animal in the middle of the cephalic shield. The plate was a backwards continuation of the marginal undershelf—the doublure—at the edge of the trilobite skeleton. It is called the hypostome. It corresponds quite closely with the front part of the glabella—but lay on the bottom rather than the top of the animal. Whatever was within the glabella was accordingly well protected by a calcite skeleton above and below: it must have been something important to the animal. In fact, this vulnerable region included the brain, such as it was, and the stomach—together, the two most vital of the vital organs.

All these shelly pieces of the trilobites were part of what is called an exoskeleton, because they lay outside the soft anat4i

T R I L O B I T E !

omy of the animal. They were the crisp wrapping of a succulent parcel. Just the opposite is true of Homo sapiens and his vertebrate relatives, in which the flesh is hung on the b o n e s — the soft parts on the outside. Man is designed so that he can be stabbed in the back. Trilobites and other arthropods purchased their invulnerability to treachery at the price of having to change exoskeletons with growth, shedding every last tiny spine and tubercle and growing them all over again in a new suit of calcific clothes. The hypostome was shed at the same time as the rest of the shelly paraphernalia.

Like the silica trilobites he studied, Harry Whittington himself has defied the passage of time. As others fade, he carries on indefatigably studying his beloved fossils. I like to think that this is a reflection of his own virtues, the unfading ones of kindness and perseverance. His hair and moustache are still hardly tinged with grey and he is 83 years old. He is a native of Birmingham, in the middle of England, but spent many years at Harvard University, which has left him with an indefinable accent—not exactly transatlantic, but unplaceable.

At the time he became my mentor he had returned from the United States to become Woodwardian Professor of Geology in the University of Cambridge—one of those ringing titles which are so characteristic of ancient seats of learning. A polished label announced this distinction on the door of the old office that had been occupied by Woodwardian Professors for more than a century. It could have been fusty, but I always felt that the place constituted a link with previous generations of scholars, and thence back through uncountable ages to the time of the trilobites. S o m e h o w one would not have been very surprised to have been greeted there by the ghost of the Revd.

Adam Sedgwick, the nineteenth-century Cambridge geologist w h o coined the term Cambrian—the strata from which my very first trilobite had been wrested.

Harry Whittington often went on fieldwork with his wife, Dorothy. She was as ebullient as he was quiet, and exemplified a remarkable principle of discovery: partners always find 42

Shells

the best specimens. Whittington and his students would be squatting in the floor of a quarry bashing at some grey, tough limestones with their geological hammers. T h u m b s would have been struck, oaths uttered. From time to time a tantalizing fragment would be found, sufficient to keep everyone beating the bedrock in a frenzy of curiosity Dorothy in the meantime would pick at the odd piece of strata in a leisurely fashion, all the while enjoying the spring sunshine. Then would come the question: "Harry, is this anything?" Sitting in the palm of her hand would be the gem of the day.

Harry Whittington is an authority on trilobites. There is a great difference between authority and authoritarianism.

Some professors qualify under both headings, but the best are those whose authority is earned through the regard of their fellows: primus inter pares. I have met some of the other variety, too. W h e n I was a visitor at the University of Gottingen in Germany I went to the coffee room at the usual time in search of refreshment. Seeing a spare chair at the table I sat down upon it and started sipping my coffee. A terrible hush fell upon the room. It seemed to have something to do with me. Puzzled, I checked my fly, and looked for other signs of disgrace. The wooden chair I sat in seemed to be identical to a dozen others around the table. After a minute of excruciating embarrassment, one of the younger m e n in the Department came over and whispered in my ear: "That is Herr Doctor Professor *****'s Chair!" Mein Gott! I leaped to my feet, blushing red from my collar upwards, and quickly found myself another, apparently similar chair. That is authoritarian.

I returned to the island of Spitsbergen in 1972. The trilobite finds on which I had worked had proved so exciting that the Norwegian government was prepared to finance a full-scale expedition to the far northern part of the island to collect still more, and to fill in the gaps that had been left unexplored.

This was a grand affair compared with my earlier visit, when there had been just the two of us, plus a tent, a small boat, and as much porridge as we could eat. The remote shore looked 43

T R I L O B I T E !

every bit as bleak on my return, an endless stretch of shingle swept by an uncompromising wind. I recognized the melt stream which ran off the great glacier occupying the middle of this part of the island. We had camped by it before. Arctic terns shrieked a neurotic welcome. N o w we had a team of eight or so, and a rather grand tent, almost a marquee, for c o m m u n a l evenings and sitting out the blizzards. It could be heated up to a delightful cosiness. Flitches of ham hung from the roof, alongside intriguing salamis. There was a sophisticated radio system and another kind of h a m to operate it. We could sit at a trestle table in the evening and exchange the sort of banter that keeps an expedition on its toes. Once in a while tempers would fray. I concentrated hard on being everyone's friend.

We had another kindly professor with us—Gunnar Henningsmoen, from Oslo—possibly the only rival to Whittington in his generosity of spirit. He presided over our suppers with unfailing good humour. I shared my little tent with David Bruton, the only other Englishman, who had long since taken up residence in Norway, and who spoke Norwegian with gusto to everyone else. For reasons of outmoded chauvinism the two of us insisted on flying a Union Jack outside our tent, which then slowly u n w o v e and unpeeled itself over the next few weeks until it was the merest tatter: so much for the British presence. The oddest experience for a foreigner like myself was not being able to share a joke around the dinner table—for jokes do not translate, and anyway they are born of the moment, and flag with repetition. You sit there with a weak smile on your lips hoping to demonstrate a sense of humour even if you have no idea what everyone else is laughing at. (You hope it is not a joke about you, but you would sit there with the same silly grin even if it were.) Little bits of Norwegian c a m e to me by a kind of aural osmosis. The most surprising linguistic fact I learned was the impoverishment of that language in swear words. In fact, there is only o n e — "jam"—which merely m e a n s something like "devil take it!," 44

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but is considered very rude by a well brought-up Viking. It has to pass muster for most of the everyday tragedies that beset an expedition. If a finger is hammered, you j u m p up and down and cry " f a r n " ; if you drop an outstanding fossil irretrievably into the sea, you splutter for a while and then mutter "farn" under your breath. If all your provisions were carried away by a hurricane and death were guaranteed, all the poor Norwegian could do would be to stand on the shingle and cry "farn" into the wind. S o m e h o w this does not seem adequate for the occasion.

We collected box after box of specimens. Sooner or later they would find themselves the subject of scrutiny under my binocular microscope back home. My small personal fragment of history—ten million years or so—was that distant time when the rocks enclosing my trilobites had been laid down. I could wander around that time in my mind as comfortably as a historian might amble among the Tudors and Stuarts. I could match the various trilobite pieces together more quickly than anyone else: cranidium with free cheeks, pygidium with cranidium. Once in a while somebody would find a complete specimen, which was like suddenly finding the lid of the jigsaw puzzle. It was a way of testing your own earlier inferences about what fitted with what. I discovered an extraordinary, goggle-eyed trilobite that I called Opipeuter inconnivus—which means " o n e w h o gazes without sleeping."

It could have been a description of me. Slowly, a picture of a vanished Ordovician ocean was forming in my mind. Why, there were probably many more species then on the site of my bleak shore than were able to live there today! The Ordovician sea was a rich one: just because it was ancient did not imply that it was impoverished. At that time there was virtually no life on land, but the sea thronged with jellyfish and trilobites, clams and snails and segmented worms. There were fierce predators related to the living pearly Nautilus. There were groves of seaweeds. There were even shoals of small, lithe animals that might, at first glance, be mistaken for silvered 45

T R I L O B I T E !

masses of fish. A palaeontologist does not only listen to the message of this fossil animal or that. What he does is to recreate a vanished world.

I was invited to give a lecture on the glories of the new Spitsbergen discoveries to the Norwegian Academy of Sciences, as august a body as you could wish for. Norway has special sovereignty in this part of the Arctic, so my invitation was not untinged with politics. It was an intimidating experience to stand before an audience of a hundred or more of the most distinguished scientists in Norway, a sea of sages. To be twenty-five years old and on stage in a fine and historic building in Oslo is not such an easy occasion to mark the transition from taught to teacher. The great Arctic explorers Nansen and Amundsen had stood on that same stage, and portraits of other notables looked on. It was just as well that there was so much to talk about: the surprise discovery of some of the richest fossil faunas in the world on the remote shore of Hinlopen Strait; w h y others might have missed the rocks before; how the trilobites proved a connection of Spitsbergen with the ancient continent of Laurentia; h o w the climate at Ordovician time had been tropical rather than Arctic. This was my first public conjuring of the excitement of deep prehistory. Once the adrenalin started to course through my system, the audience became reduced to a hundred sets of ears.

At the end a tall and courteous old m a n stood up and asked a question in impeccable English. He referred to his time on Novaya Zemlya in the early decades of the twentieth century. His name, he explained, was Olaf Holtedahl. I was astonished. It would scarcely have been more amazing if Fridtjof Nansen himself had stood up and asked me about my Arctic experiences. Holtedahl was a survivor from the heroic generation when Arctic exploration had been truly a trip into the unknown, a time when huskies were the main means of transport, and pemmican the main source of protein. In the twenties, he had written pioneering reports of the

46

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geology of the high Arctic, and particularly concerning the remote island of Novaya Zemlya, which points northwards into the Arctic ocean from the Russian coast like a crooked finger. Not much had been published about this island since his pioneering visits there—and what there was was in Russian, because it was a highly secret military area during the Cold War. So here was a figure of romance and scientific derring-do w h o had stepped off the page, from the realm of my imagination, and into the flesh, dressed in a rather immaculate suit.

This incident made me understand a connection with a past different from that remote one reached by listening to the messages of the shells: the past of my scientific forebears. In the egotism of investigation there is a tendency to forget that there were students before us w h o m a d e the discoveries on which our interpretations still depend. Science is an odd venture, at the same time co-operative and competitive. The motive force is often the desire to beat a rival investigator to the credit for a discovery. But in the long term such human rivalries recede, and what started as a race seems more closely to resemble a series of logical advances linked together by a roster of names of discoverers.

The first name on the trilobite list is exactly 300 years old as I write: Dr. Lhwyd, whose letter to Martin Lister concerning "the sceleton of some Flat-Fish" opened this chapter. The letter was published in 1679 in the Philosophical Transactions of the

Royal Society, the oldest scientific journal in the English language; the title of the article: "Concerning some regularly figured stones lately found, and observations of ancient languages." I like to think of these misplaced "flatfish" rubbing shoulders in the same journal with the reports of the pioneer microscopist van Leeuwenhoek listing the discovery of red blood corpuscles, and microbes, and other such m o m e n tous stuff. Trilobites were smuggled in as observers of mighty things from the very first. The early volumes of the Transac-

47

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T h e "flatfish" figured in the Philosophical Transactions of the Royal Society by Dr. L h w y d (1679)—in fact, the trilobyte Ogygiocarelta debuchii from the Llandeilo (Ordovician) rocks of South Wales. T h e trilobite itself is photographed at fig. 1.

Hons are treated with some reverence, as they should be; the best leather bindings are no more than they deserve.

Those w h o know the rocks in the vicinity of Llandeilo are in no doubt as to the identity of the "flatfish"—it is a trilobite called

Ogygiocarella

debuchii

(see

above).

In

many

places

around the castle—Dynefor Park, just outside L l a n d e i l o — there are pits where masses of flat-lying, limy flags are 48

Shells

exposed; they can be pulled from the hedge banks in slabs like so many polygonal plates, and on some of these plates flatfish are indeed served up: the size of small plaice, and nearly as flat, they have two eyes goggling up at the surprised collector.

The modern observer can perceive that they have a thorax with eight segments and a large pygidium, too, and therefore that they are no manner of fish—but you can see how Dr. Lhwyd made his mistake. He embellished the drawing a little to show something resembling a marginal fin. He was right only about the eyes.

Trilobites were recognized as a distinct group of animals in 1771 by a German zoologist called Walch, in a work of such obscurity that I am still not sure whether we have discovered the right edition in any British library. But within ten years articles by such scholars as M. T. Briinnich were using "trilobite" on the title page, so it must have achieved wide currency—and it is, after all, a euphonious and descriptive name. More and more of these distinctive "organic remains" had evidently been discovered across Europe. By the first two decades of the nineteenth century m a n y more trilobites were receiving scientific names, especially in Scandinavia, France, and Germany. Lhwyd's animal attained its appropriate recognition in 1822 when the French palaeontologist Alexandre Brongniart published a short treatise on our animals, Les Trilobites, in which he named the species debuchii from a specimen from Lord Dynefor's estate. The flatfish had finally vanished, and in its place was a strange animal with a calcareous skin and segments like a lobster.

One hundred and forty years after the note in the Philosophical Transactions Lhwyd's "flatfish" would be used to recognize and correlate rocks all the way between Llandeilo and Shropshire. In Sir Roderick Murchison's book The Silurian System (1839) trilobites like Ogygiocarella debuchii are illustrated not only for their interest, but also for their utility in identifying rocks of a particular age. By then the name "trilobite" had achieved a certain familiarity among the educated 49

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classes which it would never lose again. The classical names which guaranteed their identity as animals were given when all scholars knew the Aeneid, and were as familiar with mythology as we might be with the cast of EastEnders. Ogygiocarella was named for Ogygia, the seventh daughter of Amphion and Niobe. And in turn both of these names from Greek mythology were attached to other trilobites. It is actually quite difficult to find a classical name that has not been used for one animal or another, be it an ever-so-obscure Phrygian nymph or a goatherd from the flanks of Mount Olympus. There are layers of time and levels of antiquity: there is a primal layer, the original ancient time of the trilobites; then there is the Greek or Latin source of the names—the time of the "ancients"; then there is a history of research; and finally there is a personal history which animates all those earlier times in the shape of the specimen to hand.

It was not long before similarities between trilobites and living animals were noted. Segmented creatures were among the fauna that could be found crawling around on seashores or forest floors—indeed, they were among the commonest of animals. Insects, crustaceans, spiders, centipedes—all were constructed from linked segments which articulated with one another. They shared another common feature: jointed legs.

At first glance, it may be difficult to appreciate the similarities between the legs of a fly and the legs of a lobster. But they are jointed in a similar fashion so that each joint can rotate or swivel relative to its neighbours in a programmed way according to exactly how they are hinged. They have the slightly infuriating predictability of one of those jointed reading lamps: you soon discover that they will swivel in a finite number of ways, but nonetheless it is possible to direct them into the most improbable corners once you have mastered the joints. You can get the measure of the range of possible movements if you hold a struggling lobster upside down—the legs kick in and out in a mechanical way. Watch a beetle kicking its legs when stranded on its back and the similarity is evident.

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Shells

The meat in these animals is all inside the leg; muscles contract to effect movements along joints. They pull themselves up by their own internal bootstraps. Jointed-legged animals are called arthropods, and there is no doubt at all that trilobites were another kind of arthropod (even though it was a long time before their legs were found fossilized); had they survived they would have been lined up alongside scorpions and crabs, butterflies, beetles and bedbugs as another example of the most diverse and varied of all animal designs. Carl von Linne (or Linnaeus), the father of biological classification, had recognized the trilobite pedigree even before the close of the eighteenth century. Had they not died out, I imagine that on the beach mothers would plead with their children: "Jimmy, please don't pull the legs off that poor trilobite!"

J i m m y would not have been able to resist the temptation to wiggle the limbs of his captive beast to see how they could be bent preferentially in certain directions. He would wave the creepy-crawly trilobite about to scare Aunt Margery, w h o cannot stand that kind of thing.

But the trilobite shells I studied in Spitsbergen were only empty carapaces. Lacking a calcareous coating, the limbs had vanished into oblivion. I could almost feel the tickle of legs crawling over my palm, I could imagine the living animal scuttling through the Ordovician seas. In my mind's eye I could cross-breed the trilobite with a prawn or a scorpion according to my fancy. But there are places—rare p l a c e s — where such speculations can be fleshed out with real specimens, where even the most delicate and fragile hairs on the most spindly of appendages are miraculously preserved. It is to these places we must go if we wish to discover the whole truth about trilobites, and allow them to tell the tales they have to tell.

5i

Ill

Legs

It you wish to snare a rare butterfly it is no use using a blunderbuss and a suitcase. To search for something elusive, subtlety and intelligence is required—and no small measure of luck. Most quests for unusual goals are motivated by the conviction that the end is attainable if only the correct combination of fortune and persistence can be struck. So it was with the case of the trilobite legs.

By the middle years of the nineteenth century several hundred different trilobites had been named and described. These were heroic years for monographs. Geologists were mapping and exploring ancient rocks in a systematic way for the first time. They were beginning to understand geological time, and creating names for its divisions, m a n y of which we still use today. As they mapped the strata in succession they recognized the utility of fossils in discriminating strata of a particular age. T h e sequence of fossil species was a thoroughly pragmatical w a y of unscrambling the chaos of the strata. In Britain, the explorers of trilobite-bearing strata were tramping on foot or progressing in carriages across Wales; they were true pioneers, the first to crack open ungrateful shales. In North Wales the Revd. A d a m Sedgwick—in whose eponymous m u s e u m I studied in Cambridge—named the Cambrian 52

1

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System (Cambria—Roman name for Wales) for ancient rocks that underlay all the other fossil-bearing strata—the most fundamental package of geological time. The n a m e Cambrian eventually replaced a rival n a m e , "Primordial," which hinted at the fundamental position of the organic remains these strata contained in relation to the subsequent history of life.

While Sedgwick explored North Wales, Sir Roderick Murchison was crossing South Wales, mapping and classifying his Silurian System (1839) (Silures—a tribe that once inhabited South Wales). Even more than Sedgwick, he used the fossils to spell out the narrative of geological time. Trilobites were easy to recognize; they became the familiar face of various parts of the Silurian. It is easy to imagine Sir Roderick imperiously summoning the rock-hunting vicar of some distant Welsh parish to present his discoveries from his local stream or cwm—and a smile playing on the aristocratic lips as he identified Trinucleus fimbriatus, or some other old trilobitic friend.

Just as a numismatist might intimately k n o w a seemingly freshly-minted coin of Hadrian, so the palaeontologist would greet the familiar face of a species first encountered fifty miles away and a decade before. Geological time was written in a thousand trilobites.

The palaeontologists Henry Hicks and John Salter were the first to tread those cliffs that I visited as a schoolboy in P e m brokeshire. I have a photograph of them in the 1870s grinning in comradely satisfaction at their latest discoveries. The trilobites they found still bear the imprimatur of their names.

W h e n we cite the Latin name of a species we are obliged to add the n a m e of the scientist who first gave it its official name.

Ampyx salteri Hicks was an interesting species from the dark slates exposed in the cliffs north of St. David's, first described in a publication of the Geological Society of London in 1873.

Here Henry Hicks presented a gift to his friend—he named a trilobite species for him: Salter's Ampyx. Salter reciprocated by naming one of the beautiful Cambrian trilobites from the Pembrokeshire coast Paradoxides hicksi Salter. I have done it 53

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A fantasy trilobite from J. S. Schroeter ( 1 7 7 4 ) — t h e first portrayal of legs. This animal combines one head (right way round), one head (reversed) and a tail (possibly upside down) with purely speculative legs.

myself: to celebrate the devotion of Frank Cross to collecting trilobites in Welsh ditches in all weathers on behalf of myself and my friend Bob Owens there is a delightful small species called Shumardia crossi Fortey & Owens. Our debt to Mr. Cross will thus be recorded in perpetuity.

Wales was only one area which was the subject of intense palaeontological scrutiny in the period 1830-75. James Hall was using every means, fair and sometimes foul, to secure publication of his great monographs on the Palaeontology of the State of N e w York; and in Bohemia Joachim Barrande was calibrating the same time interval with different fossils. But as first dozens and then hundreds of different trilobites were discovered, and the bounteous variety of their form became apparent, so too did the great gap in knowledge of the animal itself. All the fossils were shells, husks, mute carcases that could not speak fully of their vanished lives. There was no trace of the jointed limbs that every observer felt should have propelled the animals along the sea-bed. Some early investigators simply m a d e them up (see above). Without their limbs these wonderful fossils were geological cyphers, patterned stones that spoke only of geological time, as passive in their way as that coin of Hadrian—no more than a token of real life.

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Until their legs were discovered it was impossible really to know the trilobite.

There had to be a way to discover the identity of trilobite limbs—but how? Their covering must have been the same thin sheath of the organic polymer chitin, which covers the legs of shrimps and centipedes today. This does not fossilize as readily as mineral shell does, but it is not impossibly evanescent, like the glutinous shadow of an amoeba, say.

There must be circumstances that might favour the early entombment of these limbs in a sediment soft or special enough to favour the preservation even of a wisp, a shadow.

There were hints. Many species of trilobites were capable of rolling up tight into a ball (see fig. 16). This is a method of protection in dozens of living animals—even humans instinctively curl up under a hail of blows. The hedgehog protects its vulnerable belly this way, and thereby renders itself pathetically liable to be crushed under wheels for which evolution had never prepared it. The best comparison of all is with many species of little isopod—crustaceans that swarm under rotten wood. Almost any old woodpile will yield them in their hordes: turn over a rotten log, and their miniature armoured capsules will crawl rapidly away from the light. They are called woodlice, slaters, or pillbugs according to where you come from. Like trilobites they have a shell on their backs and vulnerable legs. Many of them adopt the same protective strategy—they roll up. I have seen some woodlice so tight and perfect that they resemble ball bearings—they even have a sort of sheen. Their segments are perfectly designed to slide past one another in enrolment. Their legs are adapted to tuck up inside, like stowing oars inside a boat. Although not closely related to trilobites (other than being fellow arthropods) they offer a useful comparison. Many trilobites are equally tightly enroled—but bigger. You can hold a rolled-up Symphysurus (see p. 188) in your hand like an egg: it has the same satisfying feel to it. Look closely, and you can see how the edges of the thoracic segments have telescoped together, 55

T R I L O B I T E !

the tips sliding past one another like the blades of a Japanese fan. The thoracic segments have special facets to permit this.

At the same time the axis of the thorax has extended, and here an extra "half-ring" is revealed between the segments to cover the gap that otherwise would open up. You can see a similar arrangement on the flexible elbows of a suit of armour.

Clearly these animals took their enrolment as seriously as a jousting knight took his protection from sneaky blows. Some trilobites even had little locks to make sure that the fit was extraordinarily tight.

Inside one of these enroled carapaces is it not possible that the stowed limbs would be preserved? This could be the true time capsule. What was needed was a specimen killed even as it enroled, and then preserved in sediment quickly— maybe beneath an ash fall akin to that which buried the unfortunate inhabitants of Pompeii and Herculaneum. Such volcanic eruptions frequently showered into the sea in ancient times, causing mass mortalities. It would also be important that the rolled-up ball should not have been distorted or flattened after burial in the strata. It seems a lot to ask, but well preserved, whole, encapsulated animals are known from a number of localities—they were recognized long ago in the Ordovician limestone rocks of Sweden and Estonia, and the Silurian ones of England. The trilobites were sliced through and then polished patiently with emery powder. Surely the traces of those elusive limbs would show up on the polished section. Sadly, it was not to prove so. The enroled balls were filled with fine sediment, which must have oozed in after the animal was buried but too late to save the limbs from obliteration: the bacteria got to work and left nothing behind.

Quite possibly the bacteria lived in the very sediments that came to occupy the capsule. Maybe, just maybe, on one or two specimens, a hint of a leg cross-section marked by a delicate dark circle, a suggestion of something else . . . but the mystery of the detailed structure of the delicate limbs remained unsolved.

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In 1876 a young palaeontologist called Charles Doolittle Walcott (1850-1927) made the first progress in solving the riddle. He was an avid collector of trilobites in the vicinity of Trenton Falls, N e w York, and one of the most remarkable selfmade men in a century when self-improvement was a watchword. He came from a farming family, stolid and god-fearing and with no particular intellectual bent. Without any formal geological degree, he progressed to become the Director of the United States Geological Survey and Secretary of the Smithsonian Institution in Washington, DC. He undoubtedly had the most inappropriate middle name in biography. For as well as becoming the ultimate Washington operator, cultivator of politicians and professors alike, and a very busy administrator, he found time to produce a great series of publications on trilobites—and many other kinds of fossils besides. His books fill a library shelf. He named dozens of the trilobites which calibrated the Cambrian strata of the whole North American continent. He investigated the succession of rock formations in the Grand Canyon, often under the most punitive conditions. This was before the trails had been cut that make the geologically aged depths accessible today—and even now you see exhausted walkers who have collapsed by the track because they have ignored all the notices about bringing water with them. After all, w h o really believes that wilderness can be only an hour or two away from the luxury of a Holiday Inn? Walcott is most widely remembered as the original discoverer of the celebrated Cambrian Burgess Shale, in British Columbia, but, even if he had never made this find, his place in the history of science would have been assured. The m o d ern worker gapes in wonderment at Walcott's output. "Well, he did not have to answer the telephone all the time," his contemporary counterpart might grudgingly allow, "and in those days he could afford to live near the office in D C . " There follows a diatribe on the price of real estate. All true, no doubt, but it does also seem to be true that a century ago there were 57

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more people like Walcott, with an extraordinary capacity for hard work which transformed talent into achievement by force of will. One thinks of Sir Walter Scott grinding out his great pile of novels (and that partly to pay off his publisher John Murray's debt). Method was no doubt part of it; I am sure that Walcott always knew where he had placed that important piece of paper on the previous afternoon. He sidestepped those diversions that always persuade us to delay until tomorrow what we have already deferred from the day before yesterday. He even found time to compile a diary on a regular basis—another activity which is most often the subject of good intentions rather than consistent practice. I only wish that the diary entries were more interesting—for the most part they reveal nothing of the man, but a lot about his appointments with the influential. He exposes raw emotion only after the tragic early death of his first wife, Lura, at a time when he was yet to receive his first professional appointment. As he rose to greatness the entries became more and more perfunctory. But it was in the weeks following his bereavement, when he worked incessantly to keep grief at bay, that he made the discovery of the elusive trilobite limbs.

Around the town of Trenton Falls there are limestones which crop out sporadically along road cuttings or in the sides of streams. These are the strata that Walcott knew so well. The seams have also been exposed in lime quarries and other pits, which these days are often in danger of being infilled with the profligate detritus of the consumer society: a hole is often more valuable than what was once extracted from it. The Ordovician limestones are exposed in bench-like beds, and in contrast to the contorted shales of Wales or Cornwall, these strata are usually horizontal, or nearly so. It is clear that such rocks have not been mangled by convulsions of the planet such as those that elevated ancient mountain chains. They record, virtually undisturbed, a succession of ancient seafloors, one after another, which the young Walcott was lucky enough to explore for the first time. In some cases a single rock 5ÂŤ

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Charles Doolittle Walcott (centre) in the field.

bed an inch or so thick was the product of a storm that culled the life of a vanished afternoon—and afterwards the c o m m u nity of animals would re-establish itself by the time of the deposition of the next rock layer. Even after more than a century of collecting, the abundance of fossil shells is still exceptional, and in Walcott's day it must have been astounding.

Often a piece of rock resembles a slab of fruit-cake with trilobites and brachiopods and snails and sea mats, and many more organisms besides, dotted over the surface like so many plums and raisins and sultanas. You want to pluck them out, but they are firmly lodged in the surface, and dusted with a paler limestone which may obscure their finer details. Patient cleaning with a pin will clean out the most magnificent examples. Charles Doolittle Walcott could have first pick.

On 1 March 1876, just over a month after Lura died, Walcott wrote in his diary: " C u t up several C. ps. had fair success.

I think I shall determine their interior structure." This was nothing less than his note that evidence of limbs might be 59

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preserved in " C . p s . " The abbreviation stands for Ceraurus pleurexanthemus (you can understand why he might want a shorthand!), a trilobite with a spiny pygidium and a knobbly glabella, which is one of the most exciting finds that can be made from the Trenton rocks. It had been known as a carapace for more than forty years, since J. Green had named it as one of his in A monograph of the Trilobites of North America in

1832.*

But there was no hint that this species would offer the key to fleshing out the reality of trilobite limbs, until Walcott sectioned and polished the "Ceraurus l a y e r " — a two-inch-thick band of limestone in which these animals were common. This single rock bed had m a n y individuals of the same species. At the bottom and top of the layer were beautiful, entire, but empty individuals—shells alone—the ornament of many a collector's cabinet, but no more informative than a thousand other specimens. The animals seem to have been trapped by an sudden inrush of limy sediment such as might have followed upon a tempest—a minor tragedy in the life of a generation of trilobites, but a boon to the scientist w h o followed 440 million years later. In the middle of the layer were animals that were overwhelmed and killed; some died struggling towards the surface of their sediment tomb. One can imagine a quiet sea-floor on which trilobites crawled about in profusion; suddenly the water darkened with a blanket of fine mud that settled in a choking blanket before some of the animals could effect an escape. The poor things had no time to roll up completely, but m a n y of them had started to flex their bodies, curving towards an enrolment they never achieved at the moment of suffocation. Perhaps the idea of the enroled time capsule was half right, after all. The limbs of these animals trapped in mid-layer did not immediately rot as did those of

T h i s is a most peculiar book, for it came with a set of coloured models of the species described, which can still be found in the drawers of some of our oldest academic institutions. Green hoped that the sale of the sets would make an additional attraction for the purchaser. Sadly, some of the reconstructions are somewhat approximate.

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animals near the top. Instead, there was time for them to become filled with lime-charged water. What had once been filled with muscle became replaced with white calcite. Like the mummification process perfected by Pharaonic priests, a preserving ichor flooded the soft appendages. The mineral calcite filled the limbs so that, even when the tissue surrounding was eaten away, infilled moulds remained as testimony of the soft parts. Walcott had the insight to recognize that when his polished sections revealed tiny white circles which contrasted with the surrounding grey limestone, these were the infilling of the arcane appendages. Within a few days he had repeated his observations on another species. "Found that Calymene senaria has the same character of appendages that C. p. has. Wrote description of C. p. after supper," he recorded in his laconic diary entry on 10 March 1876. One can imagine that he would have reported almost any discovery in like fashion: "Found Holy Grail this a.m.; have expectations of Excalibur tomorrow." Trilobites were never the same again.

Consider what Walcott still had to do. The discovery required him to grind—by hand—a whole series of crosssections. He needed to assess h o w m a n y limbs there were, and whether they branched or were simple, jointed legs.

Limestone is not soft (tap your nearest Victorian fire surround to prove the point), and he used a cutting wire and a rotating lap to cut and polish his sections—a slow business. A n d , most difficult of all, he needed to match drawings of sections one to another to obtain a three-dimensional picture, something that in modern laboratories even computers find challenging. One can imagine him assuaging his grief by working on late into the night, curiosity and ambition displacing other, darker thoughts. Nonetheless he managed to write his report of his discoveries, which was published in preliminary form before the year was out. It carried the ponderous title "Preliminary notice of the discovery of the remains of the natatory and branchial appendages of trilobites." While true to the letter of the discovery, it could scarcely be a best-seller with that title.

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Charles Doolittle Walcott's first, and inaccurate, attempt at portraying the limbs of trilobites Ceraurus discovered from sections ground through rock surfaces. Right, a m o d e r n reconstruction of the branched limb of Triarthrus (after H. B. Whittington and J. A l m o n d ) .

In any case Walcott continued to make new observations on further sections cut over the next eighteen months, and modified his original reconstruction. But the first version shows several interesting features. Walcott had noticed one important fact that still remains true. There were paired appendages on each segment, and so far as he could judge they were rather similar along the length of the animal. The appendages hung down below the body cavity, where the " g u t s " were.

This visceral mass was largely under the axis of the a n i m a l — 62

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the middle lobe of the "tri-lobes." So the legs and other appendages operated underneath the body of the animal, safely enclosed by the sloping parts of the pleural areas.

Towards the middle were jointed legs—the kind that are typical of all arthropods, from beetles to tarantulas, scorpions to centipedes. The biological affinities of the trilobite were placed beyond dispute at a stroke. These were the "natatory appendages"—Walcott evidently favoured their function as swimming limbs. Outside these legs were some other branches, three in Walcott's original reconstruction, one of which branched off the inside of the leg. The outer ones arose from a common base and were very slender, with an odd, corkscrew structure. These were the "branchial" appendages—gills for breathing, absorbing oxygen from sea water, as all arthropods must do. All in all, it was a most plausible arrangement.

Walcott had been influenced in his reconstruction by using the limbs of living crustaceans as a model. He admitted as much to his diary. " T h e more I study & compare with the recent Crustacea, the more clearly can I see the true relations of the more fragmentary parts" (12 July 1877). Though scientists offer a convincing pretence of independent observation, even the best of them are inevitably carried forward by preconceptions—they have plausible scenarios lodged in the back of their minds, and such provisional versions of the truth are based upon previous reading and experience. Walcott carried with him the notion of trilobites as related to crustaceans, an idea that was "in the air"—recall Thomas Hardy's description, "one of the primitive Crustacea called trilobites": that was published in 1873. Walcott's provisional facts* and Hardy's fictional use of the same presumptions converged in the same decade on opposite sides of the Atlantic. W h o knows if these utterly different intelligences had once fingered the same textbooks? * Before ten years had passed Walcott had favoured an alternative view that trilobites were related to the horseshoe crab, Limulus.

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Trilobite limbs were to leap clearly into three dimensions thanks to another discovery in N e w York State. The relevant specimens were from rocks which looked very different from the limestones that Walcott studied. They were dark shales, as black as the formal hats that gentlemen wore for their visits in polite society. Cleaved with a hammer they could be split into thin sheets. The Utica Shale was exposed in a quarry in the vicinity of the town of R o m e (this part of N e w York State was, and still is, a veritable classical gazetteer). Specimens of a trilobite called Triarthrus a centimetre or so long abounded on certain levels within the Utica Shale. A fossiliferous slab could look as if so many large woodlice had crawled into the rock and died there. On one such piece a graduate student, W. D. Matthew, noticed something projecting from the front of the cephalon of the trilobite; it was like two threads of gold, gently curved. Under a hand lens the delicate threads tapered, and were divided into segments. They were antennae! These were appendages that Walcott had not recognized in his sections. Antennae are the advance guard of the arthropod body: nose and fingers combined, they apprehend their environment with exquisite sensitivity. The description "feelers" that we used as children hardly does them justice. Trilobites had eyes to see, and antennae to smell and touch; already, they begin to seem less "primitive."

Professor Beecher of Columbia College was quick to appreciate the importance of the find. The source of the magical trilobites became known as " B e e c h e r ' s trilobite b e d , " and by the end of the same year, 1893, he had recorded the new information in print. He then found the rest of the limbs on the underside of Triarthrus, but rather than obscure sections, here were whole legs laid out, outlined in gold. What had originally attracted attention to the antennae was a gilded film that had replaced the original delicate cuticle of the trilobite: not gold itself, but fool's gold, iron pyrites. What a miracle of preservation—as if a preternaturally delicate hand had sprayed a shiny preservative over the most evanescent por64

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tions of the anatomy, down to the last fine spine. Some specimens preserved on their backs look pinned down almost as if for a biologist's inspection. These were the specimens that at last resolved the ambiguities of trilobite anatomy: the end of a journey towards comprehension that began with Edward Lhwyd's "flatfish." N o w it could be seen that slender legs, composed of many joints, lay underneath another appendage. There were not two entirely separate appendages, as in Walcott's original sketch, but a far simpler arrangement. An upper appendage was attached to the jointed leg at or close to its base (the limb was therefore described as biramous: with two rami, or branches), and comprised a fine, feather-like brush of filaments. Every segment along the length of the animal carried a similar pair of branched appendages. The trilobite underside was thus composed of a series of repeated units of rather similar design—one per segment, a dozen or more under the thorax. Even the segments on the pygidium seemed to have a pair of appendages of like form, getting smaller and smaller towards the rear of the animal. Under the headshield there were three pairs of similar paired limbs, in front of which were a pair of antennae—unbranched and curved slightly outwards. Professor Beecher m a d e a series of models of Triarthrus from the underside which set his vision of the anatomical truth in sculptural form. I have one of these models in front of me: it is a plaster-of-Paris creation about twice life-size. Such is its verisimilitude that I have more than once been asked to display it as "the real thing."

It is not the real thing, of course. About every thirty years since Beecher's original report, other eyes have looked at the Utica Triarthrus and noticed different things. The latest of these observers was the meticulous Harry Whittington, w h o in the early 80s employed a young researcher called John Almond delicately to excavate the pyritized limbs with an air abrasive—a tool that blows fine powder on to the surface of the shale. The powder is harder than the shale but softer than the limb material, which is therefore revealed without 65

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damage (or so the theory goes). Whittington and Almond were able to see clearly the structure of the jointed walking limb, as explicit as a lobster limb laid out on a plate—they even found little bristles at the tip of the "feet." The upper limb, the delicately combed one, was thought to be a gill, a respiratory organ. It extended almost horizontally under the pleural lobe; indeed, successive combs may have overlapped one another. M a n y arthropods have a pleated " l u n g " through which oxygen dissolved in water can be absorbed over the folded surface. In their modern fashion, Whittington and Almond confirmed Walcott's original interpretation of "branchial appendages" more than a hundred years after his first tentative sketches. But they noticed some new things, too: for example, that the base of the walking legs—and some of the other joints—were equipped with surprisingly stout spines. Triarthrus was an altogether pricklier proposition than Beecher would have had us believe.

There is no final truth in palaeontology. Every new observer brings something of his or her own: a new technique, a n e w intelligence, even new mistakes. The past mutates. The scientist is on a perpetual journey into a past that can never be fully known, and there is no end to the quest for knowledge.

John Dryden put it well: In

this

wilde Maze

their vain

Endeavours

end:

How can the less the Greater comprehend?

Or finite reason reach Infinity?

There is always a new thought, or a new observation. Those w h o crave the certainty of absolute knowledge had better not embark on the endeavour, for they will be frustrated.

Every cherished truth will be revised by those that follow.

Real advances are made, of course, but how do we know that the end of the path has been reached? This applies to trilobites as m u c h as to the fundamental particles of matter. Professor Beecher thought he had seen the truth of trilobite legs, 66

Professor Beecher's reconstruction of the Ordovician trilobite Triarthrus from the underside, showing the branched limbs and the antennae. There have been many changes since, but the basic facts are here. The head is n o w known to include three pairs of appendages (plus antennae).

Right, the ventral surface of Triarthrus, showing the pyritized limbs prepared by John A l m o n d from " B e e c h e r ' s Trilobite B e d . " an-antenna ey-eye gl-glabella g.a.-genal angle hy-hypostome f.s.-facial suture fr.c.-free cheek f i x - f i x e d cheek py-pygidium

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and sought to preserve that truth in his models—to fix his authority—but work that followed was to produce a new truth.

The latest visitor to Beecher's trilobite bed was Derek Briggs. A hundred years after Beecher there were still new steps to take along the path of discovery in the same q u a r r y — although it had to be re-excavated. Derek, like myself a student of Harry Whittington, had become fascinated by the most obvious but mysterious aspect of the fossils, the preservation of their limbs by iron pyrites. He wished to understand w h y this one bed of rock produced wonderful specimens, with their golden limbs, where most rock formations yielded only empty shells. After all, the first slab I ever cracked open in South Wales was a dark mud-rock superficially like Beecher's b e d — b u t where were the legs, and why no antennae? It was clear that the covering of iron pyrites must have happened very quickly, otherwise the legs would have decayed away. The animals themselves probably died suddenly, and were then protected from the activities of scavengers, which normally pick carcases apart even before the decay bacteria can get to work. There were clearly special conditions on the Ordovician sea-floor in N e w York State at this one m o m e n t in geological time.

Close study of the shales showed that the sea-floor of the time was very low in oxygen, and beneath the surface of the soft m u d lacked it completely. Such inhospitable environments, termed anaerobic, are well-known today. They are capable of supporting very little in the way of animal life, but there are special kinds of bacteria which revel in them. In the almost complete absence of oxygen, they have developed special methods to extract energy from their own biochemical reactions. High concentrations of iron and sulphur are typical; the bacteria use the sulphur in their metabolism. It is very likely that it was the activities of millions of these tiny bacteria that promoted the deposition of iron on the limbs.

Derek is currently trying to understand the process by devis68

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ing experiments to reproduce artificially what nature did millions of years ago. It is proving complicated, but enough is known to visualize the scene. Poor Triarthrus was overwhelmed and died, possibly poisoned by a sudden drop in oxygen—nothing can breathe in its complete absence. No scavengers dared struggle through the lifeless water. The limp limbs were enfolded in the soft embrace of the m u d , where only bacteria thrived in a soup rich in iron and sulphur. They painted the surface of the limbs before decay could obliterate them. So preserved in iron pyrites, casts of the limbs defied time.

N o w it is my turn briefly to enter the story. One mystery about Triarthrus remained unsolved. If this Ordovician seafloor was so inimical to life how could it be that so many of these little trilobites seemed so happy to live there together, at least until they were killed? Very often they are found almost alone, with no other trilobite species (or indeed other fossils) alongside them. Nor was this unique. Triarthrus is only the youngest of a whole trilobite family, known as Olenidae, with a history going back more than 50 million years into the C a m brian strata. I had come across Olenidae first on the bleak shores of Spitsbergen, where they abounded in similar, but older, Ordovician black rocks, which were deposited on a seafloor where nothing else could thrive. These rocks were so sulphurous that they stank of rotten eggs when you broke them under your geological hammer. It was obvious that these trilobites had some special secret that enabled them to prosper in a home redolent of brimstone. Triarthrus was there, but so also were some related—and hitherto undiscovered—larger trilobites: one of these I christened Cloacaspis, after the Roman sewer cloaca, for reasons which will by now be obvious. (The original, constructed by Tarquinius Priscus, conducted the filth from the streets of R o m e into the Tiber.) I was to see similar, still older rocks around the Norwegian capital, Oslo, where the Cambrian ancestor of all these trilobites, Olenus itself, abounded. The smelly nodules which yielded 69

T R I L O B I T E !

their remains are probably the only noisome thing in this most orderly and spotless city. Olenus was one of the earliest k n o w n trilobites, named by the pioneer Scandinavian geologist J. W. Dalman in 1827 after the husband of Lethaea.

Together husband and wife were turned to stone by the gods—the most appropriate classical names were grabbed by early palaeontologists! All these olenid trilobites flourished in sulphurous muds rich in iron, in a habitat in which there was very little oxygen—conditions which effectively banned all the competition.

It is only in the last few years that animals adapted to a similar habitat have been investigated in detail. Nature is adept at making a virtue of necessity, by turning hardship into opportunity. In stinking mud today there are types of clams that grow special bacteria in their gills. The bacteria process sulphides, and the clams can maintain just enough oxygen to allow the bacteria to do their work—too much oxygen would actually oxidize the sulphur compounds that provide the bacteria with their food. They are thus animals on the edge.

They live only in low-oxygen habitats, where below the soft sediment surface there is no oxygen at all and sulphur compounds abound. The special bacteria are known as colourless sulphur bacteria, and they require modern microscopical and molecular techniques for their study. Neither Beecher nor Walcott could have had a clue as to their existence. Clams can absorb nutrients from the bacteria directly, but other creatures that "cultivate" them use them as food.* W h e n I studied olenids I, too, had concluded that they lived in a low-oxygen, marine environment stinking of sulphides. Then I came across records of the living symbionts that grew their own sulphur bacteria, and discovered under what conditions they thrived.

It was a grand moment. Suddenly it was possible to make sense of so m a n y features of Olenidae. It was now obvious

* For those w h o like polysyllabic descriptions to impress people I should say that these animals are correctly referred to as chemoautotrophic symbionts.

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why they lived in numbers together to the exclusion of other species, and in company with such unpleasant rocks: this was their speciality. They had long bodies with large numbers of segments in the thorax—all the more space to grow bacteria.

They may even have grown them along the long "filaments" of the gill branch, like the living clams. Safe from predators they had very thin shells. There was iron available to replace the limbs. All the facts hung together: these particular trilobites were the first known animals to live symbiotically with sulphur bacteria.

The Utica Shale was not unique in its exquisite preservation of trilobite limbs. In Germany, to either side of the River Mosel and in the adjacent parts of the Rhineland, another dark slate comes to the surface. The Hunsriick Slate has been used for roofing since medieval times, and by the middle years of the nineteenth century there were many productive quarries. Even today, an open cast working at Bundenbach still employs thirty slate splitters. In geological age this slate lies between the Utica Shale and the Carboniferous with which this book began; it is early Devonian (about 390 million years). The slates were squeezed as part of the complex Hercynian earth movements, the same convulsion that affected the slates that made wild Pentargon Cliff on the Cornish coast.

At certain levels in the Hunsriick Slate fossils are replaced by iron pyrites, just as they were at Rome, N e w York. But the circumstances differ. In Hunsriick an entire, rich marine fauna is pyritized: starfish, sea lilies, worms, fish. Creatures with soft bodies were caught by surprise, as in a snapshot. If this book had been about starfish I could have filled pages with a celebration of the Hunsriick wonders. There was nothing restricted or peculiar about this Devonian sea-floor: it was bursting with life, and there was presumably plenty of oxygen. Trilobites were just one of many kinds of arthropods that crawled around on the soft Devonian muds, although they were the most abundant. It is now thought that the whole seafloor was overwhelmed by occasional m u d d y slurries that

71

T R I L O B I T E !

T h e legs of the Devonian trilobite Phacops preserved in iron pyrites from the Hunsriick Slate, Germany. (Photograph courtesy Prof. W. Haas.)

were sufficiently charged with iron to effect the pyritization of the fossils. Professor Wilhelm Sturmer perfected a technique of taking x-ray photographs of these buried animals.

Although it is possible carefully to dig out the fossils, as John Almond did from the Utica Shale, how much better to peep inside the solid rock to photograph the buried animal, which William Conrad Rontgen made visible by his discovery of xrays in 1895. The iron pyrites is more opaque to x-rays than the surrounding slate, and the fossils are outlined on their radiographs as if drawn by a deft artist in a soft, dark pencil.

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They have a ghostly quality; one might imagine they had been called up from the past by incantation rather than by science.

The commonest of the trilobites in the Hunsriick Slate is an animal some centimetres long called Phacops. I have in front of me a wonderful x-ray of this animal (fig. 6) in which the appendages are shown clearly, but superimposed by the xrays, as if they were in a state of fluttering movement, like the walking figures in the Futurist paintings of Umberto Boccione. They are the nearest thing we will ever see to a living trilobite, but we see it through a photographic plate, darkly.

Phacops is not closely related to Triarthrus, and it is surprising to find that their appendages were in many ways alike: similar antennae, similar paired limbs on every segment. The x-rays reveal the fine tips of the gill branch better than a pin ever could. Here is proof that fossils could record something more delicate than lace, and as fugitive as a cobweb.

As more and more trilobites with preserved appendages were discovered, most of them were found to have limbs of similar kinds along the length of the animal—and each limb comprised a paired walking leg and gill branch. Trilobites did not develop the specialization of individual limbs which happened in many other kinds of arthropods. Think of the nutcrackers of the lobster, or the extensible sucking pad of the fly Instead, most trilobites retained a comparatively unspecialized locomotion; it was the shell that evolved into an array of fantastical shapes. Carnival floats flaunt colourful and extravagant paraphernalia, and it comes as a surprise when the dressing is removed—beneath is a h u m d r u m Ford. We have laid bare the workings of the trilobite: what lies under the chassis is no longer mysterious. We are ready to envisage a parade of trilobites walking past on their paired limbs: and it will be as odd a parade as any carnival could offer. Some smooth as eggs, others spiky as mines; giants and dwarfs; goggling popeyed popinjays; blind grovellers; m a n y flat as pancakes, yet others puffy as profiteroles. There are thousands of species. They are so prolific that they have been 73

T R I L O B I T E !

dubbed "the beetles of the Palaeozoic," and beetles are the most bewilderingly diverse of living organisms; biologists are left breathless trying to calculate just how m a n y species there may be. Nor are we anywhere near knowing how many kinds of trilobites still lurk undiscovered in the rocks. Our trilobite march-past can only be a selection of a selection. It will cover 300 million years of history in a page or so. A glance at the illustrations will give a better idea of the extraordinary variety of form that the trilobites achieved. The parade will be in approximately geological order, with the oldest first. How they evolved into such a variety will be the subject of a subsequent chapter, and the trilobites described here nearly all appear as characters elsewhere in this book. To me, all the creatures named are as familiar as kin.

First comes Olenellus (fig. 10), commonest of the earliest Cambrian trilobites (535 Ma). It was discovered in the midnineteenth century by the pioneer N e w York State palaeontologist James Hall, and has subsequently been found very widely, including as far away as Scotland. Although it is so ancient, its large and long cephalon already carries a pair of extended eyes. The widest part of the animal is at the head end where there are prominent spines at either corner, behind which the body tapers gradually backwards along a thorax comprising many, rather flat segments with prominently spiny tips. One of the thoracic segments, near the front, is much more strongly developed than the rest, so that the pleural spines project beyond the rest of the body. Then there is a long spine rising from the middle of the axis of the thorax, near the back end of the animal, behind which the segments are very tiny, and the pygidium is really minute. Somehow this looks like a primitive trilobite. It has not yet developed the sutures crossing the headshield that helped its relatives during moulting. The tapering glabella is very clearly divided by furrows into segments, and its front is almost round, like a boss.

Olenellus is followed by a giant, the size of a large lobster. It 74

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is a rapid mover, striding purposefully in pursuit of smaller fry, which it can spot with its glistening eyes. This is Paradoxides (see p. 224), which has already been introduced as having a name to match its oddities. It was originally discovered in Sweden in the early nineteenth century; n o w it is known very widely. It too has many thoracic segments, but lacks one considerably larger than the rest. The genal spines are fearsome, extending backwards like a pair of swords. Pleural spines at the back end of the animal extend backwards beyond the tail like the kind of drooping moustaches sported by the bad guys in westerns. The tail, although a little larger than that of Olenellus, still does not amount to much. But the furrowed glabella is swollen—the whole thing expands forwards, and beneath lies a stomach which must also have been enlarged, probably to engorge prey. Paradoxides is mid-Cambrian in age, fifteen million years younger than Olenellus; still early days, one might say, but Paradoxides clearly meant business.

N o w there is a flickering swarm—are these trilobites, too?

They look like tiny animated beans, just a few millimetres long. This is a fly-past (or swim-past) rather than a parade, for these little animals are sculling through the water like so many water fleas. They are so small that you to have to squint hard to see how different they are from their other Cambrian relatives. Some of them seem to be rolled up tightly. They are as different from Paradoxides as can be imagined, and not only with regard to size, for these animals have very few, perfectly hinged thoracic segments—in fact, only two, which are bluntly tipped as if chopped off with a tiny scalpel. And it is hard to tell head from tail: both are equally large, and there is no sign of eyes. So these are little blind trilobites which have turned into something totally different from the crawling spectator of Mr. Knight's clifftop predicament. They are strange miniatures, specialized, sophisticated, and so successful that when there was plenty of plankton on which to feed they must have turned the late Cambrian (505 Ma) seas dark with their numbers. They are found in every continent in 75

T R I L O B I T E !

rocks of the right age. Agnostus is the name for these little enigmas—and how appropriate!—and the species that is so common in our parade is called Agnostus pisiformis (fig. n ) — literally, the "pea-like u n k n o w n o n e . " The genus name was given to Agnostus in 1822 by Brongniart, who will be recalled as having named the "Flatfish" from Llandeilo as a good trilobite. I have handled limestones from Sweden which are made of almost nothing but this tiny agnostid trilobite—rocks that can look like petrified pea-soup, a cobble of knobbles. Curiouser and curiouser.

Here comes another stately animal. It is the size and shape of a small silver salver, rather convex and smooth, and, like Agnostus, it has a pygidium as large as the headshield. But there the resemblance ends, for this trilobite has eight thoracic segments, each perfectly faceted so that rolling-up can be effortlessly achieved. Its eyes are prominent, shaped like crescent moons and elevated on stalks so that they resemble a pair of up-periscopes perched atop the head. The glabella is not so clearly marked as in Paradoxides, neither are its furrows so deep. Nor are there are any genal spines, so that this trilobite looks polished and rounded off at the corners, built for smooth ambulation. One of these animals has partially buried itself in the soft m u d , where it can be recognized only by a vague disturbance in the sediment surface, and by its eyes projecting above it, unblinking in their vigilance. Isotelus (fig.

12) is a more convex version of Lhwyd's Ogygiocarella from Llandeilo in South Wales—and indeed it is one of its close relatives, and of similar Ordovician age (470 Ma).

Isotelus dwarfs some of its contemporaries, one of which is a little medallion-like creature with a puffy head, and almost flat thorax with six segments and a perfectly triangular tail.

These trilobites have enormously long genal spines—far longer than the rest of the body, so that the animal is supported on them like a sled upon its runners. The glabella is higher than the rest of the animal, and inflated like a pear; it is hard to see any evidence of eyes, so this was probably another 7

6

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blind trilobite. Most extraordinary of all, the head was surrounded by a border full of perforations, like a colander. The pitted fringe lay at the front of the head in the manner of a halo—and the pits were not just scattered willy-nilly. Instead, they were organized clearly into rows and lines, each species having its own particular arrangement. Each has the size and perfection of a coin, minted to a design as precise as a dynastic intaglio. On the underside, rather feeble little limbs propelled the little medallion from spot to spot: these species did not leave the safety of the sea-floor for long. The n a m e Trinucleus (fig. 13) is too obvious to require any explanation from a Latin thesaurus; it was donated to these peculiar animals by Sir Roderick Murchison in 1839 after he had made his seminal Welsh traverses (1833-7). Modern study has shown that the fringe around the head is matched closely by a modified lower layer of shell, a "lower lamella" on which every pit is opposed by a corresponding tubercle. The fringe is a complicated piece of natural engineering, a double-up plate punctured by little tubes. This animal must have been as specialized in its Ordovician fashion as anything in the modern ocean. But how it lived remains an enigma: five generations of palaeontologists have studied these perfect little animals and wondered. Trinucleus itself is confined to Wales, but its close relatives are found worldwide.

N o w some swimmers scull into view. Here are trilobites that are extraordinarily gifted with eyes. They bulge prominently, as if they suffered some thyroidal condition. Almost the whole of the side part of the headshield has become a great, inflated visual surface: the free cheeks have become converted into nothing but eyes. The honeycomb pattern of the lenses is as clear as in any dragonfly. Even more bizarrely, the eyes have actually fused together at the front of the animal, so that effectively there is just one huge visual organ, or headlamp. This is Cyclopyge, discovered originally by the Bohemian palaeontologist Joachim Barrande in 1845. (A very close relative is shown at fig. 15.) The name is derived from 77

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the Cyclops, mythical one-eyed giants of classical Thrace. Our trilobites are not giants except in the optical department; overall, they are the size of large bees. But in the matter of eyes, what a wonder! The rest of the creature is smoothed out, and compact. It is hard to see exactly where the glabella is on this trilobite: it remains as a flat area between the eyes; there are six strong thoracic segments, each one well-articulated to its neighbours. This animal was built for swimming. The pygidium was nearly semicircular, and had a short axis. While Trinucleus grovelled on the sea-floor, Cyclopyge cruised above it.

Illaenus is about as convex as trilobites get: the whole animal resembles an armoured carrier, with all its edges rounded off. Its eyes were rather small and set high up on a head that sloped steeply down to its margin. Glabella and thorax merged smoothly into one another, and the thoracic pleurae hung down steeply. The tank-like profile continued into a large semicircular tailshield, which was also nearly smoothed out, so that you have difficulty guessing how many segments went into it. W h e n Illaenus rolled up it attained a nearly perfect sphere, unbreachable by any predator. It was an armadillo among trilobites. (Bumastus, a close relative, is shown on fig.

3.) It is not hard to imagine a predatory Ordovician or Silurian contemporary of Illaenus trying in vain to prise open one of these tight capsules; and all the while the crystal eyes gazed on to register the frustration of its foe, as the animal bided its time until it could unroll and scurry off to safety. As with so m a n y trilobites, Illaenus was first discovered in Sweden in the early nineteenth century, and has since been recognized on nearly every continent.

Calymene is regarded by many as the typical trilobite. This is probably for no better reason than that it has appeared in so many textbooks as the first example for students to learn. It is one of the commonest trilobites in Silurian strata (about 425 Ma) and was found in the classical Wenlock district, where are exposed some of the first British Lower Palaeozoic rocks to be fully investigated. A. E. Housman's Wenlock Edge is a bluff of 78

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Wenlock Limestone, commanding a view westwards to Wales, where heads of fossil corals weather out slowly under the gentle wash of the Shropshire rain. In the town of Dudley, Worcestershire, quarries which were active in the eighteenth and nineteenth centuries yielded hundreds and hundreds of beautifully preserved examples of Blumenbach's Calymene (Calymene blumenbachii). A n y collection worth its salt has one or two of these specimens. They are singularly satisfying things, palm-sized, plump, emanating an undeniable, primal charm. One of the objects I have to lock away in the collections I look after is a marvellous, gold-mounted Calymene brooch (fig. 17) which once must have made a most arresting conversation piece when pinned on the b o s o m of its former owner.

The "Dudley locust" appears on the coat-of-arms of that town (and surely those w h o named it knew an arthropod when they saw one, even though "locust" is a little approximate).

The enthusiastic curators of the local museum want to build a great education centre in the old quarries in the form of a huge Calymene where visitors can dine under the glabella and learn history under the thorax. I am all for it. The convex trilobite had a tapering glabella carrying very deep furrows; free cheeks like two-thirds of a circle; twelve thoracic segments with a very prominent axis; and a neat downsloping tail smaller than the head, which tucked underneath the cephalic rim when the animals enroled. I like to hand round rolled-up Calymenes to schoolchildren so that they can weigh more than 400 million years of history in their hands. Such an engagement with the real object is worth a dozen videos. A sense of wonder is not to be bought over the counter at the superstore.

Nor is it something which can be wheeled out of a corner cupboard at the behest of some curriculum or other; instead, it steals up on the child unexpectedly.

Radiaspis is a hymn to prickles. It is smaller than Calymene, but makes up for it by sprouting spines everywhere. All around the front of the cephalon there is a comb of spines; there are genal spines; there is not one, but two spines arising 79

T R I L O B I T E !

from the tips of each of the flatfish thoracic segments; and there are long, elegant spines arrayed around the pygidium.

You have to look hard to recognize that the stalked eyes are not yet another pair of spines. Radiaspis is an odontopleurid trilobite, which means "toothy pleura" and you can see why.

The glabella is divided into curious round lobes; there are further spines on the axis of the thorax. You instinctively know that this w a s another specialized animal, because it evokes that same sense of oddity you experience when you see a seahorse for the first time, or a long-eared bat. You feel suddenly in awe of the richness of the natural world. Odd it m a y be, but the odontopleurid design (see fig. 32) was singularly successful, lasting from the Ordovician until the Devonian ( 5 0 0 - 3 7 0 Ma) and generating hundreds of different species, each bedecked with a different arrangement of the spines. The related genus Dicranurus is illustrated on the cover of this book carrying its ramshorn-like spines at the back of the head.

A n d still they come. We have already met Phacops (fig. 18), a large Devonian trilobite having special eyes with enormous lenses, through which we shall see the ancient world with special clarity in the next chapter. The first Phacops specimens were discovered in G e r m a n y in the 1820s; then they were found in Britain, France and North America. The carapace is covered with coarse, warty tubercles. As I write I am running my hand lightly over the surface of a large Phacops from Morocco. These particular trilobites have been commonly available on the market since about 1985, and most are rather roughly dug out from their limestone b e d , so that they almost have the look of a sculpture. My own specimen feels rough, like one of those old-fashioned dill cucumbers; my fingers feel out its eleven thoracic segments. This trilobite is so welldefined by ridge and furrow it can be read like Braille. The glabella expands forwards into a triangle; the pygidium is deeply segmented. One of the common species is Phacops rana—the describer must have had the warty " s k i n " in mind, rana being the Latin for a frog. Some specimens from the 80

l. Probably the first trilobite to be recorded in a scientific journal, Dr. L h w y d ' s "flatfish," n o w k n o w n as Ogygiocarella debuchii, from the Ordovician rocks of South Wales, near the town of Llandeilo. Eight thoracic segments and a large pygidium, and big crescentic eyes.

Natural size.

2. Silicified trilobite headshields, dissolved out of limestone using acid. Harry Whittington's preparation of the Ordovician trilobite Ceraurus from the Ordovician of Virginia. This headshield from the underside (b) shows the h y p o s t o m e in position, and viewed from the front (c) you can see h o w it bulges d o w n w a r d s beneath the glabella to house the vital head organs of the trilobite.

3. Bumastus, a lo-cm-long trilobite in which m a n y of the features have b e c o m e smoothed out, or effaced. You can hardly discern the glabella, though the eyes are quite prominent. T h e whole animal is very armadillo-like. Silurian, Shropshire, UK.

4. Radiaspis, a fantastically spiny trilobite from the Devonian rocks of Morocco. Delicate spines originating from the thorax curve back over the spiny pygidium; another pair of spines c o m e backwards from the " n e c k " region.

5. Dalmanites, one of the first trilobites to be discovered, a b o u n d s in the Silurian rocks of Europe, often about 10 cm long.

A short spine at the back of the tail is characteristic. This specimen is from Shropshire, UK.

*f

m

6. X-ray of the Devonian trilobite Phacops from the Hunsriick Shale of Germany. T h e legs appear ghost-like and the fringes of the gill branches show at the edge.

7. Olenoides serratus from the Cambrian Burgess Shale. Details of the limbs taken from Harry Whittington's incomparable photographs: the thoracic segments are on the left; the strongly spinose walking legs extend below.

8. An olenid trilobite, Hypermecaspis, approximately life size, showing small headshield and long thorax with numerous segments. This specimen is preserved upside d o w n so that it shows the h y p o s t o m e (covering the stomach) more or less in life position. Ordovician, Bolivia.

9. A " g r a v e y a r d " of the olenid trilobite (see p. 69) Leptoplastides from the early Ordovician shales of Shropshire, UK. You can see individuals of more than one size on this single piece of rock, and about equal numbers are right way up or upside down. Most of these individuals are a centimetre or two long.

i o . Olenellus, one of the oldest trilobites from the Lower Cambrian rocks; the example illustrated is from Pennsylvania. In spite of its antiquity it has clearly developed, large crescent eyes. Notice how the third thoracic segment is larger than the rest.

The pygidium is m i n u t e — partly concealed beneath a spine towards the rear of the thorax. Olenellus is often as long a s 1 0 cm.

1 1 . T h e tiny, blind Aguostus pisiformis, a few millimetres long at most, from the late Cambrian strata of England. Cephalon and pygidium are almost identical in shape, and there are only two thoracic segments.

12. T h e e l e g a n t Isotelus f r o m t h e O r d o v i c i a n o f N e w York State. Eight thoracic segments show t h i s t o b e a r e l a t i v e o f Ogi/giocnrelln. T h e o u t l i n e o f t h e h e a d a n d tail m a t c h c l o s e l y — a m a t c h that w a s used during enrolment. T h e curved eyes stand proud of the head. About 10 cm long.

13. T h e b l i n d , m e d a l l i o n - l i k e trilobite

Trinucleus

fimbriatus,

w i t h its r e m a r k a b l e " f r i n g e , " the function of which remains debatable. This is a m o u l t — the genal spines are missing.

Specimens are a few centimetres long. O r d o v i c i a n of Wales.

14- T h e head of an Ordovician t r i l o b i t e r e l a t e d t o Trinucleus, Protolloydolithus,

recovered

from

a b o r e h o l e in eastern E n g l a n d .

This beautiful trilobite has a s y m metrical " f r i n g e " perforated by a h u n d r e d pits.

15 - T h e head of the giant-eyed trilobite Pricyclopyge, which s w a m in the deeper waters which covered southern Wales in the Ordovician period; Pricyclopyge is usually 3 - 5 c m long.

1 6 . Derek Siveter's photographs of the Silurian trilobite Calymene from Gotland, Sweden, in four different views. T h e forward view shows how the tail is perfectly shaped to tuck up inside the headshield.

ij. A u n i q u e a n t i q u e gold brooch with the S i l u r i a n t r i l o b i t e Calymene a s t h e c e n t r e p i e c e .

1 8 . A l a t e r a l v i e w o f a p e r f e c t l y p r e s e r v e d e n r o l e d Phacops f r o m the D e v o n i a n limestones of M o r o c c o . Very similar species occur in North A m e r i c a and E u r o p e and the Far East. T h e glabella carries g r e a t t u b e r c l e s . T h e e y e w i t h its s p h e r i c a l a n d slightly s u n k e n lenses is s h o w n well in this e x a m p l e .

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Silica Shale in Ohio weather out from the white shale as if moulded in burnished pewter. They are found in clusters, and at least one observer thought that they gathered to mate before being overwhelmed by disaster. If so, a m o m e n t of procreation would have become the moment of preservation.

There are many more trilobites which scuttle past so swiftly that we can see only one or two salient details before they pass from view. Here is Crotalocephalus (fig. 19) with a tail like a cat's claw carrying a few large, curved spines; then Dalmanites with its single spine extending from the back of the pygidium like a marlin spike. N o w comes Scutellum (fig. 21), flat as a flounder, but with a huge pygidium shaped like a ribbed fan—one flip and it is past us. A gigantic Lichas is nearly as flat, but with the glabella blown up, like so many bubbles, and with a fluted pygidium with a coarse saw-edge.

Nearby, there are some tiny trilobites buried in the soft mud, probably diminutive blind grubbers called Shumardia (p. 231).

There follow more spiny m o n s t r o s i t i e s — C o m u r a (fig. 34), with so many vertical spines it looks like a fakir's nightmare. A n d so the parade passes on and on.

The very last trilobite is a smallish one, Phillipsia (close relative Griffithides, fig. 23). This animal is named after John Phillips,

whose

Illustrations

of the

Geology

of Yorkshire

(1836)

earned him the right to be so immortalized in stone. At first glance this new trilobite does not seem such a remarkable animal compared with some of the phantasmagoria which have flickered before us. But it would have been a relative of this species which Thomas Hardy placed into Beeny Cliff in North Cornwall; it was a Carboniferous (330 Ma) crawler with large crescentic eyes, and the whole shell dotted with prominent tubercles as if it were suffering from an attack of Palaeozoic measles. The tapering glabella seems as badly infected as all the other body parts. The tailshield is very large, and deeply furrowed. Maybe Hardy had seen illustrations of this very animal drawn by Phillips from Yorkshire, and saved the image in his eclectic mind. There is no particular feature that 81

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marks it out as a survivor, but that is what it was, for several relatives of Phillipsia were the last trilobites of all. They lasted into the Permian period (260 Ma) before they and their kind became extinct. At last, the 300-million-year-long parade has come to an end.

It should be clear by now how a lifetime can be spent trying to catch a few moments of this parade. There is so much history to learn, and only a handful of shells to reveal it to us.

For every animal that clearly comes into sight another dozen escape, or leave only their footprints in the soft mud. A puzzled fellow commuter on the train once asked me how I could go to the office day after day to study a trilobite. I think he believed that there was only one trilobite, rather like the Mona Lisa, and that my day was spent contemplating it and making up new theories about its enigmatic smile. I had to explain that my work was more like attending to an almost infinite system of galleries hung with Mona Lisas, and that often all we had was the smile. And every time the end of one gallery was reached, there was another gallery beyond still to explore, and further again another . . . and hardly ever the legs.

There are some curious advantages in belonging to a small scientific world like the circle of trilobite specialists. You know almost everybody: it is like an extended family. As in all families there are feuds and disagreements, but kin loyalty wins out in the end. As in all families there is an acute awareness of family history. Charles Doolittle Walcott is regarded as one would a famous ancestor; we suffer with those that went mad, like poor John Salter, or died under Nazi persecution, like the tragic Rudolf Kaufmann. There is a solidarity that transcends generations and national barriers. It does not matter where you go; if there is a "trilobite person" there you will find a friendly face at the airport, and before long you will be swapping the names of fossils like unofficial passports. When I arrived at Almaty airport in Kazakhstan in 1996, in the middle of winter, I stood outside the rather large shed which passed as the International Terminal. Sleek limousines pulled u p — 82

Legs

but they were not for me, they were for the new post-Soviet generation of businessmen, intent on buying and selling oil or minerals, or, for all I know, their grandmothers. As I loitered, now on my own and feeling a little disconsolate, my breath coiling up into the frosty night air, I spotted in the distance an ancient Trabant. Stuttering along like a jalopy in a Pluto cartoon, scattering rusty flakes like dandruff, it wheezed to a halt beside me. Out of the window leaned the beaming face, gold teeth flashing, of my Kazakhstan colleague Mikhail Apollonov. "I have arrived!" he stated grandly, if unnecessarily.

Within minutes we were swapping trilobite intimacies and gossip.

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IV

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Eyes

It might seem hardly worth questioning the idea that the world is made for seeing, or that eyes are consequent upon the undeniable fact that there is so much to be seen. Yet think for a moment and the inevitability of vision is much more uncertain. The world is full of other signals that may be used to describe it: there are smells, chemical signals both subtle and ubiquitous, and touch is as sensitive to shape as sight—more so, because it cannot be misled by trompe I'oeil or by camouflage. Imagine a world in which the eye had never developed—not the eye of insect, nor of fish, nor of mammal, nor yet Mankind. It is easy to conceive of the other senses having taken over the comprehension of their surroundings. It would be a world of palpation, of feelers, a world in which caresses would have rendered glances superfluous. The twitching and waving of antennae would accompany every action. It is not difficult to imagine that a different evolutionary course would have selected those organs most delicately attuned to the passing molecule: even now we know of moths so sensitive to the pheromones of the opposite sex that the most evanescent whiff of a mate can stimulate a love flight across kilometres. In a sightless world, sensitivity to such stimuli would be selected

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and refined: it would be a world of nuance so delicate that our gross maulings would be inconceivable.

In conscious animals this most sensory of environments would entail everywhere the language of touch and smell: beauty would be aural or tactile or olfactory. Poetry would not celebrate the unfathomable mysteries of eyes and their unplumbable depths, nor compare hair with flax, for visual similes would be redundant. Rather, the texture of skin might be the supreme erotic stimulus, or natural selection might have favoured an ever more elaborate array of perfumes and chemical attractants, which in turn would evolve a language of which we can only dream. There might be symphonies of perfume, Mozarts of musk. Novelists might construct nasal narratives, versifiers sonnets of scent. Sculpture would entail subtleties of shape that only fingers trained through hundreds of millions of years of tactile evolution could discriminate.

There would be no word for "blindness."

So I don't believe that light inevitably engendered sophisticated sight, simply that that particular path was taken by life on this planet, elaborating and improving upon the simple photosensitivity of single-celled organisms. The eyes of the trilobite are tangible proof of a selection of one special branch of evolution from an array of possible alternatives—an innovation that made the world visible. Once passed, this threshold could not be forgotten, even if some animals—trilobites included—once more lost sight of the world in favour of tumblings in the dark.

Recent laboratory work has revealed the pervasive influence of the genes that control the sequence of development of the various organs as animals grow from embryo to adult.

The master control is the family of H O X genes. It is astonishing to find that similar genes control the placing of the head in the locust as in the fish (or kangaroo, or human). These are genes so deeply embedded in the unconscious mind of our bodies that the m e m o r y of their origin is lost far in the Pre-

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Cambrian history of development of the earliest animals. We can never, ever, directly sample the genetic code of the trilobite—but we can be sure that its development was under the control of H O X genes of kinds that we could still recognize in living animals.

The argument that allows this assertion is entirely a matter of logic. Embryologists who study the cell-by-cell growth from fertilized egg to recognizable organism have been able to develop techniques of staining tissues which are responding to the bidding of particular genes. This is how they know that the development of the standard experimental insect Drosophila proceeds in a similar fashion to the developing embryos of vertebrates. What they have discovered is a list of instructions about how to order a body that operates whatever kind of body is being constructed. The conclusion follows that the genes that control this sequence of development must be so ancient that they go back before the last common ancestor of insect and vertebrate. This is an evolutionary "split" of such antiquity that it must precede even the oldest trilobite, because we k n o w for sure that trilobites were already typical arthropods (like their distant cousins—the fruit flies, Drosophila). So the common ancestor connecting backboned animals and joint-legged animals—an animal that must have owned the right genes in c o m m o n — m u s t lie further back in time from the first trilobite fossil. In fact, the split between the arthropod and the vertebrates is one of the deepest branches on the tree of life—it is even likely that arthropods are more closely related to snails than they are to vertebrates. We cannot readily conceive of this remote ancestry; probably we will never k n o w what that common ancestor looked like. We can infer that it was small and soft-bodied, and it will have left no fossils. Nonetheless, its legacy still tells the developing embryo which cells shall form a head, and how the body shall be arranged from front to back. It inexorably follows a blueprint originally drawn up in the most ancient times. It is rather wonderful to imagine this distant 86

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manifesto at work on the growing trilobite, directing the brain to be enclosed within the h e a d — a n d , of course, issuing instructions for the growth and development of eyes.* For eyes are part of this ancient list of instructions. It seems that the making of an eye is the same impulse in fish or fly or man. As the cells develop in the embryo there is a point at which eyes begin to differentiate. They start as a bundle of cells, which divide, and divide again. The end product may be very different—after all, insects have compound eyes and vertebrates sophisticated, lensar eyes—but the impulse, the instruction " m a k e eyes!," may be common to all animals. The deep language of the genes is an Esperanto of biological design which can be understood by a Babel of organisms. The deep-seated genes represent an organizing principle that predates the extraordinary proliferation of life that made the living world as rich as it is today: to understand this deep structure we have to strip away differences to the commonality of ancestry. The eyes have it.

Maybe this democracy of eyes stretches as far back as the flatworm, a little, wedge-headed organism that still abounds in moist places in soils and under stones. Many readers will know the flatworm only as a clever cipher in one of M. C. Escher's ever-retreating symmetrical designs. In his drawing, flatworm interlocks with flatworm into an infinite regress that flaunts geometrical meshing finer and finer until it reaches a kind of reductio ad absurdum. It is a favourite subject for posters on the walls of advanced biology classes. The flatworm has a kind of surprised look—expressed with its e y e s — as well it might, being the victim of such an exercise in facile geometry. Many biologists place the flatworm (or, to be accurate, several different flatworms) close to the common ancestry of most higher animals. Hence, the ancestor of both trilobite and train driver may be a tiny, flattened invertebrate *The gene controlling eye development is not a HOX gene, but a homeodomain gene called PAX6.

«7

T R I L O B I T E !

with minute eye spots. And the instruction that bids the eye grow in a flatworm may be the same instruction that instructs it to form in ourselves.

So when you see—with your own eyes—the eyes of the trilobite, you recognize a kinship of vision stretching across hundreds of millions of years. It's too bad that the trilobite cannot manage a conspiratorial wink. The trilobite reminds us of that moment—at least, a moment in geological t e r m s — when the first organism developed a cell that was sensitive to light. Then the elaboration and proliferation of such cells that followed was sealed for ever into the blueprint of development for our own sight-dominated world. W h o can doubt that as soon as vision became a realized possibility it must have conferred on its possessor an exceptional advantage? Food could be identified by shape alone, and the approach of enemies would blot out the sunlight. Surely there must have been a premium on seeing the world more clearly, recognizing subtler movements, that would encourage the evolution of more and better vision. N o w there was a point in painting-up to attract a mate. Colour would have a purpose. The delicate deceptions of camouflage, the machinations of mimicry, the whole of Nature's palette, would follow as a logical consequence. Without that moment of vision, colour in the natural world would have been haphazard, a splash of red here, a flash of green or yellow there. Although colours are incidental properties of many biological molecules, it requires vision to recruit them into useful roles and to paint the Earth with a purpose.

As to when this happened, we know that the first trilobites in the early Cambrian already had a sophisticated visual system. The eyes of one of the oldest of all, Fallotaspis from Morocco, are quite large. This animal dates from approximately 540 million years ago, hence the origination of eyes must have been before that. Several of the soft-bodied animals from the Chengjiang fauna of the early Cambrian of China also had eyes—some of them on stalks. Arthropods like 88

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Fuxhianshuia seem to have their eyes positioned far forwards, whereas trilobites, of course, carry them on top of the head, within the shield. So it is clear that there had already been a lot of evolution of variety in eyes among the jointed-legged animals almost at the inception of the Cambrian. Whether or not this happened in a burst of accelerated evolution—the C a m brian "explosion"—is a subject to which I will return. For the moment we can say that solid fossil evidence that cannot be misunderstood proves that eyes originated before—and probably well before—540 million years ago.

An estimate of when the first eyes might have originated in the Precambrian can be obtained in a different, indirect fashion. Recall that body fossils, actual organic remains, are rare in Precambrian rocks, and of animals with eyes there is no really solid evidence. Perhaps these animals were very small and soft-bodied: they certainly lacked the hard and readily preservable shells of their trilobite successors. We have to do without direct evidence, and infer distant events from effects that linger on even in living animals. Since we know that animals descended one from another, we would like to know when one, basal group of eyed animals "split off" on the tree of life from their eyeless relatives. The eye-bearing animals in question may have taken very different paths subsequently— to have become as unlike as a whale and a flea, or an octopus and an orangutan. This is of no concern in the question of origins. What we are interested in is dating the branch in the road map of evolution where the different routes were initiated—this is called the "divergence time." It will be important to learn when "higher" animals split off from the flatworms, carrying with them message to " m a k e eyes!" that still operates its imperative. The divergence time can be guessed at by summing up the changes that have accumulated in the genetic code after the split occurred. Mutations happen, and such changes gather in the genetic code like bad memories stocking a guilty conscience; the effect is cumulative. These accreted mutations can provide a kind of clock, which can be reckoned 89

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in terms of millions of years if the right part of the genome is examined. There are "fast" clocks and " s l o w " clocks, and to try to look back into the Precambrian we need almost the slowest clocks of all, located in parts of the genome that are enormously conservative. We need to look for the genetic Collective Unconscious shared by all animals.

There are some parts of the genetic code which have proved particularly useful in trying to date distant evolutionary events. Inside every living cell there are large numbers of tiny particles called ribosomes; they are where life-giving proteins are synthesized. About 60 per cent of the ribosome is composed of ribonucleic acid (RNA). Parts of the ribosomal R N A molecule have been claimed to have just about the right degree of conservatism to measure and calibrate the changes in which we are interested窶馬either so " s l o w " as to have remained for ever unchanged, nor yet so "fast" as to have run around the clock more than once. This vital molecule is possessed by all the animals with which we might be concerned, and so the genetic changes that have accumulated over hundreds and thousands of millennia permit a common time calibration. However, the claim that R N A "clocks" are reliable is still controversial, and many of my colleagues wonder how much " n o i s e " there is in the signal, that has nothing to do with the ticking of geological time.

Over the last ten years or so (I write in 1999) there has been a large number of estimates of divergence times based on a variety of genes and different "bits" of the R N A molecule.

Recently, as the enormous, cryptic library of the D N A molecule itself has gradually been decoded, other evidence has been brought to bear on the question of divergence times.

Some of those genes which code proteins, and the D N A found in the mitochondria of the cell, have been used as "clocks" to check on ancient genetic legacy. What convinces me that there is some truth in estimates of deep Precambrian divergence times is the fact that m a n y of the divergence times are within the same order of magnitude. Many unsatisfactory estimates 90

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have been recognized and rejected. It is like walking into an old-fashioned horologist's shop with no idea of the time, and through the cacophony of ticking and murmuring of electric pulses seeing that some of the clocks are clearly dancing to their own music of time, while a majority are reading some time about half past two. You could not be certain of the exact time, and certainly not that it was half past two, but you could feel pretty sure that it was not before one o'clock, nor yet teatime. So with the molecular "clocks." It seems likely that the far distant common ancestor of the line that led to starfish and man on the one hand, and trilobite and fly on the other,* lived at some time between 750 million and 1250 million years ago—after lunch in the history of life, but before teatime. This common ancestor probably carried a pair of primitive eyes.

If this figure is even approximately correct, it places trilobites more than 250 million years after the origin of eyes, and quite possibly at about 500 million years. Trilobites offer visible evidence of the halfway stage in eye development, a testimony to the continuity of the genes that still intervene in the development of every embryo. Inspired by our modern genetic knowledge, we can feel a bond with the trilobite that would not have been apparent when the nineteenth-century investigators first looked into those stony eyes. To these earlier scientists, the trilobite was an alien creature, whose connection to the world of living animals was remote, almost imponderable. They might have perceived some thread of common ancestry, but I doubt that they intuited that aspects of the design of a trilobite were perpetuated in our own 'This is correctly known as the join between the Protostome and Deuterostome animals. The former includes all the arthropods, as well as molluscs and many worms, while the latter comprises the vertebrates (including us) and echinoderms (sea urchins and relatives). The distinction between these great assemblages of animals w a s recognized by nineteenth-century embryologists as a fundamental difference in body development; it has stood the test of a century of biological investigation and, more recently, molecular analysis. Recently, the Protostome idea has been refined by the recognition of a large group of animals that have moulting hormone.

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embryos. An advance in knowledge has served to entwine us closer with the past. "Look into my eyes," the trilobite seems to s a y "and you will see the vestiges of your own history."

This shared history of vision is far from trivial. In our visually-dominated world sight is almost synonymous with understanding. We acknowledge light dawning by saying: "I see!" The metaphor of vision suffuses our attempts to convey comprehension: we bring issues into focus, we clarify our views, we sight our objectives, we look into things. We accept the evidence of our own eyes. The conjurer turns the veracity of sight head over heels: now you see it窶馬ow you don't. We find his tricks disturbing because we are so wedded to the truth of sight. To understand the deep history of vision gives us a way of perceiving how even the most distantly-related animals, far off in remote geological time, managed to comprehend their world. We can describe how they understood their vanished seascapes in terms that we can still apply to our own habitats, a compound of sight, images and colour.

For us to see that the trilobites once saw, too, is to bring them within the compass of our own understanding.

Trilobite eyes are m a d e of calcite. This makes them unique in the animal kingdom.

Calcite is one of the most abundant minerals. The white cliffs of Dover are calcite; the bluffs along the Mississippi river are largely calcite; the mountains stacked like giant termite mounds in Guilin Province, China, are composed of calcite that has resisted millennia of weathering. Limestones (which are calcite) have been used to build many of the most monumental and enduring buildings: the sublime crescents of Bath, the pyramids of Gizeh, the amphitheatres and Corinthian columns of classical times. Polished slabs composed of calcite deck the floors of Renaissance churches in Italy, still grace the interiors of Hyatt-Regency hotels, or conference halls, or

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wherever architects wish to suggest the dignity that only real rock seems to confer. Rubbly limestone builds our rockeries; its finer, whiter counterpart provides the raw material from which great sculpture grows. Only silica sand seems as ubiquitous. Surely one could expect no surprises from a substance so common and so familiar. Yet it was calcite transformed that allowed the trilobite to see.

The purest forms of calcite are transparent. In building stones and decorative slabs it is the impurities and fine crystal masses that provide the colour and design: the yellows and greys and fine mottling. The dark red of the scaglio rosso so typical of Italian church floors is a deep stain of ferric iron.

Purge calcite of all these impurities and it is colourless. But it may not be transparent even then. Chalk is almost pure calcite, but it is a mass of tiny grains—fossil fragments most of them—which scatter and reflect the light: hence its almost indecent whiteness. When the Seven Sisters on the southern English coast emerge from a sea mist it is like observing a line of undulating starched sheets, so frigid is their purity. But when a calcite crystal grows more slowly in nature, then it may acquire its perfect crystal form, and be glassy clear. The chemical composition, calcium carbonate (CaC0 ), is simple as minerals go. As the crystal grows the constituent atoms stack together in a lopsided way, and do not allow other stray atoms to intrude to cloud its mineral exactitude. Layer builds on layer to reveal the crystalline form, the macrocosm of the gem reflecting exactly the microcosm of atomic sructure. As with the handiwork of a master mason, there is no mistake permissible in the atomic brickwork. Large, fine crystals often grow in mineral veins. These are often rejected by miners in search of rarer booty, for precious metals sometimes hide in grey and opaque minerals that seem dull by comparison with calcite's perfectly formed spar. Some of these crystals are sharply pointed and then are described as dog's tooth spar, looking much like the zig-zag ornament favoured by Norman 3

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craftsmen over church doors; others, blunt-tipped, are termed nail head spar. But the clearest crystal, transparent as a toddler's motives, is Iceland spar.

Look into a crystal of Iceland spar and you can see the secret of the trilobite's vision. For trilobites used clear calcite crystals to make lenses in their eyes; in this they were unique.

Other arthropods have mostly developed "soft" eyes, the lenses made of cuticle similar to that constructing the rest of the body. Within this limitation there is enormous variety: many-lensed eyes like those of the fly; large complex eyes such as those of most spiders; eyes that can see in the dark; eyes that function best in brilliant sunshine. The octopus among the molluscs has an eye that is famously like that of backbone-bearing animals, and provides one of the best examples of convergent evolution in the animal kingdom. Most of us will have contemplated the sorry eyes of a dead fish, and remarked the comparison with our own, large, focusing eyes.

Trilobites alone have used the transparency of calcite as a means of transmitting light. The trilobite eye is in continuity with the rest of its shelly armour. It sits on top of the cheek of the animal, an en suite eyeglass, tough as clamshell.

The science of the eye demands a little explanation. It all depends on the optical properties of calcite, and this depends in turn on its crystallography. If you break a large piece of crystalline calcite it will fracture in a fashion related to its fine atomic structure: such cleavage of the mineral does the bidding of the invisible arrangement of matter itself. You are left with a regular, six-sided chunk of the mineral in your hand, termed a rhomb. Neither foursquare like a cube, nor rectangular like a chunk of chocolate, the sides of a rhomb lean away from the perpendicular. The geometry of mineral shape can be described quite simply by the orientation of a few main axes passing through the centre of the crystal: the simplest case is the cube, in which axes passing through the centre of the faces and meeting at the middle are all at right angles and all the same length. These axes are termed a, b, and c, respectively, a 94

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case of science for once taking the simplest route to make a name. In the structure of calcite, one major axis has three axes perpendicular to it set at 120 degrees from one another, hence the configuration of the rhomb. T h e clear calcite of this notquite-a-cube treats light in a peculiar way. If a beam of light is shone at the sides of the rhomb it splits in two; this is known as double refraction. The rays of light so produced are the "ordinary" and the "extraordinary" rays: their course is determined, just like the shape of the rhomb, by the stacking of the individual atoms. There is a huge specimen of Iceland spar on the first floor of London's Natural History Museum through which you may peer to see two images of a Maltese cross, one generated by the extraordinary, and the other by the ordinary rays. But there is one direction, and one direction only, in which light is not subjected to this optical splitting. This is where a ray of light approaches along the c crystallographic axis; from this direction it does not split into two rays at all but passes straight through.

The way that calcite treats light might have remained no more than an odd fact to be trotted out as an esoteric answer in tests of general knowledge. But what the selectivity of the c axis guarantees is that light approaching from the angle at which it points is specially favoured. If a crystal is elongated in parallel to the c axis into the shape of a prism light will still pass unrefracted through the crystal along the long axis of the prism. But light approaching the same prism from other angles will be split into ordinary and extraordinary rays, which will in turn be deflected to reach the edge of the prism, where they might be partly internally reflected, or refracted yet again. When the prism is long enough the only light to pass clearly through to the far side of the prism is that which approaches from the direction of the c crystallographic axis.

To put it the other way round, the light that such a crystal " s e e s " approaches from one particular direction. It is an astonishing fact that trilobites have hijacked the special properties of calcite for their own ends. They have crystal eyes.

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The eyes of trilobites are composed of elongate prisms of clear calcite. Most eyes have many such prisms stacked side by side. By comparison with dozens of other kinds of arthropods the prisms obviously functioned as individual lenses, in just the same way as a fly's eye is a honeycomb of hexagons, each one a lens—or the dragonfly's, or the lobster's. The trilobite carries on its head another example of such an arthropod compound eye—an eye composed of numerous small ocular units, which had to collaborate to paint a portrait of the world.

Each component unit is a lens. The unique difference is that the trilobite's lenses are composed of a rock-forming mineral.

It would be no less than the truth to say that the trilobite could give you a stony stare. One is reminded of the strange lines from that strangest of Shakespeare's plays, The Tempest: Full fathom Of his

five

thy father

bones are coral

Those are pearls

that

Nothing of him

that

But Into

doth

suffer a

something

rich

lies:

made: were his

eyes:

doth fade, sea-change and

strange.

If to travel back to the time of the trilobite is a historical seachange then there can be nothing stranger than the calcareous eyes of the trilobite. And pearls are chemically the same as the trilobite's unblinking lenses, being yet another manifestation of calcium carbonate, although pearls are exquisite reflectors of light rather than transmitters of it. The weirdness of Shakespeare's line results from his suggestions of pearly opacity, the hints of a corpse transformed; dead, yet seeing. The trilobite saw the submarine world with eyes tessellated into a mosaic of calcified lenses; unlike the dead seafarer, his stony eyes read the world through the medium of the living rock.

Trilobite lenses were orientated so that the c crystallographic axes ran along the length of the prisms comprising each lens. In most lenses this axis is exactly at right angles to 96

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the surface of the lens. If you can see the whole surface of an individual lens (perhaps using your own hand lens) then the chances are that the lens could look back at you. The lens, of course, can not itself see. But it permits light from a favoured direction to pass through it. The average trilobite eye was a stacked mass of tiny, elongate prisms, each pointing in a subtly different direction. A long, semicircular eye might have hundreds or even thousands of such lenses. Some of the lenses might have their c axes pointing forwards; some sideways; some backwards. O n e has to imagine all the c axes poking out of the centre of the lenses like a battery of tiny needles.

A large eye would carry a veritable hedgehog (or porcupine) of such imaginary needles: each needle can be thought of as representing the beam of light that could pass through the lens, like a host of tiny arrows each with a particular target.

Every arrow of light contributed a small ray of understanding to the eye, each lens having its own dedicated field of view.

It is very likely that the trilobite eye functioned in the same way as that of living arthropods with compound eyes. So we might expect to find at the base of each lens a receptor cell which could respond to an incoming ray of light. These cells were evanescent, as fragile as the rocky lenses that lay above

Light

c

How the trilobite's eye works. Rays of light passed through calcite lenses in the preferred direction parallel to the major c crystallographic axis. T h e light receptors lay on the inside of the eye.

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them are permanent. They cannot be preserved as fossils, but their existence was surely necessary to turn a mechanical agglomeration of beams of light into images. Light of itself cannot generate understanding, any more than an image reflected in a pool interprets the scene it so faithfully duplicates. Information has to be gathered by nerves, and interpreted by brains. Because of the selective field of view from each lens the ancient world of the trilobite must have been perceived as a mosaic, a shuttle of tiny images, overlapping, subtly changed from lens to lens. The resolution of the image must have depended to some extent on the number of lenses.

A more detailed perception was possible with many l e n s e s — the more, the better. Hence it is not particularly surprising to find that some trilobites had an almost unreckonable number of tiny lenses.

One of the most difficult jobs I ever attempted was to count the number of lenses in a large trilobite eye. I took several photographs of the eye from different angles and then made enormous prints magnified large enough to see individual lenses. I started counting as one might: "one, two, three, four" . . . and so on to a hundred or two. The trouble was that you had only to look away for an instant, or sneeze, to forget exactly where you were, so it was back again to "one, two, three . . ." Teeth were gnashed, imprecations muttered, deities' names taken in vain. Eventually I hit upon the notion of pricking each counted lens on the photograph with a pin, so that it wasn't counted twice. The trouble was moving to the next photograph: what was the last lens that I'd identified and how did they link from one picture to the other? Was it that one with the little scratch, or that one a mite larger than its neighbour? The work was undeniably suitable for an obsessive with insomnia. I got to a total of more than three thousand before I vowed that, in future, I would simply estimate the number of lenses in a bit of an eye, and use my best arithmetic to estimate the whole number.

Across their many species the number of lenses in trilobite

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eyes varies from a mere one to several thousands. No doubt the effectiveness of the eyes varied accordingly. But, large or small, they received light along the c axes of the calcite crystal of which they were made.

This fact carries an interesting corollary. If we know where the light came from to pass through an individual lens then we also know exactly where the trilobite could look. Turn the tiny arrows of the c axes around and they dart out into waters of the marine world surrounding the trilobite, spearing any object in vision. To understand what the animal knew of its environment we only have to sum the lines of vision of its lenses. We can look through the eyes of the trilobite to see the world as it was observed hundreds of millions of years ago.

Eyes made of pure crystals are attuned to the images of ancient scenes. Lenses ranked in horizontal lines may just see a horizon, whereas curved eyes with m a n y lenses may see a wider view. Learn where the lenses face and you will have a prospect of a trilobite's field of vision.

The first investigator of details of the field of view of trilobite eyes was Euan Clarkson from the University of Edinburgh. Euan always refers to trilobite eyes as " p e e p e r s " after the line in the song: Jeepers, Where'd

creepers! ya

get

those

peepers?

What he did was to mount trilobites in such a way that he could with great accuracy measure the direction of the pole (c axis) of each lens. Then he plotted the spread of directions of these axes on to a stereographic net, which is a way of displaying which part of the full 3 6 0 sphere of vision the trilobite actually utilized. He saw what the trilobite saw.

0

The majority of the trilobites that Euan studied did not see all around them. He proved that m a n y common trilobites preferred to see alongside. The eyes looked sideways and forwards and often a little backwards: they glanced askance. But 99

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why? The field of view was directed over the area surrounding the animal, as it might be a searchlight sweeping over the ground and low bushes, but unconcerned with the province of the sky. There is a simple explanation of why their field of view was limited in this way. Most trilobites lived on and around the sea-floor, and this was the world they wished to appraise. It was a world where enemies approached on scuttling limbs across the surface on which they lived, where potential food may have lain half buried in soft sediment, or slowly crawled or ambled over the surface of the mud. A likely mate was a possible neighbour working an adjacent plot on the sea-floor, but deserved a closer inspection, just in case. A rival might come sidling up at any minute, and needed to be spotted before acquiring the advantage of surprise.

Antennae swept the water in front of the advancing animal to sniff or taste any chemical signals born on currents which might complement the evidence of their own eyes; tactile and olfactory senses played their age-old complementary role to visual acuity. It was a world atop the sediment, where most of the events of the day or night carried on in the same small hemisphere.

The modern equivalent of this world is still present everywhere on muddy sea-floors—but does not have the sort of glamour to rate the television coverage of coral reefs. It is a place where a variety of humble worms process nutrients from the sediment itself, many more burrow within it, still others stir it up to make a nutritious soup. It is an environment where innocuous grazers are hunted by sneak thieves and footpads, where some animals disguise themselves as seaweeds, still others breed so fast as to outstrip their hunters.

It is a world full of the subterfuge of survival, all fed by the organic richness of the sediment itself; a sideways world, where you watch out for your neighbour, for he may not be what he seems. It is no wonder that the average trilobite was concerned with its muddy environs: whether it was hunter or hunted it had to look out across the undulating view, twitch100

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ing and perceptive, for its life depended upon it. For most trilobites their eyes were a key factor in their survival (although we have met some blind ones). W h o can fail to be impressed by the trilobite's petrified tokens of the triumph of vision one hundred and fifty million years before even the first tentative excursions had been taken by plants towards colonizing the land?

Look closely at a trilobite eye and you will see a honeycomb of tiny lenses. Like m a n y packed things in nature, the lenses are mostly hexagonal. They follow the bidding of geometry just as many corals do, or insect eyes, or even many patchwork quilts. Where small, similar objects squeeze together cheek by jowl until they touch and jostle for a c c o m m o dation they naturally tend to compress into hexagons. It is a way of equalizing the pressure for space with all the neighbours. The centres of adjacent hexagons are all equidistant from one another. So the average trilobite lens is long and thin, a few tens of thousandths of a millimetre (p) across, with its c crystallographic axis running along its length, and is hexagonal. If the eye were perfectly flat, its design would be as uneventful as that of a sheet of patterned linoleum. But the geometry of "bending" a sheet of hexagons around a curved surface is not straightforward, and you will find the occasional odd-shaped lens or a shuffle in the lines of lenses, to make a little space around a curve. (We all know the compromises that have to be made when wrapping a football in Christmas paper.) But even so, some trilobite eyes seem to be astonishingly regular, lines of hexagons making gentle spiral curves that run obliquely across the eye from bottom to top.

Euan noticed something else about the construction of the trilobite's eyes: the smaller lenses were concentrated at the top of many eyes. The eye surface—known as the corneal surface—had to be moulted along with the rest of the animal's hard exoskeleton as it grew. The eye itself grew in size in harmony with the rest of the animal: more lenses were added after each moult as the new skeleton hardened. N e w crystals 101

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were added in from the top of the eye in a zone of generation.

With successive moults these lenses were incorporated into the main body of the eye, passed downwards in a graded chain. These differences in lens size also helped to maintain the regularity of the design across the curved surface of the eye. It is fiendishly clever (as Hercule Poirot would to say) that these "primitive" animals could play such games with the mineral world in the service of eye geometry.

We cannot know exactly how the trilobite saw with its crystal eyes: the nerves have left no trace. It is like finding an artefact from some remote civilization—we may be able to assume its general function, but we will never know the thoughts that passed through the mind of its user. The trilobite will always keep a certain distance from us; there will be limits on the intimacy we can attain. What we can guess is that the honeycomb-like trilobite eye may have permitted comprehension of the world in the same fashion as the similar compound eyes of living arthropods. Apposition eyes do not form complete images of their surroundings (some other arthropod eyes have lenses arranged in such a way that they are able to collaborate and produce a single, complex image). Denselylensed eyes of trilobite type are particularly good at detecting movement. Another animal approaching across the sediment surface will trigger one lens after another as its image impinges on different parts of the field of view. If the change is alarming the trilobite may be stimulated to take evasive action: maybe to roll up into a ball or to swim away as fast as possible. To look through the eye of the trilobite is to see the world as fragmented pieces of information—trilo-bytes, I am tempted to dub them. The animal was not able to see as we see, but appreciated the world in a thousand fragments of light, as if the brain were a pointilliste with a palette of prisms.

There is still more to tell of crystal eyes. Although the great majority of trilobites have eyes such as I have just described, there are some which are obviously different. One of the commonest trilobites in the Devonian rocks of N e w York, Ohio 102

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and Ontario, and also in Germany and Morocco, is the compact beast called Phacops, which we have already met in the parade of trilobites in the last chapter. Moroccan Phacops can be bought for a handful of dollars and they are cheap at the price. If you work in a large m u s e u m Phacops is one of the most frequent trilobites to walk in through the door accompanied by its owner. One greets it as one might an old friend. It is always a pleasure to point out its large crescentic eyes, that stand proud of the cheeks like the retractable headlamps that grace the front of a Porsche. But wait! There is something peculiar about these eyes. Instead of the lenses being so minute that it requires a microscope to see them properly you can discern them quite clearly unaided. To the naked eye they look like a series of tiny, perfectly formed balls—a real case of those are pearls that were his eyes. The lenses line up quite con-

spicuously in vertical files, often with a little space between them, and they are stacked in the manner of hexagons, so that any lens has six neighbours. It is another example of close packing, and not different in principle from that displayed by lenses of other eyes. But it is the regularity of the eye that is so striking. We are accustomed to expect a little sloppiness in nature's designs: the leopard's spots are hardly mechanically repetitive, no two snakes have identical zig-zags on their backs. But these eyes seem to have been turned out by a machine, neat as billiard balls arranged in a box. They are obviously something different from the minutely lentiferous eyes of the usual trilobite. Instead of averaging many hundreds to thousands, this kind of eye had lenses which n u m bered a hundred or so, or could even be counted on the collective fingers of the average family.

If the trilobite eye is something out of the ordinary, then the phacopid eye is odder still.* One way to study it more closely is to cut a section through the lenses, so that the optical T h e "normal" kind of trilobite eye is known in the trade as holochroal; the special kind that Phacops and its relatives had is termed schizochroal.

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properties can be studied under a high-powered microscope.

Even though the animal has been dead for so long, there is a hint of the sacrilegious in taking one of these beautiful creatures and cutting across its head with a circular saw. Those serried pearls which have lasted inviolate for several hundreds of millions of years may now be destroyed in an afternoon.

But sections made in this way reveal strange secrets. First, the lenses are indeed nearly spherical, or perhaps slightly drop-shaped. A phacopid lens has a disquieting resemblance to a glass eye. As a student I once did a labouring job alongside an old boy with a glass eye, who would pop it out whenever there was a lull in the conversation, toy with it for a bit, and then pop it back in again. In or out, it made no difference—he could not see through it—whereas the schizochroal lens was evidently functional. Nor could it be dislodged and replaced, as it was sealed in a solid sheet of calcite (although, like everything else on the trilobite, it would have been moulted). Second, there is usually a little " w a l l " between adjacent lenses, a kind of baffle which stopped light from one lens overlapping with that of the next. Often, the lenses are slightly sunken, and the areas between the lens are a little swollen.

The optical arrangement is clearly a very sophisticated structure which quite belies the antiquity of the animal. This may come as something of a surprise: we might expect an eye from half-way along optical history to have a slightly slungtogether look, or at least broadly to resemble the eyes of many other lowly animals, as does the run-of-the-mill trilobite eye.

But the eye of Phacops is something unexpected, a sports coupe in the age of the boneshaker. Not only does it have calcite lenses, but they are of a singular type.

Surely such specialized eyes must have functioned in a very specific fashion. In the living fauna there are no really convincing analogies: one investigator drew attention to the ant-lion larva which has somewhat similar drop-like e y e s — but not m a d e of calcite crystals. It was an American investiga104

Trilobite eyes. T h e holochroal eye consisting of numerous hexagonal lenses (above)—Pricyclopyge, an eye adapted to detect the smallest m o v e m e n t ; (below) the specialised schizochroal eye of Phacops showing fewer spherical lenses, each one finely tuned to its habitat. (Photographs courtesy Euan Clarkson.)

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tor at the Smithsonian Institution in Washington, Kenneth M. Towe, w h o in 1972 demonstrated the efficiency of the phacopid eye lenses in the most graphic way: he took photographs through them.

W h e n you are a scientific visitor to the Smithsonian Institution, the National M u s e u m of Natural History, you enter with the crowds through the public entrance, but then wheel off to one side to telephone through to your contact behind the scenes. Within a few minutes you pass through an inconspicuous door into a different world of cabinets and collections, a cool, scholarly enclave away from the metropolitan throng.

W h e n Ken Towe worked there his office had a view across the grand avenue to the FBI building. Visitors to the Smithsonian were taken there for lunch, an experience so unexciting as to defuse any paranoia about spooks and fifth columnists. Using the trilobite lens as a substitute camera lens Ken photographed the FBI building—not perfectly, but recognizably.

What more curious tribute to J. Edgar Hoover than to have his workplace photographed through the eyes of an ancient fossil! Another photographic attempt successfully captured the grinning " h a p p y buttons" that were in vogue at the time. It was as transparent as calcite that the phacopid lens could form sharp images, bringing into focus objects of different sizes at varying distances. The phacopid lens saw larger pieces of the world than the tiny lenses of most trilobites, and saw them clearly. It was an astonishing feat of optical engineering accomplished using calcite, the most quotidian of minerals.

H o w this trick might have been done was discovered by Euan Clarkson and Riccardo Levi-Setti not long afterwards. It was already apparent from the spherical structure of the lenses of Phacops—and their large size—that some different method was being used by these trilobites to form their images when compared with the tiny lenses of their relatives.

These were fat, biconvex lenses, designed to bring beams to a focus. If you hold a clear glass marble up to the light and peer 106

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through it you can get some idea of the process: you will see an upsidedown world, all bent and distorted. The trilobite images seem to be much clearer than that. H o w could this be?

The problem with light travelling through a convex lens to a focus is that different rays travel different distances through the lens according to their trajectory—and in a refractive material like calcite that means that they get bent to different degrees: the result is a fuzzy focus. Like my old workmate's glass eye, to be transparent is not enough to see. The technical term for this fault in design is spherical aberration.

Riccardo Levi-Setti is a nuclear physicist at the University of Chicago, a place where everyone is almost effortlessly brilliant. He also has a private passion for trilobites, which he pursues more vigorously than many a professional palaeontologist. Euan and Riccardo made an interesting combination: an extravagantly hairy and amiable Scotsman and a wellgroomed and suave Italian. What they discovered together was that Phacops had solved the problem of spherical aberration. Euan had made out a kind of bowl within the individual schizochroal trilobite lens and at the base of it, and he identified it as part of the lens with a different structure. In some kinds of preservation this bowl would weather out separately, so that the eye came to resemble a series of little dishes. Euan and Riccardo discovered by making thin sections that in this part of the eye something strange had happened to the calcite: it had become impure. Some of the atoms of calcium within the crystal structure had been replaced by atoms of its closest elemental relative—magnesium. Because the atoms are so similar, magnesium could sneak in, like a spy in an appropriate uniform infiltrating an army. Even in the purest calcite there are a few such hidden agents. The effect of this process continuing far enough to make "high magnesian calcite" is to alter the refractive index, the capacity of the crystal to bend light. With a wonderful fineness of balance the thickness of the high magnesian layer varied across the lens in just the right degree to correct the spherical aberration—for every 107

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bend to the left a compensating bend to the right. This corrective layer was what m a d e the bowl. The trilobite had manufactured what a modern optician might term a doublet, wherein two wrongs do make a right because of the way they are spliced together.

As a grace-note on this discovery, Riccardo noticed that the trilobite's design had been anticipated by the great seventeenth-century Dutch scientist Christian Huygens (1629-95) and the French polymath Rene Descartes (1586-1650). They had sketched out an optical " c u r e " for spherical aberration in a lens which proposed a compensating bowl designed almost exactly like that of the trilobite. This may indeed be a wonderful example of Art imitating Nature, or perhaps rather of Nature anticipating Science—by more than 400 million years.

S. J. Gould commented in an article in Natural History in 1984 that "the eyes of trilobites . . . have never been exceeded for complexity and acuity by later arthropods . . . I regard the failure to find a clear 'vector of progress' in life's history as the most puzzling fact of the fossil record." The point Gould makes is that it is hard to see how the trilobite could have achieved its optical design in a still more sophisticated fashion; there remains a feeling that arthropods ought to have learned some cleverer visual tricks since the Devonian. The notion of progress in life's story is an intellectual quagmire. It embodies a belief in " i m p r o v e m e n t " which is difficult to defend. Maybe the trilobite should stand condemned for having perfect eyes while its limbs were decidedly second rate.

Or maybe we should berate it for carrying such a heavy suit of armour, while at the same time acknowledging its nonpareil peepers. If you put yourself in the right frame of mind you can imagine the trilobite like one of those medieval knights, cumbersome and unwieldy, however well-protected. We might be able to talk ourselves into imagining a story of progress whereby sleeker warriors outclass the lumbering, articulated Sir Phacops. Serve him right! Progress is the thing!

This is all nonsense, of course. The eye of these phacopid 108

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T h e drawing m a d e by E u a n Clarkson and Riccardo Levi-Setti to illustrate h o w the more highly refractive b o w l inside the lens of Phacops helps to bring rays more closely to focus.

trilobites is wonderful, and unique, but I do not k n o w how to measure it against the lustrous eye of the dragonfly, that can so resolve an image as to snatch a wasp on the wing. I cannot say that it is better or worse than the eye of those marine crustaceans who use silvered boxes to focus weak light at depth into a precise image. I do not know how it stands in comparison with the several, surprising eyes of spiders. W h o is to calibrate progress, who to legislate on the unit of improvement?

The trilobite was no doubt a perfect citizen of its times, and its eyes focused on the problems of its daily life sufficiently well to allow the beasts to throng in their thousands on the sea-floor. The astonishing fact is not that the eyes were so perfectly engineered but that the sea rewarded such a specification even then. We cannot name a time when the trilobites reached their acme, after which there was either stasis or decline. Life just isn't like that.

My own engagement with trilobite eyes was an investiga109

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tion of goggle-eyed species. One of the most peculiar specimens I had discovered in the Ordovician rocks of Spitsbergen was quite unlike other trilobites that I had seen illustrated in textbooks. It was long and thin, and the axis occupied much of the body, so that the pleurae were reduced to little triangles.

But the eyes were truly extraordinary: they were enormous and inflated, puffed up like little bladders. It was weeks before I was able to convince myself that I had located the correct free cheek for this trilobite (I had no entire specimens, so it was the usual matter of completing the jigsaw puzzle). But in the end there was no question: the eye had become so enorm o u s that it abutted against the edge of the cranidium in an almost straight line running alongside its entire length. Only one eye among the selection I had cracked out from the Ordovician limestones had the right "fit." I was now able to place the eyes back in position on the headshield to reconstruct the skeleton of the entire animal. N o w it seemed even odder. It was obvious that the eyes bulged out on either side of the head in the manner of those slightly grotesque ornamental goldfish that have such a thyroidal look; in proportion these " p e e p e r s " were even larger—virtually the whole free cheek had turned into an enormous eye! What could be going on? I named this strange animal Opipeuter inconnivus, having recruited the help of a classicist friend to find out the Greek for "one who g a z e s " — O p i p e u t e r ; inconnivus means "without sleeping." Trilobites, of course, were unable to blink.

There were some other details that attracted my attention.

W h e n the eyes were "fitted o n " it was perfectly clear that they hung d o w n well below the level of the rest of the animal. If you view the majority of trilobites from the side the base of the animal makes a line parallel with the sea-floor on which they lived; not so Opipeuter. Furthermore, the edges of the cheeks were sharp, with their cutting edges directed downwards. This is where Euan's work on the direction in which crystal lenses could see became so useful. The lenses on Opipeuter were tiny and of the crowded, hexagonal type used n o

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by most trilobites, not the special Phacops type. Hundreds upon hundreds of lenses crowded together over the bulging surface of the eyes. But they differed from the crescent-shaped eyes of nearly all the trilobites I had ever seen, that looked predominantly sideways across the sea-bed. In Opipeuter there were lenses that faced sideways, of course, but there were also many dozens of lenses that " l o o k e d " forwards. If I was right about the bulging orientation of the eye, there were nearly as many lenses that were capable of looking upwards as well—and even downwards. And with the thorax so trimmed at its edges it was likely that the eyes projected out far enough to command a view backwards . . . there were lenses gawping every which way. These weren't just peepers, they were more like oglers.

Surely this trilobite needed to see all around, but what could it possibly be for? Where in the ocean is it necessary to have an all-encompassing view of the watery world? Perhaps it was my customary view of trilobites as bottom dwellers that prevented me from seeing the obvious. It must, of course, have been a swimmer! A leap of the imagination had the trilobite leaping off the sea-floor. Opipeuter had the freedom of the Ordovician oceans: it needed to see everything. Suddenly there was a different vision of the lives of trilobites: from grovelling on the sea-bed, they filled the seas as well. The former oceans could have swarmed with trilobites, just as krill throng in living seas. That was why the body of Opipeuter was long and thin compared with most trilobites, and w h y its design was so poor for resting on the sea-floor. It had a vaulted axis to house the muscles used to power its swimming limbs, but economized on the rest of its shell so as not to overburden the work of the sculling appendages. Some of the rocks in Spitsbergen were almost made of this trilobite and its relative, Carolinites, so that it was not hard to imagine a sea alive with thousands of these little animals, swimming in the brilliant sunlight while, far below on the sea-bed, Triarthrus slowly ambled through the soft mud.

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My reconstruction of the giant-eyed Ordovician trilobite Opipeuter—swimmer across the ancient oceans—from the top and the side.

There proved to be a number of different trilobites with this free-swimming design; the one-eyed Cyclopyge had been noticed already as a swimmer by the great early twentiethcentury geologist Eduard Suess. He made a comparison with some huge-eyed, living crustaceans. When I discovered this observation, buried in the middle of his great work The Face of the Earth, I understood that ideas are seldom ever really new.

Cyclopyge was a more compact animal than Opipeuter, with 112

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fewer thoracic segments, but it lacked nothing in the eye department. It, too, was found in considerable numbers in company with several other genera of bug-eyed trilobites. I have studied these cyclopygid trilobites in Wales and Bohemia. They were collected from dark mudstones that were originally deposited in relatively deep water, to which they are apparently confined. I have sat under hedgebanks with rain dripping down my neck breaking open dark shales near Carmarthen—in Welsh, "Merlin's C a s t l e " — a n d could not have been more amazed if the old magician himself had popped out of the undergrowth than by my first sight of the fat eyes of Pricyclopyge (p. 105), staring out at me after an incarceration of 470 million years, some of its lenses still glistening slightly. In contrast, m a n y of the limestones which yielded Opipeuter and Carolinites were laid down in shallow seas—there were other fossils with them that proved it. Could it be that Cyclopyge and its friends s w a m at depth in a world of pervasive dimness, while Opipeuter and its allies lived in the surface waters of the sea in brilliant light?

I was able to test this idea thanks to a grant of money from the Leverhulme Trust. It is fortunate for me that a few charitable bodies still exist who will support what has been called "blue skies" research—that is, research that has no industrial or commercial spin-off. I doubt you can get bluer skies than trying to find out about the optics of Ordovician oceanic trilobites. Leverhulme supported a young post-doctoral assistant, Tim McCormick, to immerse himself in trilobite eyes for several years. We had discovered that it was possible to deduce the light intensity in which an arthropod customarily lived by making some very careful measurements on the compound eyes. This had been worked out on a variety of living species—and it seemed a good idea to try it out on trilobites.

Tim had to mount perfectly preserved specimens so that he could measure such details as the distance and angle between adjacent lenses, so as to obtain a mathematical quantity termed the eye parameter. It was a labour that lasted for six 113

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months. Imagine our delight when our alleged surface swimmers came out with the right value for bright illumination, and the trilobitic Cyclops condemned itself to live in gloom.

Thus we were able to insinuate ourselves into the daily lives of our favourite animals. We had no Steven Spielberg to animate these creatures into plausible simulacra. Our vision of trilobite lives remains lodged in our own imaginations, but all the more intense for that. N o w we can visualize an Ordovician sea with a clarity that would have astonished Adam Sedgwick, James Hall or Sir Roderick Murchison. We can see—literally, through the eyes of the trilobite—an ocean teeming with swimming animals, some grazing on tiny zooplankton near the surface, others deep down in a twilit world, and both above a sea-floor where a profusion of other trilobites again scurried or ambled.

Nor was this the end of our vision. A m o n g the small, deepwater cyclopygids, there were rare examples of a different and larger kind of animal. This trilobite, too, had big eyes, but they did not bulge out; instead they were tucked into the side of the head. And what a peculiar cephalon! It was extraordinarily long, largely because it was produced forward into what can only be described as a snout or nose. This " n o s e " comprised the front part of the glabella (which was itself unusually smoothed out, and had lost all its furrows) and an extended section of doublure beneath it; together they made something that looks like the " n o s e " of a dogfish or small shark. The rather large pygidium had a dished appearance. The whole thing was beautifully smoothed out, like a torpedo. The shape of the animal reminded me of an illustration I had once seen in a textbook of an idealized hydrofoil—a shape designed to cut through the water with a minimum of frictional resistance.

Could this trilobite have been the porpoise of its kind? I needed advice.

Just up Exhibition Road from the Natural History Museum is the famous Imperial College of Science and Technology.

Imperial has long been one of the leading institutions for all 114

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the sciences that make things work: somewhere there, there must be a B & Q Professor of Gadgetry. I soon learned of a lecturer called David Hardwick w h o could help me design an experiment to test the streamlining of my dogfish-nosed trilobite (which goes by the inelegant name of Parabarrandia). In the hydraulics department there were all manner of flume tanks and watery experimental gear. The simplest thing that could be done was to suspend life-sized models of various trilobites in a transparent-sided tank, along which a current flowed. If you then streamed a dye into the tank you could see which animal shapes produced the best streaming past the body. Most of the models we tried had all kinds of turbulent wakes: projecting eyes, for example, showed little coloured eddies behind them. N o w we could see why it was an advantage for Parabarrandia to have its eyes flush with the sides of its body. In fact, the dye streams flowed past this trilobite as if they were long, straight tresses swept out in a breeze: it was a wonderful demonstration of the streamlining theory. We could now imagine this animal elegantly outpacing all other swimmers in the Ordovician. But we needed proof to convince our sceptical colleagues. So we now went further by designing a way of measuring the drag itself, by seeing how far carefully scaled models were deflected when suspended in a gentle current—the poorly streamlined species would experience the greater deflection as their bodies offered resistance to the movement of the current. This required an experiment in an open-topped tank. The trilobites were suspended in the tank as if they had been bait for some Palaeozoic fisherman.

Now the current was turned on, and the deflection measured with a travelling microscope. In a white lab coat and with my sensitive measuring equipment I felt like a real boffin.

I nipped out for a quick cigarette (I was a smoker then) while the experiment was still running and was horrified when I returned to find the whole laboratory floor several feet deep in water. I had visions of being banned from Imperial College for ever, and having my screwdriver confiscated by " 5

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The

free-swimming

trilobite

Parabarrandia

(Ordovician,

Czechoslovakia) immersed in a flume tank. The stream of dye to the right shows the excellent streamlining.

the B & Q Professor. Mortified, I sought the aid of the laboratory technician. Giving me that look which I have often received from garage mechanics, he waded into the middle of the floor and pulled out the most enormous bath plug I have ever seen. Within minutes the water had gurgled away down the plughole, while I stood by with my mouth hanging open slightly, damply rueful. But the experiment had proved the point. There were streamlined trilobites that sped through the Ordovician ocean.

It is a curious fact that, despite the beauty and complexity of trilobite eyes, it seems curious that plenty of trilobites could do perfectly well without them. A large number of them were blind. Eyes, apparently, could be readily jettisoned. In some examples we can even show how it happened. An ancestral species had large eyes, and a succession of daughter species had smaller and smaller ones, until the facial sutures ran across the cheeks leaving no sign of lenses at all. Some of the trilobites related to Trinucleus had just one lens left perched 116

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high on the cheek. My colleague Bob Owens from the National Museum of Wales and I collected in some localities in South Wales where ten or more blind, or nearly blind, trilobite species lived together, and they must have crawled about the sea-floor in a dark world. Appropriately enough, the quarry from which we collected them was also profoundly gloomy, the muddy Ordovician rocks from which the trilobites emerged sooty black—and probably always had been from the time of their deposition. So we were finding black trilobites that lived in perpetual darkness in a dim quarry full of black rock. My eyes have never really recovered. Even odder, the other trilobites in the same rocks were huge-eyed swimmers. It did not take us long to deduce that the swimmers swam well above the lightless sea-floor on which the blind animals dwelt. They joined one another only in death.

Eyes were lost because they were surplus to requirements.

These trilobites had an affinity with blind cave crustaceans, new species of which are discovered every year: pallid creatures, in which pigment has bled from the body and light from the eyes. When they are brought to the surface, they look diseased, like tubers stored too long in the cellar. They are not ill, of course, merely drained of superfluities which are not necessary for their dim existence.

Blind trilobites were not confined to the deeper seas, although they were probably commonest there; others may well have been burrowers, for example. Nor would it be correct to think of them as degenerate. I was brought up in a tradition of thinking of animals in their geological history reaching some kind of acme, and afterwards—those that ultimately went extinct, in particular—having a phase of decline.

There was, inevitably, the image of human frailty blended with this. Blind or otherwise specialized creatures might be described as degenerate, almost in the way of the Victorian black sheep of the family who contracted unnameable diseases and squandered the family fortune. I must confess that I once found something about this scenario attractive, and not 117

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merely because it dramatized episodes in the history of life in novelistic terms. It tied in with some inaccurate notions of Darwinian "fitness," too. Some animals were destined for (literally) blind alleys from which they never emerged. Other, fitter, ones prospered and brought forth evolutionary progeny.

Curiously, it is true that I know of no example of eyes once lost and then regained. It is certain that trilobites primitively possessed eyes—their loss is always therefore a secondary adaptation; and, like virginity, sight can never be regained once it is lost. But the important point is that all blind trilobites were excellent citizens of their time. Sometimes they outnumbered their sighted cousins. In Shropshire, England, there are soft, greenish shales that crop out in the banks of Sheinton Brook, near the odd-looking hill known as The Wrekin, which are covered with the remains of the blind trilobite Shumardia, a perfect little miniature with only six thoracic segments and a glabella shaped exactly like the ace of spades. The same animals are abundant in Ordovician shales in Argentina; and I collected them again in southern China, equally in their hundreds. No dissipated roues these—they clearly spread around the Ordovician world in their millions. If there is a moral to draw from this it is that what we describe as adaptive success is also about the opportunities presented by the environment.

Just as the ingenious inventiveness of the trilobite eye opened up a range of habitats so that they could hunt or swim in the open sea, even the loss of that same organ could qualify the animals to prosper in a sea-floor of soft mud. The glorious richness of the natural world is about multiplicity of adaptations, and it was so from the time of the trilobites.

The story of trilobite eyes I have related illustrates, appropriately enough, the principle of progressive illumination.

This is the way science often works. As we learn more, we think of new questions to ask. We proceed from calcite to calculation to something like certainty. Imagination plays its part, of course, but our appreciation of vision is not, as Samuel Taylor Coleridge said, A sight to dream of, not to tell, for we try 118

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to convert our dreams into the solid stuff of published scientific articles. Advance in knowledge was dependent first upon recognition of the different kinds of eyes, and then of the ways they might have worked. At root, this is another form of taxonomy, another expression of humankind's talent for discrimination. Nor does the process come to an end. As I write this, a paper has just arrived from a Hungarian scientist suggesting that some trilobites may have had bifocals! I do not know yet whether this idea will pass the criticism of the next generation of investigators. What I do know is that there will be more to find out about trilobite eyes. That combination of imagination and rigour which is what science is all about has not yet probed out all the secrets: there is sight, and there is insight.

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The play's the thing! As the theatre curtain rises we butt into the lives of the characters without preamble. There is no biographical account of the dramatis personae printed in the programme notes, describing their lives before they are presented to us on stage. We expect no more history than is given to us in the three hours or so that we occupy our seats. If it is a good play, as with any work of art, the experience will be satisfying within its own boundaries—we won't be left fretting to know about the early history of the characters, any more than we will demand that Macbeth overcome his remorse and next time triumph over his foes.

Drama is often used as a metaphor in the history of life.

Animals have been described as "actors" on the ecological "stage." Mass extinction events that have interrupted more routine oscillations of fortune, the stuff of everyday evolution and decline, are "dramatic" interruptions in the "narrative."

This kind of description engages the attention more readily than strictly scientifically-correct statements about "statistically significant elevations of extinction above background rates." Well, what's wrong with a little theatre? There will have been episodes in the history of life as dramatic in their way as that instant above the sea where Stephen Knight faced 120

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the trilobite and transformed his destiny. A long view of life does indeed see dramatic twists, where roles are reversed—as when mammals replace dinosaurs centre stage—or one old stager is replaced by another in a familiar part. I have heard it said that trilobites once played the ecological role now taken by crabs and lobsters, and most people with a passing knowledge of natural history will know that ichthyosaurs have been described as the porpoises of the Jurassic. We will let it pass that neither of these nostrums is exactly true.

When a play (particularly a whodunnit) is beginning to stall a little, one standard bit of theatrical "business" to bring it alive is to introduce an explosion. Boom! The audience jumps to attention; and, of course, under the cover of gun-shot it is possible to get away with murder, dramatically speaking.

Fossils of trilobites appeared suddenly in the geological record during the early part, but not quite at the base of the Cambrian period, perhaps 540 million years ago. If you are tempted by the word "dramatic" then this is one occasion where you could be forgiven for weakening. W h e n you visit a rock section spanning the right bit of the early C a m b r i a n — and there are such profiles in Newfoundland, Mongolia and Siberia—there will be not a sniff of a trilobite as you work your way upwards from one bed to its successor: this is the most methodical way to trudge upwards through geological time. Then, quite suddenly, a whole Profallotaspis or an Olenellus as big as a crab will pop out into your waiting hands as you split the rock. These are trilobites with lots of segments and big eyes: striking things, not little squitty objects. It is an appearance as dramatic as that of the sorcerer in Swan Lake, who accompanied the first theatrical explosion I ever experienced. You are tempted to cry out: "bang!" And as you continue to collect a foot or so higher into younger strata, the first trilobite will be joined by others, maybe half a dozen or so different species, and all individually distinctive ones at that.

More than a decade ago I examined the trilobitic early Cambrian rocks on the island of Newfoundland. Its Northern 121

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Peninsula sticks up as stiffly as an abusive finger on the western side of the island. There is only one road running northwards up the Peninsula* from Deer Lake to St. Antony. After less than an hour on this road you enter the Gros Morne National Park. The road winds alongside Bonne Bay, a beautiful, huge, drowned inlet into which the surrounding hills plunge somewhat recklessly. The valley which is now occupied by Bonne Bay was long ago excavated by a river, but the rise in sea level at the end of the last Ice Age drowned it, so that n o w the sea probes impertinently into its every corner.

Firs and aspen and birch vie with scrubby alder to make the inland almost impassable on foot. Blackflies and mosquitoes are further discouragements. The road loops and curves, not allowing any driver to take his eyes off it for long. Strata have been sliced through to make the road passable: they were folded in such a way that they now plunge at various angles into the sea. On a great, flat brown bedding plane of rock some foolish exhibitionists have painted their initials a foot or so high in white paint: " R W luvs S D M . " What they should have written is: " A m a z i n g trilobites found here!" But any such search would have to be frustrated, because Parks Canada have strict rules about collecting by permit. If you do have permission, as I did, you can break open shales to your heart's content, and if you are lucky you will be rewarded with a big, juicy Olenellus, or you may find fragments of another

trilobite like

Bonnia—presumably

named

after

the

B a y On the other hand, you may well discover completely different kinds of fossils: I recall that I found a fine specimen of a very primitive echinoderm (the group which includes starfish and sea urchins) called Protocystites walcotti—no prize

*Newfoundlanders are often humorous and hospitable people. They have been used as the butt of jokes by mainland Canadians, allegedly for their lack of sophistication. The only instance I can recall of a real "Newfie joke" w a s when I w a s leaving the Gros Morne Park in search of food. At the inn at C o w Head a laboured hand had scrawled a notice in jagged chalk letters: " C o w Head MOTEL best food on the whole PENISULA."

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for guessing after w h o m it was named. Nearby, a small mollusc turned up.

The early Cambrian level is like this almost everywhere. A variety of shells can be found, some of which can be placed with their living relatives in one or another of the great "phyla"—the major divisions of the animal kingdom, like Mollusca, Arthropoda or Echinodermata. The Cambrian strata which lie below those including the first trilobites often yield a variety of small shells, tubes, plates and nets sculpted into a host of shapes, m a n y of which defy ready recognition as any part of an animal we k n o w about. They are collectively referred to as "small shelly fossils." It has recently been shown that the variety of these m a y be more apparent than real, because Simon C o n w a y Morris and John Peel have proved that many different "small shellies" belong together to make up a much larger, plated organism, called Halkieria. The little plates may be no more than the components of a kind of chain mail. But what is real enough is the sudden appearance of shells—hard parts, skeletons, call them what you will. Animals contrived to use minerals to support their soft anatomy over (geologically speaking) a very short period of time at the base of the Cambrian. Not only that, there is now a number of fossil faunas from the Cambrian that exceptionally preserve animals without hard skeletons—those soft-bodied animals which are generally so rare in the fossil record.

The most famous of these localities is the Middle C a m brian Burgess Shale in British Columbia, arguably the most illustrious fossil deposit anywhere in the world, thanks to S. J. Gould's account of its treasures in Wonderful Life (1989). But fossil faunas have now been recovered from even earlier— Lower Cambrian—rocks which are almost as diverse. Those discovered in Chengjiang in China and Sirius Passet in Greenland are the most spectacular. They all confirm the same idea: that a great diversity of life was already present in the C a m brian period. Some of these animals had hard exoskeletons or shells, others did not. Some were familiar, others strange and 123

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puzzling. There were assuredly more arthropods than anything else窶馬obody could mistake those jointed legs. But what an extraordinary bounty of articulated phantasmagoria were propped upon those typically spindly legs! I cannot here elaborate on all the other odd animals in these faunas: I will only reiterate that, like the devils that persecuted Christ's m a d m a n , they were legion. Gould even famously, and erroneously, argued that there was more "diversity" (or, not to misrepresent him, what he termed "disparity") in the Cambrian than was seen ever again in the subsequent history of life.

The curtains had been drawn on a vital drama, and up on stage there was an elaborate cast, all dressed up to the nines in both familiar and unfamiliar garb. It was a coup de theatre that could not have been bettered by Peter Brook. Dazzled by the brilliant array of costumes the onlooker is confused and overawed by the sudden burst of spangles and tulle. Surely this is the ultimate show, a more heterogeneous parade than could have been dreamed by a zoomorphic imagination in the grip of hallucinogens (why, one animal is even called Hallucigenial). This was a show without precedent, for, like all shows, the cast had no history, their stage presence was a portrayal of the moment; a sudden, glorious, opening night. There was an explosion of characters after a dearth of drama.

Where the theatrical analogy fails is that, unlike a stage play, the history of life does demand a before and after, a beginning and (in some cases) an end. We can be stage struck for only so long, before we try to peel off the make-up, and strip away our initial astonishment to determine the substance of the characters. Life has a biography that is rooted back in time, because all animals are ultimately descended from a common ancestral species, an evolutionary Adam. This accounts for the shared genetic legacy of all creatures, be they ever so great or ever so small.

The sudden appearance of fossils of so many kinds at this geological moment has become well-known as the Cambrian 124

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evolutionary "explosion." The dramatic metaphor is no coincidence. It embodies the idea of a chain reaction somewhat out of control: that is, a hugely elevated rate of evolution.

And, as in all explosions, the b o m b is small but the effects are disproportionate. But this is a creative explosion, rather than a destructive one, so that when the curtains of the fossil record are drawn back suddenly the whole bang-shoot is revealed in the spotlights after the chaos of creative "explosiveness." And why the necessity for explosiveness at all? This is because virtually the only fossils found below the Cambrian in the late Precambrian, or Vendian, strata are either simple plants and bacteria, or else soft-bodied oddities—known as the Ediacara fauna—which are difficult to interpret as any kind of ancestors of what was to follow. The earlier stage was strangely lacking any characters that we could recognize. It is as if the players in the Cambrian drama had appeared from somewhere else, having dressed and made up in secret. Where are the late Precambrian brachiopods, molluscs, echinoderms and arthropods that might have provided the Prologue?

I must confess to a certain diffidence in writing about the Cambrian "explosion" question. It has excited so much passion and disgreement among its several interpreters, some of it remarkably ill-tempered, that I doubt whether it is wise to walk into this volatile environment without a safety helmet. I recall the words of Charles Darwin in his Autobiography: "I rejoice that I have avoided controversies, and this I o w e to Charles Lyell,* who . . . strongly advised me never to get entangled in a controversy, as it rarely did any good and caused a miserable loss of time and temper." However, the trilobites demand it. It might seem strange to the reader that events which happened more than 500 million years ago are still capable of causing the secretion of abundant venom in living organisms. It is undeniable that some of the most obvi-

*Sir Charles Lyell, whose Principles of Geology w a s a profound influence on the young Darwin.

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ous "explosions" are to be heard from the proponents of one theory or another. The puzzle of the sudden appearance of shells at the base of the Cambrian has been with us for a long time. Darwin certainly recognized it; in Chapter 9 of On the Origin of Species (1859) he had despaired that "the case at present must remain inexplicable . . ." One hundred and forty years later there is no shortage of explanations: there is just a shortage of agreement. I am compelled to join the fray because, of course, trilobites were among the observers of the explosion—if indeed there was one—and were hardy survivors from the Cambrian into the Ordovician and beyond, outlasting m a n y of those animals, termed Cambrian evolutionary "experiments," which perished without benefit of descendants. Because trilobites appeared alongside the first arthropods in the Cambrian they must be part and parcel of the "explosion"—caught in the crossfire at the very least.

One of the Burgess Shale fossils is a trilobite called Olenoides. It is another of those rare species in which the limbs can be clearly observed: the peculiar preservation in the Burgess Shale allows us to see shiny impressions of legs and gills, and even guts. Like Triarthrus, Olenoides (fig. 7) has been examined by most of the leading trilobite specialists from the time of its discoverer, Charles Doolittle Walcott. It will come as no surprise by now that the definitive description of the animal was m a d e by Harry Whittington in the 1980s. In its essentials, the trilobite had a similar arrangement of limbs to that I have already described for other species. On the cephalon there were three pairs of limbs and flexible antennae; each thoracic segment also had the usual biramous limbs. One difference from the usual pattern was that Olenoides also had a pair of special antenna-like appendages at its rear end, known as caudal furca. But the basic trilobite design was confirmed yet again. Harry noticed that the bases of the walking legs were truly massive and equipped with sharp spines which faced inwards towards the centre line of the animal. He interpreted this spiny corridor as an area where prey items were 126

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Olenellus, one of the earliest trilobites from the L o w e r C a m brian strata: already a specialised creature.

shredded and passed forwards to the mouth at the back of the hypostome: Olenoides was a predator well able to gobble up a variety of " w o r m s " — w h i c h also abound in the Burgess Shale.

Predator and prey made their debut together.

Trilobites were one of the many animals which were so dramatically exposed when the curtain was lifted on the C a m brian Burgess blockbuster. But for many years before the discovery of the Burgess Shale by Walcott in 1909, trilobites were almost the only arthropods known from the Cambrian strata, preferentially preserved as they were by virtue of their calcite exoskeleton. They had come to be a surrogate for all that was primitive among joint-legged animals. It was accepted on the nod that trilobites could stand in for an arthropod ancestor.

Even early observers could clearly understand that they were 127

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quite complex animals, eyes and all. H o w then to account for their sudden appearance? Charles Darwin was unusually confident in the Origin of Species: "I cannot doubt that all the {Cambrian} trilobites have descended from some one crustacean which must have lived long before the {Cambrian),"* he wrote, thirteen years before Thomas Hardy confronted his hero with another such "primitive crustacean." The attribution of trilobites to the arthropods may be almost instinctive.

The anthropologist Kenneth Oakley made known a perforated specimen, a pendant probably, recovered from the Grotte du Trilobite in Yonne (France). This is a late Palaeolithic cave, and records the first interaction between mankind and trilobite. In the same cave there was found a beautiful carving of a beetle. "It does seem reasonable," says Oakley in 1965, "to infer that the trilobite would have appeared to the untutored yet observant and thoughtful Magdalenian as a kind of insect in stone." Quite so. The Magdalenian saw an insect, Darwin a crustacean, Walcott (eventually) an arachnid, that is, a relative of the spiders and scorpions—they cannot all be right.

But an objective answer to the simple question: what is the trilobite's closest relative? has proved rather elusive, and is, like it or not, intimately bound up with the question of the Cambrian evolutionary "explosion." In the first place, the wealth of different arthropods n o w known to be present in the Cambrian robbed the trilobites of their right to claim exclusive primitiveness. Any one of these other animals might have a prior claim. Several of them also had the kind of branched limbs with which we are n o w familiar. "Tracks" scraped by such limbs are familiar as fossils, even predating the appearance of the body fossils themselves by a short time. It had been assumed that these tracks—which carry the names Rusophycus and Cruziana—were made by trilobites, but that was

T h e original text reads "Silurian" where I have written {Cambrianl. At the time Darwin wrote the distinction between Cambrian and Silurian strata had not yet been recognized (see Chapter 2).

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when trilobites were the only k n o w n possible culprits. N o w there were many other possibilities. So the discovery of the Burgess Shale and other, even earlier Cambrian fossil softbodied faunas made everything more complicated.

Notwithstanding, I shall try a simple explanation.

When Harry Whittington and his research students Derek Briggs and Simon C o n w a y Morris (now famous professors in their own right) minutely studied the Burgess Shale animals in the 1970s and 80s they tended to emphasize the peculiarities of the fossils they studied. They were, after all, describing the costumes of spectacular performers for the first time in detail since Walcott had pulled back the stage curtains.* T h e distinctiveness of the limbs of some species, carapaces of others, uninterpretable features of yet others seemed to support a notion then current that arthropods (and by extension other kinds of animals) had appeared from more than one ancestor.

This is correctly described as "polyphyletic" origin.

At the height of the popularity of "explosivism" polyphyly was rife. Harry Whittington once believed that the various kinds of Burgess arthropods arose separately from different soft-bodied ancestors in the Precambrian. At its extreme, this view had it that some of the Cambrian animals were so different in design that they merited being placed in the highest category of animal classification—a phylum. They were not molluscs or arthropods, or whatever, at all, but merited a separate phylum of their own, or so it was alleged. Simon Conway Morris is famously quoted as opening a drawer, encountering a new fossil animal, and exclaiming, " O h fuck, not another new phylum!" He has probably had cause to rue these words. At a more modest level, awkward arthropods that showed peculiar characteristics were regarded as repre*I should mention that a number of previous professors have had their turn at the Burgess animals. The arthropod studies of Percy E. Raymond of Harvard University in the 1920s and Lief Stormer of Oslo in the 1940s contributed much of interest to the story of their interpretation, notably the recognition of the "trilobite-like" limbs of these animals.

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sentatives of "failed designs." There was no shortage of these curiosities: arthropods with giant frontal appendages, or great feathery antennae, or huge numbers of segments. All were supposed to have appeared as a result of a special burst of evolutionary creativity at, or just before the base of the Cambrian, 545 million years ago. This was the "explosion." The dramatic appearance of a plethora of life on the geological stage was considered a true measure of evolutionary history.

Trilobites were just one of many designs thrown up at the same time, but they were undoubtedly part of it, and must have observed their idiosyncratic spindly or bristly neighbours through their unique crystal eyes. No other Cambrian "experiment" mastered that particular optical trick.

W h e n S. J. Gould explained an early version of the explosion theory in Wonderful Life, he described the various animals and laid out the conclusions he drew from them. He attributed, with some generosity, much of the novelty of the interpretation of Cambrian events to Simon Conway Morris; "as for so much of this book, I owe this example to the suggestion and previous probing of Simon Conway Morris" (p. 293) was a typical endorsement. The redescription of the Burgess Shale fossils was a team effort overseen by Harry Whittington. Different beasts were studied by Conway Morris, Derek Briggs, David Bruton and Chris Hughes. I had recently gained my first employment as a trilobite specialist when the "Burgess b o y s " were ensconced in their offices in the Sedgwick M u s e u m , Cambridge, where they spent all day, every day, feverishly preparing and photographing and discussing their marvellous animals. I was a fascinated bystander who participated in the conversations and speculations as they happened.

I pored with Derek Briggs over fossils of the arthropods Sanctacaris or Canadaspis on their quotidian wooden trays, containing slabs of black shale which looked so ordinary yet carried on their surfaces such extraordinary objects. From the outset, I was interested in how the newly interpreted animals would cast light on the affinities of trilobites. Curiously, I do not 130

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remember hearing the word "explosion" once in those early days.

As with most new and attractive theories, it was not long before all manner of other sources of evidence were recruited in support or explanation of rapid evolutionary turnover at a critical time. We met Hox genes in the last chapter: those genes which control aspects of the sequence of development in all animals. Arthropods are typically composed of "packages" of segments—the reader will by now be familiar with the trilobite's own arrangement of cephalon, thorax and pygidium. But these packages are differently arranged in the various major kinds of arthropods: the head may contain different numbers of segments, as may the thorax. They are like trains buckled together with different arrangements of carriages and cars. One theory suggested that the Cambrian "explosion" might record a critical period in the expression of Hox genes, which at that time, uniquely, were "switching o n " new arrangements of batteries of limbs and segments. The Hox genes functioned like the presiding genius of a biological marshalling yard, mastering new rolling stock. In the grand democracy of the early Cambrian a swarm of these creations could survive, and devil take the hindmost. Some would produce evolutionary progeny, others would fail after a geological moment of improbable fecundity. Yet another theory invoked a phase of doubling up of lengths of the genetic code at this creative time, a genetic change which increased the possibility of innovation and variation in body designs. It seemed for a while that Darwin's "inexplicable case" might be solvable after all. The "explosion" was a special moment in time—triggered, possibly, by some environmental threshold that had been crossed in the Cambrian world—when the possibilities of life gloriously expanded, and when parts in the evolutionary play became suddenly multifarious. For a while, any strange role was permitted. In popular accounts it became an ancient moment of madness, a magnificent evolutionary Mardi Gras, when a parade as bizarre as could have been 131

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devised by a surrealist on speed would be permitted for a geological day. "See the crystal-eyed monster!" "Roll up, roll up, for the shiny, tubiferous wiggly orphan thing with no relatives!" The freak show was open for trade.

It seems almost a pity to spoil the show, to strip away the dressing and reveal the actors beneath. Most of us prefer glamour to analysis—glamour can be enjoyed with a smile and a cheery wave, whereas analysis requires thought and intellectual work. But it is necessary to do this critical work, if only to understand the place of the trilobites in the Cambrian charivari.

From the first there were a number of scientists who doubted the account that Steve Gould had presented, however much they admired the manner of its delivery. I was one of the doubters myself, ever since I reviewed Wonderful Life in the magazine Nature shortly after its publication. At the time I had already started an attempt to look at the Burgess animals and their relatives in a different way.

This work was done jointly with Derek Briggs, who was so familiar with the details of the Burgess arthropods. Instead of emphasizing their peculiarities, we were looking for the significant similarities they shared with one another. The technique of analysis we used is called cladistics. Although its details are technical, the main principle of cladistics is very simple: it is an attempt to classify organisms on the basis of evolutionarily derived characteristics. To give an easy example: if a cladistic analysis were made of a shrew, an elephant and a lizard, the shrew and elephant would share several characters, such as uterus, m a m m a r y glands, warm-bloodedness and (patchily in the elephant, admittedly) hair, which would readily identify them as being more closely related to one another than to the lizard. Both shrews and elephants are mammals: we don't imagine that complicated characters like m a m m a r y glands arose on more than one evolutionary occasion. On the other hand, that both shrews and lizards eat insects while elephants digest trees is not an indication of 132

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biological affinity at all, but an expression of adaptations for earning a living. Nor does the peculiarity of the elephant, its ineffable trunk, make it a m a m m a l , or help us to decide whether or not it was more closely related to the shrew than to the lizard. Cladistics identifies only the significant advanced characteristics as the basis of classification, while similarities which are just a reflection of an earlier, shared history do not figure. The four limbs of lizard, shrew and elephant reflect the fact that all belong within a greater group—the t e t r a p o d s — with an ancestry stretching back to the Devonian, and do not contribute to solving the particular problem in hand.

So Derek and I had the job of enumerating all the characteristics of the Burgess Shale arthropods which were present on several animals—features of the legs, or the number of limbs incorporated into the head, for example. From the distribution of these characters we wanted to draw a tree diagram of the relationships of the fossils. As in any family tree of the Cholmondely-Smythes or the House of Windsor, we should be able to see who is most closely related to w h o m and how the more distant members of the family slot in. Except that we were dealing with c o m m o n ancestry, rather than pinpointing Uncle Ernest as an actual ancestor. The more animals you study, the disproportionately more possible ways of arranging them into trees there are; so you soon need a computer programme to sort out the best arrangement, especially if some characters may genuinely have appeared more than once during evolution. "Best" is, of course, a charged w o r d — how do you know what is best?—and cladistics programmes have various ways of deciding this, but most boil down to a preference for the simplest tree. In the late 80s most scientists interested in this technique were using a programme called PAUP (a simple acronym for the intimidating Phylogenetic Analysis Using Parsimony) developed by an American from Illinois, David Swofford. In evolutionary circles Swofford's name is about as well known as Hawking's in astrophysics.

We were stripping these Cambrian arthropods—including 133

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the trilobite Olenoides—down to their essentials to see if they would "fit" into a tree of descent. If some of the "oddball" animals could be accommodated convincingly into the tree, then it would mean that their distinctiveness might have been over-emphasized by the explosionists. They might have been too easily dazzled by their spectacular motley, to the extent that they failed to see that underneath they shared a common dress.

What surprised us was h o w easily we could produce a tree relating nearly all of the Burgess Shale arthropods. This was the first time that such an objective tree of descent had been produced, and one of the most interesting things to us was that the trilobites were quite high up within it. So much for their traditional role as the archetypal primitive arthropod!

If they had been primitive then they would have been somewhere near the base. Suddenly the distinctiveness of the crystal eyes seemed to make more sense. Then the idea that the different arthropods arose independently was knocked severely by the fact that a perfectly reasonable tree of descent could be reconstructed,

with all

the arthropods having

descended, ultimately, from a c o m m o n ancestor. Some of the strange arthropods from the Burgess Shale were truly no stranger than trilobites—it is just that we have had a hundred years or more to get used to trilobites. Familiarity breeds, well, familiarity. If there was an "explosion" then it was a remarkably orderly one. In detail there were many problems with our aboriginal tree, which was very much a first attempt—and crude, as such attempts always are. But in the ten years that followed other people have tried their own versions, including our own friend Matthew Wills, and many of the original features have been preserved. In other words, our tree must have had a germ of truth.

Derek and I thought we would publish this tree as a paper in the journal Nature, but Nature had other ideas. The reader should k n o w that publication in a scientific journal is no sim-

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pie process. You must submit the manuscript to the journal, obeying to the letter all caveats about format and length. Then the journal will send the paper out to referees, and if it is Nature you will probably have the pickiest referees in the business. In the majority of cases they will recommend "rejection."

Only geniuses like Richard Feynman or Stephen Hawking routinely get a " y e s " — e v e r y o n e else endures some degree of pain. No first-time novelist suffers more when the terse note comes back, saying "The editors r e g r e t . . ." So you can imagine our level of disgruntlement when the paper describing the Burgess tree was given the b u m ' s rush by Nature. We licked our wounds and resubmitted our paper to the North American equivalent of Nature—Science (New York)—which is about the only scientific journal with an equal reputation. To our relief, after a month or two's agony, the little paper was accepted and was published in 1989.

Since then a great deal more has been learned about the fossil faunas that preceded the Burgess Shale in even earlier Cambrian time. It has been made abundantly clear that many of the arthropods that were described from the Burgess Shale now have relatives in older Cambrian strata. From China, the Chengjiang fauna has yielded many beautiful animals. The story of their description makes the Burgess Shale controversies seem almost decorous. Rival teams of collectors have been racing to be first. Peasants have been paid to come up with the goodies, even whisking fossils out from under the noses of their competitors. There have been rival publications.

Cloak and dagger has been followed by backstabbing. Chen Jun-yuan and his team of westerners have tried (with some success) to race ahead of Dr. Hou and his alternative team of westerners. Sometimes, you don't know which n a m e you should use for a given fossil, Chen's or Hou's. Greg Edgecombe, an incorrigibly amiable naturalized Australian, w h o has done much to make these animals known to the world, whistles through his teeth when I mention future Chengjiang

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visits to him. " N e v e r again!" he says. "Not f****ing likely!"

There is something about these ancient fossils that excites four-letter words.

Science, of course, does not give a fig for these examples of internecine warfare. The truth will out, and it matters not if it is at the cost of bruised egos or skulduggery. Some time in the next decade or two all the vested interests that have fought over Chinese fossils will seem as tragi-comic as the nineteenth-century battles between Professors Marsh and Cope to name the greatest numbers of dinosaurs in America. As far as the "explosion" is concerned, the continuation of evolutionary lines back into strata earlier than the Burgess Shale simply increases what Gould later called the "intrigue and mystery" of events at the base of the Cambrian. If you add to the brew the B r i g g s / F o r t e y tree (or one of its better subsequent versions) there is a very simple question to be asked. If the different kinds of arthropods extend to the early Cambrian (including trilobites, which are near the top of the tree), then must it not be the case that the only time for the still earlier branches on the tree to have split is within the Precambrian?

And since these arthropod branches will connect in their turn with still more and deeper branches in the branching history of the whole of animal life, this takes us somewhere still older and more profound again. You cannot have a great-grandson without a great-grandfather. We have already met this argument with regard to the history of eyes in the last chapter.

Eyes are deeply implicated in the history of life. The eyes of trilobites are tied by a genetic bond to other eyes in other animals, all the way back to the first simple eye-spots. The estimates of divergence between major animal groups based on molecular clocks (which have faults, admittedly) is somewhere between about 1000 Ma and 650 Ma, but both are substantially before the Cambrian at 545 Ma. Maybe that dazzling opening scene of animal life blinded us to a modest, and much longer earlier drama after all.

Some years ago I made a straightforward observation 136

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about the very earliest trilobites. W h e n they first appear in the Cambrian strata, they are already different in various parts of the world: not just different species but different g e n e r a — even families. If you go to China you will find specimens of a compact little trilobite called Parabadiella—but not Olenellus. If you go to N e w York State you will find Olenellus and its friends—but no close relatives of Parabadiella. If you go to Siberia along the Lena River in the mosquito-ridden summer you will see the best exposed Cambrian in the world, but the first trilobite you find will be yet another one, Profallotaspis.

Since all trilobites probably descended from a single ancestor it seems obvious that we must be missing a phase of their fossil record—the time required to evolve their different forms in different areas. It all points to some considerable history missing from these particular rock sections at the base of the C a m brian. This is proved beyond doubt in those beautiful Lena sections where you can see the effects of erosion before the appearance of the Cambrian fossils. Is this erosional phase the time for the trilobite to be "descended from some one crustacean . . . before the beginning of the C a m b r i a n " described

by Charles Darwin?

One thing of which we may be sure is that the trilobites were not descended from any sort of crustacean—trilobites and the arachnid horseshoe crab Limulus (p. 158) shared a common ancestor, which in its turn shared a c o m m o n ancestor with the crustaceans. Trilobites were distant cousins, not progeny of the crustaceans. But it is also true that m a n y of the fossils that fit in low on the tree of descent of the arthropods shared features that once upon a time would have been thought of as typically trilobite. Those limbs with two branches that C. D. Walcott laboured so hard to reveal turn out to be very common among all manner of Cambrian soft-bodied arthropods, too. Arthropods leading to crustaceans probably had them—as did those that would lead on to Limulus and scorpions. In a word, biramous limbs are primitive. Any one of these animals could have scraped simple 37

1

T R I L O B I T E !

trails like the ones found in the earliest Cambrian of all in eastern Newfoundland. Some other facts are also becoming clearer. The closest relatives of the typical arthropods are some little animals with stumpy legs known as velvet worms (Onychophora). They still live today—mostly under rotting logs in warm, d a m p climates. In the Cambrian they were m u c h more numerous and varied, but also submarine. Graham Budd has shown how a number of really weird-looking creatures are velvet worms at heart. So is the once nonpareil oddball from the Burgess Shale, Hallucigenia. It is a measure of h o w misleading Gould's theory would have been if taken at face value: these animals which were once touted as designs of u n c o m m o n originality would have been simply labelled "failed experiments" and there's an end to it. As it now is, they have been recognized as important steps in our understanding of the subsequent history of life. The lesson of cladistics is that it is what animals share that is important in identifying their relatives, not our subjective judgements about oddity. We must focus on the elephantine w o m b , not the trunk, if we want to place the pachyderm in the scenario of Nature.

So now we are left with a paradox. There is a tree of descent which helps us understand the history of our characters before their spectacular appearance on stage—but of this earlier history there is no evidence. Even the traces left by animals, their scratches and burrows, are rare before the latest Precambrian.* Where can the animals be? Either all the rates of origination must be speeded up beyond comprehension in the " e x p l o s i o n " — a n d out of this "explosion" a variety of trilo-

*As this is written there are new reports from India of much older tracks and trails, in rocks up to a billion years old or more. There is little doubt that these markings were made by animals, and indeed it is a scandal that previous reports

by Indian geologists and published in Indian journals have hitherto been ignored.

There is however some reason to question the accuracy of the dating, and for the moment final judgement must be suspended.

1 8 3

Exploding

Trilobites

Anomalocaris, at first claimed as a "weird wonder," but n o w known to be related to primitive arthropods and hence to trilobites.

bites must crawl alongside everything else—or there must be some other explanation. Like T. S. Eliot's Mystery Cat: But

when

you

reach

the scene of crime McCavity's

not

there!

The explanation of missing time might apply to some rock sections, like the Siberian ones, but it does not work for eastern Newfoundland where the rocks record a complete narrative. My favoured theory is that the earlier branches in the tree were tiny animals, which were not easily preserved as fossils.

It is not necessary to be large to be a perfectly good arthropod (or mollusc, come to that). The sea swarms with tiny arthropods today that have left no fossil record. I like to quote the tiny copepods, which are members of the plankton so numerous that they can turn the seas black. Yet almost their only fossil is a species preserved in the body of a fossil fish. Were it not for their miraculous preservation in amber our knowledge of 139

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past insects would be dreadfully inadequate (as it is, we know from amber hundreds of the most delicate of all, mycetophyllids, the fungus gnats, so delicate in life that a puff of wind destroys them). What happened at the base of the Cambrian was probably as much an increase in size as a sudden appearance of n e w types of animals. This may well have been a genuinely rapid change. We know from many fossils that increase in size is quite an easy goal in evolutionary terms. Mammals, for example, seem to have undergone a very rapid increase in size after the demise of the dinosaurs 65 million years ago. It even seems possible that the same size increase allowed the possibility for the secretion of shells. Muscle support becomes m u c h more crucial when an animal reaches a certain critical size. So the "explosion" was a dramatic appearance of characters that had been rehearsing out of sight for more than a hundred million years.

The explanation just given holds out the possibility of discovery. M a y b e one of the readers of this page will discover the Precambrian equivalent of amber. Very recently, a late Precambrian animal embryo was discovered in China, amazingly preserved cell by cell in the mineral calcium phosphate; age by itself is evidently no proof against miracles. It would be wonderful to amaze the world with proof of the missing stages of evolution, tiny animals that set the designs for the future of life. Somewhere, there should be a small trilobite, an animal with the potential for spinning an almost endless variety of costumes for three hundred million years. The search continues.

This is not quite the end of explosions.

There have been several more accounts of the Burgess Shale and the Cambrian since Wonderful Life. Most of the arguments about the truth or otherwise of the "explosion" of phyla have been in the pages of scientific journals, in which a convention of decorousness is observed. Toujours la politesse!

Steve Gould knew that I did not agree with his conclusions, but this made no difference to the cordiality with which we 140

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could meet: we could wave across a conference room without any gritting of teeth. I do not suppose he was tempted to take a small model of me and stick pins in it, any more than I was tempted to steal some of his personal effects and cast a hex.

Scientists seldom do things like that: what they are chiefly interested in is the advancement of truth. Richard Dawkins tells a good story about a senior professor coming on stage to shake the hand of the young scientist w h o has just disproved the old man's most cherished theory: the older man earns a standing ovation. Well, that is how it is supposed to be, according to the etiquette books.

The Smithsonian in Washington, D C , mounted a Burgess Shale exhibition, where the public can see the extraordinary beasts for themselves: the accompanying literature is unobjectionable, and factual enough. At about the same time as this exhibition was being opened, the extreme of "explosiveness" emerged in a book by the two McMenamins, Mark and Dianna—professors in a small East Coast university—called The Emergence of Animals (1990). In this work they claimed up to a hundred* animal phyla "exploding" into life in the C a m brian; most of them are also claimed to have died out, leaving no progeny. They popped up like so m a n y jack-in-the-boxes, and then auto-destructed, in the manner of some post-Dada extravagance designed to outrage. This view out-Goulded Gould ten-fold. The extraordinary thing to an objective reader is that there is no attempt to justify why these hundred or so "Cambrian phyla" should be recognized as one of the great divisions of the animal kingdom—how, exactly, do they differ from each other so much that they " d e s e r v e " to be called a phylum? Not a word. How do so m a n y of these separately evolved creatures share curious similarities unless they were descended from a common ancestor? And if they were so *Most modern textbooks list about thirty phyla in the living fauna, which embraces all the extraordinary diversity of organisms. Each phylum represents a fundamentally different design in anatomical organization. Thus the McMenamins identify at least a three-fold richer world in the Cambrian.

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T h e place of trilobites in the emergence of animals in the early Cambrian, after M c M e n a m i n and M c M e n a m i n , The Emergence of Animals ( 1 9 9 0 ) . But where are the ancestors of the trilobites?

descended—then surely they belong to the same phylum? Not a scintilla of discussion. O n e is driven to the conclusion that these particular writers regard it as only necessary to appear on the Cambrian stage dressed in any sort of odd costume to be called a phylum. The time of the performance alone is a guarantee of novelty.

Nearly ten years after Wonderful Life appeared another book made an even more explosive sally into this arena. This time it was written by the star of the original Cambridge enfants

terribles—and

the hero of Gould's Cambrian

Weltan-

schauung—Simon C o n w a y Morris. In the ten years or so since Steve Gould transcribed the significance of the Burgess Shale for the world (at least, his view of what was then understood in Cambridge), Simon had had plenty of opportunity for second thoughts. His revised view now is apparently like 142

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that I sketched earlier: a rather defused "explosion." Simon both accepted the need for an earlier history of animals and rightly pointed out the ways in which the Cambrian remained a distinctive period, when shells appeared, genuinely rapidly, alongside good fossil faunas of animals that lacked them.

There was nothing very incendiary here. I would say that Simon had come around to seeing the Cambrian faunas in their context at a crucial phase in the genealogy of life. The explosions were reserved instead for Stephen J. Gould. I have never encountered such spleen in a book by a professional; I was taken aback. Gould doesn't write, says the author, he produces "perorations." He lacks originality, while laying claim to it. This little passage from The Crucible of Creation (1998) will give something of the flavour: "Again and again Gould has been seen to charge into battle . . . strangely immune to seemingly lethal lunges . . . Gould announces to awestruck onlookers that our present understanding of evolutionary processes is dangerously deficient. . . We look beyond the exponent of doom and there standing in the sunlight is the edifice of evolutionary theory, little changed." This is a rather gassy way of saying that Gould is a mountebank.

It is one of humankind's less attractive foibles that success breeds envy, and since there is probably no one in biological science to rival Steve Gould in worldly and critical s u c c e s s — at least among the literati—it is not surprising that some of his rivals for the spotlight focus their attention upon him. It is, of course, perfectly legitimate to have differences of scientific opinion—in fact, it is an essential ingredient of progress. But what surprised me here was the unwonted explosiveness, the bilious ballistics. The detail of the attempt to cast Gould in a poor light extended into the depths of footnotes. Gould (and R. C. Lewontin) wrote a famous paper in 1979 with the rather overblown title " T h e spandrels of San Marco and the Panglossian paradigm: a critique of the adaptationist programme." But it addressed an important point about whether all structures found in Nature had to have a purpose. In one of 143

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his virulent footnotes Simon Conway Morris takes Gould to task for architectural inaccuracy—apparently the structures in San Marco should not be called "spandrels" at all! Tsk, tsk—as if such a terminological pinprick could puncture all the inflations of the paper. Such hypercritical zeal has to well up from a deep source. W h y should Simon wish to bite the hand that once fed him? If you look at those little silvery fossils in their neat trays it is hard to believe that they can be the origin of such dispute; nor should trilobites and their allies take responsibility for any verbal bombardments. Conway Morris and Gould subsequently slugged it out in the pages of the magazine Natural History. I do not subscribe to the cynic's view that such disputes are part of the " h y p e " to increase book sales—such antipathy cannot be faked. I was reminded of a ballad by Bret Harte ("The Society upon the Stanislaus"), describing a nineteenth-century fracas in a scientific society over—what else?—fossil bones: Now, I hold it is not decent for a scientific gent To say another is an ass—at least, Nor should Reply In

less

In a And

by

the individual heaving

rocks

who at

to all

happens

him

intent;

to

be meant

to any great

extent...

time than I write it, every member did engage warfare with

the remnants of a

the way they heaved

Till the skull of an

those fossils

palaeozoic age; in

old mammoth caved

their anger was a sin, the head of Thompson

in.

I could only diagnose the cause of Simon's ire as being the very praise that Gould once heaped upon him. To return to Richard Dawkins's story, this is like the young professor stamping hard on the foot of the older professor. Wonderful Life was such a global success. There, preserved in the aspic of a print that could never be unprinted, was the Conway Morris of "oh fuck! not another new p h y l u m ! " — t h e Conway Morris of the early 1980s. The nineties version disowned the ideas of 144

1 9 . Crotalocephalus. T h e glabella has b e c o m e completely c r o s s e d by strong furrows. The thoracic tips are produced into long spines, as is the pygidial margin. The lateral view shows h o w the thorax can arch up, and shows the convex eye lobe. Devonian, Morocco.

20.

RICHT

Acanthopyge, a trilobite related to Lichas. T h e size of a crab, with a very peculiar glabella and a pygidium which is larger than the headshield. Devonian, Morocco.

21.

FAR

RIGHT

A relative of Scutellum, Thysanopeltis, with an e n o r m o u s , fan-like pygidium which is much longer than the head shield. S p e c i m e n s are often 10 cm long.

Devonian, Morocco.

2 2 . A cluster of five Ci/phaspis from the Devonian limestones of Morocco; very similar trilobites can be found worldwide. This particular species had a pair of "devil's h o r n s " on the glabella. A long spine on the thorax may have helped the trilobite right itself if it landed on its back; the pygidium is comparatively small.

23. O n e of the survivors among the trilobites, Griffithides, from the Carboniferous (Mississippian) rocks of Indiana. Specimen about 5 cm long.

24. Paraharpes, a remarkable animal in which the genal spines are prolonged into a " b r i m " which extends alongside the length of the trilobite.

T h e outer part of the brim is flattened for resting on the sediments. This trilobite has very degenerate eyes and numerous thoracic segments (length usually 5 - 6 cm). Ordovician, Scotland.

25- A close relative of Ampi/x, Cnemidopi/ge, from the Ordovician shales of central Wales. A blind species, which carries a spine on the middle of its head like a rapier. T h e genal spines are equally long (the one on the right is shown here) and extend backwards beyond the body of the animal, which has six thoracic segments and a strongly furrowed pygidium.

26. Three blind trilobites. A group of three specimens of Conocoryphe from the Cambrian of Bohemia (modern Czech Republic) made famous by Joachim Barrande. Two of the specimens are preserved right way up, the third on its back. Note the comparatively small tail, and the fourteen thoracic segments. This is one of many Cambrian trilobites with a "flowerpot-shaped" glabella.

27. A B O V E O n e of the " s t r a w b e r r y - h e a d e d " trilobites of the Silurian period, Balizoma variolar is, beautifully etched out in natural relief. T h e pygidium begins after the twelfth thoracic segment. T h e head is richly covered with coarse tubercles. From the Wenlock Limestone (Silurian) of Dudley, Worcestershire, UK.

29. Selenopeltis, a trilobite in which the tips of the thoracic segments, like the genal spines, are enormously elongated. This specimen is from the Ordovician shales of Wales; similar specimens can be found in France, Spain, the Czech Republic and Morocco. These occurrences help to define the Ordovician continent of G o n d w a n a .

28.

O P P O S I T E B O T T O M Pagetia, a diminutive, flea-sized trilobite with two thoracic segments and a long pygidium the same size as the head. This trilobite is related to the blind

agnostids, but actually retains a small eye set far out on the cheeks. This example is from the Cambrian rocks of British Columbia, Canada.

30. A beautiful moulted, cast-off exoskeleton of Leonaspis. See how the free cheeks have been cast off to either side as the facial sutures have been opened under the influence of moulting hormone. The "soft-shell" trilobite crawled off forwards and away to grow a new hard shell. Specimen about 1.7 cm long.

31. Sao hirsuta from the Cambrian of Bohemia (modern Czech Republic). The growth from babies of this species is illustrated on p. 225.

This trilobite has a strongly furrowed glabella, moderate-sized eyes and tubercles on its cheeks. Sixteen thoracic segments, and the pygidium is small.

32. O n e of the plates from Barrande's magnificent work on the trilobites of Bohemia. The original is quarto, and so the details are even clearer. These are odontopleurid trilobites.

33- Trilobites as sympathetic magic. A piece of one of the "swallow stones" from the Cambrian of Shandong, China, abounds with heads and tails of at least three species of trilobites. (Photograph courtesy Adrian Rushton.)

34. The fantastically spiny trilobite Comma, from the Devonian of Morocco. T h e vertical spines are a masterpiece of preparation from inside the limestones in which this trilobite is found.

Exploding

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the earlier one, and quite right, too: scientists are supposed to move with the times. But what was lacking was any acknowledgement that the earlier version had existed at all. It was an extraordinary revision of history in favour of the present.

So the root cause of Simon's explosion was not envy of Gould, but resentment of the hold he had on the past. The casual reader of The Crucible of Creation, unaware of the history, would never gather that the author's views had once been close to (if not actually shared with) Gould's.* Such a reader would never guess that Simon received the Schuchert Medal of the Paleontological Society of America, a signal honour, in 1991, and endorsed by Gould. "History is b u n k ! " Henry Ford said in 1919. Such sentiments may not be inappropriate for an automobile manufacturer, but they do little credit to a historian.

As for the trilobites, they have witnessed it all, and I shall try to take the long view through their crystal eyes, indifferent as they are to the splenetic explosions of mere humans. In the minds of their devotees they have travelled from being unexplained mysteries to becoming cousins of crustaceans; they have journeyed briefly towards being a phylum all of their own; now they have arrived back, where they belong, among the other arthropods, and closer to Limulus than Darwin believed. They have had theories about their closest relatives exploded and they have been caught in explosions. Maybe it is time to pack away the dynamite and let the explosion metaphor rest for a while. It's caused quite enough trouble. *Some of those, like Richard Dawkins, w h o have responded positively to C o n w a y Morris's criticisms of Gould also seem to have been poorly versed in the history of the "explosive" opinions. Opponents of Gould in other arenas, they have used the book as a stick to beat "the sage of Cambridge (Mass.)," operating on the principle: "my enemy's enemy is my friend."

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VI

Museum

W h e n indolent holiday crowds saunter through the galleries past mounted skeletons of extinct animals, or scan simulacra of dinosaurs jerkily attempting to persuade the viewer that a hundred million years can be wished away with latex and mechanical bones, perhaps one in a dozen of the visitors might notice a door in the wall behind the monsters. A wellpolished mahogany entrance, it can only be opened with a special key. Once in a while, a curator will emerge from the door and pause for a second, as if slightly overwhelmed by the sight of the throng. This is the door which leads away from the show of exhibition and into another world: the reality of collections of bones and shells.

I went through that inner door for the first time more than thirty years ago. W h e n I joined the staff of the Natural History Museum in London it was known in the trade as "The BM." The British Museum: it was a grand title inherited from grand days. The natural history collections had long since split off from the antiquities which stock the shelves in the great building at Bloomsbury: pharaohs and pharmaceutical phials, longboat treasures and lorgnettes; and their research departments of Antiquities, Egyptian, Classical, Oriental or whatever. But the BM we remained—officially, the British Museum (Natural 146

Museum

History). In Italy, my colleagues still refer to us as "II Britannico," a wonderfully absolute description that embodies an essentialist view of the nation in its collections. It was, I realized, akin to entering a holy order, complete with the vow of poverty. But I was a fortunate man, one of the few whose dreams of employment coincided exactly with reality. I, who had fallen in love with trilobites at the age of fourteen, was to be one of the few people in the world paid to do what I would have done for nothing! I was issued with The Keys. These were a set of heavy steel keys, of the kind usually used to lock up prison cells. They were held on a steel ring, and, so I was told, I had to keep them on my person at all times. On the keys were etched the words "20 shillings reward if found," dating from the days when a quid would take you and your sweetheart out for a fish supper, and the change would pay the bus home.

Almost all doors opened effortlessly under their charms. There was a full-time locksmith closeted in a room that Charles Dickens would have recognized, whose job was to ensure that keys glided into locks with the intimacy of warm handshake.

I was assigned to the Palaeontology Department—to the vanished world of extinct life. W h e n I first joined the staff of the Natural History M u s e u m my office was part of the maze.

Tucked inconspicuously under the great ceremonial M u s e u m entrance, a Gothick cathedral door decked with motifs from nature, my office also housed most of the trilobite collections in magnificent old cabinets—the room exuded the scent of scholarship. There was even an iron balcony that ran around the midriff of the room, with more cabinets above. Outside the office, an elephant, no longer required for display, peered out from under a dust sheet. In this place the world authority on barnacles, T. H. Withers, had once worked. So had my predecessor, W. T. (Bill) Dean, who had also studied trilobites in the same room, before he had been tempted to a job in Canada.

This was fortunate for me, because jobs at "The B M " were rare opportunities. A round hole opened, and a round peg was available to fill it.

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A tray of trilobites from the huge collection in the Natural History M u s e u m , London. Their labels recall essential information about where and when collected, and by w h o m — a n archive for civilization.

W h e n I received my first job description it said "to pursue research upon the trilobites" which was rather like saying " a m u s e yourself for money." To my fellow commuters on the 8:02 from Henley-on-Thames, Oxon, it probably still seems like that. As they prepare to wrestle with takeover bids, draft complex memoranda for Civil Service Committees, or design new ways to advertise beefburgers, I still march off to the trilobites. " W h a t do you actually do?" they ask with genuine and bemused curiosity. Well, the basic job in a national natural history museum is to do research on species. Other things flow from it, but an understanding of diversity underpins just about everything else. I am one of a few researchers privileged to name species (in the somewhat pompous language of the trade, "a species new to science"). These are, if you like, the atoms of all subsequent speculations. This is not the glam148

Museum

our end of science, where galaxies are playthings and subatomic particles the stock in trade. This is the biological shop floor. Let me explain.

Nobody knows exactly how m a n y living species there are.

Some kinds of animals—birds, for example—are large and showy enough for new discoveries of unnamed kinds to be rather rare. But as for beetles, only a fraction of the species that thrive in trees or under rotten logs have been named: the job of nomenclature is endless (ask any Beetle Man). For the geological past the problem is a little different. We can sample only a fragment of everything that once lived. We depend on the preservation of the fossils in the rocks, itself a capricious business; we depend on luck in discovery—the right hammer in the right place at the right time. Trilobites, it will be recalled, are usually fragmentary, so we depend most of all on the persistent collector to find all the bits and pieces. Then we can set about deciding if there is a n e w species under the microscope. This is not an easy business.

In the first place: what is a species? A m o n g living animals it is usually easy enough to discriminate species: closely related species differ consistently in details which can be readily recognized by the trained eye. Two common European birds included in the same family, song thrush and blackbird, are easily distinguished by their plumage, eggs, songs and behaviour, despite a general similarity; nor do the even more closely related mistle thrush and song thrush long confuse a practised bird watcher: the differences in their songs and habits are discriminants enough. But for fossil trilobites all we have to go on are shed carapaces. Fortunately, trilobites are rather like thrushes in one respect—they have different "plumages"—their surfaces often carry beautiful and characteristic details of design and sculpture that are very probably the reflection of true differences between species. Separate but related species often advertise their distinctiveness in just this way: it is a method of making sure that breeding with the right mate occurs. It is broadly the same principle that ensures 149

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that rockers bond with other rockers (studded leather jackets), rather than with, say, followers of the Hare Krishna sect (robes and shaven heads). Given well-preserved material we can recognize a fossil species as truly distinctive with almost the same confidence as with a living species. How, then, do we record this realization—turn our recognition of a new species into an official statement?

This is where scientific publication comes into the procedure. You cannot just get out of bed on a wet Monday morning and decide to make some new species. A species does not officially exist until its publication in a scientific journal. The author—often an authority—proposes the species as new and says exactly why, with appropriate illustrations. It is a serious business. You must discriminate the new species from all the others described within the same genus: in the jargon, you are obliged to "diagnose" it. This means that you have to sift through a dozen or more scientific papers, to compare the specimens in hand with all the other related species which have ever been named. This can be a laborious process, not least because the papers in question may well be published in obscure journals originating from Novosibirsk, Norwich or N e w Delhi. It will be obvious that to have a good library to hand is a tremendous boon to the specialist. The reference libraries attached to the great museums complement the collections as fuel does a motor. If, by mischance or laziness, you do not do your literature search thoroughly you could neglect a publication which actually named your species first: then, sadly, your name would be doomed to synonymy (which is a taxonomist's way of saying sunk into oblivion) because the oldest name carries priority. Scientific names are not like the street names in East European cities that change according to the political complexion of the day. They are well-nigh permanent.

A rose by any other name will always be Rosa to the botanist.

A new species has to have a new second name—the specific name. Long years of tradition (shortly to be brought to an end) have set up rules about the classical form of species 150

Museum

name. It has to be derived from the Greek or Latin root of the appropriate word, so, for example, a beautiful species could be christened pulcher, or even pulcherrima if it was very beautiful indeed (from the Latin). It could not be verypretti, or jolliattractivi (from the vernacular). Rosa pulcherrima would be quite in order. Rosa pulcherrimus would not, because the endings of the genus and species are supposed to agree in gender—it is a matter of euphonious sound, if nothing else. I have always rather liked this adherence to classical roots, if only because it serves to link me with the pioneer taxonomists of the eighteenth century, who wrote in Latin and probably thought in it.

This much I share with the great John Ray and the incomparable Carolus Linnaeus (or Karl von Linne, to delatinize him).

We are all linked through the great endeavour of classifying the natural world; across more than two hundred years we share the same passion for ordering our knowledge. I actually rather relish trawling through heavy old dictionaries compiled by learned classicists (I have Lewis and Short's Latin Dictionary in front of me as I write) to look up the word for, say, "blushing," or "warty," to attach it to a species, and I love to read the quotes from Ovid that justify the usage. This adherence to a past classical culture is a bond, not bondage.

The next stage is that you are obliged to fix your new scientific tag on a particular specimen, the fons et origo of the name, which will carry its imprimatur for ever. This is the type specimen (or holotype) of the n e w species. Here the m u s e u m acquires its peculiar importance. The type specimens of species are housed there in perpetuity. The collections are the ultimate reference for the variety of the natural world, past and present. Alongside the type specimens are all the other collections made from everywhere from Antarctica to Ecuador, Tien Shan or Timbuctu, an inventory of everything alive or dead. In the Natural History M u s e u m the fossil collections alone occupy an area larger than a football pitch—and there are four floors of them. Each floor has row upon row of cabinets, and within each cabinet there may be forty drawers 151

T R I L O B I T E !

or so. Fifty specimens or more may reside within a single drawer: the mind soon reels if it tries to compute the number of specimens altogether in the collections. If I wish to compare a trilobite with some arthropod that is still alive I have to go to the Zoology Department. In the Spirit Building there are thousands upon thousands of jars containing fish or snake, octopus or lobster, pickled to the life. There are lizards collected by Charles Darwin. There are worms dredged from the bottom of the deep sea. Here is the one I wanted: a large relative of the woodlouse called Serolis which lives on the sea-floor under the Antarctic icecap. It looks superficially like a trilobite (although it is not a close relative) and I wanted to check a detail of its thoracic structure. Passing on, I do not have to be overtly anthropocentric to see in the turned-down lips of codfishes a depressed commentary on spending a hundred years in a jar. Colour fades, so that the ghostly quality of spirit preservation seems to match the antiquity of the specimens.

As you slide the doors back upon this pallid parade of containers and bottles your voice automatically loses decibels.

You reflect: mortality, this is your sad face; you defy decay only as a ghastly pickle.

Thus, after a species has been named, other scholars can always refer to the type specimen itself if they wish to know whether an example they have in hand is the same, or a different species. A number, usually written on a little label and glued to the specimen, is assigned by the curator, official scribe to biodiversity, which uniquely identifies that particular individual for reference (computers have made all this information much more easily available). The holotype has somewhat declined in importance since a less essentialist view of species has prevailed; it has been realized that a population of a type collection is preferable so as to give some account of variation in nature—after all, no two animals or plants are exactly alike. This enhances the importance of the whole collection m a d e along with the type (some of these specimens are referred to as "paratypes"—literally, by the 152

Museum

side of the type). In the Spirit Building there are types of species so rare that one of those pale faces looking out at me from their jars might be the only specimen known. Perhaps it is no wonder that it has a gloomy demeanour.

I look forward to the time when images of these type specimens can be summoned up globally on the World Wide Web. Suppose a researcher in Sibumasu wonders whether he has the same butterfly species as one named a hundred years before by one of the early western explorers: all he need do is log into the appropriate website on his field computer, and there will be a gallery of holotypes in living colour for him to compare with the specimen he has in his hand. All that century-long tending with naphtha balls, and the curator's dedication to numbers and records will have been justified in that moment. Only by such definitive reference can we truly know what lives where, and in what numbers. I believe it will remain necessary to summon such living, visual images for a long while yet. D N A "fingerprints" of species are becoming increasingly important, but they do not substitute for the wonderful subtlety of the h u m a n eye in judging similarities and differences. It will continue to be more practical and speedy (and cheaper) to " d o it by e y e . " After all, fine discrimination is probably the reason why the eye and brain have become so supremely gifted in our own species.

My part in this endeavour is to be one of the few people privileged to name new species of trilobites. The routine with fossils differs little from the procedure with butterflies, although the holotypes of new species are usually less fragile than lepidopterans—I have collected many of them myself, and with a hammer. Some fossil species are rare because they are difficult to collect, which may not reflect their original rarity in nature. They m a y be very spiny, for example, or thinshelled. Over the years I have named more than 150 n e w trilobite species, and it still gives me a little buzz to know that I have discovered a species "new to science." There have been a few genera, too. Only once have I skirted nomenclatural dis*53

T R I L O B I T E !

aster. I decided to name a pretty new trilobite after an obscure Phrygian nymph, Oenone, a name I had trawled from one of my classical sources. It just sounded rather attractive, suitable for the animal. Fortunately, I discovered at the last minute that the same n a m e had already been used for a worm, of all things. This is completely against the rule-book, which is a tome published in English and French called Rules of Zoological Nomenclature. I have to say that of all forms of bedtime reading, with the possible exception of Kennedy's Latin Primer, the Rules take the biscuit for being the dullest conceivable. It is a set of "thou shafts" and "thou shalt nots" for the naming of animals. Like annual accounts and railway timetables the Rules are necessary for the smooth running of the (naming) system,* but are also a pedant's paradise. One of the most important rules is not using the same generic name twice.

Happily, I was able to quickly alter my name to Oenonella before it got published, and this name had never been used before—so Oenonella it became, and remains to this day.

W h e n you name animals you are not allowed to be insulting to anyone, but the Rules do permit you to be nice and n a m e animals after colleagues. Two Czech palaeontologists named a trilobite Forteyops, and there is a Whittingtonia, and a Walcottaspis; thus may the worker be commemorated in the beast. Taxonomic legend has it that somewhere in the animal kingdom there is a suffix -chisme (from the Greek, and pronounced "kiss m e " ) which invites a researcher to add the names of would-be girlfriends before it—as in Polychisme, Anachisme, etc. I named a trilobite with a singularly hourglassshaped glabella monroeae (after Marilyn), and a friend of mine named a hunchback-looking fossil quasimodo. These little diversions actually help to make names more memorable.

To remind readers w h o may not be familiar with taxonomy, the generic name is the first one, and capitalized, and a given genus may contain a number of species, characterized individually by the second, specific name, which is not capitalized. Scientific names are always italicized to distinguish them from the vernacular.

154

Museum

The Rules do not allow you to n a m e a species after yourself, but jokes in naming are permitted if they do not cause affront.

It is not flattering to name a new species jonesi in honour of Jones, if you go on to describe it as "this diminutive and undistinctive species is a typical inhabitant of dungheaps."

Usually, species names just tell you, in Latin or Greek, something about the animal in question: Agnostus pisiformis (the pea-like agnostid trilobite), Paradoxides oelandicus (the Paradoxides from the island of Oland), and so on.

To the name is appended the namer. Thus, an unusually attractive Ordovician trilobite from Spitsbergen (named after my wife, naturally) is correctly known as Parapilekia jacquelinae Fortey, 1980. This detail serves the useful purpose of directing subsequent researchers to the reference where the species was originally described and named: a paper published by Fortey in 1980. In the case of species named a century ago, or more, subsequent accounts of the same species (revisions) may also have been prepared. Many palaeontologists that I have never met face to face probably k n o w me as an appendix to a name. I hope that they will be astounded by my youthfulness when we finally get to meet.

The familiar, if slightly garbled, quote from Romeo and Juliet, "A rose by any other n a m e would smell as sweet" implies that the naming of names serves little purpose. This same stricture might be thought to apply to the kind of science which was famously labelled "stamp collecting" by the physicist Ernest Rutherford—and taxonomy may well have been in his mind. That view could not be more misguided. Although the dubbing of scientific names may be fun, these same names can also be deployed for real intellectual purposes. Critical identification is central to some of the important questions I shall examine below. H o w can you talk about the diversity of life in the past unless the units of measurement (species, genera and the like) are accurately defined by competent taxonomists? How can you speculate on evolution unless you know that the species you are examining are likely to be real entities?

1 53

T R I L O B I T E !

H o w c a n y o u c e r e b r a t e a b o u t t h e a n c i e n t g e o g r a p h y o f life i f there are no reliable labels to place on this a n i m a l occurring in this continent a n d that o n e on the other? Three rhetorical questions in a r o w is about as m u c h of an indulgence as any book should be allowed, so I shall merely ans w e r my o w n chall e n g e s with: " O f c o u r s e y o u c a n ' t " a n d get off m y s o a p b o x .

B u t I s h o u l d say, pace R u t h e r f o r d , t h a t t h e p e r f e c t l y a m i able activity of s t a m p collecting differs f r o m scientific taxonomy. For any postage stamp, we can look up the date of issue in Stanley G i b b o n s ' s catalogue, check the colour, check the watermark, and check the perforation, even check the current v a l u a t i o n — t h e r e i s a s i n g l e , u n i q u e , right a n s w e r w h i c h i d e n tifies a n y s t a m p . B u t all q u e s t i o n s i n r e a l s c i e n c e a r e j o u r n e y s t o w a r d s the right answer. It is appropriate to recall Robert Louis Stevenson's aphorism: "to travel hopefully is a better t h i n g t h a n to a r r i v e . " S c i e n c e exists in a c o n t i n u o u s spirit of m o v i n g o p t i m i s m . W e c a n n e v e r k n o w for sure t h a t a t r i l o b i t e species recognized by my considered and experienced observations of features of the glabella and p y g i d i u m w a s actually a real, biological species w h e n it lived h u n d r e d s of millions of years ago. It often happens that another worker comes along a n d disagrees w i t h my species, alleging that it m i g h t merely be a variety (usually of o n e of his). T h e r e is no final arbiter on such matters. Nor can we ever reconstruct a long-vanished biological w o r l d w i t h certainty, for every reconstruction is only as g o o d as the scientific inferences that have b e e n m a d e about

it,

and

these

inferences

are

subject

to

continuous

change. H e r e are t w o e x a m p l e s . First, it is only a few years since we realised that there w e r e phases of high and l o w carbon

dioxide

atmospheres

in

the

past—producing

"green-

h o u s e " and " i c e h o u s e " worlds, respectively. These conditions influence

almost

everything

on

the

Earth's

surface,

from

s e d i m e n t type to s u n l i g h t — a n d m u s t affect living organisms.

S e c o n d , at o n e time it w a s believed that fishes only b e g a n to evolve at the end of the Silurian, but n o w n e w discoveries h a v e s h o w n that there w e r e primitive relatives of fish along-

156

Museum side trilobites for m o s t of their history; this in turn forces us to look at the ecology of the Ordovician with n e w eyes. T h e s e are changes in perception of the past. E v e n as time's arrow m o v e s forwards, the past is redesigned in retrospect.

In the nineteenth century, a m u s e u m sprang up in almost every large town of the developed world. This w a s partly the consequence of a widespread belief in their improving value, in both an educational and m o r a l sense. It w a s often a matter of civic pride. W h e r e a s in m e d i e v a l times w e a l t h y w o o l m e r chants e n d o w e d churches, their equivalents in the industrial age endowed museums.

In Britain there are m u s e u m s in

Hardy country, in Dorchester and L y m e Regis; and in Wordsworth country, the Lake District, as at Keswick; and of course in the great industrial cities: M a n c h e s t e r , Liverpool, B i r m i n g h a m and Leeds. In the United States every major city in the East has a m u s e u m , some of them associated with great phila n t h r o p i c n a m e s like P e a b o d y (Yale) o r C a r n e g i e (Pittsburgh).

You

can

find

similar

museums

in

Australia

and

central

Europe. M a n y of these m u s e u m s have natural history collections, as well as the spoils of the f o u n d e r ' s taste in art. O f t e n , their collections include important type s p e c i m e n s . For the researcher,

tracing

these

specimens

can be

an

adventure,

because not every small m u s e u m k n o w s exactly w h a t it has got. M y friend A d r i a n R u s h t o n d i s c o v e r e d s o m e s p e c i m e n s o f trilobites from the K e s w i c k M u s e u m described by J. Postlethwaite

in

a

book

on

Mines

and

Minerals

of the

Lake

District,

p u b l i s h e d i n a v e r y l i m i t e d e d i t i o n i n t h e 1880s. A r c a n e i n f o r mation, you might suppose, until y o u learn that trilobites are inordinately rare in the L a k e District, and that Mr. Postlethwaite named and found m a n y of them. Then it should be a d d e d that the w h o l e h i s t o r y of t h e L a k e District in its g e o l o g ical y o u t h hinges on the identity of these rare animals.

The creation of great m u s e u m s is one of the hallmarks of civilization. During periods of cultural decline such treasuries of k n o w l e d g e are a b a n d o n e d — w i t n e s s the virtual loss of great works of Greek science during the Dark Ages. T h e y *57

T R I L O B I T E !

T h e horseshoe " c r a b " Limulus, n o w regarded as the closest living relative of the trilobites. (Photograph courtesy Richard Kolar, Oxford Scientific Films.)

were saved because the caliph a l - M a m u n ordered the construction of a m u s e u m a n d library in B a g h d a d , the Bait alH i k m a (House of W i s d o m ) , completed in 833. This was no dull s t o r e h o u s e — i t w a s a vital link b e t w e e n classical civilization and the Renaissance. I see the natural history m u s e u m s of today as bearing witness to w h a t m a n k i n d will do to his planet and the creatures he shares it with. Even the most curious items m a y yet prove their worth. Consider the collection of d o g breeds that Lord Rothschild m a d e , n o w stored outside L o n d o n at Tring in the very m o d e l of a nineteenth-century p a r a d e - g r o u n d exhibition. Surely this kind of thing is passe a n d r e d u n d a n t ? But is it not possible that a future researcher might want to investigate the history of domestication, and that the old skins might be the source of molecular information? E v e r y d o g shall h a v e his D N A ; a n d a great m u s e u m should never die.

158

VII

A Matter of Life and Death

T r i l o b i t e s , l i k e all o t h e r c r e a t u r e s , e v o l v e d . I d o n ' t j u s t m e a n that they c h a n g e d through time: that m u c h is o b v i o u s . Trilob i t e s l i k e Olenellus, f r o m t h e L o w e r C a m b r i a n , a r e d i f f e r e n t from those in the late C a m b r i a n , a n d these in turn are distinct from those in the Ordovician, w h i c h differ again from specim e n s found in the overlying Silurian a n d D e v o n i a n strata.

W i t h e v e n a little e x p e r t i s e a trilobite l o v e r will be a b l e to cast an eye over a g r o u p of fossils a n d guess their age, e v e n if they cannot put an exact n a m e to them. T h e y respond to what bird w a t c h e r s call t h e " j i z z , " a k i n d of overall i m p r e s s i o n that rarely

misleads.

Clearly,

trilobites

replaced

one

another

through the geological ages. In m o s t rock sections, though, we a s s u m e that every trilobite novelty that appears w a s an e v o l u tionary innovation even w h e n the rocks themselves m a y often p r o v i d e n o d e t a i l s o f its o r i g i n . T o s e e " e v o l u t i o n i n a c t i o n " i s rather rare. This rather m u n d a n e truth has b e e n m i s a p p r o p r i ated by creation "scientists" as evidence that "fossils don't provide support for e v o l u t i o n " — w h i c h is not the s a m e thing a t all. I n f a c t , t h e o r d e r o f a p p e a r a n c e o f t r i l o b i t e s i s c e r t a i n l y consistent

with

evolution:

Cambrian

trilobites

have

more

primitive characteristics than those in the Ordovician and younger, as we have already seen in the case of the peculiar,

159

T R I L O B I T E !

and evolutionarily a d v a n c e d , schizochroal eye. It is just that it is g e n u i n e l y difficult to catch the a p p e a r a n c e of n e w species in the act of creation. In a burglary, it is rare to c o m e u p o n the scene with the miscreant standing there, caught red-handed and carrying the swag: the subsequent m a y h e m is what people usually c o m e h o m e to. So with the generation of s p e c i e s — the e n d u r a n c e of the species after the event is relatively long, so that this part of their history will be m o r e likely to be discovered, just by the laws of probability, which have no respect for wishful thinking w h e t h e r creationist or Darwinian. To maintain the criminological metaphor: sampling bias alone l e a v e s little c h a n c e of conviction.

S o e x a m p l e s w h e r e y o u can s e e e v o l u t i o n a t w o r k b e c o m e doubly

precious.

Our

own

genus,

Homo,

and

its

several

species related to m o d e r n Person, is not a particularly good subject: h o m i n i d s h a v e f e w fossils a n d the m o s t arguments.

This does not m e a n that we are not finding out m o r e and m o r e a b o u t h o m i n i d s — n e w fossils turn up every year—it is just that h u m a n history m a y not be the best choice for studying f e a t u r e s o f s p e c i a t i o n itself. T h e f o s s i l s a r e still t o o r a r e . B y contrast, trilobite e x a m p l e s h a v e b e e n central to s o m e of the most vigorous debates about h o w evolution happened. Since they

are

complex

and

abundant

fossils,

they

might

be

expected to be particularly useful "experimental material" to cast light u p o n h o w n e w species are generated. In the laborat o r y , a n o t h e r a r t h r o p o d , t h e f r u i t f l y Drosophila, h a s f o r m a n y y e a r s b e e n u s e d as the e x p e r i m e n t a l a n i m a l for genetics-inaction. T h e classical studies on inheritance w e r e carried out u p o n t h i s l i t t l e fly. W h e n t h e r o l e s o f s p e c i f i c g e n e s w e r e i n v e s t i g a t e d — m o s t recently the family of H O X genes that c o n t r o l s e q u e n c e i n d e v e l o p m e n t — i t w a s Drosophila t h a t w a s manipulated to produce hopeless but informative monsters w i t h extra pairs of w i n g s , or legs in place of antennae. Fossils o f flies are too delicate for a n y b u t the m o s t exceptional preservation in amber. M a y b e robust trilobites could be the fruit flies of the rocks.

160

A

Matter

of

Life

and

Death

W h a t is required as a test case is a s e q u e n c e of species f o u n d one after another, in the s a m e rock succession, w h i c h can reasonably be interpreted as having an ancestor-descendant relationship. There should be large n u m b e r s of specimens collectable from m a n y rock layers recording the w h o l e history of b o t h the older and y o u n g e r s p e c i e s — s o that m e a s u r e m e n t s can be m a d e on what happens to the shape of the animals t h r o u g h o u t the time of deposition of the rocks, not least to convince the sceptics w h o d o u b t that a n y evolution is going on

at

all.

Unusual

sedimentary

successions

are

required

which lack prolonged breaks in deposition—for hiatuses m a y disguise the very m o m e n t of evolution into a different species.

M o s t rock sequences are, in practice, incomplete. It is not altogether

surprising

that

these

critical

initial

conditions

are

rarely m e t : m o s t r o c k s u c c e s s i o n s fail o n o n e criterion o r another. T h e most suitable d e p o s i t s — a n d these are of c o m p a r atively y o u n g geological a g e — a r e the rocks w h i c h a c c u m u lated on deep-sea floors, w h e r e a c o n t i n u o u s rain of plankton t i c k s o f f t i m e i n a s e t t l i n g m i s t o f t i n y s h e l l s . T h e s e little f o s sils, often b e l o n g i n g to single-celled, calcite-shelled o r g a n i s m s called foraminiferans, h a v e p r o v i d e d m a n y of the best evolutionary case histories, not least because they are so abundant.

A handful of rock m a y yield h u n d r e d s of specimens. But their small size also m e a n s that they tend to be rather s i m p l e — a few bubble-like chambers a millimetre across. A n d m a y b e plankton

has

evolutionary

properties

different

from

their

bottom-living relatives. Trilobites m i g h t , after all, p r o v i d e an e x a m p l e w h i c h i s m u c h m o r e typical o f m o s t m a r i n e life. T h e i m m e d i a t e problem is the obligation to collect s a m p l e s large e n o u g h for a convincing study. This m e a n s h o u r s of b a s h i n g rocks, e v e n if the fossils are quite c o m m o n . You cannot study t r i l o b i t e s a s y o u m i g h t g a s a f e w g e n e r a t i o n s o f f r u i t flies t o see the c h a n g e s in the genealogy. T h e long-term application of brute force is required to get a decent sample. There have been several scientists w h o h a v e this kind of d o g g e d n e s s , strength and patience. As we shall see, they c a m e to quite opposite

161

T R I L O B I T E !

conclusions on w h a t the trilobites h a d to say about the origin of n e w species.

The phrase "punctuated equilibrium" has b e c o m e rather familiar: I recently heard it referred to horribly as " p u n k e c k " by an Australian philosopher of science. F e w laymen, or even scientists, realize that its g e n e s i s w a s t h o r o u g h l y g r o u n d e d in t r i l o b i t e s . I n t h e l a t e 1960s a y o u n g A m e r i c a n , N i l e s E l d r e d g e , w a s s t u d y i n g t h e D e v o n i a n t r i l o b i t e g e n u s Phacops i n N o r t h A m e r i c a . W e h a v e a l r e a d y m e t Phacops a s t h e p o s s e s s o r o f marvellously c o m p l e x schizochroal eyes, in which each lens w a s a tiny calcite s p h e r o i d , s e p a r a t e d by a little inter-lensar sclera. T h e n u m b e r of lenses is relatively few, a n d they are easily c o u n t a b l e u n d e r a m i c r o s c o p e . It is a v e r y c o m m o n fossil in the appropriate strata e x p o s e d in the states of N e w York, Iowa a n d O k l a h o m a , a n d m a n y other localities besides. It is often w e l l - p r e s e r v e d i n l i m e s t o n e s , a p r e s e r v a t i o n t h a t p e r m i t s its m o s t intimate details to be inspected. A few taps in the right l o c a l i t y , a n d o u t a Phacops w i l l p o p ( u s u a l l y t h e c e p h a l o n ) a s i f t o say,

" j e e p e r s , c r e e p e r s ! h o w a b o u t m y p e e p e r s ? " Phacops

provides one of those rare cases w h e r e there is a h o p e of discovering the particulars of the evolutionary process between o n e species a n d the next, so prolific is the fossil record. To his credit, Niles realized this scientific opportunity quite early in his studies.

Niles noticed changes in the arrangement of the lenses in t h e e y e s o f Phacops s p e c i e s . H e c o u n t e d t h e l e n s e s i n t h e i r "dorso-ventral

files"—the

number

of

lenses

in

each

row

counted from the top to the b o t t o m of the eyes. Let him describe in his o w n w o r d s the observations that he confirmed w h i l e w r i t i n g his dissertation, as recalled recently in his b o o k The

Pattern

of

Evolution:

Bingo! Another pattern leapt out: Populations in the Appalachian

basin

seemed

to

be

invariably

17

d o r s o v e n t r a l files, for a l m o s t the entire length of M i d dle D e v o n i a n time . . . In the M i d w e s t the story w a s

162

A

Matter

of

Life

and

Death

altogether different: For 2 million years or so, the n u m b e r r e m a i n e d s t a b l e a t 18; t h e r e a f t e r , f o r a t l e a s t a n o t h e r 2 million years, the n u m b e r w a s also stable, but it w a s 17, n o t 18; f o r t h e v e r y l a s t p a r t o f m y t i m e f r a m e , t h e t r i l o b i t e s h a d 15 d o r s o v e n t r a l f i l e s . . . l a r g e c h u n k s of time were missing in the midwestern rock sections prec i s e l y w h e n t h e c h a n g e o v e r f r o m 1 8 t o 17, a n d f r o m 1 7 to 15 files o c c u r r e d . T h e s e a s in w h i c h Phacops rana . . . lived s i m p l y d r i e d up d u r i n g t h o s e intervals . . . t h e c h a n g e f r o m 1 8 t o 17, a n d l a t e r f r o m 1 7 t o 1 5 d o r s o v e n tral files i n t h e M i d w e s t s i m p l y m a r k e d a r e p o p u l a t i n g o f t h e s e a s . T h e p a t t e r n s u g g e s t s t h a t t h e 1 8 file f o r m b e c a m e extinct w h e n t h e m i d w e s t e r n s e a s first w i t h d r e w ; w h e n t h e s e a s r e t u r n e d the 17 file f o r m w a s available and took over the n e w l y reconstituted marine habitat.

Niles focused especially on the changes in the eyes because he s a w that here w e r e the crucial characters for defining the species. If he h a d b e e n s t u d y i n g b i r d s it m i g h t h a v e b e e n tail feathers or song. If he had been studying molluscs it might h a v e b e e n t h e p a t t e r n s o n t h e s h e l l . E a c h a n i m a l p a r a d e s its o w n p e c u l i a r i t i e s t o e s t a b l i s h its o w n i d e n t i t y . S p e c i e s f l a u n t their personalities to signal to their o w n k i n d .

Two

conclusions

come

out

of Niles's

observations

on

D e v o n i a n Phacops. T h e first i s t h a t t h e e v e n t s p o r t r a y i n g g e n eration of n e w species are rather hard to o b s e r v e — t h e y s e e m always to happen "somewhere else." However, subsequent to the a p p e a r a n c e of a n e w species, the successful innovation often invades, and replaces, an earlier species. In s o m e cases Niles k n e w where a n e w species originated, but entirely transitional populations b e t w e e n n e w a n d old species w e r e hard to find. This p h e n o m e n o n m a y be c o m p a r e d with the Beatles overtaking the pop music scene in the sixties—only to be replaced by Bee Gees in the seventies, or Michael Jackson in the eighties. T h e early discs are the collector's items, the later

163

T R I L O B I T E !

ones characterize a whole cultural phase and are as c o m m o n as unsuccessful lottery tickets. T h u s , the n e w species often starts out as a relatively small p o p u l a t i o n s o m e w h e r e on the edge of the range of the (then) dominant species; geographical s e p a r a t i o n i s w h a t p r o d u c e s a s p e c i e s d i f f e r e n c e . B u t w h e n its time c o m e s the n e w species replaces the ancestor and enjoys its o w n h o u r s of glory. T h i s is w h e r e the H a r v a r d U n i v e r s i t y biologist Ernst M a y r ' s influence w a s crucial, for M a y r had already observed that in the living w o r l d n e w species often s e e m e d to h a v e b e e n generated as a result of geographical isolation of a g r o u p of individuals (this process he t e r m e d allopatry); disjunct populations m a y h a v e acted as the " m o t o r " for e v o l u t i o n a r y c h a n g e . T h e i s o l a t e d g r o u p h a d its g e n e f l o w with the m o t h e r species interrupted; and separation alone c o u l d b r e e d novelty. E v o l u t i o n d i d , really, h a p p e n " s o m e where else."

Niles's second conclusion w a s that once a n e w species had a r r i v e d it e n d u r e d , often for a l o n g t i m e , w i t h little c h a n g e . We m a y n o t s e e t h e o r i g i n o f t h e s p e c i e s , b u t w e d o s e e its a c m e .

Like the burglar that b r o k e in at the d e a d of night, the significant event was clandestine: we see the aftermath, but not the d e e d . T h e m u n d a n e d e m o n s t r a t i o n of this in the rocks is the observation

that

a

particular

Phacops

species,

once

it

has

a p p e a r e d , e n d u r e d for a l o n g t i m e w i t h v e r y little c h a n g e . To the practical field geologist this m e a n s that m u c h b r e a k a g e of rock to recover trilobite fossils by w o r k i n g through metre after m e t r e of s t r a t a — t h e b l o o d i e d fingers, the w e t feet, the mosquito bites (especially in N e w York)—is rewarded by a cry of " n o change!" This is hard, hard labour to show the absence of s o m e t h i n g , w h i c h in s o m e scientific circles is often called negative evidence; strenuous w o r k for no result, you might suppose.

E x c e p t that the result w a s highly important. Species, said Niles, originate allopatrically—"somewhere else." W h e n one o f t h e s e s p e c i e s s u c c e s s f u l l y i n v a d e s , a n d t h e n r e p l a c e s , its ancestor it endures for a considerable time. Life proceeds by

164

A

Matter

of

Life

and

Death

fits a n d s t a r t s ; a s p e c i e s l a s t s u n t i l i t i s r e p l a c e d b y a n o t h e r — and that replacement is rapid. Taken together, the t w o i d e a s — the e n d u r a n c e of species, a n d allopatric s p e c i a t i o n — m a k e up the conceptual basis for p u n c t u a t e d equilibrium; the choice of w o r d s for this theory will b y n o w b e o b v i o u s . T h e e q u i l i b r i u m is the e n d u r i n g p h a s e of a s p e c i e s ' life; the p u n c t u a t i o n is its sudden replacement.

We shall all be changed, in

the twinkling of

a n eye, a s C o r i n t h i a n s p u t s it. T h e n e w t h e o r y w a s s e t u p i n opposition to the notion of "gradualism," a slow and m o r e or less c o n t i n u o u s c h a n g e or shift that n u d g e d w h o l e p o p u l a tions t o w a r d s the n e w species. This w a s c o n s i d e r e d to be the dominant model for evolution in the aftermath of the " m o d ern synthesis" of evolution in the 1930s—and a rather supine a c c e p t a n c e of this creed e n s u r e d that the " p u n c t u a t e d " view, w h e n it appeared, w a s heralded as startlingly novel. Niles joined forces with Steve G o u l d to present the n e w model, and w i t h c o n s i d e r a b l e s u c c e s s . T h e i r o r i g i n a l 1971 p a p e r a c h i e v e d an e n o r m o u s "citation i n d e x " — t h i s is a m e a s u r e of the influence of a piece of published w o r k by the n u m b e r of times it is quoted in the bibliography by other workers. T h e punctuational description of e v o l u t i o n a r y c h a n g e lent itself readily to metaphor, and other observers were quick to point out similarities in several areas of science a n d culture that w e r e not just concerned with speciation of animals. Even h u m a n history c o u l d , w i t h a little m a s s a g i n g , be d e s c r i b e d in t e r m s which seemed consistent with " p u n k eck": for e x a m p l e , cultural revolution w a s often f o l l o w e d b y d y n a s t i e s w h i c h fini s h e d in a s t a t e of s t a s i s . G i b b o n ' s Decline and Fall of the Roman Empire m i g h t e x e m p l i f y t h e i n e v i t a b i l i t y o f h i s t o r i c a l p a t t e r n s as m u c h as h u m a n foibles. In a b o o k that a p p e a r e d s o m e years a f t e r t h e s e m i n a l p a p e r , Time Frames, N i l e s h i m s e l f w e n t a l o n g with the pervasiveness of punctations in history. T h e story of our planet's development, it s e e m e d by then, w a s a tale told mostly by jerks.

This perceptual revolution w a s perhaps an inordinate burd e n to place u p o n the c e p h a l o n of the h u m b l e , if pretty, trilo-

165

T R I L O B I T E !

b i t e Phacops, w h o s e e y e s a l o n e w o u l d h a v e b e e n a b l e t o s e e the evolutionary truth. As we h a v e already discovered, they probably s a w rather acutely. O t h e r punctuational examples f r o m the fossil record soon joined the " a y " voters. Quite soon, the punctuation explanation p r o v i d e d a rational counter to creationists w h o sought to exaggerate the rarity of "missing l i n k s " in the fossil record to counter evolutionary theory. On the

contrary,

such

gaps

might

be

just

what

evolution

demanded. A s a l i f e - l o n g r a t i o n a l i s t i n d e f e n c e o f t h e e x p l i c a b l e against the n u m i n o u s , Steve G o u l d w e l c o m e d this arsenal of a m m u n i t i o n in his c a m p a i g n to educate those w h o denied the magnificent narrative of Earth history in favour of a w e e k ' s l a b o u r b y t h e C r e a t o r . Phacops h a d b e c o m e t i e d u p w i t h s o m e contentious company. A r g u m e n t s raged b e t w e e n bible purists a n d evolutionists: it w a s a case of trilobite-by-jury.

N i l e s w a s n o t t h e first t o m a k e the o b s e r v a t i o n o f " p u n c t u a t e d " c h a n g e in trilobites. N e a r l y forty years earlier, a G e r m a n from the University of Greifswald, Rudolf Kaufmann, had d r a w n similar conclusions f r o m a m i n u t e study of late C a m brian olenid trilobites from the A l u m shale of Scandinavia. We h a v e a l r e a d y m e t o l e n i d t r i l o b i t e s o f t h e g e n u s Triarthrus; t h i s w a s one of the trilobites of w h i c h the legs and antennae w e r e first k n o w n i n d e t a i l . I t w i l l b e r e c a l l e d t h a t o l e n i d s l i v e d i n a special environment in which the sea-floor was low in oxygen, while in the sediment b e l o w there w a s a complete lack of oxyg e n a n d a high concentration of sulphur. I e v e n suggested that the olenids m a y have cultivated colourless sulphur bacteria as s y m b i o n t s . A b o u t 500 m i l l i o n y e a r s a g o i n t h e l a t e C a m b r i a n an Olenid Sea spread across the w h o l e of southern Scandin a v i a , an i n u n d a t i o n that persisted for s o m e t h i n g like fifteen million years. This w a s a special time, because during much of this long period there w a s nearly continuous deposition of d a r k , shaly strata, w h i c h n o w yield frequent trilobite fossils. If y o u can find a quarry exposing the A l u m shales, you break up the smelly nodules k n o w n as "stinkstones"—often about the size of a rugby football—and find beautiful and abundant

166

A

Matter

of

Life

and

Death

A portrait of Rudolf Kaufmann, the tragic G e r m a n trilobite palaeontologist.

trilobite remains. T h e A l u m shale is a f a m o u s e x a m p l e of a "condensed deposit" where much geological time is crammed into a thin s e q u e n c e of strata that a c c u m u l a t e d w i t h o u t m a j o r breaks. This approaches the ideal case for carrying out evolutionary

"experiments"

in the field.

Kaufmann was astute

e n o u g h to recognize this, and m a d e careful collections from successive layers of strata to observe the subtlest of changes t h r o u g h time. Niles did fully a c k n o w l e d g e this p i o n e e r i n g w o r k , p u b l i s h e d i n 1933, w o r k w h i c h w o u l d c e r t a i n l y h a v e been more widely k n o w n had it not been published in a journal of G r e i f s w a l d University with v e r y limited circulation.

(This recalls G r e g o r M e n d e l ' s crucial experiments on inheritance in plants carried out in the C z e c h t o w n of Brno, a n d their long struggle into the light of international science; it

167

T R I L O B I T E !

m i g h t be e v e n w o r s e today, with ten times m o r e journals c o m peting for attention.)

What Kaufmann

observed

was

that several

species of

Olenus ( s e e p . 70) a p p e a r e d s u d d e n l y i n t h e r o c k s e c t i o n s , a n d then h a d comparatively long ranges. But during their "lifet i m e " the species w e r e not static; instead they s h o w e d small variations, especially in the shape of the pygidia,

which

b e c a m e progressively narrower and longer through time. The s a m e c h a n g e s h a p p e n e d t o t h e p y g i d i a o f d i f f e r e n t Olenus species. K a u f m a n n clearly s h o w e d the invasion of a species from elsewhere into the Olenid Sea of Scandinavia, thus presenting a g r a p h i c illustration of allopatry b e f o r e it w a s a recognized concept. F u r t h e r m o r e , he b a s e d his results on large collections, a n d analysed the results in a quantitative fashion.

Euan Clarkson has revisited the f a m o u s Swedish quarry at A n d r a r u m in the last f e w years, and repeated K a u f m a n n ' s observations. Clearly, this w a s a r e m a r k a b l e a n d far-seeing scientist.

I was puzzled by Rudolf Kaufmann's apparent disappearance f r o m the trilobite f i r m a m e n t after this seminal paper. Scientists can usually be m a p p e d through a career of twenty-five y e a r s o r m o r e (in s o m e c a s e s y o u w i s h i t w e r e n o t quite s o long). They leave behind a legacy of papers, which can be u s e d t o t r a c k a n i n t e l l e c t u a l l i f e t i m e — l i t e r a l l y a p a p e r trail; not least, p e o p l e tend to quote themselves, so that y o u can find out a b i o g r a p h y f r o m a b i b l i o g r a p h y at the e n d of a paper.

To an experienced researcher with a good m u s e u m library such sleuthing is almost routine. Not so with Rudolf Kaufm a n n ; h e s i m p l y v a n i s h e d . I t w a s n o t u n t i l 1998 t h a t I d i s c o v e r e d w h y . I t i s a n e x t r a o r d i n a r y a n d m o v i n g story.

T h a t w e k n o w the story a t all i s b e c a u s e R e i n h a r d Kaiser b o u g h t a m i x e d b u n d l e of letters a n d postcards at a s t a m p a u c t i o n i n F r a n k f u r t - a m - M a i n i n 1991. H e p a i d 500 d e u t s c h e m a r k s for t h e j o b lot. A m o n g t h e b a t c h w e r e R u d o l f ' s letters to I n g e b o r g M a g n u s s o n , his S w e d i s h lover. Kaiser w a s so e n g a g e d by the p o i g n a n c y of the tale they revealed that he

168

A

Matter

of

Life

and

Death

discovered w h o Rudolf Kaufmann was, and pieced together the narrative. Sadly, I n g e b o r g ' s letters to R u d o l f h a v e not survived. H e r devotion is indicated by the fact that she n e v e r married, and kept the letters from Rudolf until her death in 1972. T h e y h a d m e t i n 1935 w h e n h e w e n t t o B o l o g n a , t h e ancient university city in north-eastern Italy; he h a d fallen instantly in love with the d a r k - h a i r e d S w e d i s h girl. S h e w a s only united with h i m again for a few days b e t w e e n their Bologna idyll a n d his tragic death. T h e story is g l i m p s e d in fragments

through

their

correspondence;

it

tells

of

his

attempts to reach her S w e d i s h h a v e n during the ghastly years of Hitler's

dictatorship.

Kaiser

called

his

story

Konigskinder

(king's children) after a c o m p a r i s o n K a u f m a n n h a d m a d e in o n e of his letters to the figures in a folksong: Es

ivaren

Sie

konnten

zvoei

Konigskinder,

zusammen

die hatten

nicht kommen,

das

einander Wasser

so

lieb. war viel zu

tief.

(There w e r e t w o king's children, they loved each other.

They could not c o m e together because the water was too deep.)

Rudolf Kaufmann was Jewish by birth, although a practising Christian. His masterly w o r k on olenids w a s published just two days after Hitler b e c a m e Chancellor, a n d took over the g o v e r n m e n t , o n 3 0 J a n u a r y 1933. K a u f m a n n w a s f i r e d f r o m his job at Greifswald University almost immediately. This did not prevent him from pursuing his palaeontological studies outside G e r m a n y , b u t the B o l o g n a visit w h e r e he m e t Inge w a s to be his last.

K a u f m a n n w a s well aware of the importance of his studies on the trilobites w h i c h w e r e his second love. He wrote to Inge that he w o u l d s e n d her everything that he h a d written as a geologist because "it will soon no longer be true that I have d o n e all t h i s r e s e a r c h , " a r e f e r e n c e t o H i t l e r ' s d e n i a l o f t h e intellectual a c h i e v e m e n t s of Jewry. "I am very p r o u d of my

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T R I L O B I T E !

great w o r k on trilobites. I h a v e b e e n able to prove that there is a d e t e r m i n e d d e v e l o p m e n t in t h e life h i s t o r y of these a n i m a l s .

I think I will be m u c h m o r e f a m o u s than at present m a n y years from now, w h e n zoologists and palaeontologists begin fully t o u n d e r s t a n d m y w o r k . " H e has not yet h a d his d u e .

W h i l e separated from his lover, K a u f m a n n s u c c u m b e d to t e m p t a t i o n . H e w a s i m p r i s o n e d i n C o b u r g i n 1936 f o r i l l e g a l sexual c o n g r e s s w i t h an A r y a n w o m a n . In fact, he h a d visited a prostitute a n d c a u g h t a venereal infection; it w a s the doctor who

treated

him

who

subsequently betrayed

him

to

the

p o l i c e . O n 1 3 A u g u s t 1936 h e w r o t e t o I n g e : " I w a n t e d t o c o n fess e v e r y t h i n g to y o u in S w e d e n , b u t n o w it's too late for that.

I am no longer w o r t h y of y o u , a n d I b e s e e c h y o u to try to forget m e . I thank y o u for y o u r faithful, pure love . . . y o u were so good to me and I proved myself to be weak, and n o w I have t o pay for m y actions . . . S o m u c h has already been taken f r o m me in my life; my m o t h e r , my b e l o v e d career . . . This time, however, I h a v e failed out of foolishness and I must bear your decision."

A l t h o u g h I n g e readily forgave h i m , his lapse cost h i m dear.

B y t h e t i m e h e g o t o u t o f p r i s o n o n 1 2 O c t o b e r 1939, h o s t i l i t i e s h a d already c o m m e n c e d . H a d he b e e n released six w e e k s earlier, b e f o r e B r i t a i n a n d F r a n c e d e c l a r e d w a r o n G e r m a n y o n 3 September, he m i g h t well h a v e m a d e g o o d his escape. Several other trilobite experts fled f r o m N a z i s m . A l e x a n d e r A r m i n O p i k w a s a m e m b e r of a d i s t i n g u i s h e d Estonian scientific f a m i l y (his brother w a s a f a m o u s a s t r o n o m e r ) w h o eventually escaped to Australia; his fellow Estonian Valdar Jaanusson became

doyen

of

Scandinavian

trilobite

experts

at

the

S w e d i s h N a t i o n a l M u s e u m . T h e Baltic Sea w a s not the s a m e barrier to them as it w a s to the "King's children." By N o v e m b e r 1939 K a u f m a n n w a s i n C o l o g n e . " A n d w h e n I a m a l o n e ? " h e wrote. " I a m with m y m u c h - l o v e d Trilobites, o f w h i c h y o u can already be jealous. I recently read the Odyssey. I m u s t learn f r o m O d y s s e u s . . . see h o w he b o r e his longing for Penelope, and

treat it as t h o u g h it w e r e written for m e . "

170

He

A

Matter

of

Life

and

Death

remained optimistic in the face of growing evidence that w o u l d h a v e r e d u c e d s o m e b o d y less b u o y a n t t o despair. B u t , gradually, his hopes d i m m e d of ever being united with his l o v e r ; b y J u l y 1940 h e c o n f e s s e d t h a t h e " h a d n o c o u r a g e f o r the future." He d o u b t e d w h e t h e r he had the strength to continue. "Yet I c a n n o t lie. T h e short t i m e we w e r e together, a n d the long separation, a n d the w o r r i e s of last m o n t h , a n d of every m o m e n t , and the hopelessness of the future. These are all t o b l a m e . . . T r y t o b e f r e e , a s f r e e a s y o u c a n . T h e r e i s t o o little h o p e t h a t w e w i l l s e e e a c h o t h e r f o r a l o n g t i m e i n t h e foreseeable future. Wouldn't it be better if we weren't so close, if we did not have to torture ourselves so m u c h ? . . . I take you i n t o m y a r m s o n c e a g a i n a n d k i s s y o u w i t h all m y h e a r t . " B y 1941 R u d o l f K a u f m a n n w a s i n e x i l e i n K a u n a s , L i t h u a n i a . T h e B a l t i c S e a w a s n o t f a r a w a y , b u t i t w a s still t o o d e e p and too wide. He h a d given up h o p e of joining Inge. He w a s shot in cold blood by t w o guards w h o h a p p e n e d to recognize him, and b e c a m e just another digit in the m o s t disgraceful statistic o f t h e t w e n t i e t h c e n t u r y . T h e p r o g e n i t o r o f p u n c t u a t i o n had fallen victim to o n e of the m o s t aberrant cultural shifts in h u m a n history. R e i n h a r d Kaiser d i s c o v e r e d p h o t o g r a p h s o f Rudolf: with his slicked-back b l a c k hair, h a n d s o m e regular features, and a rather G e r m a n i c high seriousness, he was the very model of a young Professor, and you can understand Ingeborg's passion for h i m .

So it is that the s t u d y of trilobite evolution casts light b o t h u p o n the f u n d a m e n t a l s of h o w n e w species are generated, and, as I discovered through Kaiser's detective work, also u p o n the paradoxes of the best and the worst in the h u m a n c o n d i t i o n . T h e e n t h u s i a s m K a u f m a n n felt for his trilobites, and

his

passion

for

the

investigation

of

the

truth

they

revealed, w a s m a t c h e d by his love for Ingeborg M a g n u s s o n .

W h o knows what reputation he might have forged if he had been permitted to follow both his heart and his m i n d ?

171

T R I L O B I T E !

Punctuated equilibrium was not the only pattern of evolution t h a t t r i l o b i t e s r e v e a l e d . D u r i n g t h e l a t e 1970s a n o t h e r y o u n g m a n , an E n g l i s h m a n this time, w a s studying the trilobites of the area around the old spa towns of Builth and Llandrindod Wells, part of the borderland region between England and W a l e s . T h i s is hilly country, a p a t c h w o r k of d e e p g r e e n fields where sheep are the main crop, interspersed with w o o d e d holts and

little s t e e p - s i d e d

valleys

w h e r e fallen branches

thickly covered with feathery mosses vie with tangled bramb l e s t o i m p e d e t h e p r o g r e s s o f t h e g e o l o g i s t i n h i s Wellington b o o t s a n d t h o r n - p r o o f jacket. P h e a s a n t s s u d d e n l y start from the u n d e r g r o w t h uttering sharp cries. In the streams you will m e e t toads quietly going about their business a m o n g the ferns. T h e r e is a sense of moist a b u n d a n c e : so rich is the v e g e tation that the o v e r h a n g i n g foliage cuts out m o s t of the light.

T h e best time to do fieldwork is in the spring, before the stinging nettles have sprouted and hidden the rocks, and before the g e n e r o u s leaves of chestnuts or hazel h a v e fully unfurled. In late April there are bluebells on the b a n k s , a n d drifts of yellow celandine, and blackbirds everywhere. In the banks of the streams, encrusted with liverworts, there are heavy, black m u d s t o n e s , w h a t t h e W e l s h t e r m "rab," w h i c h y o u c a n p i c k out in small slabs with the pointed end of the geological h a m mer. Split the slabs in the right direction a n d y o u will be r e w a r d e d with trilobites. Carefully w o r k your w a y upstream to s a m p l e successive rock b e d s , a n d y o u will be party to a narrative that spells out evolutionary changes through geological time. T h e rock succession is relatively t h i c k — m a n y tens of m e t r e s — c o m p a r e d w i t h the " c o n d e n s e d " shales that Rudolf K a u f m a n n had sampled in Sweden. This is an advantage: if y o u cannot find fossils in a f e w feet of strata the chances are that y o u have not passed a major geological event—in Swed e n , a c o m p a r a b l e thickness w o u l d be a vital contribution to the narrative of time. The rocks are of Ordovician age, about 470 m i l l i o n y e a r s o l d .

Peter Sheldon spent years collecting these dark rocks. With

172

A consummate

Matter

patience,

of

he

Life

and

split

the

Death ungrateful

shales

for

m o n t h after m o n t h , slowly a c c u m u l a t i n g a n d labelling s a m ples of trilobites w h i c h he w o u l d later analyse. Mostly, he f o u n d i s o l a t e d tails o r h e a d s ; o c c a s i o n a l l y h e w a s r e w a r d e d with a w h o l e specimen. T h e c o m m o n e s t of the trilobites w a s a n o l d f r i e n d , t h e a s a p h i d t r i l o b i t e Ogygiocarella, w h i c h w i l l b e r e c a l l e d a s t h e first e v e r t r i l o b i t e t o b e d e s c r i b e d — a s a " f l a t f i s h " — b y Dr. L h w y d i n t h e v i c i n i t y o f t h e S o u t h W a l e s t o w n of Llandeilo. In these dull shales there w a s a trawl of flatfish sufficient to satisfy N e p t u n e himself. T h e semicircular, furr o w e d tails s p l i t f r o m t h e e n c l o s i n g rab; w i t h a l i t t l e s k i l l t h e y could be d i s p l a y e d perfectly, little fans m o s t l y larger t h a n a butterfly's wing. T h e n a r r o w axis occupies the central part, and is divided into n u m e r o u s rings; the flat pleural fields are divided into an equal n u m b e r of ribs w h i c h get shorter a n d r a t h e r l e s s d i s t i n c t t o w a r d s t h e p o s t e r i o r o f t h e tail. A l o n g s i d e these large trilobites, a n d slightly less a b u n d a n t , are smaller ones no more than a few centimetres long, and more comm o n l y found in a complete state. T h e s e b e l o n g to the blind genus

Cnemidopyge

(fig.

25),

a

trilobite

with

a

semicircular

head and with a long spine extending forwards from the front of the glabella. This a n i m a l h a d o n l y six flat thoracic s e g m e n t s , a n d a t r i a n g u l a r p y g i d i u m w h i c h w a s , l i k e t h a t o f Ogygiocarella,

strongly furrowed.

Occasionally,

it is

p o s s i b l e to

find o n e that has rolled u p . T h e r e w e r e o t h e r trilobites, too, i n c l u d i n g a c l o s e r e l a t i v e o f t h e " D u d l e y B u g " Calymene, a n d d i s t i n c t i v e little m e d a l l i o n - l i k e t r i n u c l e i d s .

All these animals were collected by the persistent Peter Sheldon. He got to k n o w the country and the strata with an intimacy which must surpass even the farmers w h o o w n the land. He had to m o v e from one stream to another to obtain a complete picture of the succession of rocks by carefully tracing an individual stratum across country. T h e w o r k w a s very s l o w , a n d m a d e still s l o w e r b y t h e f a c t t h a t P e t e r i s o n e o f t h o s e e n t h u s i a s t s w h o l o v e t o e x p l a i n t h e i r w o r k t o all c o m e r s .

He is friendly, sempiternally youthful a n d tirelessly opti-

173

T R I L O B I T E !

m i s t i c , all o f w h i c h h a s s e r v e d h i s d e d i c a t i o n a s a t e a c h e r a t the O p e n University for a n u m b e r of years. While he w a s writi n g the d i s s e r t a t i o n for his P h D h e w a s a l w a y s r e t u r n i n g for "just o n e m o r e collection." In the trilobite world he b e c a m e notorious for his reluctance to leave the outcrop and write up.

N o r m a l l y P h D theses are supposed to take three years, four at m o s t , b u t P e t e r ' s s e e m e d to go on for ever. He d o d g e d the censorious glances of the senior faculty, and just p l u g g e d on, splitting m o r e and m o r e black shales and collecting more and m o r e trilobites. Just w h e n he m i g h t h a v e tried the patience of his s u p e r v i s o r b e y o n d e n d u r a n c e — b i n g o ! (as Niles E l d r e d g e would

have

p u t it)

he

published

the

result

in

Nature.

It

instantly m a d e him quite famous.

W h a t he claimed w a s that the trilobites from the Ordovician strata around Builth Wells s h o w e d a kind of gradualistic c h a n g e t h r o u g h time. He s h o w e d that this kind of c h a n g e affected not only o n e , b u t several of the different trilobites that ranged through the black m u d s t o n e s and shales. The most o b v i o u s e x a m p l e f r o m the largest and c o m m o n e s t trilobite, Ogygiocarella

debuchii,

showed

an

increase

in

the

number

of

ribs on the p y g i d i u m , f r o m n to 14 on a v e r a g e . In the last century the p i o n e e r i n g British trilobite expert, J o h n Salter, had r e c o g n i z e d t h e f o r m w i t h m o r e r i b s a s " v a r i e t y angustissima."

These are exactly the kind of subtle changes which trilobitologists u s e to distinguish fossil species. W h a t Peter s h o w e d w a s that

there w a s a

angustissima.

The

seamless

large

t r a n s i t i o n b e t w e e n debuchii a n d

populations

he

collected

showed

a

g o o d deal of variation at a n y o n e level—that is, there w e r e s p e c i m e n s with various n u m b e r s of ribs found together at any o n e time. On s o m e e x a m p l e s , there w e r e even half-ribs on one side of the p y g i d i u m , but not the other. In general, though, there w a s a n u n m i s t a k e a b l e trend—-at the p o p u l a t i o n l e v e l — to h a v i n g m o r e ribs t h r o u g h geological time. W h e n he collected at a very m i n u t e scale he found that there were even short-lived b a c k w a r d steps in rib n u m b e r within the overall increasing trend. The progression from one form to another

174

A

Matter

of

Life

and

Death

resembled the tottering steps of the cartoon d r u n k rather than a smooth progression. E v e n m o r e exciting, Peter found that t h e tail o f Cnemidopyge w a s u n d e r g o i n g a p a r a l l e l s e r i e s o f changes

at

the

same

time

through

the

same

strata—Ogygiocarella

was not unique.

There were subtler c h a n g e s in s o m e of the other trilobites, t o o . I t all p o i n t e d t o a v e r y d i f f e r e n t m e c h a n i s m f o r c h a n g e f r o m t h a t w h i c h h a d a f f e c t e d Phacops. E v e n i f t h e s h a l e s a c c u mulated at a rapid pace u n d e r the Ordovician sea, each of these changes must have taken several million years to have proceeded to c o m p l e t i o n — t h i s is c h a n g e of a different order of magnitude from the rapid alterations induced by allopatric separation. It is actually rather difficult to think of a m e c h a n i s m t h a t w o u l d r e s e t s o m e t h i n g t h i s slowly—after a l l , f r u i t f l y breeding experiments can drive an advantageous mutation throughout

a

population

within

a

comparatively

modest

n u m b e r of generations. Could it be "drift," with no particular a d a p t i v e function? O t h e r critics s u g g e s t e d that the c h a n g e s seen in the pygidia w e r e not e v o l u t i o n at all, b u t w e r e a response

to

slowly

changing

conditions

on

the

sea-floor.

These kinds of pygidial modification might be a response to changing

oxygen

levels,

for

example.

Where

gradualistic

c h a n g e h a d been o b s e r v e d in other fossil e x a m p l e s it w a s u s u a l l y p l a n k t o n t h a t d i s p l a y e d it. T h e r e w a s r e a l l y n o q u e s t i o n that

Ogygiocarella

and

its

friends

were

bottom-dwellers,

so

t h i s e x a m p l e r e t a i n s its p u z z l e s a n d d i s p u t e s . W h a t n o b o d y q u e s t i o n s i s t h e r e a l i t y o f w h a t P e t e r o b s e r v e d a n d its r e l e v a n c e t o e v o l u t i o n a r y q u e s t i o n s , a n d w h o c o u l d fail t o a d m i r e the unusual persistence that inspired the observations?

T h e r e is a n o t h e r test case for e v o l u t i o n w h e r e trilobites h a v e a s s u m e d a starring role: as a field d e m o n s t r a t i o n of w h a t is k n o w n as heterochrony. T h e t e r m is G r e e k for " o t h e r t i m e , " and is simply explained. Trilobites g r e w from a larval state starting as little d i s c s — p r o t a s p i d e s — a m i l l i m e t r e or less in length. T h e y then passed through several moults as they increased in size to achieve the adult state. T h e small g r o w t h !75

T R I L O B I T E !

s t a g e s first s h o w t h e d e m a r c a t i o n o f t h e ( p r o t o ) tail f r o m t h e head. T h e n the thoracic s e g m e n t s are " r e l e a s e d " into the thorax, o n e at a time in most species, and very probably at successive moults, until they reach the adult n u m b e r of segments.

Thereafter, in most trilobites, segment n u m b e r remains the s a m e even t h o u g h the trilobite m a y increase quite dramatically in s i z e — t h e m a t u r e n u m b e r of s e g m e n t s in the thorax m a y be

achieved

while

the

trilobite

is

still

quite

small.

C h a n g e s t o a l m o s t all p a r t s o f t h e c a r a p a c e o c c u r d u r i n g t h i s growth, properly called ontogeny. T h e growth story is k n o w n for a large a r r a y of trilobite species, a n d this m a k e s t h e m e s p e cially important in studying the relationship b e t w e e n the d e v e l o p m e n t of the individual (ontogeny) and the appearance of novel features in n e w species (phylogeny).

T h e smallest trilobite, Acanthopleurclla, a diminutive, blind trilobite with four thoracic segments mature at just over a millimetre in length. Ordovician, Shropshire, western England.

176

A

Matter

of

Life

and

Death

S o m e years ago Adrian R u s h t o n and I noticed that the tiny trilobite

Acanthopleurella,

with

only

w a s p r o b a b l y r e l a t e d to Shumardia pleurella

is

even

smaller

than

four

thoracic

segments,

( p . 231) w i t h s i x . Acantho-

Shumardia,

and

we

concluded

t h a t i t w a s d e r i v e d f r o m its a n c e s t o r w i t h s i x s e g m e n t s b y a process

of

"arrested

development"—it

became

sexually

mature when only four segments had been released. This e x p l a i n e d its m i n u t e s i z e , m a t u r e a t j u s t o v e r a m i l l i m e t r e . I t w a s p a r t i c u l a r l y s a t i s f a c t o r y t h a t w e i d e n t i f i e d Shumardia a s an ancestor, since Sir J a m e s Stubblefield h a d used this very trilobite to prove that the thorax g r e w during o n t o g e n y by release of thoracic s e g m e n t s from the front edge of the pygidi u m — t h e y were "budded off" there and m o v e d forwards, like c u s t o m e r s in a g r o w i n g q u e u e , as m o r e w e r e a d d e d on b e h i n d . We could feel confident that the last t w o segm e n t s w e r e r e p r e s s e d i n Acanthopleurella b y c o m p a r i s o n w i t h Shumardia.

At about the same time, K e n M c N a m a r a w a s making m o r e d e t a i l e d o b s e r v a t i o n s o n t h e L o w e r C a m b r i a n t r i l o b i t e Olenellus f r o m S c o t l a n d . Olenellus w i l l b e r e m e m b e r e d a s t h e m o s t primitive trilobite f r o m o u r p a r a d e , a f o r m w i t h n u m e r o u s thoracic segments and a tiny p y g i d i u m . Soft, yellowish shales crop out in a few places in the bleak but beautiful coastal north-west Highlands, where sphagnum bogs and tussock grassland are populated by a f e w highlanders and rather m o r e sheep, both equally hardy. This is f a m o u s g r o u n d for geology, because the interpretation of the M o i n e Thrust there w a s the subject of a great H i g h l a n d s C o n t r o v e r s y in the latter half of the n i n e t e e n t h century. T h e C a m b r i a n shales lie u n d e r neath the older Moine rocks, which were eventually proved to have been thrust over on top of the C a m b r i a n . T h e trilobites from the shales provided u n d e n i a b l e evidence of their age. I h a v e s p e n t a v e r y w e t a n d cold s u m m e r field s e a s o n in the area a r o u n d t h e little t o w n of D u r n e s s — a b o u t as far northwest as you can go on mainland Britain—snuffling rather unsuccessfully o v e r the o u t c r o p after fossils.

177

My woollen

T R I L O B I T E !

s o c k s s p e n t m o s t o f t h e t i m e d r y i n g o v e r a m e a g r e b u t a n e fire.

I w a s left w i t h r e d o u b l e d a d m i r a t i o n for the geologists P e a c h a n d H o m e w h o h a d w o r k e d out every detail o f this u n c o m promising landscape, a n d most of it on foot. In the century since these heroes solved the geological m a p we've become a n a m b y - p a m b y lot.

K e n M c N a m a r a w a s interested in the trilobites for reasons other than their antiquity. He had realized that the genesis of s e v e r a l s p e c i e s o f Olenellus c o u l d b e u n d e r s t o o d v e r y r e a d i l y as an example of heterochrony. He already k n e w the developm e n t ( o n t o g e n y ) of the c o m m o n e s t species,

Olenellus lapwor-

thi, n a m e d f o r t h e g r e a t C h a r l e s L a p w o r t h , t h e s c i e n t i s t w h o in turn h a d n a m e d the Ordovician. K e n recognized that various

other

Olenellus

species

from Scotland

had

adults

that

r e s e m b l e d t h e immature g r o w t h s t a g e s of O. lapworthi. To c i t e o n e feature, the single pair of spines on the edge of the c e p h a l i c s h i e l d o f O . lapworthi w e r e p o s i t i o n e d a t t h e g e n a l angle, m o r e or less on a level with the back end of the glabella.

In various of these other species the spines w e r e shifted forwards, opposite one or another of the glabellar furrows, so that the b a c k b o r d e r of the h e a d curved forwards to the genal a n g l e . T h i s i s e x a c t l y w h a t w a s f o u n d i n small g r o w t h s t a g e s o f O . lapworthi, b u t l o s t i n t h e a d u l t . S i m i l a r k i n d s o f c h a n g e s h a p p e n e d with the size and position of the eyes. M o s t striking o f a l l w a s a s m a l l t r i l o b i t e w i t h three p a i r s o f s p i n e s o n t h e e d g e of the headshield, so spiky a creature that it had been d u b b e d armatus b y its d i s c o v e r e r , a n d s o d i f f e r e n t f r o m Olenellus t h a t it h a d b e e n p l a c e d in a s e p a r a t e g e n u s , Olenelloid.es.

K e n M c N a m a r a realized that this oddity closely resembled a " b l o w n u p " version of one of the smallest growth stages of Olenellus

lapworthi.

Not

only

that,

this

strange

little

animal

only had nine thoracic segments, compared with the fourteen or so of O. lapworthi. L o o k e d at in t h i s l i g h t , O. armatus s e e m e d to cry out: " I ' m an overgrown b a b y ! " Ken arranged

five

Olenellus

species

( w i t h lapworthi a t t h e

base) in a kind of sequence of progressive babyhood, culmi-

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A

Matter

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Life

and

Death

n a t i n g in O. armatus. He b e l i e v e d t h a t O. lapworthi m i g h t h a v e l i v e d i n t h e d e e p e s t w a t e r , a n d c o n s i d e r e d t h a t O . armatus probably lived in the shallowest m a r i n e environment, with the other species arranged in between. He speculated that warmer, shallower C a m b r i a n environments stimulated earlier maturation. T h e five successive species then slotted neatly into different ecological niches related to water depth. H o w e v e r i n t e r p r e t e d , Olenellus p r o v i d e d t h e m o s t v i v i d d e m o n stration of h o w apparently major differences b e t w e e n species m a y a c t u a l l y j u s t b e a q u e s t i o n o f a l t e r i n g rates o f d e v e l o p m e n t . O. armatus a n d O. lapworthi l o o k l i k e v e r y d i f f e r e n t t r i l o bites—so

much

different

genera—but

so

that

they

they

had

are

once been

fundamentally

placed related,

into as

might be clocks with the s a m e m e c h a n i s m s but different faces.

Similar heterochronic variations have n o w been recognized in m a n y different kinds of animals and plants: differential development seems to be an important source of novelty througho u t t h e b i o l o g i c a l w o r l d . Olenellus's a n c i e n t e x a m p l e g i v e s a n e w twist to Wordsworth's aphoristic line " T h e child is father of the m a n . " * If the child can b e c o m e a precocious g r o w n - u p , there are also counter examples, w h e r e the i m m a t u r e p h a s e of a descend a n t s p e c i e s r e s e m b l e s its

ancestor.

The descendant does

everything that the ancestor d o e s d u r i n g d e v e l o p m e n t , but a d d s o n a little m o r e , a n o v e l t y o f its o w n u n s e e n i n a n y e a r lier, o r m o r e p r i m i t i v e s p e c i e s . T h i s i s t h e f a m i l i a r c a s e o f r e c a pitulation, of "ontogeny repeating phylogeny," w h i c h biology students used to have to learn as a kind of mantra. T h e grossly simplified version that once portrayed the h u m a n e m b r y o as p a s s i n g p r o g r e s s i v e l y t h r o u g h p r o t o z o a n a n d f i s h o n its w a y

*For those w h o like technical terms, this kind of heterochrony is k n o w n as paedomorphosis, of which Stephen J. Gould and Ken McNamara have distinguished several varieties. The "paedo" root is Greek for childhood. Its mirror image, where new features are added late in ontogeny of more derived species, is known as peramorphosis. Again, peramorphosis has been classified into several varieties.

179

T R I L O B I T E !

to m a m m a l has long b e e n discarded. T h e living horseshoe c r a b , Limulus, w a s s u p p o s e d t o h a v e a " t r i l o b i t e l a r v a " i n d i c a tive o f its c o m m o n a n c e s t r y w i t h m y f a v o u r i t e a n i m a l s , b u t t h i s is a r e s e m b l a n c e d u e to a s h a r e d s i m p l i c i t y as m u c h as a s h a r e d a n c e s t r y . B u t l e g i t i m a t e e x a m p l e s a r e still t o b e f o u n d in fossil lineages. A m o n g the pelagic, seafaring trilobites I s t u d i e d , f o r e x a m p l e , h u g e - e y e d a d u l t s a c t u a l l y h a d larger goggle-eyes than their larvae and i m m a t u r e growth stages, w h i c h w e r e m o r e like the relatively normal-eyed

trilobite

f r o m w h i c h they h a d d e s c e n d e d . In this way, development timing m a r c h e d on b e y o n d the ancestor; a good n e w feature w a s exaggerated; and what started as a novelty became an institution.

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Trilobites can d e m o n s t r a t e seminal facts about evolution.

Modern biologists' evolutionary study has disappeared progressively into the g e n o m e , a n d there it has wrought w o n d e r ful things; but w h a t is lacking is a t i m e f r a m e , case histories that see evolution in process in real time a n d real space.

Experimental biologists have at most a few years to play with; to a palaeontologist a f e w million is " b u t the blinking of an e y e . " Trilobites can, i n d e e d , p r o v i d e evolutionary e x a m p l e s w o r t h y o f p o o r Dr. K a u f m a n n ' s y o u n g l i f e . C h a n g e s i n d e v e l o p m e n t timing, with their profound results in shape, m a y be the result of no m o r e than tinkering w i t h the genetic code. T h e molecular finger that resets the clock m a y do it with no m o r e than an insouciant tweak: even a single gene might control the time switch that creates a difference as p r o f o u n d as those b e t w e e n Olenellus lapworthi a n d O. armatus. It is t h e j o b of m o l ecular biologists to identify the controlling genes (and I doubt n o t t h a t t h e y ' l l still b e t h e r e t u c k e d a w a y i n t h e D N A e v e n a f t e r 500 m i l l i o n y e a r s o r m o r e ) , j u s t a s i t i s t h e d u t y o f t h e palaeontologist to describe examples of the same genes in action, and h o w long in geological time a n d space they take to spin their creative magic.

There is no change without death. I have portrayed the creation of a species, b u t n o t its d e s t r u c t i o n . T h e h i s t o r y of the trilobites w a s a history of the p a s s i n g of the old as m u c h as the appearance of the new. This turnover of species—life after death after life—is the stuff of n o r m a l evolutionary c h a n g e (scientists often refer to it as " b a c k g r o u n d rates"). T h e better adapted replaced the w o r s e ; or the species that originated allopatrically replaced another that shared a c o m m o n ancestor merely b e c a u s e climate c h a n g e d to favour an interloper.

Life has a l w a y s b e e n a m e s s y business, a n d prosperity has alternated between luck and virtue in biology, as in h u m a n affairs. M a y b e we can turn to trilobites for objective w i t n e s s of the respective influences of chance and design. Their mole-

181

T R I L O B I T E !

cules are lost for ever, naturally. But the signature that their m o l e c u l e s left u p o n their b o d i e s , w h i c h w e r e s a v e d i n the g e o l o g i c a l r e c o r d , e n d u r e s till r o c k c r u m b l e s .

Ultimately, trilobites did not cut the evolutionary mustard.

They were extinguished without progeny. My hope has faded that, w h e n today's m i d - o c e a n ridges w e r e explored by bathys c a p e , i n s o m e d i m l y - k n o w n a b y s s t h e r e m i g h t still d w e l l a solitary trilobite to bring Palaeozoic virtues into the age of the s o u n d b i t e . Sadly, there h a s b e e n no trilobitic coelacanth to astonish biologists, no atavistic survivor w h o might answer directly all t h o s e q u e s t i o n s we w o u l d like to a s k of the genes.

Three hundred million years was course enough.

W i t h o u t d e a t h there is little i n n o v a t i o n . E x t i n c t i o n — d e a t h of a species—is part a n d parcel of evolutionary change. In the a b s e n c e of this kind of extinction n e w d e v e l o p m e n t s w o u l d not prosper. In our o w n history, periods w h e n ideas have been perpetuated by d o g m a , preventing the replacement of old by n e w ideas, h a v e also been times of stultifying stagnation. The D a r k A g e s in w e s t e r n society w e r e the m o s t static, least innovative of times. So the fact that trilobites w e r e replaced by batches of successive species through their long history was a testimony to their evolutionary vigour.

Just as m e c h a n i s m s for generation of n e w species can be u n d e r s t o o d in the field a n d in the laboratory by s t u d y i n g trilobites, so we can m a p out the reason underlying their slow decline. D u r i n g their heyday, h u n d r e d s of different genera w e r e spread through a l m o s t every m a r i n e habitat that we know. If y o u measure success by sheer n u m b e r s and variety then the true A g e of Trilobites ranged from the middle of the Cambrian to the Ordovician period. But they were fecund t h r o u g h o u t their history: e v e n in the latest strata to yield their remains several species can be f o u n d together. It is tempting to p o r t r a y t h e i r h i s t o r y a s a r a p i d l y b u i l d i n g crescendo f o l l o w e d b y a s l o w diminuendo w h i c h l a s t e d u n t i l s i l e n c e f i n a l l y p r e vailed. Such an analogy would be misleading. As in much of the story of biological diversity, trilobites prospered and suf-

182

A

Matter

of

Life

and

Death

fered setbacks by turn. Their extinction phases coincided with those that affected m a n y o t h e r k i n d s o f a n i m a l s . T h e s e w e r e times w h e n the usual rates of extinction were accelerated, w h e n losers were w e e d e d out a n d winners favoured to survive and subsequently prosper. S o m e animals that appeared at about the s a m e time as the trilobites—clams are a good e x a m p l e — e n d u r e d the seesaws of fate alongside their arthrop o d c o n t e m p o r a r i e s , a n d i n t h e e n d o u t l a s t e d t h e m all. W i t h trilobites, there w e r e m a n y casualties along the way. Extinction events

close to

the b e g i n n i n g of the late C a m b r i a n

r e m o v e d m a n y trilobite families that had appeared early in the history of the group. A better studied event at the e n d of t h e O r d o v i c i a n , s o m e 440 M a , e x t i n g u i s h e d m a n y m o r e o f t h e families

which

had

given

earlier

faunas

their

particular

f l a v o u r . T h e tiny, b l i n d a g n o s t i d s , t h o s e e n i g m a t i c m i n i a t u r e s f r o m t h e C a m b r i a n , d i s a p p e a r e d . T h e y h a d l a s t e d n e a r l y 100 million years—reflect on the few millions of years that our o w n genus has survived, and p o n d e r the m e a n i n g of "succ e s s . " M a n y l a r g e t r i l o b i t e s r e l a t e d t o Isotelus a n d Ogygiocarella also died out, as did small ones like trinucleids w h o s e m e d a l lion shields w e r e so typical of O r d o v i c i a n strata—in fact, m o s t of those animals Peter Sheldon studied in such detail perished without progeny. Then, too, the free-swimming, giant-eyed, pelagic trilobites of w h i c h I had g r o w n so fond are never found again after the Ordovician, a n d I believe that trilobites failed to o c c u p y that particular ecological niche after that period. Olenids died out, my favourite family from my Spitsbergen days, which had patiently prospered ever since C a m b r i a n t i m e s , h o l d i n g t h e i r o w n a g a i n s t all c o m e r s . T r u l y t h i s w a s the end of a biological world.

T h e termination of the Ordovician w a s also w h e n a great Ice A g e , centred u p o n the S o u t h P o l e — w h i c h w a s at that t i m e in n o r t h e r n A f r i c a — s p r e a d its refrigeration a l m o s t c o m p l e t e l y around the world. Ice ages recur in Earth history, rarely a n d irregularly, and a l w a y s with p r o f o u n d effects. T h e Pleistocene I c e A g e w i t h its w o o l l y m a m m o t h s a n d c a v e b e a r s w a s m e r e l y

183

T R I L O B I T E !

T h e head and tail of Mucronaspis (here from the Ordovician of Thailand), a ubiquitous trilobite at the time of the great Ordovician glaciation.

the latest of t h e m . Ice ages yield characteristic rocks, those d u m p e d by retreating glaciers or p r o d u c e d by the fallout from floating icebergs. They share a kind of promiscuous variety: large and small boulders or pebbles lumped and jumbled t o g e t h e r , a n d r o c k s o f d i f f e r e n t o r i g i n s all m i x e d u p . I c e s i m ply acts as a carrier, and w h e n it melts everything it picked up along the w a y just drops. T h e resulting rocks have a l u m p y texture, looking from afar like a badly cooked p l u m pudding.

T h e s e characteristic tillites a b o u n d i n m a n y rock sections c o n taining strata w h i c h w e r e deposited close to the end of the Ordovician, a n d associated with t h e m fossils can very often b e c o l l e c t e d w h i c h a r e k n o w n a s t h e Hirnantia f a u n a . (Hirnantia is n o t a t r i l o b i t e — i t is a b r a c h i o p o d t h e s h e l l s of w h i c h a r e typical of this Ice Age.) It is astonishing h o w w i d e s p r e a d the Hirnantia f a u n a is. A s p e c i a l t r i l o b i t e , Mucronaspis, is o n e of its typical denizens, but other trilobites are usually very rare. It is r e c o g n i z a b l e b y a little s p i k e a t t h e e n d o f its tail. I h a v e c o l lected it from a wet and breezy hillside in North Wales, where C w m Hirnant provided the inspiration for the n a m e of the d i a g n o s t i c shell. I h a v e collected it a g a i n in a h u m i d q u a r r y in

184

A

Matter

of

Life

and

Death

southern Thailand, where beads of sweat from my brow blobbed on to the cephalic shields as soon as I wrested t h e m from their enclosing sandstone. I h a v e seen the s a m e trilobite from shales collected from beneath the Tablelands of South Africa. I have seen it from Poland, and Norway, and China.

The implication is perhaps rather obvious, but no less interesting for that. T h e s e w e r e " c o o l " trilobites. T h e y c h a s e d out o t h ers f r o m climates w h i c h h a d b e e n m o r e t e m p e r a t e b e f o r e the ice sheets a d v a n c e d — a n d the effects of the glaciation p e n e trated

to

the

equator.

Mucronaspis

imposed

a

uniformity

almost as pervasive as the blue suits that blanketed C h i n a during the ascendancy of the Maoists. It is n o w k n o w n that extinctions also o c c u r r e d in the d e e p seas at m o r e or less the same

time

as

Mucronaspis

spread

over

continental

shelves,

and affected planktonic organisms as profoundly. M a n y of the trilobites w h i c h b e c a m e extinct p r o b a b l y s p e n t their larval life in the o p e n sea as part of the p l a n k t o n , a n d this m a y h a v e rendered t h e m particularly vulnerable. T h r o u g h this critical bottleneck, only fortunate trilobites passed. There w a s no w a y of k n o w i n g in advance that being "cool," or not having planktonic larvae, might e q u i p for survival. T h e s e trilobites did not store up the genetic equivalent of ships' biscuits to see t h e m through the hard times. S o m e simply p o s s e s s e d — b y c h a n c e — features that w o u l d serve t h e m well in the crisis. This is an important discovery about the very nature of mass extinction.

W h o k n o w s if lessons m a y yet be d r a w n from my animals which might influence the actions of another a n i m a l — t h e one e e c u m m i n g s called M a n u n k i n d ? A n d w h o is n o w causing another extinction as severe as that e n d u r e d by the trilobites at t h e e n d of t h e O r d o v i c i a n . . .

But the end of the Ordovician w a s by no m e a n s the beginning of the end for the trilobites.

Families which passed

through from the Ordovician a b o u n d e d in the Silurian—in fact, there m a y h a v e b e e n a l m o s t as m a n y species as earlier, but derived from a m o r e limited set of c o m m o n ancestors.

Crusty-headed

encrinurids

and

185

spiny-tailed

Cheirurus

grace

T R I L O B I T E !

m a n y collections, a n d it is tempting to believe that the evolving ecosystem p r o d d e d trilobites into yet m o r e inventiveness with their versatile exoskeleton. This w a s the time w h e n phacopids, w i t h their clever eyes, started to c o m e into their own.

R o c k surfaces can be covered with them: the Silurian sea-floor could be as crunchy underfoot as it w a s at any earlier time.

Many

of

these

trilobites

continued

into

Devonian

strata,

w h i c h w a s t h e a c m e f o r all t h i n g s s p i n y a n d b l i s t e r e d , p u s t u lose, scrofulose a n d carbunculate. B u t alongside such trilobite e x t r a v a g a n z a s w e r e m o r e o r d i n a r y c i t i z e n s l i k e Proetus w h i c h m i g h t , at a g l a n c e , be m i s t a k e n for an a v e r a g e C a m b r i a n or Ordovician animal.

I t w a s Proetus a n d its a l l i e s (Gerastos, p .

188) t h a t s u r v i v e d t h e n e x t c r i s e s l a t e i n t h e D e v o n i a n — t h e trilobites had by then enjoyed s o m e 80 million years of plenty since the last m a s s extinction. In s o m e w a y s , the Devonian events are m o r e p u z z l i n g than the Ordovician. T h e r e are several of t h e m , o n e after the other, a n d each is associated with an invasion of oxygen-poor waters over the continental shelves, w h i c h h a d the effect of r e m o v i n g the coral reefs in w h i c h m a n y trilobites lived. This w a s m o r e like death f r o m a thous a n d c u t s t h a n f r o m a s i n g l e a s s a s s i n a t i o n . T h e coup de grace w a s t h e F r a s n i a n - F a m e n n i a n e v e n t ( t h e n a m e d e s c r i b e s its stratigraphical level b e t w e e n t w o geological divisions), which has been ascribed to a gigantic meteorite i m p a c t — t h e kind of p h e n o m e n o n usually cited as the cause of dinosaur extinction, a c a t a s t r o p h i c e v e n t w h i c h h a p p e n e d 180 m i l l i o n y e a r s a f t e r t h e last k n o w n trilobite.

W h a t e v e r the cause, after the F r a s n i a n - F a m e n n i a n only Proetus a n d its a l l i e s s u r v i v e d i n t o t h e C a r b o n i f e r o u s . W h a t h a d b e e n d o z e n s o f f a m i l i e s h a d d w i n d l e d t o a h a n d f u l , all o f t h e m closely related. E v e n so, m a n y n e w types o f trilobites appeared as innovations during the Carboniferous period.

A b o u t twice a y e a r I get a parcel of p a p e r s f r o m G e r m a n specialists describing a n e w b a t c h of s p e c i e s — t h e discoveries never s e e m to c o m e to an end. B o b O w e n s from the National M u s e u m of Wales has found n e w forms in the familiar crags

186

A

Matter

of

Life

and

Death

of the Carboniferous L i m e s t o n e that m a k e up " t h e b a c k b o n e of England," the stone-walled, sheep-studded uplands of the Pennines. Proetide trilobites spread out into m a n y of the ecological niches that had b e e n o c c u p i e d in earlier times by trilobites from a richer selection of families. T h e y m a n a g e d to play the s a m e ecological tunes as their forebears, but they u s e d different evolutionary instruments. T h e y spread into d e e p water, and into n e w l y re-established coral reefs. As a consequence, s o m e of these late trilobites c a m e superficially to resemble their ecological twins recovered f r o m Ordovician, Silurian and D e v o n i a n rocks. T h e r e w e r e e v e n s o m e species that c a m e to

look

like

Phacops—although

they

did

not

develop

the

s c h i z o c h r o a l e y e . . . W h a t a m a r v e l l o u s d i s s e m b l e r is n a t u r e !

If I w e r e of a m o r e anthropocentric cast of m i n d I m i g h t w o n der if palaeontological puzzles had been placed in the rocks s i m p l y t o test t h e m e t t l e o f s c i e n t i f i c i n v e s t i g a t o r s . B i o l o g i s t s and palaeontologists seem to spend so m u c h of their time unravelling the deceptions of nature. R e s e m b l a n c e of s h a p e is everywhere, for ecological necessity dictates form: animals earning a similar living in the wild resemble one a n o t h e r — b a t and bird, skink and snake. To pluck out deeper evolutionary truths, the origins of anatomical structures must be recognized—what

is

termed

homology.

Homology

reveals

the

deeper concordances of genes and development against the Sirens of overall r e s e m b l a n c e . Is this glabella the result of a modification

from

some

deeper

design,

one

which

truly

reveals c o m m o n ancestry with another trilobite altogether f r o m o n e w e h a d s u p p o s e d a t first g l a n c e ? I s w h a t w e s e e i n m o r p h o l o g y p r i m a r i l y r e l a t e d t o l i f e h a b i t s , j u s t a s all " f l a t f i s h , " w h i l e d o u b t l e s s flat, m a y h a v e c o m e f r o m m o r e t h a n one

ancestor?

Maybe,

while

he

contemplated

Ogygiocarella,

L h w y d sensed the important resemblance—ecological equiva l e n c e — w h i l e m a k i n g n o n s e n s e o f t r u e b i o l o g i c a l affinity. A trilobite m a y yet be a fish in spirit. In p a l a e o n t o l o g y , as in h u m a n affairs, there is m o r e than o n e kind of truth.

By the Permian only a m o d e s t n u m b e r of trilobites re-

187

Gerastos. Three fine individuals of this neat little proetide trilobite, which almost seem to be saying "two's company, three's a c r o w d . " Large eyes are very close to the glabella, genal spines are shot, and thorax has ten segments. Devonian, Morocco. (Photograph courtesy Prof. Brian Chatterton.)

LEFT:

O n e of the last trilobites, Ditomopyge, from the Permian of Wichita, K a n s a s — t w o views of an enroled specimen (X3). (Photograph courtesy Bob Owens.)

BELOW:

A B O V E : Enroled example of the Ordovician trilobite Symphysurus from S w e d e n , natural size.

188

A

Matter

of

Life

and

Death

mained, twenty or so genera. Even so, they can occasionally be c o m m o n fossils. T h e v e r y last trilobites s e e m to h a v e d i s a p p e a r e d a little b e f o r e a n o t h e r great m a s s e x t i n c t i o n at t h e e n d of the Permian; by then, they were minor players in the marine drama. Their great days had passed. These postscript animals are m o s t l y f o u n d in rather s h a l l o w habitats in w h a t were tropical seas: p e r h a p s this m a d e t h e m especially v u l n e r able to climate change. I regret that, unlike s o m e of their contemporaries a m o n g the molluscs and brachiopods, n o n e of these late trilobites w e r e a d a p t e d to d e e p - s e a life, w h e r e they might have seen out the traumas that swept across the land and continental shelves. As it w a s , they were part of a scenec h a n g e that p r e s a g e d a n e w act in the s t o r y of life. I d o u b t that w e h a v e y e t d i s c o v e r e d t h e very l a s t s p e c i e s , t h a t r a r e s u r v i v o r t h a t still p l i e d its P a l a e o z o i c h a b i t s w h e n t h e a n c e s t o r s o f t h e dinosaurs were strutting around the streamsides of G o n d w a n a . T h e trilobites did e n d with a w h i m p e r rather than a bang. I am reminded of the piece that Joseph H a y d n wrote as a subtle protest against the m e a n musician's w a g e s at the c o u r t o f E s t e r h a z y . I n t h e f i n a l m o v e m e n t o f t h e Farewell Symphony t h e m u s i c i a n s l e a v e o n e b y o n e , w h i l e t h e m u s i c c o n t i n ues vigorously to unfold. In the end a solitary fiddle carries on a l o n e — a n d only then is there silence.

189

VIII

Possible

Worlds

I h a v e s p e n t m u c h of my w o r k i n g life r e m a k i n g the w o r l d . I have p u s h e d half of Europe across half an Atlantic. I have closed ancient seaways and opened up others. I have been able to n a m e an ocean greater than the Mediterranean, and then c o n d e m n e d it to perdition. My job has been to describe the outlines of vanished continents, and

to plot the seas

around them: in short, to d r a w a m a p of the Earth as it was n e a r l y 500 m i l l i o n y e a r s a g o . T o d o t h i s , I h a v e u s e d t r i l o b i t e s .

W h e n I meet s o m e of my c o m m u t i n g acquaintances on the 6:21 h o m e t o H e n l e y - o n - T h a m e s t h e y o c c a s i o n a l l y e n q u i r e w h a t I h a v e d o n e that day. I h a v e b e e n k n o w n to reply: "I m o v e d A f r i c a 600 k i l o m e t r e s t o t h e s o u t h . " T h e y u s u a l l y t u r n quickly to the soccer page.

O n e o f t h e first b o o k s t o o p e n m y e y e s t o t h e s e d u c t i o n s o f t h e s c i e n t i f i c m e t h o d w a s a c o l l e c t i o n o f e s s a y s c a l l e d Possible Worlds b y p e r h a p s t h e g r e a t e s t o f s c i e n c e w r i t e r s , I . B . S . H a l d a n e . O n e of t h e c h a p t e r s w a s c a l l e d On being one's own rabbit; and

this

spirit of e x p e r i m e n t a l

adventure w a s typical.

It

encouraged me to speculate u p o n the m a n y mysteries of the world, and h o w unravelling one or two small ones might be the b e s t t h i n g to do w i t h a life. N o w , by a twist of f o r t u n e , I am privileged

to

create

my

own

190

possible

worlds:

vanished

Possible

Worlds

worlds, written in a geography generated in my imagination, and

argued

out with

a

dozen

of my

colleagues.

I

have

dreamed of chains of volcanic islands belching fumes and spewing lava into archipelagos s w a r m i n g with trilobites and nautiloids. I h a v e seen these a n i m a l s suffocate on a r a v a g e d sea-floor, killed a n d i m m o r t a l i z e d at o n e stroke. On a W e l s h mountainside I

have tested the truth of such an ancient

tragedy by breaking a hard rock in which memories of volcanic ash render the surface grey as w o o d s m o k e , and in which l i e s e n t o m b e d t h e s h a d o w o f a t r i l o b i t e , p e t r i f i e d t o tell o f i t s dreadful end. In my mind's eye I have seen volcanic archipelagos collapse and die as continent collides with continent, squeezed b e t w e e n m a s s e s so vast that an ancient Stromboli m i g h t be as v u l n e r a b l e as a g r a p e in a nutcracker. This is the O r d o v i c i a n w o r l d , a g l o b e so alien that it b e a r s little c o m p a r i son with the atlas of today. T h e r e is land and sea, to be sure, but the continents are not those we have learned by rote in our first c l a s s r o o m . T h e y a r e s t r a n g e s h a p e s , c u r i o u s l y a r r a n g e d .

It is not so long ago, geologically speaking,

that our

present-day g e o g r a p h y w a s a matter for speculation. In Hereford Cathedral, in the m i d d l e of E n g l a n d , the M a p p a M u n d i is d i s p l a y e d i n a d i m l i g h t f o r its o w n p r o t e c t i o n , b u t i t s e e m s a n appropriately mysterious illumination by which to inspect Richard of H o l d i n g h a m ' s p a r c h m e n t w o r l d of the late thirteenth century. A n d w h a t a curious construction it presents.

W i t h its d o m i n a t i o n b y l a n d r a t h e r t h a n s e a , t h e M a p p a Mundi looks quite unlike the familiar Mercator projection of o u r o w n w o r l d . I n its c e n t r e l i e s J e r u s a l e m . T h e B r i t i s h I s l e s are placed on one edge. But the cathedral t o w n of Lincoln is portrayed with s o m e t h i n g a p p r o a c h i n g realism: a street lined with houses runs d o w n to the River W i t h a m from the cathed r a l on a h i l l . L i k e t h e f a m o u s c a r t o o n c o v e r of The New Yorker s h o w i n g a detailed M a n h a t t a n Island f r o m w h i c h the rest of the world retreats in ever sketchier outline, Lincoln m u s t have been the axis of the k n o w n world for the creator of the M a p p a Mundi, and the detail b e y o n d w a s approximate. Travel w a s

191

T R I L O B I T E !

difficult; c a r t o g r a p h y w a s imprecise (and p e r h a p s Richard w a s as reluctant to explore as some N e w Yorkers to venture beyond

Brooklyn).

At

first

glance,

the

lands

around

the

Mediterranean s e e m impossibly vague, but closer inspection s h o w s C y p r u s a n d Sicily, a l m o s t r e c o g n i z a b l e . I n t h e m o r e remote regions dwell m o n s t e r s a n d giants: the satyr in Egyptpeople resembling birds birds

called

avalerion

(cicone)

which

near Samarkand;

produce

two

eggs

in India

after

sixty

years, and then drown themselves as they hatch; unicorns.

T h e accurate cartography of the Renaissance and beyond banished these mythical beasts to ever more remote redoubts.

S o m e w o u l d still h a v e t h e m l u r k i n g i n d e e p l a k e s i n t h e A n d e s , or in r e m o t e A m a z o n i a : the last hiding places. In m a k ing geographical m a p s of the Ordovician I, too, am sending dragons packing, firming up v a g u e shapes, and restoring s o m e kind of truth.

The Permian M a p p a M u n d i , which is the continent of Pangaea, has b e c o m e a l m o s t familiar. T h e supercontinent that b o u n d all o u r p r e s e n t c o n t i n e n t s i n t o o n e i s n u m b e r e d a m o n g those facts that m a n y p e o p l e tend to p a c k a w a y in their portm a n t e a u of m e m o r a b l e scientific c o n c e p t s , like the notion that pi can n e v e r be exactly evaluated, or that black holes eat matter. T h e p e r s u a s i v e , c o m p l e m e n t a r y s h a p e s o f t h e c o a s t s o f eastern South America and western South Africa now seem to m a k e sense: they are a legacy of the divorce of the supercontinent. T h e South Atlantic ocean w i d e n e d , progressively, from a fissure to a w i d e sea, as oceanic crust w a s a d d e d at the midAtlantic ridge. Africa and South America moved apart on their r e s p e c t i v e plates. W h a t o n c e s e e m e d a n o u t r a g e o u s idea c a n n o w b e a c c e p t e d w i t h a n o d — o f course t h e c o n t i n e n t s w e r e o n c e u n i t e d : it's o b v i o u s ! India rifted f r o m the eastern side

of Africa

(leaving

Madagascar

stranded)—and

as

it

impinged on Asia squeezed into existence the highest range of m o u n t a i n s o n e a r t h — t h e H i m a l a y a . O n satellite photographs t h e w r i n k l e d r a n g e s e e m s t o c r u m p l e b e f o r e t h e w e d g e o f the s u b c o n t i n e n t , a n d o n e can a l m o s t feel the pressure that threw

192

Possible

Worlds

up M o u n t Everest. F r o m the vantage point of space, it seems as if mountains can be m a d e as easily as one m a y scrunch up a tablecloth by leaning on a place-mat. T h e Alps, similarly, w i n d in a line t h r o u g h E u r o p e , a r u m p l e d s e a m of tectonics that tells a n o t h e r t a l e o f c r u s t b u c k l i n g u n d e r t h e m o t o r o f m o v e m e n t — i n this case m o v e m e n t of Africa n o r t h w a r d s , shuffling a w h o l e series of plates across the Mediterranean. Pangaea b r o k e u p , a m a r r i a g e pro tern, a m a r r i a g e m a d e n o t in h e a v e n but in the tectonic b a s e m e n t of the world.

T h e unity of Pangaea corresponded with the trilobites' demise. S o m e researchers h a v e sought to relate the former splicing of the continents

to major extinctions,

and

it is

unquestionable that the n e w l y a n n e a l e d supercontinent created unusual conditions to w h i c h f e w organisms could successfully adapt. As we h a v e seen, the trilobites w e r e already v u l n e r a b l e . B u t w h a t o f t h e e a r l i e r h i s t o r y , w h e n t r i l o b i t e s still ruled the world? (I realise I am being over-emphatic in my imagery here, but just occasionally I lapse from scientific propriety a n d c o c k a little s n o o k at the h e g e m o n y of t h e d i n o saurs.) For twenty-five years or so it has b e e n recognized that P a n g a e a itself w a s b u t a p h a s e in the history of the continents.

Plate tectonics did not begin with the break-up of Pangaea, any more than it has ended with the volcanic eruptions on Monserrat. Rather, the trajectories of continents are the surface expression of the internal engine of the Earth, deep convection driven by the heat of the interior carrying the superficial plates like skin on a c a u l d r o n of broth: u n s t o p p a b l e currents, n e a r l y a s o l d a s E a r t h itself. B e f o r e P a n g a e a t h e r e w e r e o t h e r Possible Worlds, o t h e r d e s i g n s f o r t h e M a p p a M u n d i . P a n g a e a i t s e l f a c c u m u l a t e d f r o m t h e c o l l i s i o n o f still e a r l i e r c o n t i n e n t s : it was but a brief phase of unification preceded, as it w a s followed, by a longer period w h e n continents and oceans divided the Earth's surface piecemeal. These earlier continental m a s s e s c a m e t o g e t h e r t h r o u g h t e c t o n i c e v o l u t i o n t o s t i t c h P a n g a e a together, like an ill-made quilt. T h e s u b s t a n c e of the earlier continents w a s the s a m e ancient, P r e c a m b r i a n conti-

193

T R I L O B I T E !

n e n t a l c r u s t t h a t still m a k e s u p m o s t o f A f r i c a , N o r t h A m e r i c a (Laurentia), Siberia or the Baltic Shield. But it w a s cut into different p a t c h e s f r o m t h o s e we r e c o g n i z e on the school atlas.

T h e r e w a s no obligation on the part of Nature to use the s a m e pieces to design an Ordovician continent.

O c e a n s once separated these earlier continents. T h e oceans w e r e d e s t r o y e d little b y little a s t h e m a r r i a g e o f P a n g a e a w a s c o n s u m m a t e d . Oceanic crust w a s obliterated by subduction w h e r e plates plunged d o w n w a r d s into ocean trenches; it was the s a m e m e c h a n i s m in the Palaeozoic as is seen today off the eastern coast of Japan. Ordovician volcanic rocks yielding the remains of trilobites m a y h a v e been p r o d u c e d around islands c o m p a r a b l e to the great volcanoes of I n d o n e s i a — t h e s e are the explosive expression of plate destruction; the trilobites are testament to a sea troubled by blasts of steam a n d incandescent clouds of ash.

If the oceans of the Ordovician have vanished, h o w do we k n o w they were once there? If they had simply disappeared without trace they w o u l d indeed be invisible now. But virtua l l y all a n c i e n t o c e a n s l e a v e t h e i r s i g n a t u r e u p o n t h e E a r t h ' s surface. Continents originally separated by oceans eventually collide with one another and throw up mountain ranges—in just the s a m e w a y as India's collision with Asia generated the H i m a l a y a n ranges. A n c i e n t m o u n t a i n ranges cross today's continents like old scars. T h e s e linear w o u n d s m a r k the course of the margins of former oceans. Erosion over tens of millions of years has w o r n a w a y m o u n t a i n chains of great age, so that they are l o w c o m p a r e d with the comparatively juvenile Alps or Andes. Look at any topographical m a p of Asia and you cann o t fail to n o t i c e the U r a l s , w i n d i n g across t h e v a s t n e s s of that c o n t i n e n t all t h e w a y f r o m t h e i s l a n d o f N o v a y a Z e m l y a i n t h e Russian Arctic (where my Oslo sage Olaf Holtedahl established his reputation describing s o m e of the ancient rocks) s o u t h w a r d s t o w a r d s t h e C a s p i a n Sea. It l o o k s like a s e a m , a n d t h a t i s e x a c t l y w h a t i t is: a m o u n t a i n r a n g e m a r k i n g t h e s e a m b e t w e e n a Baltic a n d a Siberian plate. In the Ordovician, these

194

Possible

Worlds

plates were far apart, an ocean apart: different w o r l d s destined to collide. T h e y b e c a m e annealed only w h e n the ocean between them had been entirely c o n s u m e d by s u b d u c t i o n — a n d this unification h a p p e n e d long before the greater m a r riage of Pangaea. T h e former existence of an ocean is betrayed by extinct volcanoes of the type associated with subduction, or by volatile minerals a n d c o p p e r ores that leak up from the interior of the Earth w h e n oceans die. Very old plate b o u n d aries m a y not be so obvious, especially if they have b e e n partly covered by younger rocks. To reconstruct primeval g e o g r a p h y the scientist m u s t find a n d u n z i p those old scars, open out once more the vanished oceans, running the tape of time backwards, further and further into the past. T h e m o r e distant the past, the m o r e the uncertainties in positioning a n y continent, the m o r e like Richard o f H o l d i n g h a m w e b e c o m e .

My travelling c o m p a n i o n s on the H e n l e y - o n - T h a m e s train m i g h t h a v e a s k e d , w i t h s o m e j u s t i c e , " M o v e d A f r i c a 600 k m ?

W h y n o t 900 k m ? O r t w o t h o u s a n d ? " F o r w e s t r u g g l e t o k n o w the Ordovician world imperfectly, like trying to solve a jigsaw puzzle through the w r o n g e n d of a telescope: a h u n d r e d kilometres or so can represent the t e m p o r a r y amnesia of a b a d afternoon.

So we have to forget the g e o g r a p h y we know, and think afresh of Possible Worlds. There are s o m e tools to help us. Several rock types contain m a g n e t i c m i n e r a l s . T h e heavy, d a r k i r o n o r e m a g n e t i t e w a s t h e m a t e r i a l u s e d first t o i n v e s t i g a t e the properties of m a g n e t i s m by William Gilbert, court physic i a n to Q u e e n E l i z a b e t h I, w h o s e De Magnete (1600) p r e s c i e n t l y observed that the Earth " b e h a v e s like a giant m a g n e t . " T h e m a g n e t i c field s t r e a m s b e t w e e n the m a g n e t i c p o l e s just like the "lines of force" that iron filings trace on p a p e r a r o u n d a bar magnet. Accordingly, suspended magnets inevitably point to the Earth's poles. Magnetite is a c o m m o n mineral in nature, often occurring as disseminated grains in sandstones, scattered like s e e d s in a c a k e . W h e n a r o c k is d e p o s i t e d (or a l a v a erupted), if it contains magnetic minerals they will acquire the *95

T R I L O B I T E !

magnetization

prevalent

at

the

time.

This

magnetization

r e m a i n s , a fossil of its o w n k i n d , e v e n w h e n the plate on w h i c h t h e r o c k u l t i m a t e l y r e s i d e s m a y h a v e m o v e d f a r f r o m its p l a c e of origin. By m a k i n g s o m e comparatively simple measurements on the angles of inclination and declination of magneti s m the position of the pole at the time of magnetization can be r e c o v e r e d — l i k e an accusing finger pointing polewards, the r o c k m a g n e t i s m b e t r a y s its p l a c e o f origin. T h e ancient latit u d e ( o r palaeolatitude) i s r e v e a l e d b y t h i s m e t h o d , b u t l o n g i t u d e is m u c h less precisely constrained, so that the position of a g i v e n c o n t i n e n t i s n e v e r exactly l o c a t e d . B u t t h e s e d a t a p r o vide a w o n d e r f u l starting point to reconstructing an ancient global g e o g r a p h y : so m u c h so that p a l a e o m a g n e t i c i a n s are often referred to as " p a l a e o m a g i c i a n s " by their colleagues, with only a hint of sarcasm. T h e further y o u go back in time, t h o u g h , the m o r e p r o b l e m s there can b e , until by the era of the trilobites m a n y of the m e a s u r e m e n t s of the palaeopoles prove u n r e l i a b l e ; r o c k s c a n be r e m a g n e t i z e d later, for e x a m p l e , or the signal can b e c o m e corrupted. This has led to conflicts between the palaeomagicians and the palaeontologists, each defending their different ancient geographical interpretations. Occasionally, t h e s e g e t t o b e s h o u t i n g m a t c h e s . T h e p a l a e o m a g i c i a n s p r o n o u n c e that only their science is " h a r d " science, and once I heard one of their n u m b e r p r o n o u n c e that " o n e palaeopole is w o r t h a t h o u s a n d fossils." I suspect that the s a m e scientist w o u l d proclaim that o n e physicist is w o r t h a dozen palaeontologists—the misguided cad.

T h e use of fossils in reconstruction of vanished worlds has a l o n g a n d h o n o u r a b l e tradition. Fossils w e r e , after all, k e y ingredients in the a r g u m e n t s about the reality of Pangaea, and this before m a n y physicists h a d accepted the idea of a great continent. H o w could y o u h a v e such similarity b e t w e e n the floras a n d faunas of P e r m i a n South Africa, South America and India unless they h a d b e e n o n c e conjoined? Trilobites can be used to rehearse similar arguments: we can use them to m a p ancient continents. T h e y s w a r m e d in the shallow seas that

196

Possible flooded the

interior

of

Worlds

Ordovician

North

America;

they

a b o u n d e d w h e r e the seas w a s h e d over the frigid shores of G o n d w a n a ( s e e p a g e 202); t h e y c r a w l e d i n s o f t m u d s o v e r what we n o w k n o w as southern Sweden and Estonia. The trilobites despise our political barriers: they follow only the b i d d i n g of their o w n taste in geography. Trilobites that lived in these shallow seas were influenced by climate and environm e n t , just as m a r i n e o r g a n i s m s t o d a y are different at the tropics a n d a t t e m p e r a t e latitudes. S e a c r e a t u r e s h a v e their o w n thermometers, and most of them are picky gourmets about w h a t they eat, a n d w h e r e . Predators specialize on prey w i t h t h e care of a c o n n o i s s e u r sorting o u t a C h a t e a u Lafite f r o m a vin ordinaire. S o m e animals revel in lime; others choose sand a s a h i d i n g s i t e ; still o t h e r s d o t e o n s t i c k y , b l a c k m u d . I n s h o r t , sea animals h a v e a sense of place, a n d trilobites w e r e no exception.

W h e n the Ordovician continents w e r e dispersed a r o u n d the world's oceans the trilobites d e v e l o p e d differently on separate plates—especially w h e n they were at different latitudes.

E a c h c o n t i n e n t a c q u i r e d a c h a r a c t e r o f its o w n — p e r h a p s I s h o u l d rather say a cast of c h a r a c t e r s of its o w n — a n d m a n y of the characters w e r e trilobites. M a p the trilobites a n d y o u m a p the continent. With help from palaeomagnetism it is possible to pinpoint the latitude to w h i c h each set of trilobites w a s adapted. Then, too, different rock types tend to accumulate at different latitudes. If we can recognize an a p p r o p r i a t e set of rocks then it is possible to m a k e an informed guess at the ancient environment. Limestones laid d o w n u n d e r tropical sunshine are distinctive enough. T h e y often f o r m great thickness of strata w h i c h are consolidated f r o m m u d s of calcium carbonate k n o w n as aragonite. Today, y o u h a v e to go to places like the B a h a m a s to find their m a t c h . Collecting fossils f r o m g r e a t cliffs o f f o r m e r t r o p i c a l l i m e s t o n e s c a n b e a d i s p i r i t i n g experience, as y o u r h a m m e r b o u n c e s helplessly off the intransigent surfaces. With m o r e experience, y o u scan the rock face f o r little, t e l l - t a l e s i g n s o f t r i l o b i t i c l i f e — a b i t o f a p y g i d i u m ,

197

T R I L O B I T E !

p e r h a p s , subtly projecting f r o m the rock. You curse the fact that limestone and trilobites are m a d e of the s a m e material, calcite, as y o u try to lever out a block with your precious speci m e n s s o m e w h e r e in the m i d d l e . I h a v e lost t w o fingernails this way. But the trilobites in limestone are usually beautifully p r e s e r v e d — i f only y o u can get t h e m out. At the other end of the ancient w o r l d , there w e r e no limestones in areas close to the poles. Shales are typical trilobitic rocks, from w h i c h w h o l e carapaces can be collected with ease, but they are seldom as beautiful as the limestone examples. Thus sedimentary rocks, fossil species,

a n d p a l a e o m a g n e t i c m e a s u r e m e n t s all c o n -

tribute to a picture of w h e r e any given locality w a s at the time w h e n the trilobites thrived.

I m a g i n e that y o u are o n e of a t e a m of alien geologists visiting

this

planet

200

million

years

hence,

after

mankind's

excesses had sterilized the continents as naked as they were in the Ordovician. The engine of plate tectonics would not have s t o p p e d , f o r all o u r p a s s i n g . N o w i m a g i n e t h a t A u s t r a l i a h a d been split a p a r t — i n the s a m e fashion as P a n g a e a w a s r i v e n — into three great fragments, w h i c h h a d drifted on their o w n course to Antarctica, p e r h a p s , Africa a n d Asia respectively.

H o w could the alien palaeontologist reconstruct the former a n t i p o d e a n continent? S h e m i g h t w e l l start b y recognizing the geological integrity of e a c h of the three f r a g m e n t s . N e x t , fossil collections w o u l d soon reveal a strong b o n d between these dispersed pieces—kangaroos, wombats, possums, koalas, and a w h o l e battery of other marsupials w o u l d be recognized as endemics s h a r e d b e t w e e n t h e t h r e e f r a g m e n t s . P l a c e t h e m c l o s e together, a n d the marsupials h a d a h o m e to match their family resemblance. Unless the subsequent tectonics had blurred the outlines, it might even be that the three fragments w o u l d lock together in a m a n n e r as particular as a jigsaw p u z z l e solved.

So w i t h the trilobites: in this case, we are the visitors f r o m the future, a n d we travel to as strange a world. It m a y be objected that Australia's m a r s u p i a l s are terrestrial animals, and therefore a better g u i d e to a f o r m e r continent than ani-

198

Possible

Worlds

mals that could s w i m across seas. This is undoubtedly true.

But the Ordovician w a s very different from the present day because then the seas extended m u c h further over the continents than they do now. Shallow seas w e r e like evolutionary cooking pots for e n d e m i c species. It w o u l d be the s a m e today if the sea once more flooded over the vast plains of Australia, seeping into w h a t is n o w desert a n d endless scrub. I h a v e collected trilobites in the v e r y centre of Australia, in a spot so r e m o t e that e v e n the dingoes w e r e t a m e , a n d slunk up for a l o o k at m e . In the O r d o v i c i a n , this s a m e site w o u l d h a v e b e e n as remote from the continent edge as it is today—the sea had flooded an extraordinary distance. The dingo looked at me with the s a m e curiosity w i t h w h i c h I g a z e d on a trilobite never before seen by m a n — w e w e r e both aliens in our differe n t w a y s . F r o m m y v a n t a g e p o i n t o n a l o w hill I c o u l d s e e f a r a w a y across the p e n e p l a i n , a p l a c e w h e r e e r o s i o n h a d d o n e its b e s t , a s t h e b o o k o f I s a i a h tells u s , t o m a k e " e v e r y h i l l a n d m o u n t a i n l o w . . . a n d the r o u g h p l a c e s p l a i n . " It w a s n o t difficult to imagine a w a r m , shallow sea d r o w n i n g this barren land, and I could reanimate the trilobites in my m i n d readily e n o u g h — a sea t h r o n g i n g w i t h life. I n t h e s a m e r o c k s w e found evidence of w h a t p r o v e d to be one of the earliest fish k n o w n to science: another alien. S o m e of the trilobites proved to be as distinctive as kangaroos.

I will n o w try to d r a w an O r d o v i c i a n atlas, my o w n possib l e w o r l d , a M a p p a M u n d i o f 485 m i l l i o n y e a r s a g o ( s e e p a g e 201). S o m e l a n d m a s s e s s e e m n e a r l y f a m i l i a r . T h e r e i s L a u r e n tia—North America and Greenland—united then as now. But it is lying on its side, a n d t h e e q u a t o r p a s s e s t h r o u g h its m i d r i f f . W h a t i s ( n o w a d a y s ) its e a s t e r n s i d e i s d i f f e r e n t , t o o . I t has "bitten off" part of the w e s t e r n side of the British Isles.

T h e trilobites f r o m north-western Scotland a n d w e s t e r n Ireland are the s a m e as those from western N e w f o u n d l a n d and Greenland. The rocks from the island of S k y e — t o which Bonnie Prince Charlie fled—are the s a m e kind of limestones, precipitated u n d e r the gaze of a tropical sun, as are f o u n d in N e w

199

T R I L O B I T E !

Y o r k S t a t e . C o n v e r s e l y , o n l y t h e western p a r t o f N e w f o u n d land is part of Laurentia, the Great N o r t h e r n Peninsula, that long p r o m o n t o r y w h i c h sticks up like an optimistic t h u m b on the side of the island adjacent to C a n a d a , w h e r e trilobites and r o c k s tell o f c o n n e c t i o n s w i t h N e v a d a a n d O k l a h o m a .

Elkanah Billings, a pioneer palaeontologist in the middle of the n i n e t e e n t h century, n a m e d m a n y of the fossils. His Bathyurellus a n d Petigurus w e r e t r i l o b i t e s b e l o n g i n g to a f a m ily, B a t h y u r i d a e , w h i c h w e r e a s t y p i c a l o f t h e O r d o v i c i a n tropics of Laurentia as kangaroos are of Australia. Find these animals in the rocks, a n d y o u k n o w that the ground on which y o u stand w a s part of Laurentia. In N e w f o u n d l a n d , they are f o u n d only on the w e s t e r n side of the island; their c o n t e m p o raries on the eastern side are utterly different. A suture representing a vanished ocean (called Iapetus) passed b e t w e e n the t w o sides of the island. In the early Ordovician, the east and w e s t coast o f N e w f o u n d l a n d w e r e a s w i d e l y separated b y sea as Brazil a n d Nigeria are today. T h e m a p of the Bathyuridae extends northwards into Scotland and Greenland; Spitsbergen, my geological cradle, w a s part of the same Laurentian continent. T h e telltale trilobites are there in the Canadian Arctic in Ellesmere Island, and in Alaska, and through weste r n C a n a d a , a n d all d o w n t h r o u g h t h e w e s t e r n p a r t o f t h e U S A into the Great Basin of Utah, N e v a d a and Idaho—then across through Texas, O k l a h o m a , and up the western edge of the Appalachians to N e w York State, where the omniprese n t C h a r l e s D o o l i t t l e W a l c o t t first d e s c r i b e d

Bathyurus.

The

labours of dozens of palaeontologists mapped the course of the continent stamped with the unmistakable signature of their trilobites. W h e n I c a m e to w o r k in N e v a d a , m a n y years after my stay in N e w f o u n d l a n d , I h a m m e r e d out s o m e of the v e r y s a m e t r i l o b i t e s u n d e r t h e f r a g r a n t pinon p i n e a s I h a d first c r a c k e d f r o m the h a r d l i m e s t o n e s in the Arctic, while b e i n g s c o l d e d by a tern w h o s e nest I h a d a p p r o a c h e d too closely. T h i s striking similarity p r o v e s that in the Ordovician the equator ran lengthwise through North America, rather

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Siberia

The early Ordovician world, 485 million years ago, as the trilobites reveal, with explanatory m a p labelling the principal continents. This is a Mercator projection with the ancient equator through the centre. T h e upper m a p will help you recognise the present-day continents in their Ordovician positions. The crosses on the lower m a p indicate the lines of latitude on present-day geography.

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T R I L O B I T E !

than

the

continent having the north-south

orientation of

t o d a y . ( T h i s , I m i g h t say, i s t h e s i m p l e s t o f t h e a n c i e n t c o n t i nents to illustrate.)

At the other climatic extreme lay western G o n d w a n a . The n a m e of the " L a n d of the G o n d s " has a distinguished part in the story of the recognition of Pangaea. The great turn-of-thecentury geologist Eduard Suess used it to denote the concordance of geology between South America, peninsular India and Africa (and now, as we know, Antarctica also). They were conjoined in the P e r m i a n , a n d t h e n they w e r e split asunder.

But G o n d w a n a existed long before the Permian: it is one of the greatest parts of the Collective Unconscious of the planet.

Forged together in the late Precambrian, the basement rocks o f G o n d w a n a a r e m o r e t h a n h a l f a s o l d a s t h e E a r t h itself: incorruptible, u n c h a n g i n g through half a dozen convulsions w h i c h affected vast s w a t h s of the crust. T h e textbooks that I w a s brought up with referred to such ancient, stable blocks as " s h i e l d s " (as in t h e C a n a d i a n Shield) a n d it is a designation I like b e c a u s e of the connotations of shield as armour, as s o m e thing that resists attack. In the Ordovician the western edge of G o n d w a n a w a s close to the South Pole, which probably then lay in northern Africa. T h e great continent mostly huddled in the southern half of the world, but was so extensive that it stretched all the w a y f r o m the pole to the equator, which crossed through Australia. No present-day continent is c o m p a r a b l e in extent. A n o t h e r suite of trilobites observed their loyalty to the g e o g r a p h y of G o n d w a n a , just as the Bathyuridae had in Laurentia.

A third continent is k n o w n as Baltica. On present geography

Baltica

comprises

Norway,

Sweden

and

the

Baltic

republics—Lithuania, Estonia, Latvia. Eastwards, it extends as far across Russia as the Urals. Recall that this m o u n t a i n chain m a r k e d the former e d g e of a continent, a s e a m only annealed w h e n continental Asia w a s a s s e m b l e d by the collision of Siberia w i t h Baltica. Siberia itself w a s a separate plate in the O r d o v i c i a n — a l l c o n t i n e n t a l s e a m s w e r e u n p i c k e d t h e n , all

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Possible

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zips u n z i p p e d . I e x p l o r e d the O r d o v i c i a n of Baltica w i t h a Swedish schoolmaster called Torsten Tjernvik in

1975.

He

guided me around a succession of small limestone quarries in southern Sweden, where the rocks lay horizontal and undef o r m e d — n o t h i n g had disturbed t h e m since their deposition a b o u t 450 m i l l i o n y e a r s b e f o r e m y v i s i t . W h a t w a s r e m a r k a b l e w a s h o w m u c h t i m e w a s d i s t i l l e d i n t o s o little r o c k . I n W a l e s , I w a s used to h u n d r e d s of feet of d a r k m u d s representing a million or t w o years of s e d i m e n t a r y deposition. In S w e d e n , half of the entire Ordovician timescale—30 million years or m o r e — could be i n s p e c t e d in a single quarry. A single s u b d i v i s i o n of the Ordovician timescale could be as thin as a biscuit: in our jargon,

the

sequence

was

condensed

(deposition

was

very

slow). Yet there w e r e trilobites aplenty, a n d they w e r e a different set of a n i m a l s a g a i n f r o m t h o s e I h a d collected in N e w f o u n d l a n d . B i g tails w e r e e v e r y w h e r e o f a c r e a t u r e ( r e l a t e d , but distantly,

to

Ogygiocarella)

c a l l e d Megistaspis.

Not a whis-

per of a bathyurid. Tjernvik w a s in his eighties w h e n I visited S w e d e n . His English w a s r e m a r k a b l y fluent: he h a d learned m u c h of his use of the idioms from the novels of P. G. W o d e house, and the result w a s charmingly anachronistic. W h e n a particularly

fine

Megistaspis

turned

up

he

would

say,

"absolutely top hole, old b e a n ! " If he wished to impart s o m e important item of information it w o u l d be, " c a n I h a v e a w o r d in your shell-like?"* At the end of the day: "Toodle-pip, old b o y ! " Everything I s a w s h o w e d me that Baltica w a s a separate continent. Both the types of rock and the trilobites (and subsequently palaeomagnetism) suggested that Baltica w a s located at temperate latitudes, m i d w a y b e t w e e n Laurentia a n d G o n d w a n a in the early Ordovician. As for the trilobites, they w e r e "absolute corkers!"

There is something intimidating about long inventories of n a m e s and places, and the capacity to r e m e m b e r such details

*Wodehousian abbreviation of "shell-like ear," a poetic cliche originally applied to pretty females.

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T R I L O B I T E !

Ogyginus, a trilobite typical of Ordovician G o n d w a n a . An example from Shropshire, UK. Life size.

a n d directories can recall the extraordinary but pointless p o w e r s o f t h e idiot savant. W h o r e a l l y w a n t s t o k n o w t h e d a y o f t h e w e e k o n w h i c h 2 9 F e b r u a r y fell i n t h e l e a p y e a r s o f t h e l a s t f e w c e n t u r i e s ? E v e n lists o f trilobite n a m e s are tedious. But the patient c o m p i l a t i o n s of lists of fossils f r o m d o z e n s of localities p r o v i d e the r a w i n g r e d i e n t s for m a p s of distribution: these, in their turn, describe the boundaries of former contin e n t s . T h i s i n f o r m a t i o n c o u l d s c a r c e l y b e o f more i m p o r t a n c e .

Today l i s t s — t o m o r r o w the world! So, to break my rule about a v o i d i n g lists, here is a roll-call of s o m e of the trilobites w h i c h are found in the earlier Ordovician rocks of western G o n d w a n a , a n d only there, a n d lived in the cool waters close to the Ordovician Colpocoryphe,

pole:

Neseuretus,

Calymenella,

Zeliszkella,

Selenopeltis,

204

Ormathops, Pradoella,

Ogyginus, Placoparia,

Possible

Worlds

Merlinia . . . a s f i n e a p a r a d e o f c l a s s i c a l t o n g u e - t w i s t e r s a s y o u could wish, and I could go on. Each one of these animals is distinctive; taken together they describe half an ecosystem. I m e n t i o n t h i s list i n p a r t i c u l a r b e c a u s e i t s a v e d m y s c i e n t i f i c bacon.

England and Wales and the eastern part of N e w f o u n d l a n d together comprise Avalonia, a n a m e bearing the flavour of Arthurian r o m a n c e , but in fact taken from the part of N e w foundland on w h i c h St. J o h n ' s is situated—the Avalon Peninsula. T h e r o c k s tell u s that e a s t e r n N e w f o u n d l a n d a n d W a l e s were once a single entity; in contrast to east and west N e w foundland which were separated by the Iapetus ocean in the Ordovician.

Avalonia

is

what

is

termed

a

microcontinent—a

relatively small fragment of continental crust which m a y have a history of " d r i f t i n g " — i n d e p e n d e n t of the great continents of Laurentia and G o n d w a n a . M a y b e the Arthurian connotation i s n o t s o i n a p p r o p r i a t e a f t e r all: A v a l o n i a s t r u c k o u t o n i t s o w n o n a k i n d o f g e o g r a p h i c a l d e r r i n g - d o , a n d its s t o r y i s a t a l e o f d e p a r t u r e s a n d s k i r m i s h e s . I n t h e 1980s t h e r e w a s a s c i e n t i f i c conflict about the position of Avalonia relative to G o n d w a n a .

With my old friend Robin C o c k s — a brachiopod expert—I had proposed that in the earlier Ordovician Avalonia w a s probab l y p a r t o f G o n d w a n a . I n s u p p o r t I h a d a list o f G o n d w a n a n trilobites Ormathops,

from

Wales

Colpocoryphe,

and

Shropshire:

Ogyginus,

Neseuretus,

Placoparia,

Calymenella,

Merlinia.

Now

t h e i m p o r t a n c e o f t h i s t a l l y w i l l b e e v i d e n t : c a r r y i n g s u c h a list h o w could Avalonia have been a n y w h e r e else? A n d since there w a s nothing in c o m m o n with Baltica either—not one trilobite, hardly a b r a c h i o p o d — w e c o n c l u d e d that cool water Avalonia m u s t have been separated from temperate Baltica by another ocean, which, in

1982, w e c a l l e d

Tornquist's Sea.

(Tornquist was a f a m o u s geologist w h o had w o r k e d on the critical area.) This is h o w I c a m e to n a m e a v a n i s h e d ocean.

Later in the Ordovician, c h a n g e s in the trilobite faunas told us that A v a l o n i a h a d rifted off G o n d w a n a a n d m o v e d n o r t h wards over Tornquist's Sea to collide with Baltica. I confess to

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T R I L O B I T E !

a slight twinge of m e g a l o m a n i c satisfaction in playing god w i t h a p i e c e of l a n d that is n o w h o m e to fifty million p e o p l e .

Conflict arose because a palaeomagnetic "fix" placed Avalonia m u c h nearer the equator and closer to Baltica, several thousand kilometres from our proposed position. As is usual with such scientific r o w s opinions h a r d e n e d almost i m m e d i ately. W e w e r e t o l d b l u n t l y t h a t o n e p a l a e o m a g n e t i c d a t a point w a s w o r t h a t h o u s a n d trilobites. We riposted that if A v a l o n i a a n d B a l t i c a h a d b e e n s o c l o s e h o w c o m e all t h e f o s sils w e r e so d i f f e r e n t — w h i l e t h o s e of Avalonia w e r e so like t h o s e o f F r a n c e , S p a i n , a n d N o r t h A f r i c a ? I t b e c a m e a test c a s e for us; " s o f t " science versus " h a r d " science; fossils versus the m a c h i n e s ! I n t h e e n d , t h e f o s s i l s w o n ; Merlinia w a s v i c t o r i o u s .

Since

Merlinia

was

named

after

King

Arthur's

magician

m a y b e the fate of Avalon s h o u l d h a v e b e e n o b v i o u s for thoro u g h l y non-scientific reasons. It s u b s e q u e n t l y proved that the p a l a e o m a g n e t i c " f i x " h a d b e e n f l a w e d , a n d a later, b e t t e r o n e agreed with the trilobites. Today, Tornquist's Sea is m a r k e d on all t h e m a p s o f O r d o v i c i a n g e o g r a p h y . I t h a s c r o s s e d o v e r t h a t m y s t e r i o u s l i n e w h i c h d e m a r c a t e s w h a t i s still t h e o r y f r o m a c c e p t e d fact. Trilobites t r i u m p h a n t . But as Avalonia m o v e d a w a y f r o m G o n d w a n a t o w a r d s Baltica, T o r n q u i s t ' s w a s itself s u b d u c t e d a w a y ; a n e w o c e a n a p p e a r e d b e h i n d A v a l o n i a i n its stead. W h a t plate tectonics creates, it also destroys.

But w h a t of Australia, on the eastern side of the vast G o n d w a n a n continent? T h e w e s t e r n part of Q u e e n s l a n d and the adjacent areas of the Northern Territory were also flooded by that pervasive Ordovician sea. W h e n J o h n Shergold and I travelled to this r e m o t e area there w a s only the vaguest notion of what might be in the rocks. This is country of peculiar emptiness. Hardy eucalypts dot a vast semi-desert, where a f e w beef cattle eke out an existence only if they are watered from wind-driven " b o r e s . " The bores often turn dry or run to poison. P a v e d roads do not exist. B e y o n d Boulia tracks drive into the

nothingness,

and

there are areas

where

"gibber

plains" of wind-polished stones render the trackways virtu-

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Possible

Worlds

ally invisible. It is easy to get lost, a n d I spent m u c h of my time leaning out of the vehicle looking for broken twigs that m i g h t indicate the f o r m e r p a s s a g e of a L a n d - R o v e r in the last field season. T h e Fierce S n a k e lives in these w a s t e s , the m o s t poisonous snake in the world, a creature so spectacularly veno m o u s t h a t o n e o f its b i t e s c a n kill h u n d r e d s o f l a b o r a t o r y mice. It obviously n e e d s to be an effective predator in this terrain of thin r a t i o n s — b u t w h y so o u t r a g e o u s l y lethal? After all, snakes do not eat k a n g a r o o s . Surely this is the m o s t literal example of "overkill" in nature. T h e heat is relentless, but there is an exquisite half-hour in twenty-four as the sun squeezes d o w n into the horizon, and the beer can is cracked o p e n a n d t h e steak sizzles o n the fire, w h e n y o u w o u l d s w e a r that to w o r k here w a s the greatest privilege a scientist could earn. T h o s e years of poverty as a research student, the poorly salaried assistantship that followed, suddenly s e e m worthw h i l e . " I ' m b e i n g paid f o r t h i s , " y o u s a y t o y o u r s e l f i n c r e d u lously. T h e n it starts to get cold.

O n l y o n c e did my e n t h u s i a s m for the desert suffer a blow.

There are very few p u b s in the outback and they are sorry and functional places: a plain bar, w o o d e n floors, a flophouse out the back. Station h a n d s collect their p a y cheques after m o n t h s o n the j o b , i n t e n d i n g t o g o t o B r i s b a n e for the h i g h life. T h e y o f t e n g e t n o f u r t h e r t h a n t h e first p u b . T h e i r m o n e y i s c r e d i t e d on a "slate," and there they sit—or m o r e likely s t a n d — d r i n k i n g i t all a w a y . A f t e r a w e e k o r t w o o f t h i s a k i n d o f d o p e y , s u r l y aggressiveness is

the c o m m o n e s t condition:

eyes hooded,

b o r e d o m mired in alcohol. T h e y b e c o m e w h a t an Australian w o u l d call a " r a t b a g , " spoiling for a fight. To go into o n e of these drinking dens with a " p o m m y " accent is just the stimulat i o n t h e y h a v e b e e n l o o k i n g for. " B l o o d y p o m s — c a n ' t s t a n d ' e m , " t h e y will a n n o u n c e , fists c l e n c h i n g a n d u n c l e n c h i n g .

T h i s i s w h e r e t h e W i l d W e s t still e x i s t s , t h i s r e m o t e i s l a n d w i t h i n t h e I s l a n d C o n t i n e n t . F i g h t s still s e t t l e s c o r e s , r e a l o r i m a g i n e d . To a natural c o w a r d like myself, this is terrifying.

A f t e r m y first e n c o u n t e r w i t h o n e o f t h e s e d r u n k s I s p e n t t h r e e

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T R I L O B I T E !

h o u r s s p e a k i n g in a c o d m i d - E u r o p e a n accent to escape their further attention. It w a s hard for t h e m to d e v e l o p an attitude to somebody w h o came from Wallachia.

A u s t r a l i a n O r d o v i c i a n tropical trilobites p r o v e d to be different again. Separated by latitude from those of western G o n d w a n a , a n d b y o c e a n s f r o m t h o s e o f L a u r e n t i a , they, t o o , had evolved their o w n signature. There were strange animals w i t h l u m p s all o v e r t h e h e a d s h i e l d t h a t l o o k e d s u p e r f i c i a l l y l i k e t h e f a m o u s D e v o n i a n t r i l o b i t e Phacops—except t h a t c l o s e r inspection s h o w e d t h e m rather to be related to Dr. L h w y d ' s Ogygiocarella,

and

to

Asaphus

(we

named

it

Norasaphus).

This

w a s a fine e x a m p l e of h o w trilobites living in similar habitats could c o m e to resemble one another—like different actors d o n n i n g the s a m e clothes to play identical roles. This phen o m e n o n is k n o w n as homoeomorphy. W h e r e we pulled out these trilobites f r o m the soft, limy sandstones, living e x a m ples of the s a m e thing w e r e dozing the heat a w a y under the spinifex bushes: marsupial " m i c e " are mouse-like in design and habits, but they are truly marsupials along with wallabies and koalas. Nature revels in such deceptions. Shergold and I h a d just split a n o t h e r f r o m early O r d o v i c i a n rocks of the outb a c k s h o w i n g the s a m e trick m o r e than four h u n d r e d million years earlier.

It w o u l d be d i s i n g e n u o u s to pretend that trilobites alone reconstructed the Ordovician world, although they were crucial in resolving s o m e of the disputes. S o m e w h a t regretfully, I have to admit that my days of playing with cardboard cutouts of continents are over. N o w a d a y s , information of such c o m plexity has to be handled by computers which can integrate information f r o m m a n y sources, p a l a e o m a g n e t i s m , trilobites, s e d i m e n t s a n d a l l . C o m p u t e r s c a n h a n d l e all t h e p r o b l e m s o f projection and scaling that are indispensable to m a k e sense of the results: w o r l d s can be s w i v e l l e d w i t h the flick of a switch.

A computer has m a d e the Ordovician Mercator projection in which the G o n d w a n a continent seems so strangely squashed a b o u t the b o t t o m o f the w o r l d (it's the s a m e projection effect

208

Possible

Worlds

that m a k e s G r e e n l a n d look so triangular on m a n y m o d e r n maps). You can understand what G o n d w a n a really looked like if y o u project f r o m the pole as centre as s h o w n on p a g e 210. T o a c o m p u t e r t h a t i s r o u t i n e . B u t w h a t e v e r t r i c k s a r e u s e d it is a l w a y s difficult to t u r n a s p h e r e into a p l a n e , a n d w o r s e still i f t h e c o n t i n e n t a l s h a p e s a r e s t r a n g e r s t o u s . C o m puter reconstructions are only as good as the information with w h i c h they are s u p p l i e d — t h e a d a g e " r u b b i s h in, r u b b i s h o u t " applies just as m u c h here as it does to dating agencies.

Machines have been k n o w n to line up sad mismatches of continents, d o o m e d never to m a k e a successful marriage.

In this c h a p t e r I h a v e d e s c r i b e d the w o r l d as it w a s for a few tens of millions of years during the 300-million-year history of the trilobites. It is a l m o s t a snapshot in t i m e — a time slice m i g h t be b e t t e r — b u t it is a frozen O r d o v i c i a n m o m e n t in a d y n a m i c history of a m u t a b l e w o r l d , for the continents hardly ceased in their global peregrinations. By the Silurian, 45 million years later, the o c e a n that h a d o n c e s e p a r a t e d Baltica and Avalonia from L a u r e n t i a — I a p e t u s — h a d disappeared,

subducted

away.

The

great

mountain

chain—the

Caledonides—running through the Appalachians to Scotland, and thence to the m o u n t a i n o u s fjord c o u n t r y of N o r w a y , w a s the consequence of the subsequent continental collision, an engagement almost as dramatic and complex as that which t h r e w u p t h e A l p s 250 m i l l i o n y e a r s later. T r i l o b i t e s t h a t h a d lived apart w e r e brokered into a forced marriage. T h e faunas changed in h a r m o n y with the geography. T h e eventual reopening of the Atlantic Ocean w h e n Pangaea broke up long afterwards

followed—but

only

approximately—the

same

seam as had been closed by the Caledonian orogeny in the D e v o n i a n . As a result, f r a g m e n t s of the earlier continents w e r e stranded in positions far f r o m their O r d o v i c i a n h o m e s : now, northern Scotland is on the opposite side of the Atlantic from Laurentia, to which it originally belonged—contrariwise, the two halves of Newfoundland

are welded

together today

w h e n they were originally far apart. E v e n as Iapetus h a d

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T R I L O B I T E !

Ordovician G o n d w a n a from a polar projection, centred on Africa, with peninsular India, South America and Antarctica easily recognizable. T h e southern part of Great Britain is the small promontory at the top of the m a p .

closed, another seaway—the Hercynian—opened up, running across central E u r o p e and further to the East. We have met this o c e a n already at the b e g i n n i n g of this b o o k , for it w a s close to o n e shore of this s e a w a y that H a r d y ' s trilobite lived ( h a d i t n o t b e e n f i c t i o n ) a n d C o r n w a l l ' s t w i s t e d cliffs a n d n o b l e granites w e r e the legacy of the ultimate d e m i s e of that ocean in the next great tectonic cycle. Earth, like a nagging conscience, reopens old w o u n d s . W h o k n o w s if s o m e tens of millions of years h e n c e Asia m a y again cleave apart along the Urals? W h o k n o w s if n e w animals m a y yet evolve at the bidd i n g of a shattered h o m e l a n d ?

It w o u l d take a b o o k as long as this again to relate the w h o l e narrative of the continents as seen through the eyes of the trilobites that s w a r m e d a r o u n d them. Nearly three hund r e d m i l l i o n y e a r s s e p a r a t e s t h e b a s e o f t h e C a m b r i a n 545 m i l lion years a g o f r o m the eventual d e m i s e of the trilobites. This w a s a stretch of time that s a w the world r e m a d e twice. A n d

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with each reconstitution of the geography my animals juggled and adjusted to the n e w climatic a n d oceanic r e g i m e n , s o m e times c o m i n g together, at others rifted apart. E v e n n o w , there are scientific a r g u m e n t s o v e r w h e r e this or that great tract of land might have been in the late Ordovician or in the early Sil u r i a n . N o M a p p a M u n d i i s f i n a l , a n d o t h e r w o r l d s a r e still possible. But there should be e n o u g h here to s h o w h o w geography and evolution have waltzed cheek-to-cheek, and h o w trilobites give e v i d e n c e of the c h a n g e s in partners in the dance.

N o w , at last, it is possible to reconstruct the w o r l d of the trilobites. We can finally observe the seas that they s a w through their crystal eyes. We can understand w h a t T h o m a s H a r d y ' s desperate hero might h a v e k n o w n if a flash of intelligence could h a v e passed b e t w e e n trilobite a n d m a n in that m a d m o m e n t on the Cornish clifftops, a brief vision to strip a w a y the m a s k of d e e p time. In the Ordovician, trilobites straddled the globe, from hot tropical seas w h e r e corals were already constructing bastions we could recognize as reefs, to cold polar seas where barren landscapes, as yet ungreened, were eroding under the assaults of storms and floods that swept blankets of sediment out to sea to cover the carapaces of our animals, until they at last yielded their secrets to o u r h a m mers. We can see vast oceans w h e r e n o n e exists today. A c r o s s these oceans few trilobites could s w i m , except for s o m e b u g eyed species which braved tropical storms to spread around the equator, as indifferent to oceanic distances as tuna. Each a n c i e n t c o n t i n e n t carried its o w n c a r g o o f trilobites, s w a r m i n g in their millions. T h e seas a d v a n c e d far over these continents, and in the productive shallows specialized trilobites revelled i n t h e i r p l a c e i n t h e e c o l o g y ; f o r a l l its a l i e n s e t t i n g t h e r e w e r e still r o l e s — e c o l o g i c a l n i c h e s — t h a t w o u l d b e f a m i l i a r t o u s from living seas. (No single trilobite ever v e n t u r e d into fresh w a t e r — i f t h e y h a d , s o m e m i g h t still s u r v i v e . ) A s i t w a s , t h e r e

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T R I L O B I T E !

w e r e l a r g e t r i l o b i t e s t h e s i z e o f a t u r e e n , l i k e Isotelus, w h i c h hunted d o w n small " w o r m s " and caused their smaller cont e m p o r a r i e s to scuttle a w a y to h i d e , or roll up into protective balls. S o m e of these c o m p a r a t i v e giants grabbed their prey with their strong limb bases and shredded them into pieces, m a n g l i n g their remains against a fork at the b a c k end of the h y p o s t o m e . S o m e species m a y h a v e b e e n able to stuff their unfortunate prey into an inflated stomach underneath an appropriately inflated glabella

(Crotalocephalus, fig.

19).

Crab-

s i z e d Phacops m a y h a v e u s e d its s h a r p v i s i o n a c c u r a t e l y t o p i n p o i n t its f o o d i n d i m light. N o p r i m i t i v e a n d u n s o p h i s t i cated mud-grubbers these—they were precision-engineered agents of destruction. There w a s camouflage, and there w a s c o n c e a l m e n t . S p i n y trilobites w e r e tight as burrs w h e n rolled u p , and just as unappetizing. Others m a y have decked themselves with small o r g a n i s m s — s e a mats or hydroids—the better to conceal t h e m s e l v e s in the thronging profusion of the Palaeozoic sea-floor. O t h e r s again b u r i e d themselves in the soft sediment with only their stalked eyes warily keeping w a t c h by day, to e m e r g e at night to forage a m o n g the seaw e e d s . T h e r e w e r e thick-shelled trilobites, w h i c h lived close to the tide-line, scurrying in and out at the sea's edge, antennae twitching to the chemical " s m e l l s " of food or danger, eyes sensitive to the least m o v e m e n t . T h e s e animals w o u l d have s e e n t h i n g s w e s h a l l n e v e r s e e , l i k e t i n y a n i m a l s t h a t h a v e left n o f o s s i l t o tell u s o f t h e i r e x i s t e n c e , o r w a v i n g a l g a l f r o n d s t h a t d e c a y w i t h o u t t r a c e . N o t all h i s t o r y i s p e n e t r a b l e .

W h e r e v e r the sea-floor w a s soft, a n d c h a r g e d with organic matter, there w e r e true m u d - g r u b b e r s . Small trilobites, these, l i k e t h e C a m b r i a n Elrathia ( p . 243), t h e y s e a r c h e d t h e s e d i m e n t s for edible particles, incessantly shuffling about the bottom, ploughing through the sediment surface, gleaners and c l e a n e r s . T h e y left t r a c k s in a f e w p l a c e s , p l o u g h i n g f u r r o w s , braided and scratched by their questing limbs, sometimes flanked by grooves cut by the genal spines. Like footsteps imprinted on a sandy beach, m o s t of the tracks were d o o m e d

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to erasure, the m e m o r y of an afternoon forgotten in the m o r n ing tide. But if there w e r e an influx of s a n d at the right m o m e n t they might be p r e s e r v e d — a petrified m o m e n t frozen into r o c k — a n occasion w h e n the dance to the m u s i c of time left s t e p s b e h i n d . S o m e o f t h e s e m u d - g r u b b e r s m a y h a v e ploughed b e l o w the surface layers of the sediment like so m a n y trilobitic m o l e s . A t h o u s a n d species of s h r i m p - l i k e animals have the s a m e habits today. T h e s e w e r e the foot soldiers o f t h e t r i l o b i t e w o r l d , t h e lumpenproletariat, t o i l i n g a w a y i n c e s santly on the sea-floor for a f e w short seasons. Trilobites with this habit usually h a v e the h y p o s t o m e m o b i l e , not rigidly attached on the underside of the head, the better to scoop in their

squashy

and

unprepossessing

nutriment.

They

all

l o o k e d s u p e r f i c i a l l y s i m i l a r , t o o , all t h e w a y f r o m t h e C a m b r i a n t o t h e C a r b o n i f e r o u s , c o m p a c t little trilobites w i t h g e n a l spines and comparatively small glabellas, and quite a few segments in thorax and tail—they needed limb pairs for sorting out the w h e a t f r o m the chaff in their diet of slurry. L i k e the G o o d Soldier Schweik, they survived w h e n other trilobites, more showy, perhaps, or higher in the marine food chain, failed to survive the extinctions at the e n d of the O r d o v i c i a n and late i n the D e v o n i a n . W e h a v e f o u n d t h e m w i t h " b i t e s " out of their s i d e s — s o s o m e predators evidently f o u n d t h e m tasty enough. I m i g h t conclude that it is better to grovel h o p e fully and survive.

T h e n t h e r e w e r e filter f e e d e r s . T h e s e w e r e g e n e r a l l y n o bigger than the sediment grubbers, but their headshields w e r e inflated and convex, m u c h m o r e so than the b o d y b e h i n d , creating an interior chamber u n d e r the head. F r o m the trilobite p a r a d e , s t e p f o r w a r d Cnemidopyge, w i t h its f r o n t a l s p i n e l i k e a l a n c e i n a t o u r n e y , a n d Trinucleus, w i t h its s t r a n g e f r i n g e o f d o u b l e d - u p pits. S e d i m e n t w a s w h i p p e d up by the limbs into the head c h a m b e r into a fine suspension, f r o m w h i c h the edible particles were sorted and ingested. Imagine stirring up a bowl of soup and picking out the noodles. T h e y were sluggish animals, these mud-whisking crawlers, with w e a k muscles

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T R I L O B I T E !

sufficient t o p r o p e l t h e m f r o m o n e s p o t t o a n o t h e r t o stir u p their m e a g r e rations w h e n they ran short. T h e y rested on sledlike genal spines. M a n y of t h e m w e r e blind, as if their quiet world w a s not too troubled by predators. But w h e n threate n e d t h e y c o u l d f l i p t h e i r t h o r a x a n d tail u n d e r t h e v a u l t e d h e a d c a r a p a c e , tucking a w a y the soft limbs f r o m sight until the danger passed.

P r e d a t o r s , m u d - g r u b b e r s , a n d filterers could live together in a single c o m m u n i t y . N o w i m a g i n e , if y o u will, a series of different c o m m u n i t i e s o f t h e s e a n i m a l s s t r e t c h i n g a w a y f r o m the centres of the d r o w n e d continents into the d e e p s that surround them. Progressive depths and different habitats, and in each a host of trilobites did their hunting and scavenging, their digging and searching through sediments, and where m u d w a s soft e n o u g h , stirred it into suspension. In deeper e n v i r o n m e n t s w h e r e t h e o x y g e n level w a s low, specialists like Triarthrus, d e s c r i b e d i n C h a p t e r 3 , t o o k o v e r f r o m o t h e r t r i l o bites in a habitat w h i c h diced between plenty and death t h r o u g h s u f f o c a t i o n . A b o v e the sea b e d , little a g n o s t i d s s w a m like a n i m a t e d lentils. At d i m m e r d e p t h s again eyes b e c a m e useless. This w a s the territory of the blind, where touch and smell outbid vision, a d a r k w o r l d of palpation a n d subtle signalling. A r o u n d each ancient plate the continental shelves w e r e s t a c k e d in order, c a r r y i n g tier after tier of different trilobites, each m i n d i n g their o w n particular business. N o w we can b e g i n t o u n d e r s t a n d h o w there can b e s o v e r y m a n y trilobite species. Divided by habitat and divided again by geography, trilobites dissected their w o r l d into throngs of niches: this is h o w they b e c a m e the "beetles of the Palaeozoic."

If we c o u l d h a v e sculled o v e r the O r d o v i c i a n sea it w o u l d h a v e tasted a s salty, s p a r k l e d a s b r i g h t l y u n d e r the s u n , a n d b e e n as stirred by storms as the sea is today. On the horizon a smoking volcano might bear witness to the unseen, ineffably slow but inexorable creep of tectonic plates. We would, perh a p s , miss the k e e n i n g cries of gulls, or the silver-sided flash of a shoal of fish. If we t h r e w a d e e p trawl o v e r the side of the

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Possible

Worlds

boat, when it is retrieved and tipped out on deck it would have b e e n c h u r n i n g with trilobites. A monster, big as a serving plate, tries to m a k e g o o d its e s c a p e by s c u t t l i n g t o w a r d s a sluice, its sight bedazzled by the bright light of the surface. M o s t of the catch would be small b e a s t s — t h e size of beetles—-some of them lying helplessly on their backs, legs threshing ineffectively out of their w a t e r y m e d i u m . In the b o t t o m of the net there are s o m e balls, r o u n d as m a r b l e s : a closer l o o k s h o w s that they, t o o , a r e t r i l o b i t e s — B u m a s t u s p e r h a p s ? — t i g h t l y e n r o l e d against the shock of disturbance. Their protective stance won't do them m u c h good on dry land, but as you lob one back into the w a t e r it falls b a c k to the sea-floor, d r o p p i n g like a stone, a n d t h e trilobite finally c r a w l s a w a y u n h a r m e d b y its e x p e r i e n c e . E v e n the m u d itself i s h e a v i n g w i t h tiny trilobites, s o m e as small as ladybirds. These diminutive, blind mud-grovellers are a m o n g the smallest of their kind. As y o u pick through the tangles of w e e d brought up in the trawl a fantastically spiny trilobite is hidden a w a y in the thicket, an odontopleurid; ouch! you withdraw your probing fingers smartly.

Perhaps we should find out w h a t else is in the catch, besides trilobites . . . Picking t h r o u g h the residue there are s o m e animals that s e e m quite familiar: a few snails, easily recognizable ramshorns, and a dozen or so small clams. There are shrimp-like creatures, too, a n d b r y o z o a n s (sea m a t s , colonial animals often f o r m i n g patches on s e a w e e d s ) , a n d a variety of seashells like brachiopods,

including one remotely

r e l a t e d t o s o m e s p e c i e s still l i v i n g n e a r N e w Z e a l a n d . S o n o t everything is a stranger to us. A n d delving further into the m u d a host of w o r m s of various kinds are revealed—polychaetes and sipunculans—and if we h a d been able to take a m i c r o s c o p e t o the m u d itself w e w o u l d h a v e seen singlecelled o r g a n i s m s — f o r a m i n i f e r a n s — a n d bacteria, w h i c h have been processing the waste of the seas since Precambrian times. The Ordovician marine world is a curious mixture of strangeness a n d familiarity, a n d w e , the fishermen, p e e k at the nets agog, trying to identify w h a t we k n o w and a c k n o w l e d g e

215

T R I L O B I T E !

w h a t we don't. T h e trilobites are l o d g e d in this betwixt and b e t w e e n c a t e g o r y , f a m i l i a r a s a r t h r o p o d s , y e t s t r a n g e i n all their particularities. If we n o w r o w the boat o n w a r d s into deeper water, a n d trawl again, we will bring up another netload of w o n d e r s , a n o t h e r s q u i r m i n g m a s s of trilobite characters, f e w of t h e m the s a m e as those f r o m the previous haul.

T h e sea is rich.

The biological world is composed of m a n y small compon e n t s , y e t e v e r y t h i n g m o v e s t o g e t h e r i n the great d a n c e o f life.

T h e smallest organism has enjoyed a role in the s c h e m e of t h i n g s , a locus naturae. N a t u r e m a y h a v e b e e n p r o f l i g a t e w i t h species, but every species has had a place in the connectedness of things. T h e small truths of trilobites can be extended to interconnect w i t h a w h o l e w o r l d . As a plea for interdependence of culture and science, E. O. Wilson has recently m a d e a case for the unification of k n o w l e d g e — w h a t he termed "consilience." T h e trilobite story retailed here s h o w s a consilience of a s m a l l e r k i n d , w h e r e i n e v e n identification lists can be m a r ried with g e o m a g n e t i s m and plate tectonics to give a portrait of a v a n i s h e d Earth. T h e b e a u t y of science is not just the abstract purity of mathematical theorems, which have been celebrated in the b i o g r a p h i e s of great practitioners like Einstein, J o h n N a s h , or Heisenberg, or n u m b e r theorists and inventors of geometries and algebras. There is no question that reductionist brilliance has yielded s o m e of the greatest t r i u m p h s of the scientific intellect. But synthesis can be almost as important as analysis. T h e attraction of fundamental equations is that they offer h o p e of an ultimate truth from w h i c h e v e r y t h i n g else m a y b e d e d u c e d , e v e n our m e s s y a n d irred e e m a b l y c o m p l e x w o r l d . In following the trilobites we have b e e n looking, instead, at the fruitful marriage of different fields of k n o w l e d g e , a kind of P a n g a e a of thought. Or y o u c o u l d think of it as b e i n g w h e r e different paths converge, like t h o s e f o o t w a y s o n t h e C o r n i s h cliff t o p s w h e r e H a r d y ' s c h a r acters m e t their pivotal m o m e n t , a n d w h e r e the path of the trilobite w a s j o i n e d w i t h t h e trail o f a n o t h e r v a n i s h e d o c e a n a s

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Worlds

revealed in the evidence of twisted shales. My o w n footsteps, and the account in this chapter, h a v e followed the s a m e pathway. We have explored a past of w h i c h trilobites w e r e both witness and victim: and they h a v e been called u p o n to testify in the reconstruction of their o w n times and possible worlds.

Then by a generous process of reciprocal illumination the world so reconstructed helps us to k n o w m o r e of the trilobite.

I see nothing w r o n g in t a k i n g the p a t h to this reconstruction by w a y of poetic images. In a consilient frame of m i n d , everything m a y contribute to an accurate description of the world. I r e c a l l t w o l i n e s f r o m T h o r n G u n n ( M o / y , 1971): Parrot,

moth,

What germs,

shark,

wolf,

what jostling

crocodile, mobs

217

there

ass, flea. were

in

me.

IX

Time

W e all s t r u g g l e w i t h t i m e . M o r t a l i t y m a k e s t i m e o u r m a s t e r , yet we continue to pretend that we can bend time to our w i l l : w e make t i m e f o r t h i n g s , p e o p l e a r e s a i d t o d i e before their t i m e , as if we all, briefly, h a d a p e r i o d w h e n o u r existence a n d the time of it coincide perfectly, as with a surfer successfully m o u n t i n g a n d m o v i n g with the curling crest of a w a v e . My children ask questions that begin: "In your day .. . ? " implying that in s o m e w a y my time has already passed; was it yesterday, p e r h a p s , a n d if so w h y didn't I notice? A palaeontologist h a s m o r e c a u s e t h a n m o s t t o reflect u p o n t i m e : its m e a s u r e m e n t , i t s s p a n , a n d its c o n s e q u e n c e s . T i m e c a n n o w be measured by the vibrations of atoms to an accuracy which o n l y the leading e d g e of t e c h n o l o g y requires. A fraction of a n a n o s e c o n d is irrelevant to our o w n lives, a n d to the pace of a biological lifetime, although it m a y be germane to the chemical c h a n g e s that affect a single n e u r o n in the cerebral cortex.

O u r thoughts are flashes of inspiration, and a flash is brevity itself. H o w e v e r , t h e d u r a t i o n o f a s i n g l e d a y i s p r o b a b l y o u r most natural biological temporal unit. W h e n Scarlett O ' H a r a s a y s , at t h e e n d of Gone with the Wind, " T o m o r r o w is a n o t h e r d a y ! " w e d o n ' t c r y c l i c h e , b e c a u s e w e all r e c o g n i z e t h e o p t i m i s m of a n e w m o r n i n g . Witnesses in court are expected to

218

Time recall a single day; not e v e n an A m e r i c a n attorney-at-law would demand a narrative of seconds. The great Argentinian writer J. L. Borges has a s h o r t story, " F u n e s the M e m o r i o u s , " about an unfortunate soul w h o recalls everything—together with

every

interlinking

ramification—and

whose

mastery

of time has the effect of paralysing h i m completely. We function thanks to a kind of selective a m n e s i a . This d o e s not release us (especially scientists) f r o m the obligation to speak the truth, a rule w h i c h , as we shall see, has b e e n b r o k e n even by trilobitologists.

The reader will by n o w be either insouciant or bewildered in the face of h u n d r e d s of millions of years. I have been w a v ing the continents past, ten million years at a shot, w i t h a flick o f m y w r i s t . T h e C a m b r i a n w a s 545 m i l l i o n y e a r s a g o ; t h e D e v o n i a n lasted for 50 million years. It might be thought that this broad scale pertains to the time of the trilobite; the further back in time the less precision, a f e w million years is nothing to notice. To the trilobite, M a n k i n d ' s d o m i n i o n of the Earth is less than the duration of a single species of their kind.

A l l t h i s i s t r u e , y e t i t i s still p o s s i b l e t o l o o k i n t o a d a y i n t h e life o f a t r i l o b i t e — t o c h e a t t h e g r e a t r e v e r s e t e l e s c o p e o f t i m e which m a k e s distant events s e e m so small a n d so far away.

S e d i m e n t surfaces can preserve a m e r e day, a true diary of P a l a e o z o i c life. I f that d a y w a s b u r i e d fast e n o u g h i t m a y yet be disinterred.

I h a v e already described trilobite e n r o l m e n t — t h e instant response to threat which b e c a m e a time capsule, a m o m e n t ' s panic solidified. T h e n I h a v e described h o w trilobites g r e w by moulting. Their cast-off exoskeletons are testimony to the m o m e n t of sloughing off the old coat before g r o w i n g the new.

S o m e t i m e s the pieces are cast aside as carelessly as teenage c h i l d r e n c a s t t h e i r g a r m e n t s o n t h e b e d r o o m floor. I n o t h e r cases it is clear that the trilobite a d o p t e d a careful strategy for m o u l t i n g : after all, it w a s t h e m o s t v u l n e r a b l e stage in the a n i m a l ' s life a n d c a u t i o n w a s at a p r e m i u m . It w a s n o t just the hard shell that w a s m o u l t e d : e v e n the finest hairs on the limbs

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T R I L O B I T E !

shed their coats at the s a m e time. W h e r e the sea-floor was c a l m , t h e cast-off shells a r e left u n d i s t u r b e d a n d y o u m a y s a m p l e the anxiety of the m o u l t i n g m o m e n t for yourself.

I m a g i n e , y o u are s a m p l i n g a f e w snatches of time from a larger lifetime, itself a f r a g m e n t of the t i m e of e n d u r a n c e of a species, w h i c h is but a brief instant in the c o m p a s s of geological t i m e . Y o u can relish the privilege of catching an ancient moment.

Moulting w a s preceded by a p h a s e in w h i c h a special horm o n e s o f t e n e d t h e v e n t r a l c u t i c l e ( s e e fig. 30); t h e s u t u r e s which crossed the head w o u l d then have loosened. W h e n the m o m e n t c a m e , m a n y trilobites used their genal spines as levers d u g into the s e d i m e n t to release the free cheeks from the rest of the c e p h a l o n (the h y p o s t o m e w a s shed at the s a m e time). Since in the majority of trilobites the eye surface w a s attached to the free c h e e k this m o s t delicate part w a s released o f its o l d c o r n e a l c o v e r i n g a t a h e l p f u l e a r l y s t a g e . I n p r i m i t i v e trilobites this s a m e surface c o u l d be s h e d separately thanks to a suture r u n n i n g all a r o u n d the eye. T h e c h e e k s g o n e , a g a p o p e n e d at the front, and the trilobite could then wriggle forw a r d s o u t o f t h e r e s t o f its e x o s k e l e t o n , l e a v i n g b e h i n d a c r a n i d i u m a n d t h o r a x t o tell o f its a d v e n t u r e .

This w a s often not as easy as I h a v e described, and the thorax will be f o u n d separated f r o m the p y g i d i u m , or the trilobite

will

have

crawled

off

with

the

cranidium

still

a t t a c h e d o b s t i n a t e l y t o its h e a d ; t h e t r i l o b i t i c e q u i v a l e n t s o f those terrible tank-tops that y o u can s o m e h o w never get out of. T h e r e are trilobites that g a v e t h e p r o c e s s a h a n d by inverting their h e a d a n d s c r a p i n g off the c r a n i d i u m ; this leaves the cheeks to either side with an inverted cranidium between t h e m — a n d behind the thorax and pygidium, right w a y up. In t r i l o b i t e s l i k e Phacops, i n w h i c h t h e f u n c t i o n a l s u t u r e s o n t h e h e a d h a v e b e e n lost, the w h o l e h e a d often gets inverted, or the trilobites m a y even h a v e m o u l t e d u p s i d e d o w n . The observer really feels as if he is w a t c h i n g the most personal gymnastics.

S o m e trilobites m a y h a v e m a t e d at the "soft shell" stage, as do

220

Time m a n y living arthropods, a n d this w o u l d h a v e a d d e d an extra urgency to the w h o l e procedure. The Palaeozoic sea w o u l d have been soaked in hormones—ecdysial, pheromonal, spermatogenic. There are a few examples of "soft-shelled" trilobites preserved, killed before their n e w carapaces h a r d e n e d : they h a v e a kind of ghostly quality, a thin and feeble s h a d o w o f t h e r e a l Phacops. S o m e o f t h e s e a n i m a l s m a y h a v e h i d d e n quietly a w a y d u r i n g this critical stage; my colleague Brian C h a t t e r t o n tells me of a D e v o n i a n b u r r o w in soft s e d i m e n t (presumably m a d e by s o m e other animal) packed with trilobites in the process of g r o w i n g their n e w shells. T h e b u r r o w served to bury them rather than protect them: the brief time of their tragedy served to ensure the greater time of their survival as fossils.

I mentioned the growth of an individual trilobite w h e n I described

e v o l u t i o n a r y m e c h a n i s m s in C h a p t e r

7.

Such

g r o w t h d e f i n e s a l i f e t i m e , t h e m o s t i n t i m a t e o f all t e m p o r a l scales, birth to death. It is extraordinary h o w m u c h we k n o w about

the

trilobite's

personal

trajectory.

Since

trilobites

m o u l t e d — c a s t i n g off their stiff e x o s k e l e t o n a n d g r o w i n g a new, larger one—it is an obvious question to trace the s a m e species backwards in time, looking for smaller and smaller carapaces. What was needed was an unusual place where juveniles and adults were incarcerated in the rocks together, undisturbed. Such a locality w a s discovered "under the pear tree" in one quarry in B o h e m i a by arguably the greatest n a m e i n t r i l o b i t e r e s e a r c h , J o a c h i m B a r r a n d e (1799-1883). I n w h a t i s n o w the Czech Republic there are remarkably rich sections of Palaeozoic rocks, a n d B a r r a n d e set out to be their biographer.

In the Rare Books R o o m of the Natural History M u s e u m in L o n d o n a privileged visitor c a n inspect a shelf-full of large v o l u m e s , each bigger than a t e l e p h o n e directory, the fruit of B a r r a n d e ' s o w n l i f e t i m e of l a b o u r : t h e Systeme Silurien* de la

'Recall that in Barrande's time, what we n o w know as Cambrian, Ordovician and Silurian were all subsumed under "Silurian."

221

A trilobite moult, Paradoxides, the giant Cambrian trilobite, this example from the M i d d l e Cambrian of eastern Newfoundland. Paradoxides is frequently as large as a lobster.

Notice the fat glabella and the long spiny thorax with spines extending beyond the small pygidium. In moulting, the free cheeks have been reversed and lie under the rest of the body twisted into this position as the trilobite shed its " o l d " skin, or exoskeleton, and crawled a w a y forwards. Specimen about 15 cm long. (Photograph courtesy H. B. Whittington.)

Time

Joachim Barrande, the great Bohemian palaeontologist and namer of trilobites.

Boheme. T o s t u d e n t s o f t r i l o b i t e s t h e s e a r e t h e n e a r e s t t h i n g t o holy tracts. Plate after plate of beautiful lithographs (for m o s t of his life B a r r a n d e e m p l o y e d the b e s t artists) d e l i g h t the e y e today, as they m u s t h a v e a s t o n i s h e d his c o n t e m p o r a r i e s (one i s r e p r o d u c e d a t fig. 32). I t i s d e b a t a b l e w h e t h e r t h e m o s t sophisticated m o d e r n p h o t o g r a p h y could do better.

B a r r a n d e did m o r e than treat trilobites; he described m o l luscs and corals a n d m a n y other fossils besides. H o w e v e r , he d i d l a v i s h s p e c i a l a t t e n t i o n u p o n t h e m , b e g i n n i n g i n 1852, d r a w i n g u p o n c o l l e c t i o n s m a d e f o r t h e first t i m e f r o m u n u s u ally fossiliferous localities. By the e n d of the nineteenth century every specialist w a s familiar with the localities we k n o w today as Sarka and Kraluv Dvur. There is a smart suburb of Prague k n o w n as the Barrandov, w h e r e y o u m a y h a v e a drink a t t h e T r i l o b i t e Bar. I n f a c t , a l m o s t all o f t h i s b e a u t i f u l c i t y i s

223

T R I L O B I T E !

deeply trilobitic. B a r r a n d e himself started his career by accid e n t . H e f o u n d t w o p y g i d i a o f t h e t r i l o b i t e Odontochile rugosa close to Z l i c h o v C h u r c h d u r i n g a S u n d a y stroll. He took t h e m h o m e , b u t his h o u s e k e e p e r B a b i n k a * threw t h e m out (wives h a v e been k n o w n to do this before a n d since). J o a c h i m m a d e h e r retrieve t h e m , a n d his life w o r k w a s o r d a i n e d . T h e s e t w o s p e c i m e n s , together w i t h the rest of his h u g e collections, reside in the N a r o d n y M u s e u m , a grand, columned building which looks d o w n the length of Wenceslas Square in Prague.

T h e y are treated with a reverence usually accorded to saint's bones. T h e visiting scientist will be brought them two at a time, each o n e immaculately labelled with the original figure of the great m a n . In his h o n o u r a h u g e p l a q u e w a s erected on a D e v o n i a n hillside in P r a g u e , just o n e year after his death.

O n e of Barrande's books describes what we would now call M i d d l e C a m b r i a n trilobites; o n e plate s h o w s a s e q u e n c e of

a

kind

related

to

Paradoxides

davidis,

a

trilobite

I

first

e n c o u n t e r e d i n t h e c l i f f s a t St. D a v i d ' s , W a l e s , i n m y e a r l y days. In Bohemia, Barrande discovered the whole growth series f r o m b a b e to a d u l t — a nursery preserved. Since the adult could be as large as a lobster this w a s a w o n d e r i n d e e d , for the smallest babies w e r e hardly larger than a pinhead.

A n o t h e r s p e c i e s , Sao hirsuta, w a s l a i d o u t i n e v e n m o r e d e t a i l .

I visited the f a m o u s pear tree near the B o h e m i a n village of Skryje s o m e years ago—it w a s shrunken now, putting out only a few, sad leaves, I doubt whether Barrande would have r e c o g n i z e d it. T h e r e w e r e still a f e w l a r v a e t o b e d i s c o v e r e d i n t h e s h a l e s f r o m t h e q u a r r y b e n e a t h it.

T h r o u g h o u t growth, trilobites c h a n g e d in appearance, but n o w h e r e m o r e s o t h a n w h e n they w e r e v e r y small. T h e trilobite g r e w — m o u l t by m o u l t — f r o m a tiny individual the size of a p i n h e a d . B a r r a n d e recognized that trilobites got larger by the progressive addition of thoracic segments up to the maxim u m n u m b e r characteristic of a g i v e n species: if a trilobite 'Barrande later named a fossil clam Babinka in her honour—if having a clam named after y o u is not, rather, a veiled comment.

224

The growth of the Cambrian trilobite Sao hirsuta from the Cambrian of Bohemia. The tiny larva, or protaspis, is shown top left. T h e progressively larger growth stages have additional thoracic segments, until the adult number is reached. The smallest two stages are a millimetre long or less. The specimens illustrated show, progressively, one thoracic segment, three thoracic segments, four thoracic segments, six thoracic segments and thirteen thoracic segments. At the six thoracic segments stage it is just over 2 mm long. The " e " marks the eye position in the larva.

T R I L O B I T E !

had

eight

segments,

like

Lhwyd's

Ogygiocarella,

the babies

w o u l d add segments o n e at a time until eight were reached, a n d after that w o u l d continue to get larger m o u l t after moult w i t h o u t a n y m o r e s e g m e n t s being a d d e d . Trilobites were not a t all l i k e t h o s e s c u t t l i n g t u r t l e s b e l o v e d o f n a t u r a l h i s t o r y p r o g r a m m e s w h i c h h a t c h out as r e a d y - m a d e replicas of their parents, b u t c h a n g e d subtly a t e a c h m o u l t . T h e final n u m b e r o f f r e e l y a r t i c u l a t e d t h o r a c i c s e g m e n t s (at w h i c h t h e t r i l o b i t e i s s a i d t o h a v e r e a c h e d t h e holaspis s t a g e ) w a s o f t e n a c q u i r e d w h e n t h e i n d i v i d u a l w a s still o n l y a f r a c t i o n o f its m a x i m u m size. T h e holaspis stage w a s preceded by a series of moults in w h i c h thoracic s e g m e n t s w e r e " r e l e a s e d " progressively into the thorax: usually, the smaller the size of the larval trilobite the f e w e r the s e g m e n t s . Taking this process b a c k to the beginn i n g , at a size of a m i l l i m e t r e or so there w e r e no free s e g m e n t s at all: a p r o t o - c e p h a l o n w a s articulated directly against a proto-pygidium with no sign of a free segment interpolated b e t w e e n t h e m . O n e s t a g e e a r l i e r , t h e first l a r v a o f all c o n s i s t e d o f a s i n g l e s h i e l d — i n w h i c h h e a d a n d tail w e r e c o m b i n e d i n t o a m i n u t e d i s c , t e r m e d t h e protaspis ( p . 225). I n s o m e s p e c i e s the protaspis can be less than a millimetre long. T h e protaspis h a t c h e d out of an egg, no d o u b t , but claimed fossils of trilobite e g g s are controversial. W e r e it not for the fact that the protaspis

is

seamlessly

connected

with

intermediate

growth

stages that connect in turn with the adult trilobite, it is perhaps rather unlikely that these tiny objects w o u l d have been r e c o g n i z e d a s l a r v a l t r i l o b i t e s a t all. M o s t o f B a r r a n d e ' s p r o taspides

show

traces

of the

trilobite's

eponymous

"three

l o b e s , " particularly the outline of the glabella, e v e n at this minute size ( m a n y others don't). But the transformation of a f l a t f i s h t i n y d i s c i n t o a g r e a t p r e d a t o r y Paradoxides is a m e t a m o r p h o s i s i n d e e d , a life s t o r y f l u s h e d f r o m the r o c k s in spite of its i m m e n s e g e o l o g i c a l a g e . It is as i n t i m a t e a story as the familiar c h a n g e f r o m caterpillar to butterfly.

It is likely that the earliest g r o w t h stages of m a n y trilobites

226

Time

Electron micrographs of protaspis larvae of Cybelurus from the Ordovician of Spitsbergen. These single shields show the minutest details, even though they are only a millimetre long. T h e lower larva is the larger and already s h o w s the proto-head and proto-tail.

w e r e part of the plankton, feeding u p o n tiny plants, or m a y b e other larvae, just as baby barnacles or s h r i m p s do today. At s o m e early point in the life c y c l e the l a r v a e w o u l d h a v e settled t o a s s u m e t h e b e g i n n i n g s o f a d u l t life o n t h e s e a - f l o o r . W h e n silicified trilobites w e r e d i s c o v e r e d , it w a s n o t l o n g b e f o r e

227

T R I L O B I T E !

the m o s t beautiful early larvae w e r e recognized a m o n g the "fines" in the b o t t o m of the sieve. Fitting the larvae to the correct adults w a s a matter of skilled detective w o r k , based on finding transitional s e q u e n c e s to a k n o w n species. I w a s lucky e n o u g h to find s o m e w o n d e r f u l protaspides from the Ordovician rocks of Spitsbergen, w h i c h are s h o w n in the figure on p a g e 227. T h e s e w e r e p r e s e r v e d i n c a l c i u m p h o s p h a t e , w h i c h replaced the original thin calcareous shells, and so perfect w a s the replication that tiny spines a f e w t h o u s a n d t h s of a millimetre across are faithfully recorded; just because something is small d o e s not m e a n it is featureless. A m o n g this c o r n u c o p i a o f m i c r o s c o p i c life there w e r e o n e o r t w o s p e c i m e n s that resembled b a l l o o n s — b u t balloons that carried a couple of h o r n s . H a r r y W h i t t i n g t o n h a d fitted t h e m to an adult that looked to

our

very old

different,

Remopleurides.

acquaintance

Those

Ogygiocarella

trilobites

had

rather

related similar

s m o o t h e d - o u t l a r v a e — a n d s o , i n d e e d , d i d Trinucleus; n o t r a c e on the babies of the fringe that m a k e s the adult so distinctive.

M y C a n a d i a n colleague Brian Chatterton thinks that these tiny lentils w e r e s p e c i a l i z e d in s e v e r a l w a y s for life in the plankton. Their undersides were almost entirely sealed in by s p i n y p r o t o - h y p o s t o m e s , just leaving holes big e n o u g h for t h r e e p a i r s o f tiny, t h r a s h i n g l i m b s . I n f r e s h w a t e r p o n d s y o u m a y occasionally see clouds of minute "water fleas"

(cla-

docerans) beating their w a y in automatic frenzy through the algal-rich water. My father used to catch them in great n u m b e r s a n d sell t h e m o n a s fish f o o d i n his a q u a r i u m s h o p . M y v i s i o n o f t h e O r d o v i c i a n s e a a n d its t r i l o b i t e p l a n k t o n i s coloured by afternoons spent peering into p o n d s at a vibrating m i s t of z o o p l a n k t o n . U n l i k e w a t e r fleas, the flea-like trilobite larvae u n d e r w e n t p r o f o u n d c h a n g e s a n d grew to a size that m i g h t be a h u n d r e d times that of the larva.

Naturally, there w o u l d h a v e b e e n no b a b y trilobites without sex. Sadly, w e d o not k n o w a s m u c h a s w e w o u l d like t o k n o w a b o u t the sex lives of trilobites. If they w e r e like m a n y

228

Time living marine arthropods

it is likely that

the eggs were

deposited by females a n d then fertilized by males. T h e r e are several w a y s of a c c o m p l i s h i n g this, the simplest of w h i c h is for the m a l e to release his s p e r m into the w a t e r w h e r e it is free to w a s h over the laid eggs. It has p r o v e d r e m a r k a b l y difficult to recognize the t w o sexes in trilobites. N o b o d y has identified any genitalia in the a n i m a l s that preserve the soft a n a t o m y ; nor are there obvious s e c o n d a r y sexual characteristics, like the "claspers" that certain m a l e shrimps use to h a n g on to f e m a l e s . F o r m o s t t r i l o b i t e s l a difference m u s t h a v e b e e n s u b t l e .

I n 1998 m y c o l l e a g u e N i g e l H u g h e s a n d I r e c o g n i z e d w h a t w e thought might be the female trilobites of a few species. These shared a peculiar feature: a swelling in the m i d d l e of the h e a d in front of the glabella. In s o m e e x a m p l e s the swelling w a s spectacular. There are living arthropods with such swellings, which are k n o w n to function as brood p o u c h e s for carrying eggs and larvae. P e r h a p s this w a s the trilobitic equivalent of a portable creche? W h a t g a v e this e x p l a n a t i o n a n a d d e d fillip was the position of the pouch.

A few years earlier I h a d b e e n choosing my s u p p e r in a seaside restaurant in southern Thailand w h e n my attention w a s caught by the live tank, in w h i c h various delicacies are permitted to crawl about prior to being despatched for the table.

A m o n g t h e m w a s a h o r s e s h o e c r a b , Limulus o r o n e o f i t s c l o s e relatives, slinking dejectedly a m o n g the m o r e tasty-looking f i s h a n d c r u s t a c e a n s . I w a s c a p t i v a t e d . Limulus i s t h e c l o s e s t l i v i n g r e l a t i v e o f t h e t r i l o b i t e s ( p . 158)—a s e c o n d c o u s i n , p e r h a p s . Its l a r v a h a s b e e n k n o w n f o r a c e n t u r y a s " t h e t r i l o bite larva" and does, indeed, have a passing resemblance to the protaspis stage of my o w n animals. This could be my best chance to find out w h a t trilobites actually tasted like!

I

ordered the dish. W h e n it arrived I w a s surprised to find the whole creature had been steamed, and it looked very unappetizing. My a m a z e m e n t increased as the u n d e r s i d e of the h e a d shield w a s lifted o u t w a r d s — w h a t w e w o u l d call the d o u b l u r e

229

T R I L O B I T E !

i n t r i l o b i t e s — a n d t h e r e inside t h e h e a d w a s t h e e d i b l e b i t o f the animal: big yolky eggs. Horseshoe crabs evidently carried their eggs in the head region, unlike shrimps and other crustaceans that carry t h e m u n d e r the thorax. This w a s exactly the s a m e position as the inflated b u l b s on the front of the trilobites; circumstantial evidence, of course, but m u c h better than n o e v i d e n c e a t all. A n d t h e taste? E v e n m i x e d w i t h a b u n d a n t n o o d l e s it w a s rancid and intense. I like to think that trilobites w o u l d have tasted sweeter.

T h e trajectory f r o m protaspis to adult is called the trilob i t e ' s ontogeny. A l l c o m p l e x a n i m a l s h a v e a n o n t o g e n y — o u r o w n , from fertilized o v u m through curled e m b r y o to the d e v e l o p i n g foetus a n d baby, b e i n g only the m o s t familiar.

Detailed study of trilobite o n t o g e n y has proved unexpected things. I h a v e already described a m e c h a n i s m for introducing evolutionary novelties, by playing around with timing of d e v e l o p m e n t . M a n y trilobites that are tiny as adults m a y have been derived from more normal-sized ancestors by becoming precociously sexually m a t u r e . S t u d y of g r o w t h trajectories revealed this possibility. Identification of early g r o w t h stages s h o w e d that s o m e trilobites are m o r e closely related by virtue of having very similar larvae than would be guessed by a glance at the comparatively distinctive adults. Larvae can strip a w a y history to the root of descent. This is not quite the d i c t u m t a u g h t t o all z o o l o g i s t s f i f t y y e a r s a g o t h a t "ontogeny recapitulates

phytogeny"—it

might

be

better

expressed

as:

"by

t h e i r b a b e s y e s h a l l k n o w t h e m . " S o t h e l a r v a e tell u s Calymene is p r o b a b l y r e l a t e d to Phacops; Elrathia to

Triarthrus. T h e t r i l o -

b i t e w o r l d i s still i n t h e m i d d l e o f u n r a v e l l i n g t h e s e c o n n e c tions: a n e w classification of the w h o l e prolific catalogue m a y r e s u l t . I t i s a w o n d e r f u l t h i n g t o b e a b l e t o s e e t h e Trinucleus fringe develop: it starts as a single row of pits, and gets wider, and the rows of pits organize themselves into a stippled s y m metry.

You can

watch

the

s p i n e o n Ampyx

grow

through

ontogeny, like Pinocchio's nose under the influence of an

230

Time untruth. Harry Whittington discovered that e v e n the earliest m e r a s p i s Ampyx, w i t h n o t h o r a c i c s e g m e n t s , c o u l d still e n r o l l .

As a trilobite, it s e e m s , y o u could not be too small to n e e d p r o t e c t i o n . Odontopleura a n d i t s r e l a t i v e s a r e s p i n y e v e n a s l a r v a e , a n a s t y m o u t h f u l f r o m t h e first. N o p r o t a s p i s s t a g e h a s b e e n discovered

for

the

most

primitive

trilobites:

Olenellus

and

Agnostus m a y e v e n h a v e l a c k e d t h i s s t a g e — u n l e s s i t w a s n o t calcified. T h e y b e g i n their trajectory as earliest m e r a s p i d e s .

A s t o h o w t h e t h o r a c i c s e g m e n t s a r e r e l e a s e d into t h e t h o r a x , I h a v e m e n t i o n e d that J a m e s S t u b b l e f i e l d d e m o n s t r a t e d i n 1926 that t h e y " b u d o f f " f r o m t h e front o f t h e p y g i d i u m , r a t h e r t h a n , say, b e i n g r e l e a s e d f r o m b e h i n d t h e h e a d . H e u s e d t h e g r o w t h series o f t h e s m a l l O r d o v i c i a n trilobite Shumardia t o s h o w this.

Shumardia h a s o n e e x t r a l a r g e (or m a c r o p l e u r a l ) t h o r a c i c s e g m e n t , t h e f o u r t h o n e of t h e six s e g m e n t s p r e s e n t in t h e adult. Shumardia is like other trilobites in the w a y it grows. It starts as a tiny protaspis shield; then a b o u n d a r y appears defining the proto-head from the proto-pygidium; then as it continues to moult and g r o w first o n e , t h e n t w o , t h e n t h r e e , t h e n f o u r , t h e n f i v e a n d finally six s e g m e n t s a p p e a r in the thorax. D u r i n g this d e v e l o p m e n t the large, macropleural segment appears in the thorax as t h e last, f o u r t h s e g m e n t a t t h e f o u r - s e g m e n t s t a g e o f d e v e l o p m e n t . A t t h e f i v e - s e g m e n t s t a g e i t i s still t h e f o u r t h s e g m e n t — a n d a n o r m a l - s i z e d s e g m e n t h a s b e e n a d d e d o n b e h i n d it. I n t h e a d u l t , two n o r m a l s e g m e n t s h a v e a p p e a r e d b e h i n d t h e m a c r o p l e u r a l o n e . I n o t h e r w o r d s , s e g m e n t s a r e a d d e d behind the macropleural s e g m e n t w h i c h then shuffles forwards in the thorax as a d u l t h o o d is a p p r o a c h e d : s e g m e n t s are b u d d e d off t h e f r o n t o f t h e tail. I r e s t u d i e d S t u b b l e f i e l d ' s s p e c i m e n s s i x t y four years after his paper, a n d f o u n d his account exact in a l m o s t e v e r y p a r t i c u l a r . S i n c e 1926 h i s o b s e r v a t i o n s h a v e b e e n c o n firmed on m a n y other trilobites He w a s nearly a century into h i s o w n o n t o g e n y w h e n t h i s b o o k w a s w r i t t e n i n 1999* a n d w a s

*He died whilst this book w a s in press.

231

T h e ontogeny of Shumardia. In 1926 Sir James Stubblefield showed h o w trilobites grew by releasing segments from the front of the tail. T h e largest Shumardia are only a few millimetres in length.

Time k n o w n (even by Lady Stubblefield) as "Stubbie." After his seminal

trilobite discovery he rose through ranks

of the

G e o l o g i c a l S u r v e y o f G r e a t B r i t a i n t o b e c o m e its Director, and eventually w a s d u b b e d Sir J a m e s . T h u s , the trilobitologist w h o rose the h i g h e s t d i d s o b y m a k i n g the m o s t m i n u t e o b s e r v a t i o n s o n t h e s m a l l e s t o f t r i l o b i t e s . I n t h e l a t e 1980s my colleague Bob O w e n s and I started collecting in the s a m e b r o o k s a n d dells in S h r o p s h i r e as h a d Sir J a m e s half a century earlier; from s o m e w h e r e Sir J a m e s rustled up a copy of t h e o r i g i n a l p a p e r h e h a d w r i t t e n o n t h e s u b j e c t , i n 1927. O n the cover he wrote, in blue ink:

"With somewhat belated

greetings . . . " T h e n there are trilobite tracks, the imprint of a m o m e n t , m a y b e of o n e feed in a lifetime. C a n fossil time be m o r e fleeti n g ? A s s i g n i n g a trilobite s p e c i e s to a particular fossil track has p r o v e d difficult. Tracks tend to be p r e s e r v e d in the k i n d of s a n d y s e d i m e n t s in w h i c h b o d y fossils are rare. After all, y o u w o u l d be very surprised to find a d e a d b o d y at the e n d of a set of footprints on a sandy beach. Doubtless other arthropods could m a k e tracks s o m e w h a t like the trilobite's. So h o w to finger the culprit? A few years a g o in the Sultanate of O m a n I was doing fieldwork on some hitherto unexplored Upper C a m b r i a n r o c k s , p e r h a p s 480 m i l l i o n y e a r s o l d .

Trilobites

were fragmentary and rare, but since they m a y have been the only ones of this particular a g e on the w h o l e A r a b i a n P e n i n sula they w e r e clearly w o r t h the effort. It w a s a r e m o t e area, the H u q f , a l m o s t lacking vegetation except for o n e , i m p r o b a ble tree. S a n d s t o n e s a n d l i m e s t o n e s f o r m e d l o w bluffs, so if you followed a single bedding plane you could crawl on your hands and knees over a Cambrian sea-floor which preserved every scratch and footprint. All the signs in the sedimentary rocks pointed to the rocks being laid d o w n in very shallow seas—indeed from time to time the water retreated to the p o i n t w h e r e it started to e v a p o r a t e to salt. F e w trilobites relished living in such shallow water. T h e exciting discoveries were beds of beautiful tracks; most unusually, the rocks that

233

T R I L O B I T E !

Sir J a m e s Stubblefield (right, with pipe) en route to Shetland a n d O r k n e y i n 1936, w i t h t w o o f h i s c o l l e a g u e s f r o m t h e G e o logical Survey.

filled the tracks actually c o n t a i n e d the r e m a i n s of trilobite s h e l l s o f o n e s p e c i a l s p e c i e s t h a t e v i d e n t l y l i k e d i n s h o r e life.

C o u l d we link the tracks and the animal that m a d e them? If the trilobites m a d e the tracks then they s h o u l d m a t c h for size.

I n 1994, I r e t u r n e d t o t h e S u l t a n a t e w i t h t h e g r e a t G e r m a n p a l a e o n t o l o g i s t D o l f Seilacher, d o y e n o f fossil tracks.

Together, we spent several days m e a s u r i n g track sizes and collecting trilobites. We gingerly turned over slabs, on the underside of which the casts of the tracks were best preserved.

T h e caution w a s prudent, b e c a u s e u n d e r s o m e of the platesized pieces of rock scorpions lurked during the daytime. I learned from my O m a n i hosts that the big black scorpions, large as king p r a w n s , w e r e less to be feared than the rock skulkers, half the size and

yellowish, w h i c h carried their

stings s i d e w i s e , like a lariat. In this e m p t y desert I b e c a m e aware of the most exquisite connection between these scorpions and the trilobites in the rocks that sheltered them. Scorpions are a kind of a r a c h n o i d , that great g r o u p of arthropods that includes spiders a n d mites, together with the most primi-

234

Time

Trilobite tracks. A cast of the furrows left by ploughing trilobites. Cruziana semiplicata from the Upper Cambrian of the Sultanate of Oman. The longest diameter of the specimen is 17 cm.

five living m e m b e r of the g r o u p , the h o r s e s h o e

"crab"—

whose eggs I had been lucky e n o u g h to sample in Thailand.

M o d e r n studies* of the evolution of arthropods as a w h o l e have s h o w n that the trilobite's closest relative in the living f a u n a i s Limulus, w i t h s c o r p i o n s a t o n e f u r t h e r r e m o v e . S o i n

T h e s e studies are based on cladistic analyses, as described in Chapter 5.

Such analyses derived from living and fossil arthropods have rejected an earlier idea that trilobites were closest to crustaceans in favour of their inclusion in a great arachnoid clade. Trilobites retain antennae, which are lost in the other arachnoids, or chelicerates. As this book w a s being completed a new developmental study has shown that the antennae might actually be homologues of the chelicerae, the curious frontal appendages shared by the living arachnoids.

235

T R I L O B I T E !

this r e m o t e corner of O m a n I could p a y h o m a g e to a m e e t i n g across vast stretches of time b e t w e e n ancient relatives: scorpions a n d trilobites. In the early desert morning, you can see scorpion tracks p r o d d e d in ranks across the sand, within a few centimetres of the ancient, fossilized tracks we studied.

Dolf assured me that similar scorpion tracks could be found in r o c k s a s o l d a s D e v o n i a n . T h i n k o f t h e t r i l o b i t e Phacops still flourishing in hordes at the s a m e time as animals we would readily r e c o g n i z e as s c o r p i o n s w e r e already wielding their lethal v e n o m , w h i c h h a s so effectively e n s u r e d their survival.

If they had been able s o m e h o w to travel through time and scuttle o u t o f the r o c k t h e y w o u l d h a v e left familiar tracks, a l o n g s i d e t h o s e of their living d e s c e n d a n t s . As I sat on a l o w bluff in the H u q f glowing in the m i d d a y heat I b e c a m e acutely aware of time past, time present, and time defied.

O u r m e a s u r e m e n t s w e r e successful. We found that the size of the trilobites w a s within the size range of the tracks; a n d genal spines on the e d g e of the head of the trilobite w e r e consistent with grooves cut to either side of the digging m a r k s in t h e furrow. D o l f p o i n t e d out to me that this particular trilobite s e e m e d to forage by m a k i n g tracks with a circular c o m p a s s — r a t h e r like the h a n d s w e e p s of a w i n d o w cleaner.

The track even had

a name,

Cruziana semiplicata, w h i c h h a d

been given to it m o r e than a century earlier by "the English B a r r a n d e , " J o h n Salter. T h i s trace fossil h a d originally b e e n found in U p p e r Cambrian rocks in North Wales, near Merioneth, in wild, wet, m o u n t a i n o u s country as different from the H u q f a s i s p o s s i b l e t o i m a g i n e . T h e finishing t o u c h for our theory w a s that the very trilobite we h a d fingered as the culprit from O m a n has recently been recognized from rocks not far from Salter's original tracks in N o r t h Wales. M a y b e we are g e t t i n g as close to a particular m o m e n t of trilobitic t i m e a s w e e v e r s h o u l d : o n e s c r a p e o f a l i m b , o n e flick o f a hair.

236

Time Then there is geological time.

Geological time is calibrated in millions of years, but it can also be calibrated in trilobites. Because they evolved rapidly, trilobites provide a c h r o n o m e t e r — a timepiece of personalities. We recognize the faces of trilobites in the s a m e w a y a skilled

numismatist

might

recognize

portraits

of

minor

R o m a n emperors from a n e w excavation.

T h e range through geological time of a species of trilobite is as characteristic as that of K i n g T u t a n k h a m u n through historic time. In practice, an investigator h o p e s to find a w h o l e fossil fauna s o that h e m a y c r o s s - c h e c k o n e species w i t h another. I never cease to w o n d e r at h o w well the stratigraphical s y s t e m w o r k s . My visit to O m a n r e v e a l e d a late C a m b r i a n date for the rocks within a few hours of my arrival. On another pioneering expedition to Thailand I w a s able to recognize the Ordovician a g e of s o m e trilobite limestones by c o m paring their species with those k n o w n f r o m C h i n a for d e c a d e s previously—even

though

the

rocks

had

previously

been

m a p p e d as Silurian on the geological m a p s of southern Thailand. These identifications were based on the works of a hundred minor Barrandes—indeed, one of the species from T h a i l a n d w a s first n a m e d b y o n e o f h i s C z e c h c o n t e m p o r a r i e s .

Knowledge is cumulative, and hard won. It would be tedious i n t h e e x t r e m e t o n a m e all t h e n a m e s a n d p i l e t h e m i n g e o l o g i cal order in a great i n v e n t o r y of trilobitic time. T h e r e are so m a n y t r i l o b i t e s , a n d m o r e b e i n g a d d e d t o t h e list all t h e t i m e , that a h u m a n lifetime is i n a d e q u a t e to k n o w t h e m all. E v e n a f t e r t w e n t y - f i v e y e a r s o f s t u d y t h e r e a r e still p a r t s o f t h e g e o logical c o l u m n to w h i c h I am a stranger. But while geologists a n d p a l a e o n t o l o g i s t s s t r i v e f o r e v e r g r e a t e r p r e c i s i o n i t i s still possible to m a k e a grand s w e e p through geological time to see the ebb and flow of the trilobites, as one replaced another.

I n t h e L o w e r C a m b r i a n 540 m i l l i o n y e a r s a g o a v a r i e t y o f trilobites a p p e a r e d quite rapidly. T h o s e w i t h l o n g , n a r r o w a n d o f t e n t a p e r i n g g l a b e l l a s a r e t y p i c a l . I n N o r t h A m e r i c a Olenellus a n d its m a n y a l l i e s w e r e a b u n d a n t , s h a r i n g l o n g t h o r a c e s w i t h

237

T R I L O B I T E !

m a n y segments and minute pygidia, often with a very narrow part at the b a c k end b e h i n d a particularly large thoracic segment. T h e long eyes a p p e a r to run continuously into the glabella, but there w e r e no m o u l t i n g sutures on the upper surface of the head. In China, a n d through m u c h of the N e a r East, a r a n g e o f g e n e r a l l y s i m i l a r a n i m a l s did h a v e f a c i a l s u t u r e s — Redlichia i s o n e o f t h e m o s t w i d e s p r e a d . I c o l l e c t e d f r a g m e n t s o f this g e n u s on a relentlessly h o t rocky slope in Q u e e n s l a n d , A u s tralia, reflecting at the time that this w o u l d be the nearest I w o u l d e v e r get to roast trilobite. T h e C h i n e s e divide their rocks into fine time slices using different f o r m s of these animals as i n d i c e s . I n r o c k s o f s i m i l a r a g e a p p e a r t h e first m i n i a t u r e t r i l o b i t e s , s u c h a s Pagetia, w h i c h I r e g a r d a s p r i m i t i v e r e l a t i v e s o f Agnostus. S o m e o f t h e s e d i m i n u t i v e f o r m s — u s u a l l y a b o u t t h e size of a small w o o d l o u s e — h a v e i n c o n s p i c u o u s eyes, a n d three thoracic s e g m e n t s ; others are blind a n d with two, like agnostids. T h e y carry on into the M i d d l e C a m b r i a n , by which time t r u e , b l i n d a g n o s t i d s a r e o f t e n a b u n d a n t . A l l t h e s e s m a l l trilobites are outstandingly useful for dating rocks, since s o m e species are very w i d e s p r e a d a n d they evolved quickly into other species.

If they were indeed

planktonic,

this m i g h t

account for their ubiquity. T h e y are tiny timepieces, and as prec i s e l y e n g i n e e r e d , f o r t h e y e n r o l l i n t o p e r f e c t little c a p s u l e s , a n d e v e r y bit of the skeleton collaborates in their protective stance.

Alongside a variety of agnostids Middle C a m b r i a n rocks yield

giants

like

Paradoxides,

which

certainly

stalked

the

s e a - f l o o r r a t h e r t h a n c r u i s i n g f a r a b o v e it. T r i l o b i t e s o f this type also provide useful chronometers:

if y o u can recog-

nize

Middle

Paradoxides,

you

can

recognize

the

Cambrian.

There w e r e trilobites of usual size, too, s o m e of them blind, l i k e Meneviella.

Several of these blind trilobites were k n o w n

already to Joachim Barrande more than a century ago, and their discovery from rocks in France, Wales and Spain prov i d e d a n e a r l y p r o o f o f the affinity o f t i m e a n d trilobite; t h e y c o u l d e v i d e n t l y be u s e d to d a t e rocks! Their relatives h a d n o r m a l eyes, so it is likely that these trilobites b e c a m e

238

Time

Paralbertella bosworthi, 6 cm long, a typical M i d d l e Cambrian trilobite from British C o l u m b i a , Canada.

blind, rather than being blind from their evolutionary birth.

T h e y lived in d e e p , or at least turbid seas. Their oculated kin i n c l u d e Ptychoparia

striata,

a

species

known

from

wonderful

m a t e r i a l i n B o h e m i a . I t i s , y o u m i g h t say, a J o e A v e r a g e k i n d o f trilobite, with a m o d e r a t e l y small p y g i d i u m and a s o m e w h a t tapering glabella with m e d i u m - s i z e d eyes, and fairly n u m e r ous thoracic segments: nothing exaggerated in any direction.

T h e c o m m o n e s t o f " r o c k s h o p " C a m b r i a n t r i l o b i t e s , Elrathia kingi, i s a N o r t h A m e r i c a n e q u i v a l e n t , s m a l l e r a n d w i d e r , p e r haps, but just as middle-of-the-road. T h e r e are m a n y d o z e n s of broadly similar trilobites, the n a m i n g of w h i c h causes even the most patient of specialists to gnash their teeth. Their cor-

239

T R I L O B I T E !

rect d e t e r m i n a t i o n requires skill a n d e x p e r i e n c e , for m a n y similar-looking beasts range through Middle and Upper Cambrian strata. It is m u c h easier to recognize s o m e of the spiny trilobites w h i c h appear a m o n g the M i d d l e C a m b r i a n faunas, t h e first o f m a n y i m i t a t i o n s o f p i n c u s h i o n s i n t r i l o b i t e h i s t o r y .

Trilobites with rather large pygidia b e c a m e c o m m o n at the s a m e t i m e . M o s t c o n s p i c u o u s a m o n g t h e s e a r e Corynexochus a n d i t s a l l i e s ( s e e Paralbertella, p. 239), a d i s t i n c t i v e s e t of t r i l o bites w i t h l o n g , f o r w a r d l y - e x p a n d i n g glabellas s h a p e d like pestles, often with spiny thoraces and distinctive hypostomes.

T h e M i d d l e C a m b r i a n w a s a rich time for trilobites, and w h e n y o u r e m e m b e r that there were m a n y additional kinds of arthropods in the Burgess Shale, it might be appropriate to d u b the C a m b r i a n the " A g e of Jointed Legs": it was probably the time w h e n scrabbling limbs were at the acme of design.

Agnostids and m a n y others carried on into the Upper C a m b r i a n . P e c u l i a r t r i l o b i t e s , m o r e o r l e s s r e l a t e d t o Damesella ( s e e Drepanura, p . 243), a r e f o u n d i n s t r a t a o f t h i s a g e i n C h i n a : t h e y all h a v e t a i l s w i t h d i f f e r e n t a r r a n g e m e n t s o f m a r g i n a l spines,

looking like c o m b s or strange agricultural instru-

m e n t s . O n e o f t h e m — f e a t u r e d i n C h i n e s e m e d i c i n e a s the " s w a l l o w s t o n e " — w a s g r o u n d d o w n a n d incorporated into potions. M o s t C h i n e s e r e m e d i e s I h a v e c o m e across are said to be g o o d for old age, a n d it s e e m s c o n c e i v a b l e that this most ancient of medicines w a s a case of sympathetic magic. Their a p p e a r a n c e i n t h e p h a r m a c o p o e i a m a d e Drepanura o n e o f t h e earliest C h i n e s e trilobites k n o w n in the West. Related species e x t e n d i n t o A u s t r a l i a , w h e r e t h e d i s t i n g u i s h e d E s t o n i a n emigre A l e x a n d e r A r m i n O p i k d e s c r i b e d a w h o l e r a n g e o f s p e c i a l trilobites retrieved from a m o n g the prickly spinifex bushes in central Q u e e n s l a n d . His N o r t h A m e r i c a n equivalent is Allison R. P a l m e r , k n o w n to all trilobitologists as " P e t e , " o n e of those p e o p l e t o w h o m the o v e r w o r k e d epithet " i n d e f a t i g a b l e " truly applies. H i s w o r k s on the Great B a s i n — t h a t vast area of Basin a n d R a n g e e m b r a c i n g m u c h o f U t a h a n d N e v a d a — a r e a tribute to m i n d a n d h a m m e r over matter. I have climbed some of

240

Time the same slopes, at an elevation which leaves you gasping. If y o u a r e n o t c a r e f u l y o u c a n s l i d e o f f o n a s c r e e s l o p e all t h e w a y back d o w n the w a y y o u c a m e . T h e air i s fragrant w i t h c o n i f e r r e s i n . Opuntia c a c t i s n a g y o u u n a w a r e s a n d t h e r e i s t h e occasional startling b u z z of a rattlesnake, b u t m o s t l y this is benign, if hot, country, and from Pete's slopes you can see sagebrush stands in the basins dotted with a few cows, and at the lowest point m a y b e the glistening w h i t e of a salt pan. Pete collected all the r o c k s that c r o p out on the r a n g e - s i d e s , w h e r e the trilobites provided another narrative of late C a m b r i a n t i m e , h u n d r e d s of different species t e a s e d out f r o m the flatb e d d e d limestones a n d shales, telling a story of evolutionary radiations a n d local extinctions. Pete k n o w s every particular of these animals with the kind of relentless enthusiasm that is a distinguishing characteristic of m a n y A m e r i c a n intellectuals, and no doubt o n e of the reasons w h y they h a v e so conquered the world.

Around the edge of the North A m e r i c a n continent, and in Scandinavia, as well as in Wales, the late C a m b r i a n strata yield up different trilobites, O l e n i d a e , w h i c h I h a v e already celebrated in C h a p t e r 7. T h e y preferred a specialized habitat, low in oxygen. Geological episodes as short as half a million years can be recognized using these trilobites as timepieces.

T h i s m a y n o t s e e m l i k e p r e c i s i o n , c o m p a r e d w i t h 4:39 a . m . o n 1 5 A u g u s t 1931, b u t 500 m i l l i o n y e a r s a g o i t i s p r e c i s i o n t o o n e part in a t h o u s a n d . In t i m e , precision is relative.

Ordovician time w a s p r o b a b l y w h e n trilobites lived in the most places and occupied the m o s t varied ecological niches in the sea. T h e y lived e v e r y w h e r e f r o m the shallowest s a n d s to the deepest-water shales; in sunlit reefs a n d in g l o o m y abysses. S o m e C a m b r i a n families survived, like Olenidae and a g n o s t i d s , b u t w h a t g i v e s t h e O r d o v i c i a n its s p e c i a l f l a v o u r i s the appearance of a w h o l e r a n g e of trilobites that f o r m e d the foundations of the subsequent history of the whole group: cheirurids, odontopleurids, proetids, calymenids, encrinurids, l i c h i d s , p h a c o p i d s , d a l m a n i t i d s — t h e list g o e s o n . I m i g h t a p o l -

241

T R I L O B I T E !

ogize for giving such a litany of families (typical generic e x a m ples o f m o s t o f t h e m h a v e already b e e n m e n t i o n e d i n this b o o k ) w e r e it not also an a l m a n a c of O r d o v i c i a n a n d later times. A familiarity w i t h a f e w d o z e n of these a n i m a l s will help y o u p e g d o w n time, give y o u a chronology for the splitting of c o n t i n e n t s o r t h e a p p e a r a n c e o f t h e first s c o r p i o n . T h e n a m e s themselves really do matter. M o s t diagnostic of Ordovician strata are trilobites that did not survive into the Silurian. T h e s e i n c l u d e t h e f r e e - s w i m m i n g t r i l o b i t e s l i k e Cyclopyge a n d

Car-

olinites; w h i l e o n t h e s e a - f l o o r t h r i v e d m a n y a s a p h i d r e l a t i v e s of L h y w d ' s

Ogygiocarella,

together with exquisite trinucleids,

a n d l a n c e - b e a r i n g r e l a t i v e s o f Ampyx. T h e r e w e r e t r i l o b i t e s a s spiky as p o r c u p i n e s a n d as s m o o t h as boiled eggs; trilobites larger than lobsters and smaller than gnats. Because the continents w e r e dispersed at the t i m e there w e r e different trilobites on separate continents—and each one with a chronological n a r r a t i v e o f its o w n . T h e r e a d e r m i g h t b e g i n t o u n d e r s t a n d t h e sense of a w e that a researcher feels at the m a g n i t u d e of her t a s k a s s h e m a k e s a b i d t o k n o w t h e m all.

At the end of the Ordovician there was a major, or mass, extinction, one of the most important such events in the whole h i s t o r y of life. A great g l a c i a t i o n c e n t r e d on N o r t h Africa u n d o u b t e d l y drastically cooled the climate in later O r d o v i cian times, a n d this w a s probably the m a i n cause of the faunal crisis. You can find the k i n d of deposits associated with ice ages

in Africa

and

elsewhere—and,

remarkably,

trilobites

q u i t e c l o s e by. A f e w s p e c i e s w e r e e v i d e n t l y t o l e r a n t o f t h e c o l d , a n d o n e o f t h e s e , Mucronaspis, s p r e a d v e r y w i d e l y i n t h e cool era. It w a s one of the trilobites I collected in Thailand, and it w a s w i t h no little a s t o n i s h m e n t that I identified it there w i t h a species originally d e s c r i b e d f r o m S c a n d i n a v i a . Trilobite time really w o r k s across the w o r l d ! T h e r e w a s a big loss of families at the e n d of the O r d o v i c i a n , a n d several of those that died out—like a g n o s t i d s — h a d a history going back to the C a m brian. S o m e of my favourite trilobites were a m o n g the casualt i e s : n o m o r e Trinucleus, n o m o r e Isotelus. I d o u b t w h e t h e r a n y

242

Time Elrathia, a typical mid-Cambrian trilobite a few centimetres along at most, with a "flower-pot" glabella, thirteen thoracic segments and a moderately small pygidium. There are hundreds of basically similar trilobites.

This specimen is from Utah.

T h e tail of Drepanura, the " s w a l low s t o n e " from the Cambrian limestones of Shandong, China.

f r e e - s w i m m i n g species e v e r reappeared. T h e trilobitic w o r l d after the Ordovician w a s a different one. But the survivors a m o n g the trilobites soon b o u n c e d back, a n d by the m i d d l e of the Silurian these remaining families had diversified mightily.

A little p r a c t i c e a l l o w s t h e s t u d e n t t o r e c o g n i z e S i l u r i a n Balizoma,

Calymene,

Proetus

or

Ktenoura.

They

are

enough to function as useful chronometers.

243

still

common

T R I L O B I T E !

Dicranurus, a spiny relative of Odontopleurn from the Devonian of Morocco. Life size.

T h e r e i s m u c h l e s s d i s t i n c t i o n b e t w e e n e a r l y D e v o n i a n trilobites and those of the Silurian than there w a s between those of the C a m b r i a n and Ordovician, or between Ordovician and S i l u r i a n . T h e D e v o n i a n w a s t h e a p o t h e o s i s o f Phacops a n d its relatives: for a while the schizochroal eyes had c o m m a n d .

There w a s also a r e m a r k a b l e variety of spiny trilobites. In s o m e localities, particularly in present-day Morocco, it seems that almost every D e v o n i a n trilobite b e c a m e covered in prickles a n d spikes. Just a w e e k before writing these w o r d s I s a w an u n n a m e d trilobite which carried a great trident sprouting f r o m its g l a b e l l a , a n a d a p t a t i o n a s u n i q u e a s i t i s i n e x p l i c a b l e

244

Time ( s e e p . 262). F i n d i t a g a i n a n d y o u w o u l d k n o w exactly w i t h which m o m e n t of geological time you were concerned. Otherwise, the trilobite w a s not so exceptional, just another relative of

Dalmanites.

Then

there

are

species

with

great,

curled

ramshorns originating at the neck as s h o w n in the figure on p a g e 244, o r i n t i m i d a t i n g b a t t e r i e s o f v e r t i c a l s p i k e s . S o m e trilobites

related

to

Lichas

decorated

themselves

with

the

splendour of a medieval pope; other o d o n t o p l e u r i d s — a l w a y s spinulose from their O r d o v i c i a n o r i g i n s — t r a n s f o r m e d into little m o r e t h a n b u n c h e s o f n e e d l e s . E v e n t h e z o o l o g i s t h a r d ened by decades of exposure to Nature's curiosities whistles t h r o u g h h i s t e e t h w h e n h e s e e s t h e s e a n i m a l s f o r t h e first t i m e .

Such armour was, no question, protective. Was there some n e w threat which p r o m p t e d such an exuberance of spinosity?

C o u l d it be c o n n e c t e d w i t h the rise of j a w e d fish at a b o u t the s a m e t i m e ? A s w i t h all s u c h a p p a r e n t c o r r e l a t i o n s , i t i s v e r y hard to k n o w whether a particular observation unequivocally leads to the truth. There is usually s o m e alternative explanation waiting in the w i n g s . For an appraisal of time, we do not e v e n n e e d t o k n o w why: w e c a n t r e a t t h e b i z a r r e t r i l o b i t e s a s o n e m i g h t curious statues or t o t e m s f r o m a lost culture, they t y p i f y p a r t i c u l a r m o m e n t s , t h e y fix t h e p a s t .

N e a r l y all t h e s e f a n t a s t i c a l t r i l o b i t e s f a i l e d t o s u r v i v e t h e D e v o n i a n , for later in this period there w e r e a series of extinction events w h i c h picked off o n e after a n o t h e r of the trilobite families. T h e greatest of these events w a s the latest, the F r a s n i a n - F a m e n n i a n event. Very f e w trilobites survived: e v e n t h e p h a c o p i d s w e r e d o o m e d . T h o s e t h a t d i d s u r v i v e w e r e all related to o n e of the less spectacular trilobite g r o u p s of the D e v o n i a n f a u n a : Proetus a n d its r e l a t i v e s . S m a l l a n d c o m p a c t , they mostly e s c h e w e d the spinose extravagances of their contemporaries. S o m e of them had k n o b b l y heads, but that w a s about as adventurous as they b e c a m e before the Carboniferous.

By then, time w a s written wholly in variations of proetoids. My friend B o b O w e n s will extol their varied subtleties; G e r h a r d and Renate H a h n are G e r m a n professors w h o k n o w every

245

T R I L O B I T E !

n u a n c e of these trilobites. A n d it is true that in the earlier Carboniferous, w h i l e tropical seas flooded m u c h of Europe, the proetoids p r o d u c e d m a n y different designs. S o m e of them r e s e m b l e d trilobites from older periods, probably because they a d o p t e d s i m i l a r life h a b i t s . T h e r e w e r e b l i n d i n h a b i t a n t s o f d e e p waters; in crystalline limestones we find animals that an u n w a r y o b s e r v e r m i g h t m i s t a k e f o r Phacops; t h e r e w e r e e v e n s o m e t h a t l o o k l i k e O r d o v i c i a n Harpes. H o w e v e r , s o l i d - l o o k i n g , c o m p a c t , b i g - e y e d , b u t still s m a l l i s h t r i l o b i t e s l i k e Griffithides w e r e p r o b a b l y t h e c o m m o n e s t t y p e . M y b e l i e f i s t h a t , far f r o m b e i n g in decline, trilobites k e p t their capacity for invention, r e i n v a d i n g old habitats, a n d s p r e a d i n g b a c k into d e e p water.

N e w f o r m s e v o l v e d s o f a s t t h a t t h e y a r e still u s e f u l i n c h a r a c t e r izing c h u n k s of geological time, although it w o u l d take an optimist to claim that they w e r e as c o m m o n in Carboniferous rock outcrops as they were in Silurian ones. Hardy's hero would h a v e b e e n m o r e likely to h a v e h a d a trilobitic e n c o u n t e r h a d he d a n g l e d f r o m an O r d o v i c i a n precipice. Clearly, their realm w a s shrinking; and m o r e so in the succeeding Permian. A few f a m o u s localities in Sicily a n d T i m o r s h o w that in places we m i g h t still h a v e s e e n a h e a v i n g m a s s o f trilobitic b o d i e s h a d w e w a d e d t h r o u g h t h e s h a l l o w s t h e r e 250 m i l l i o n y e a r s a g o . N e w g e n e r a still a p p e a r e d , s o t h a t e v e n c l o s e t o t h e i r e n d trilob i t e s w e r e still c a p a b l e o f t i c k i n g o f f g e o l o g i c a l t i m e . B u t t h e n , a f t e r c a l i b r a t i n g t i m e f o r a p e r i o d t h r e e t i m e s a s l o n g a s the dinosaurs, the trilobite c h r o n o m e t e r stopped.

I s h o u l d n o t g i v e the i m p r e s s i o n that this great temporal story w a s easily r e a d , as if o n e m a s s i v e a n d c o n t i n u o u s pile of s t r a t a h a d y i e l d e d o n e t r i l o b i t e a f t e r a n o t h e r , p l u c k e d i n order.

T h e r e are f e w areas that can be read that simply; it w a s m o r e a question of pasting together the timescale from snatches of narrative, here and there. There were mistakes and there were arguments, s o m e of t h e m virulent. Even the great Charles W a l c o t t e r r e d . I n 1883 h e w r o t e , i n h i s d r y f a s h i o n : " B e l o w t h e P o t s d a m S a n d s t o n e [a formation in N e v a d a ] there occurs a distinct fauna, characterized by a considerable development

246

Time o f t h e t r i l o b i t e g e n u s Olenellus, a g e n u s t h a t i n t h e e m b r y o n i c d e v e l o p m e n t of s e v e r a l of its s p e c i e s p r o v e s that it is d e r i v e d f r o m t h e Paradoxides f a m i l y a n d i s c o n s e q u e n t l y o f l a t e r d a t e . " Paradoxides y o u w i l l r e m e m b e r a s a M i d d l e C a m b r i a n g u i d e , w h i l e Olenellus w a s a L o w e r C a m b r i a n i n d e x ; h e h a d t h e m t h e wrong w a y round. Walcott had evidently confused two of the categories of time I have considered in this chapter: d e v e l o p ment time of the individual, and geological time. He had p l a u s i b l y o b s e r v e d t h a t s m a l l e r Olenellus l o o k r a t h e r l i k e Paradoxides, b u t w h a t w e n o w k n o w o f h e t e r o c h r o n y — t i m e s h i f t s in d e v e l o p m e n t — a l l o w s us a different explanation. T h e similarities are only the result of an u l t i m a t e c o m m o n ancestry.

Beware assumptions about time, for the rocks will put y o u right. A n d this is w h a t h a p p e n e d to W a l c o t t a f e w y e a r s later, w h e n the Scandinavian geologist W. C. Brogger proved that r o c k s c a r r y i n g O/ene/Zus-like a n i m a l s i n N o r w a y w e r e c l e a r l y o v e r l a i n b y Paradoxides. H e h a d f o u n d t h e m p r e s e r v e d a s c o n secutive narrative pages, in an undisturbed rock sequence.

Walcott, like his friend G. F. M a t t h e w — w h o w o r k e d in folded rocks in N e w Brunswick where the evidence was a m b i g u o u s — h a d to re-examine the evidence a n d , like the good scientist h e w a s , h e a l l o w e d t h e f a c t s t o c h a n g e h i s v i e w . H e d i d n o t p e r s i s t i n a t t e m p t s t o t w i s t t i m e t o fit h i s o w n p r e c o n c e p t i o n s .

A r g u m e n t s about the timescale will not stop; as k n o w l edge grows, so the arguments b e c o m e focused on ever smaller intervals. I h a v e s p e n t m u c h of my scientific life o b s e r v i n g slow progress towards an international agreement on h o w to define the boundary between the Cambrian and Ordovician, a process in w h i c h trilobite timepieces h a v e played a part. E s o teric t h o u g h this p r o b l e m m a y s e e m , I h a v e seen g r o w n m e n g l o w i n c a n d e s c e n t w i t h rage over this m e t a p h o r i c a l milliseco n d in life's history. C a n d i d a t e s for the place to define this time b o u n d a r y at a particular point in a rock section h a v e been proposed at various locations in N e w f o u n d l a n d , and in U t a h , i n C h i n a a n d i n N o r w a y — I h a v e v i s i t e d t h e m all.

In China, near a small t o w n called C h a n g s h a n , I c a m e face

247

T R I L O B I T E !

to face with another manifestation of time. O u r party was investigating rock sections which spanned the contentious b o u n d a r y collecting trilobites f r o m the critical interval while sitting on a w a r m hillside, h a p p y as a lark (probably happier).

E r o m time to time, h u g e b u z z i n g things flew p a s t — I w a s rapt e n o u g h h a r d l y to n o t i c e t h e m . S u d d e n l y , I felt a searing pain in my side. O n e of the giant insects had crawled up inside my field jacket, w h e r e it h a d d o u b t l e s s b e e n c h a f e d a n d irritated by my v i g o r o u s h a m m e r i n g . I leaped to my feet, and the l a r g e s t h o r n e t I h a v e e v e r s e e n i n m y l i f e fell t o t h e e a r t h . I t w a s a m y s t e r y h o w a c r e a t u r e s o e n o r m o u s a n d filled w i t h v e n o m c o u l d m a n a g e t o g e t o f f t h e g r o u n d , let a l o n e fly a r o u n d the place. As the pain intensified I attempted to interest o u r interpreter in the u r g e n c y of my case. As she didn't k n o w the word "hornet" I flapped my hands and buzzed, doing a dramatic stinging m o t i o n into my side.

" A h , " she

said, smiling warmly, "bee! Not very derangerous!" By now the p a d d y fields w e r e s w i m m i n g before m y eyes. Luckily m y friend David Bruton had seen the whole thing, and eventually m a d e it clear to our hosts that it w a s one of the flying m o n sters that h a d pierced my a b d o m e n . A very strong American called Jim Miller then carried me delicately along the narrow earth dykes that separated the paddies, w i n d i n g in a kind of rectangular confusion hither a n d thither. To escape to the road is an intelligence test. In a m o m e n t of lucidity I recall staring f r o m J i m ' s b a c k into a small p o n d full of water-chestnut plants, and thinking: " m y time has come." This, my own personal time, had apparently run out in the middle of China in pursuit of a p r o b l e m of interest to me and a few dozen others.

This w a s my connection with the search for another m o m e n t 489 m i l l i o n y e a r s e a r l i e r . F o r a m o m e n t , I u n d e r s t o o d m y insignificance in the face of geological time.

Fortunately, I m a d e it to the field vehicle, w h i c h carried me rapidly to C h a n g s h a n . T h e a p p e a r a n c e of a w e s t e r n e r in this r e m o t e t o w n i n t h e e a r l y 1980s w a s s o m e t h i n g o f a s e n s a t i o n , and the w h o l e place turned out to follow my prostrate body to

248

Time the " h o s p i t a l " — w h i c h turned out to be a simple building with no glazing

in

the windows.

Several dozen heads

craned

through the w i n d o w for a g o o d view. T h e y w e r e h a v i n g the t i m e of their lives. I r e m e m b e r little, b u t I am told that the n o w tumid swelling w a s cut with a sterilized knife and squeezed enthusiastically, resulting in satisfactory gouts of b l o o d . A poultice of mashed-up vegetables w a s then applied. N o d d i n g confidently, my doctor said, through the interpreter: " H e r e , we use a combination of traditional Chinese and Western m e d i c i n e . " I w a s given an aspirin (that w a s the Western part), a n d a vast phial of b i g pills m a d e f r o m w e e d s (the C h i n e s e part). T h e y w o r k e d , for in t w o days I w a s up and about. Curiously, the incident c a u s e d me a certain loss of face. T h e f a m o u s old C h i n e s e Professor Lu Yen-hao said to me w h e n I had recovered: "I have seen these insects m a n y times, but y o u are

the

first

person bitten."

Then,

having

thought

for

a

moment, he added: "except maybe some peasants." W h e n I returned to L o n d o n I told the hornet specialist in the Natural History M u s e u m of my experience. "Wish you'd brought back the b l o o d y hornet," he said. "I d o n ' t think w e ' v e got o n e of those in our collections."

Science depends on honest reporting. It would not matter greatly if any of the items in the previous story were exaggerated, or even if part of the account w a s m a d e up for the amusement of my readers—although I should reassure you that I recall everything as clearly as I can. But w h a t no scientist is a l l o w e d is deliberately to mislead. It is w o r s e if this d e c e p tion is in the service of self-aggrandisement. This w a s appare n t l y t h e c a s e in t h e "affaire Deprat."

Jacques Deprat was a young geologist employed by the Service Geologique de l'lndochine in the early years of the twentieth century, at the time w h e n w h a t is n o w Vietnam w a s a French colony. This w a s an heroic period for geological exploration. T h e scientific m e t h o d h a d u n r a v e l l e d m a n y

249

T R I L O B I T E !

of the complexities of the Alps a n d the Himalaya; indeed, it s e e m e d as if the w h o l e structure of the Earth might be within the grasp of a m i n d sufficiently bold. Exploration of hitherto u n k n o w n territories w a s a central part of this quest. J a c q u e s Deprat w a s , without question, a talented and courageous geologist o f great e n e r g y H e w a s a n a c c o m p l i s h e d alpinist w h o revelled in collecting information f r o m inaccessible peaks; a s y n t h e s i z e r w i t h a gift for reconstruction of c o m p l e x rock structures in three dimensions; and a palaeontologist of s o m e ability to boot. Generalists of this kind are virtually u n k n o w n today. H e w a s also s o m e b o d y w h o had pulled himself u p from m o d e s t l y bourgeois b e g i n n i n g s by virtue of talent and hard w o r k : a h e r o f o r o u r t i m e s , o n e m i g h t say. T h i s w a s n o s m a l l a c h i e v e m e n t i n a F r a n c e t h a t w a s c l a s s - r i d d e n a n d elitist. T o m a k e his reputation, D e p r a t h a d b e e n c o m p e l l e d t o find w o r k at the e d g e of the French empire, a n d even there those w h o occupied establishment positions—all, like his nemesis and superior officer H o n o r e L a n t e n o i s , p r o d u c t s of the French elite education system—despised outsiders.

B u t b y 1912 D e p r a t

h a d a w o r l d w i d e reputation; his relentless hard w o r k in the field h a d s h o w n that structures r e c o g n i z e d in E u r o p e could be applied to folded and thrust rocks in Indochina, and, most remarkably, that rocks of Ordovician age could be reliably dated f r o m this r e m o t e area by the trilobites they contained.

T h e y i n c l u d e d s p e c i e s n a m e d f o r t h e first t i m e b y J o a c h i m B a r r a n d e from the strata a r o u n d P r a g u e : a n d w h a t better evidence t h a n species d e s c r i b e d b y the greatest t i m e - k e e p e r o f t h e m all?

T h e s e s p e c i e s a r e k n o w n t o d a y as

Deanaspis goldfussi,

Dalman-

itina socialis a n d Dionide formosa. T h e first t w o n a m e d a r e f a m i l iar

fossils

from

the

late

Ordovician

Letna

Formation

in

B o h e m i a , w h e r e they are particularly c o m m o n trilobites; m o s t old collections h a v e e x a m p l e s tucked a w a y in the back of a drawer.

Dionide formosa

is

a

s o m e w h a t rarer form

from

the

Vinice Formation, but well-known nonetheless. It was evident that these reliable, old-established trilobite c h r o n o m e t e r s were capable of w i d e distribution. T h e formal descriptions of the

250

Time specimens from Vietnam were m a d e by Deprat's colleague, the in-house palaeontologist Henri Mansuy, in papers published b y t h e S e r v i c e G e o l o g i q u e i n 1912 a n d 1913. D e p r a t ' s r e p u t a tion s e e m e d to be unassailable.

But then the d o u b t s b e g a n . M a n s u y b e g a n to treat D e p r a t with caution. Lantenois went further: he asserted that the fossils o f goldfussi a n d socialis w e r e i n d e e d w h a t t h e y w e r e s u p p o s e d to be, but entirely b e c a u s e they w e r e , in fact, B o h e m i a n specimens falsely claimed as c o m i n g from the locality of Nui-Nga-Ma, near Vinh, in Indochina. They were "plants," falsehoods, cheats; at the very least, to u s e the delicate w o r d e m p l o y e d b y J e a n - L o u i s H e n r y i n h i s 1994 a c c o u n t o f Vaffaire, they were " a p o c r y p h a l " — o f doubtful authenticity. If correctly identified, such duplicity b r o k e the golden rule of honest science. Deprat defended himself vigorously, and pooh-poohed the charges as slander. He m a y h a v e accurately intuited that the less able, if better c o n n e c t e d , H o n o r e L a n t e n o i s resented the rise of this upstart in the geological f i r m a m e n t . After all, it w a s he, Lantenois, that had placed the Service G e o l o g i q u e de l'lndochine on a firm scientific footing, but D e p r a t h a d h a d m u c h of the glory. N e v e r u n d e r e s t i m a t e the p o w e r of bile. But a s o n e official i n v e s t i g a t i o n g a v e w a y t o a n o t h e r tribunal, a s the Societe G e o l o g i q u e de France b e c a m e involved, a n d the great voices of the d a y w e r e called u p o n for their opinions, things l o o k e d b l e a k e r a n d b l e a k e r for Deprat. An official e x p e dition to N u i - N g a - M a which had been convened to duplicate his findings yielded nothing definitive. D e p r a t refused t o m a k e his field n o t e b o o k s a v a i l a b l e t o the C o m m i s s i o n o f Inquiry, b e h a v i o u r w h i c h w a s decidedly incriminating. E v e n while tens of thousands of y o u n g F r e n c h m e n were being slaughtered

in the

trenches French justice

ground

slowly

onwards—for the colonial world of Indochina w a s in another realm of time. Letters took m a n y weeks to arrive by sea, to deliver the latest i n s t a l m e n t of justice f r o m the m o t h e r c o u n try. T i m e w a s a c c e l e r a t e d f o r t h e d y i n g , w h i l e D e p r a t ' s p u r suit by Lantenois w a s c o n d u c t e d in slow m o t i o n , at a distance.

251

T R I L O B I T E !

Finally, J a c q u e s D e p r a t w a s d i s g r a c e d , d e m o l i s h e d b y the s a m e g e o l o g i s t s w h o h a d o n c e b u i l t h i m u p . P r o f e s s o r Termier, his one-time c h a m p i o n a n d d o y e n of Parisian geological society, w a s the reluctant executioner of his reputation. A grand commission of the celebrated Societe Geologique de France concurred that the trilobites from N u i - N g - M a were apocryphal. Those w h o had once praised the young Deprat w e r e n o w t h e b u r i e r s o f h i s r e p u t a t i o n . I n N o v e m b e r 1920 h e w a s d i s m i s s e d . Y o u m u s t n o t lie a b o u t t r i l o b i t e s , n o r y e t a b o u t time. Falsehoods will find y o u out.

Except that the obliteration of his reputation did not happ e n — q u i t e . Jacques D e p r a t wrote an account of the w h o l e business, after a period in retreat licking his w o u n d s . He wrote

it

as

a

roman

a

clef u n d e r

the

title

Les

Chiens aboient

(The b a y i n g h o u n d s ) , a n d there y o u might find—little disg u i s e d — t h e story of his arrival in V i e t n a m , of his relationships w i t h Lantenois a n d M a n s u y , a n d a recitation of his downfall. Of course, it is a partial account, but it does have s o m e ring of truth. It is impossible for the m o d e r n reader not to sympathize with the outsider, tarred by an intolerant and p r i v i l e g e d e s t a b l i s h m e n t . I n 1990, M . D u r a n d - D e l g a m a d e a bold attempt to rehabilitate Deprat at a special session of the Societe

Geologique

de

France,

apparently

accepting

the

notion that he w a s "set u p " by those jealous of his reputation.

This w a s the eventual defence that Deprat himself adopted (after c h a n g i n g his m i n d several times). It m a k e s a good, c o n t e m p o r a r y , p s y c h o l o g i c a l thriller. N o r i s there a n y d o u b t a b o u t D e p r a t ' s real a c h i e v e m e n t s in other spheres of geological science. A n d w h a t other scientist, so vilified, m i g h t have the talent to play novelist?

But the question remains: did he or didn't he? It scarcely seems possible that H e n r i Mansuy, elsewhere an exemplary palaeontologist, w o u l d in this case relax his standards of probity out of pique. Besides, it was Deprat himself w h o photographed

the

contentious

cranidium

of

Deanaspis

goldfussi,

p u b l i s h e d i n 1913. A n d i f h e w a s i n n o c e n t w h y d i d h e c o l l u d e

252

Time with the suspicions of his e n e m i e s by refusing access to his field n o t e b o o k s ? E q u a l l y o n e m i g h t w o n d e r w h y , since his career w a s in the ascendant, he should endanger it by so foolish a deception. W a s he revelling in a feeling of o m n i s c i e n c e ?

D i d h e feel s o i n e c u r e that h e m u s t e m b r o i d e r the truth t o m a k e it m o r e appealing to the w o r l d ? W h a t e v e r the answer, Deprat w a s ruined as a geologist.

S e v e r a l y e a r s l a t e r D e p r a t r e s u r f a c e d i n a n o t h e r life u n d e r the n e w n a m e of Herbert Wild, novelist. It w a s Herbert Wild w h o w r o t e Les Chiens aboient, a n d an i n t e l l i g e n t o b s e r v e r m i g h t have readily m a d e the connection b e t w e e n Wild and Deprat.

H e e n j o y e d critical success w i t h several s u b s e q u e n t novels, o n e of w h i c h w a s n o m i n a t e d for the Prix Goncourt, and earned a sufficient living f r o m his p e n to s u p p o r t his family. He also r e t u r n e d t o h i s first l o v e , t h e m o u n t a i n s , a n d b e c a m e a c o n s i d erable alpinist, a master of the Pyrenees, a n d pioneer of several of the m o r e challenging p e a k s . So far as we k n o w , he n e v e r wrote about geology again. T h e mountains eventually claimed h i s life i n M a r c h 1935; c u r i o u s l y , h e h a d w r i t t e n a n o v e l w h i c h d e s c r i b e d i n s o m e d e t a i l t h e c i r c u m s t a n c e s o f t h e fall i n w h i c h he subsequently died. O n l y u p o n his death w a s the connection b e t w e e n Wild and Deprat finally revealed.

There is an intriguing s y m m e t r y b e t w e e n this story a n d t h e o n e w i t h w h i c h t h i s b o o k b e g a n — t h e e p i s o d e i n A Pair o f Blue Eyes. B o t h c o n c e r n f i c t i o n a l t r i l o b i t e s . H a r d y ' s d a n g l i n g h e r o f a c e d d e a t h r e f l e c t e d i n t h e e y e s o f a t r i l o b i t e ; a fall k i l l e d D e p r a t , after trilobites h a d ruined h i m . In H a r d y ' s case a p l a u sible fiction, a C a r b o n i f e r o u s C o r n i s h trilobite, w a s u s e d for dramatic purposes by a novelist w h o s e reputation is probably as high n o w as it has ever been. No one w o u l d claim that his f a m e is u n d e s e r v e d merely b e c a u s e the trilobite w a s a creature of his i m a g i n a t i o n : it is the novelist's job to w h i p up such fancies. Deprat w a s disgraced b e c a u s e his fictions w e r e created under a different convention; he w a s s u p p o s e d to foll o w the rules o f the scientific m e t h o d .

However we may

e m p a t h i z e with the tragedy of brilliance w a s t e d , or recoil at

253

T R I L O B I T E !

the vindictiveness of his persecutor, Lantenois, we k n o w that the w h o l e scientific e n d e a v o u r d e p e n d s on not doing what Deprat is alleged to have done. There is no possible comprom i s e o n this principle: n o scientist c a n b e trusted w h o tells the truth 78 per cent of the time. H o w do we recognize the flawed percentage? By an exquisite twist, Deprat b e c a m e a novelist, and one w h o m a y even have admired the works of T h o m a s H a r d y . If, a s M r . W i l d , h e h a d c a l l e d u p o n t r i l o b i t e s t o p l a y a f i c t i t i o u s r o l e i t w o u l d h a v e p a s s e d u n r e m a r k e d . T h e difference b e t w e e n the creative roles of s c i e n c e a n d art c o u l d scarcely be better d e l i n e a t e d t h a n in this Tale of T w o Trilob i t e s . T h e d i s t i n c t i o n i s t h i s : l i k e all a r t i s t s , H a r d y m a d e h i s o w n t i m e — t h e c o m p a s s o f t h e n o v e l h a s its o w n b o u n d s which the reader volunteers to enter w h e n she engages with the book. T h e veracity of the trilobite is incidental, just as it matters not a w h i t that H a r d y thought of the creature as a stony crustacean. By contrast, Deprat's avowal of time was an o a t h t a k e n on the c r e d o first laid o u t explicitly by Francis B a c o n in Novum

Organum

(1620):

But if any h u m a n being earnestly desire to push on to n e w discoveries instead of just retaining and using the old; to win victories over Nature as a worker rather than o v e r hostile critics as a disputant; to attain, in fact, clear and demonstrative k n o w l e d g e instead of attractive a n d probable theory; we invite h i m as a true son of Science to join our ranks.

H e w h o a b u s e s the call t o "clear a n d d e m o n s t r a t i v e k n o w l e d g e " by the e m p l o y m e n t of deception is no "true son of Science." Imagination m a y provide the source from which both artistic a n d scientific g e n i u s flow, b u t the artist delights in fabrication, just as the scientist revels in discovery. T i m e tests the quality of the artist's vision, just as it tests the durability of scientific revelation.

254

X

Eyes to See

M o s t scientists w o r k in small arenas. To look at popular accounts of scientific discovery y o u w o u l d think that every m a n or w o m a n in a white coat w a s seeking to solve the problems of Unified Field T h e o r y determine the genetic basis of cancer, or concoct a neurological theory of consciousness.

There are a t h o u s a n d fields of scientific endeavour, a n d v e r y f e w hit the c o m b i n a t i o n o f t i m e l i n e s s a n d i n n o v a t i o n that g e n erate N o b e l Prizes (or " t h e trip to S t o c k h o l m , " as I o v e r h e a r d o n e e m i n e n t F e l l o w of the R o y a l S o c i e t y d e s c r i b e it). But scientific w o r k is i n t e r c o n n e c t e d : like a s p i d e r ' s w e b , it is sensitive to m o v e m e n t in any part of the structure, and interlinking s t r a n d s g i v e i t its s t r e n g t h . T r i l o b i t e s , t o o , c o n n e c t t o l a r g e s c i entific issues: h o w species are b o r n a n d die; the " e x p l o s i v e " n a t u r e (or not) o f the C a m b r i a n ; h o w t h e b i o l o g i c a l w o r l d w e k n o w w a s e n g e n d e r e d ; h o w t h e a n c i e n t c o n t i n e n t s lay. I t i s perfectly possible for a researcher to l a b o u r for m a n y years, k n o w n only to a dozen or so of her colleagues, maintained by love of what she does. Then, by m a k i n g s o m e connection, she m a y suddenly be at the cutting edge, lauded by laureates, praised by prize-givers. As in the parables (not to m e n t i o n the trilobites), those that h a v e eyes to see, they will see. R u t h a n d Bill D e w e l , b i o l o g y p r o f e s s o r s f r o m a s m a l l E a s t C o a s t A m e r i -

255

T R I L O B I T E !

c a n u n i v e r s i t y , w e r e a l m o s t a l o n e i n t h e i r e n t h u s i a s m f o r tiny, stumpy-legged

tardigrades,

ubiquitous

creatures

beneath

every c l u m p of m o s s , that m a y be close to the ancestral arthrop o d s . T h e realization that s o m e early C a m b r i a n fossils m a y relate to t h e m in important features of the head, and the development

of molecular

methods

for determining

their

e v o l u t i o n a r y r e l a t i o n s h i p s , p r o p e l l e d these little o r g a n i s m s from peripheral to pivotal. The Dewels' years of patient observ a t i o n w e r e s u d d e n l y g e r m a n e t o all k i n d s o f b i g q u e s t i o n s i n the evolution of the most species-rich animals k n o w n — t h e a r t h r o p o d s , in their e x u b e r a n t variety.

T h e b e a u t y of t h e scientific life is that e v e r y h o n e s t practitioner m a y add a p e r m a n e n t contribution to the edifice of k n o w l e d g e . T h e y m a y b e r e m e m b e r e d b y few o f their intellectual successors, but their contribution counts, even if it is a n o n y m o u s . It is not necessary to be one of the famous few to m a k e a p e r m a n e n t i m p a c t . I k n o w that not o n e p e r s o n in ten thousand (outside Prague) has heard of the great Bohemian palaeontologist J o a c h i m Barrande, and he is a considerable figure in the trilobite firmament. No matter: his m o n u m e n t survives in the geological m a p s of his h o m e l a n d a n d the very fabric of geological time. T h e scholar will soon find, if he digs a little further, t h e n a m e of B a r r a n d e a t t a c h e d to a h u n d r e d scientific n a m e s of i m p o r t a n t fossil animals. T h e n he will discover that Barrande, too, m a d e mistakes, most notably a theory for the successive origin of animals from his h o m e area of Bohemia, based u p o n a mis-correlation of rocks. No matter: the errors are not incorporated into the fabric of the edifice of k n o w l e d g e . Rather, they p r o v i d e the stuff for historians to c h e w over, as they trace the complex progression of ideas from conception to acceptance. In the end, the investigator will discover J o a c h i m B a r r a n d e the m a n , the fussy perfectionist w h o d e v o t e d h i s l i f e t o m a k i n g k n o w n t h e r i c h e s o f t h e B o h e m i a n Palaeozoic rocks to the world, and w h o n a m e d a clam for his housekeeper. Like Marcel Proust, w h o s e neurast h e n i c o b s e s s i o n c r a f t e d o n e o f t h e g r e a t e s t a n d l o n g e s t o f all

256

Eyes

to

See

n o v e l s , B a r r a n d e d e v o t e d his life to his v i s i o n , a n d it w a s a grand one. Like Proust, Barrande lived in an urban apartment cared for by a s t r o n g - m i n d e d servant. Science is, at root, a n o t h e r h u m a n a c t i v i t y s h o t t h r o u g h w i t h all t h e f r a i l t i e s a n d eccentricities that b e i n g h u m a n entails. Scientists' life stories a r e l i k e o t h e r life s t o r i e s , a n d i t i s j u s t a s m u c h f u n g o s s i p i n g about the details. But, for the edifice of truth, it d o e s not m a t ter w h e t h e r B a r r a n d e w a s saint or sinner, transvestite or transubstantiationist, so long as he w a s honest.

It m a y be access to a kind of immortality, of h o w e v e r unusual a variety, w h i c h m a k e s science such an attractive option for intelligent people seeking m e a n i n g in their lives. In o u r s e c u l a r a g e , o t h e r p r o m i s e s o f c o n t i n u e d e x i s t e n c e postmortem h a v e l o s t t h e i r p e r s u a s i v e n e s s . I f m o r a l v i r t u e m u s t too often b e its o w n r e w a r d , scientific v i r t u e carries the p r o m i s e of a r e w a r d of p e r m a n e n c e , of making a difference. At its m o s t b l a t a n t t h e p e r m a n e n c e r e s i d e s i n a l a b e l , a d i s c o v e r y or an idea married forever to the n a m e of the discoverer: Creutzfeldt-Jakob

Disease,

Asperger's

Syndrome,

Heisen-

berg's Uncertainty Principle, Halley's Comet. In biology or palaeontology the author is for ever tied to a species he d e s c r i b e d a n d n a m e d f o r t h e first t i m e : t h e t r i l o b i t e s Illaenus katzeri B a r r a n d e , o r Balnibarbi erugata F o r t e y a l l o w u s b o t h t h i s small measure of immortality. T h e reward in other branches of science is similar, if m o r e subtle. D e a t h cannot be cheated, but the discoveries m a d e in one's prime might well outlive bodily decay.

I find that the creative part of the scientific process can be explained rather clearly at the trilobite scale. T h e pursuit of nuclear physics or physiology employs thousands of scientists. A d v a n c e s are m a d e w h i c h c a u s e r e g u l a r r e v o l u t i o n s i n u n d e r s t a n d i n g . I am told that n e a r l y all the articles in j o u r n a l s in these fields b e c o m e obsolete before a d e c a d e is u p . W o r k e r s find it difficult to k e e p abreast of c u r r e n t d i s c o v e r i e s , let a l o n e e m b r a c e the fullness of their past. History tends to be jettisoned in favour of keeping up with the pack. At the s a m e

257

T R I L O B I T E !

t i m e , it is n e c e s s a r y to focus on o n l y a small part of the field, especially because the problems faced tend to be both highly technical and in very competitive areas of advance. Take your e y e o f f t h e b a l l f o r a m o m e n t a n d s o m e b o d y e l s e w i l l s n a t c h it!

T h e trilobite timescale, by contrast, allows us the leisure to s u r v e y t h e w h o l e o f h i s t o r y . W e f i n d i t e a s y t o c o n n e c t w i t h Dr. L h w y d in the seventeenth century, with Linnaeus' contemporaries in the eighteenth century, or with Walcott and Barrande in t h e n i n e t e e n t h century. T h e d i s c o v e r i e s of the last h u n d r e d years exist in continuity w i t h the past: not seamlessly, for p r o g r e s s i s a l m o s t a l w a y s b y fits a n d s t a r t s . B u t H a r r y W h i t tington's discoveries about trilobite larvae are clearly built on those of his predecessors, like Sir J a m e s Stubblefield or Professor Beecher. We are constantly in touch with our past; and libraries are w h e r e we do h o n o u r to those w h o c a m e before u s . O u r literature n e v e r really g o e s out o f date. T h o u g h trilobites m i g h t lie far to o n e side of the w e b of scientific k n o w l e d g e , they feel the s a m e m o v e m e n t s , a n d respond to the s a m e stimuli, as do scientific disciplines far closer to the centre. This history s h o w s that the past, too, is m u t a b l e ; and that w h e n n e w discoveries are m a d e , we re-write historical "facts." T h e job of the palaeontologist is to reinvent the past. There could be no task m o r e d e m a n d i n g of the scientific imagination.

S o m e p e o p l e still b e l i e v e t h a t s c i e n c e a n d t h e a r t s a r e s o m e h o w o p p o s e d — t h e f o r m e r dissective, the latter creative. This i s t h e a t t i t u d e f a m o u s l y e n c a p s u l a t e d i n t h e 1950s p h r a s e " T h e T w o Cultures," w h i c h w a s coined by C. P. Snow, novelist a n d senior civil servant. S n o w ' s synopsis has a far longer p e d i g r e e , g o i n g b a c k at least to the m y s t i c , p o e t a n d artist William Blake, and to those w h o opposed the experimentalist a p p r o a c h a d v o c a t e d by the Royal Society in England in the eighteenth century, a n d by other a c a d e m i e s in the western world.

T h e artist,

it was implied,

p l u m b s greater truths

through his imaginative fabrications than the obsessed reduc-

258

Eyes

to

See

tionist, w h o seeks to e x p l o r e the secrets of the butterfly by dism a n t l i n g its w i n g s . T h e c r i t i c ' s s t a n c e i s p e r f e c t l y e x p r e s s e d i n this v e r s e b y E d g a r A l l a n P o e : Science!

true daughter of Old

Who alterest all Why preyest Vulture,

things

thou

whose

thus

wings

with

Time

thy peering

upon are

thou

dull

art! eyes.

the poet's heart, realities?

Palaeontology is a " d a u g h t e r of O l d T i m e , " or it is nothing.

A n d t h r o u g h o u t this b o o k I h a v e u s e d the i m a g e of their o w n "peering e y e s " as the key to understanding the trilobites' world, just as I h a v e consciously linked this i m a g e with the observations m a d e by scientists u p o n the fossil material they w i s h t o b r i n g b a c k t o life: e y e g a z i n g o n e y e , u n b l i n k i n g . W e peer, therefore we learn.

But I regard everything I have

described as r a w material for the poet. E v e n t h e smallest item of scientific revelation c a n be a m a t t e r for joy, a n d a truth u n e a r t h e d g l i t t e r s w i t h t h e i r i d e s c e n c e o f a t r o p i c a l Papilio butterfly.

So w h y are so m a n y people ambivalent towards science a n d scientists? Several i m a g e s of the scientist c o m e to m i n d .

First, there is a stereotype of a k i n d p r o m u l g a t e d by TV a d v e r tisements, which I might term the " b a r m y boffin." Bald of p a t e , b u t f u z z y a b o v e t h e e a r s , a n d w i t h e n o u g h facial tics t o k e e p horseflies at bay, the boffin w h i z z e s a r o u n d in a state of high excitement over his latest d i s c o v e r y — o f t e n a g i z m o of arcane purpose. T h e boffin's jacket is a b a g g y t w e e d affair with screwdrivers poking out of the breast pocket. T h e boffin a l w a y s h a s t h i c k g l a s s e s : f o r s o m e r e a s o n i t i s d e rigueur t o b e s h o r t - s i g h t e d — a n d i n d e e d , there is apparently a statistical connection between m y o p i a and intelligence. Boffins always have rather feeble physiques. There is a curious assumption that the development of the brain drains

away muscular

d e v e l o p m e n t . It is as if the b r a i n itself w e r e r e g a r d e d as a k i n d of parasite that feeds u p o n the rest of the b o d y : as the c r a n i u m

259

T R I L O B I T E !

expands so the biceps a n d pectorals shrink, until I suppose the perfect boffin is a m a s s i v e brain perched atop spindly limbs, like s o m e kind of stick insect c r o w n e d with a calculator.

Professor Calculus, in the b o o k s about Tintin, the boy detective, w a s the type e x a m p l e of the boffin: clever as you like, but always

vaguely

discombobulated,

and

needing

down-to-

e a r t h c o m m o n s e n s e t o m a k e a fist o f a n y t h i n g . H i s i n v e n t i o n s w e r e a l w a y s l i a b l e t o t a k e o f f w i t h a d i s a s t r o u s life o f t h e i r o w n . H o w e v e r , n o b o d y w a s ever in doubt that Professor Calculus's heart was in the right place. No spoiler of other people's pleasures, his inventions w e r e a l w a y s s o m e h o w linked to something magical—gadgets which might bring the impossible into unpredictable existence.

N o w a d a y s , the boffin's

equivalent is probably m o r e the intense computer nerd, playing with his m a c h i n e s with the a b a n d o n e d assurance of the concert pianist. O u t of this electronic m a s t e r y c o m e s — a b e a u tiful a n d r o i d ? a t i m e m a c h i n e ?

But P o e ' s * scientist is s o m e b o d y altogether m o r e sinister, a heartless dissecter of innocent animals, perhaps, or a genetic e n g i n e e r , o r a t i n k e r e r w i t h a n a t o m y a l o n g t h e l i n e s o f The Island

of Dr.

Moreau.

H.

G.

Wells's

story

has

provided

the

screenplay for several films; the e p o n y m o u s Doctor peoples his island with ghastly inter-species grafts. As with m u c h of Wells, what once seemed perverse imagination n o w seems a l m o s t possible, b u t s o m e h o w less sinister. W e n o longer believe that the implanted heart of a pig might convert the recipient to piggishness.

But Wells m a y have contributed

s o m e t h i n g to the d e m o n i z a t i o n of the scientist by pointing up what

happens

when

technical

facility

is

decoupled

from

m o r a l responsibility. A f t e r all, in the m i d - t w e n t i e t h century we h a v e h a d e x a m p l e s in the N a z i era w h i c h exceeded Wells's most oppressive nightmares. A perpetrator of these aberra-

*Edgar Allan Poe himself contributed several scientific ideas on astronomy and biology, which were met with indifference. His prejudice against scientists may not be entirely untinged with personal bitterness.

260

Eyes

to

See

tions can scarcely be the "vulture w h o s e w i n g s are dull realities" of Poe's p o e m , for there is a m u c h m o r e active m a l e v o lence here than provided by an opportunist scavenger. Both the b e n i g n a n d the intimidating i m a g e s of the scientist reflect t h e a m b i g u i t y o f t h e r o l e a s t h e l a y m a n s e e s it. O n t h e o n e h a n d m a n y people look to the scientist as cure-all, p u r v e y o r of the w e e k l y "breakthrough." On the other, the very success of the project, and the arcane language in w h i c h m u c h of it is conducted, leads to a feeling of exclusion, of " t h e m " leading us by the nose: we discover a character like Stanley Kubrick's Dr. S t r a n g e l o v e ; o r t h e f i z z i n g l a b o r a t o r i e s t h a t J a m e s B o n d s c u p p e r s f o r t h e g o o d o f u s all.

T r i l o b i t e s , h o w e v e r , a r e i n n o c e n t o f all c h a r g e s . I s u s p e c t that the i m a g e of the palaeontologist is going to be m o r e Professor C a l c u l u s t h a n Dr. S t r a n g e l o v e . Try as I m i g h t I c a n n o t devise a scenario w h e r e b y trilobite science is appropriated by a totalitarium regime to oppress the people. " A h a , Mr. Bond!

You have arrived just in time to witness the t r i u m p h of the trilobites, and the end of the h u m a n race." I w o u l d guess that 80 per cent of scientific e n d e a v o u r is as innocent of m o r a l implications as the trilobites. O d d l y e n o u g h , it is precisely because of the harmlessness of such research that it is m o r e difficult to f u n d ; the o n l y s c i e n c e that n e v e r h a s to fight for funding is that w i t h military or m e d i c a l significance.

S o a p l a g u e o n all t h e E d g a r A l l a n P o e s o f o u r t i m e ! T h e truly dull realities of w h i c h they s p e a k are the p r o b l e m s of getting financial support to do w o r k w h i c h is not going to yield a commodity marketable within the twelvemonth, which is w h e n the accountants w h e e l out their electronic abacuses. To determine what is really of value, it is necessary to take an altogether longer view. Consider, for e x a m p l e , the general fascination

with

dinosaurs,

and

recall

that

it

was

devoted,

p a i n s t a k i n g s c i e n t i s t s w h o first p i e c e d t o g e t h e r t h e s e f a n tastical animals. S o m e t i m e s this processs t o o k a d e c a d e : digging, preparing, piecing together disparate fragments, lastly putting

flesh

on

the

bones.

Imagine,

261

if

Tyrannosaurus

had

A trident-bearing trilobite from the Devonian of Morocco, as yet u n n a m e d .

262

Eyes

to

See

r e m a i n e d u n k n o w n , h o w m a n y children's lives w o u l d h a v e b e e n impoverished. In the end, careful scientific w o r k w a s e v e n r e w a r d e d financially, if y o u take into a c c o u n t d i n o s a u r films and b o o k s and a h u n d r e d less tasteful "spin-offs."

I speculate that my trident-bearing trilobite s h o w n o p p o site will o n e d a y stimulate a m o m e n t of w o n d e r in a child, which m a y convert a waverer to science, enthralled by the marvels that wait to be f o u n d . Or e v e n inspire a poet to take flight o n s o m e j o u r n e y o f t h e i m a g i n a t i o n : t o s u b v e r t P o e ' s image, vultures soar effortlessly, a n d are elegant in flight as an eagle.

N o r can you ever say: now, we k n o w enough. We k n o w a dozen dinosaurs—why do we need to k n o w thirteen? Aren't there e n o u g h trilobites in the w o r l d ? To w h i c h I reply: the search

is

never

complete

and

we

can

never

know

what

remains hidden behind the next bluff, or inside the next piece of shale. My trident bearer w a s a d r e a m , a chimera that should not exist; yet it did. T h e w o r l d w o u l d h a v e b e e n a p o o r e r p l a c e had it remained undiscovered. I anticipate m a n y m o r e such discoveries, facts, if y o u will, but thrilling ones. M a y b e s o m e lucky investigator will discover the limbs of a larval trilobite, s o that w e m a y k n o w h o w they lived a s c o m p a r e d with the adult. C a n it be that s o m e b o d y will discover the late P r e c a m brian ancestors of the trilobites, preserved in a state of t e m p o ral g r a c e ? Will w e b e a b l e t o see the m y s t e r i e s o f this t i m e o f innovation explained, as once Walcott surveyed the mysteries of the trilobite limb? T h e s e are not G r a d g r i n d facts, "dull realities": they are w i n g s for flights of the imagination. I w i s h I could live long e n o u g h to k n o w , a n d e v e n if I did, I s h o u l d never cry " e n o u g h ! " It is m o r e difficult to f a t h o m future connections across the w e b of knowledge, since they depend on advances in a dozen other sciences. My conviction that connections will continue to be m a d e is b a s e d u p o n the fertility of this line of r e a s o n i n g in the past. A l t h o u g h , as they say of the stock m a r k e t , "past p e r f o r m a n c e is no g u a r a n t e e of future profitability," the fact is

263

T R I L O B I T E !

that these stocks h a v e reliably yielded a return for over a century, a n d t h e s m a r t m o n e y s h o u l d still b e o n t h e m . I c a n i m a g ine that the physicists will get to w o r k on trilobite optics, a n d that we will see m o r e clearly h o w trilobites saw. Their eyes w i l l g a z e u p o n v a n i s h e d w o r l d s w i t h a p r i s t i n e clarity. W e w i l l l e a r n f r o m m o l e c u l a r s t u d i e s h o w all t h e l i v i n g r e l a t i v e s of trilobites c o m p a r e one with another; we'll k n o w what questions we s h o u l d ask a b o u t their a n a t o m i c a l structures. Surely, w e will learn m o r e a b o u t h o w trilobites laid d o w n their carapaces; already the electron m i c r o s c o p e is probing the details of the minutest crystals. M a y b e we will find that trilobite shells record tiny traces of rare e l e m e n t s that act as m o n i t o r s of d e a d seas, a m i n e r a l e q u i v a l e n t of the pollutants that are picked up in tissues of living creatures, and which are mea-

An entire specimen of the spiny Silurian trilobite Kettneraspis from Dudley, Worcestershire, UK. Specimen about 2 cm long.

(Photograph courtesy Derek Siveter.)

264

Eyes

to

See

surable to parts-per-billion thanks to the extraordinary accuracy of m o d e r n t e c h o n o l o g y We will assuredly get to m e a s u r e geological time so finely that we can turn the tables on history.

Instead of using trilobites as c h r o n o m e t e r s we will e x a m i n e their evolutionary changes against a finer-scale timepiece; thus there will be n e w insights into the evolutionary m e c h a n i s m s that so intrigued the tragic R u d o l f K a u f m a n n . Trilobites m a y e m e r g e a g a i n a s t h e Drosophila f l i e s o f t h e P a l a e o z o i c , t h e e x p e r i m e n t a l m e d i u m for the history of life.

T h e s e are d r e a m s of possibilities. Yet I k n o w that there c a n be nothing better than to p u r s u e such d r e a m s ; that the will to k n o w the truth is o n e of the better parts of h u m a n nature; a n d that trilobites will r e w a r d the investigator in a currency m o r e valuable than dollars, and more tangible than fame.

265

Acknowledgements

M y t h a n k s first t o P r o f e s s o r H a r r y W h i t t i n g t o n , d o y e n o f trilobitologists, for admitting me into the trilobite trade, and m o s t recently for his generosity in s u p p l y i n g me with p h o tographs. Professors Winfried Haas, Brian Chatterton, Euan Clarkson, Riccardo Levi-Setti, and Drs. D e r e k Siveter, B o b O w e n s , Ellis Y o c h e l s o n a n d A d r i a n R u s h t o n , together w i t h the Natural

History

Museum,

kindly

supplied

numerous

other p h o t o g r a p h s , w h i c h h a v e e n r i c h e d this b o o k . H e a t h e r G o d w i n has b e e n b o t h critic a n d supporter, a n d m y debt t o h e r i s o n e v e r y p a g e . R o b i n C o c k s read m y first draft a n d m a d e several suggestions which have improved

the final

work. My wife carefully read the proofs. I thank Claire Mellish for technical s u p p o r t , P a m H a n u s a n d N i c o l a W e b b for translation from the G e r m a n . Arabella Pike and Michael Fishw i c k at H a r p e r C o l l i n s h a v e b e e n e n c o u r a g i n g at all times.

Arabella

in

particular

spotted

and

corrected

many

small

errors, and coped with the complexities of production with u n f a i l i n g g o o d h u m o u r . M y f e l l o w c o m m u t e r s o n t h e 8:02 from Henley-on-Thames kept me cheerful on several occasions w h e n I might have succumbed to gloom. This book would not have been possible without the collaboration of my t r i l o b i t e c o l l e a g u e s s c a t t e r e d all o v e r t h e w o r l d , n o t e n o u g h o f w h o m are mentioned by name.

267

Suggestions for

Kaiser,

Reinhard,

Further

Konigskinder,

Fischer

Reading

Taschenbuch

Verlag,

1998.

Kowalski, H.,

Der Trilobiten, G o l d s c h n e c k - V e r l a g

Korb.

Ger-

m a n book, particularly good on Devonian species.

Levi-Setti,

Riccardo,

Trilobites,

University of C h i c a g o

Press,

2nd e d . , 1984. A p h o t o g r a p h i c a t l a s , b e a u t i f u l l y i l l u s t r a t e d with a w i d e coverage of interesting animals.

O s b o r n e , R o g e r , The Deprat Affair, P i m l i c o , L o n d o n , 1999.

Snajdr

M.,

Bohemian

Trilobites,

National

Museum,

Prague.

G o o d photographs of m a n y of the f a m o u s trilobites of the Bohemian region.

W h i t t i n g t o n , H.

B.,

Trilobites: Fossils Illustrated, v o l .

2, B o y d e l l

P r e s s , 1992.120 p l a t e s i l l u s t r a t e m a n y f i n e t r i l o b i t e s , b y t h e d o y e n of the field.

W h i t t i n g t o n , H . B . , a n d o t h e r s , 1997. " T r e a t i s e o n I n v e r t e b r a t e P a l e o n t o l o g y , " P a r t O , Trilobita 1 ( r e v i s e d ) , U n i v e r s i t y o f Kansas Press and Geological Society of America. T h e standard academic w o r k on the subject.

269

Index

N o t e : P a g e n u m b e r s in italics r e f e r to i l l u s t r a t i o n s .

Acanthopleurella,

ij6,177

A n d r a r u m , 168

A f r i c a , 242-3

Anomalocaris,

a g n o s t i d s , 76,183, 214,240, 242-3

A n t a r c t i c a , 152

Agnostus, 238

139

antennae, 64-5,100,235n

A. pisiformis, 76,155

Apianurus,

40

A p o l l o n o v , M i k h a i l , 83

n a m i n g of, 33

A p p a l a c h i a n b a s i n , 162-3

a l l o p a t r y , 164-5, *68,175

appendages

see also e v o l u t i o n ; p u n c t u a t e d

a n t e n n a e , 6 4 - 5 , 1 0 0 , 235n

equilibrium A l m o n d , J o h n , 65-7

c a u d u l f u r c a , 126

A l u m s h a l e , 166-8

legs,

a m b e r , 160 Ampyx, 2 3 1 , 2 4 2 - 3

see also h o r s e s h o e c r a b s

A. salteri H i c k s , 53

a r a g o n i t e , 197 A r c t i c C i r c l e , 35

166

see also S p i t s b e r g e n

a n a t o m y , 22, 28-33, 36-42, 74-83

A r g e n t i n a , 118

a p p e n d a g e s , 64-5,100,126, 3 5

1 2

a r a c h n i d s , 137, 235n

a n a e r o b i c e n v i r o n m e n t s , 68-9,

2

52-83,123-4,126-7, 9'

137-8

arthropods

n

a n a t o m y of, 5 0 - 1 , 6 4 , 73

environmental adaptations,

B u r g e s s S h a l e f o s s i l s , 123-4

6 8 - 9 , 1 6 6 , 211-17 e v o l u t i o n a r y c h a n g e s , 237-49

o f C a m b r i a n p e r i o d , 127-8

g e n d e r d i s t i n c t i o n , 229

e v o l u t i o n of, 137-8

d u r i n g g r o w t h s t a g e s , 224-8

e y e s , 94, 96, 9 7 , 1 0 2 , 1 0 8

legs,

g e n e t i c s , 86, 89

52-83,123-4,126-7, 9> 12

h a b i t a t s , 113-16

137-8

p o l y p h y l e t i c o r i g i n , 128-30

see also e y e s ; m o u l t i n g p r o c e s s ;

P r o t o s t o m e a n i m a l s , 91

individual part names

271

Index B o h e m i a , 221,224,239,250

a r t h r o p o d s (cont.)

r o c k c o r r e l a t i o n , 54

s c o r p i o n s , 234-5

s w i m m e r s , 113

s i z e of, 139-40

B o n n e Bay, 122

t a r d i g r a d e s , 256 a s a p h i d s , 173

Bonnia, 122

A t l a n t i c O c e a n , 209

B o r g e s , J. L . , 219

Australia, 206-8,240

Boscastle, 3-10,12

Autobiography ( D a r w i n ) , 125

b r a c h i o p o d s , 10-11, 59,184

Avalonia, 205-6,209

b r a i n , 41

a x i s , 31

b r a n c h i a l a p p e n d a g e s , 61, 6 3 , 6 5 - 6 see also l e g s Briggs, Derek, 68-9,129,130-5

B a c o n , F r a n c i s , 254

B r i g g s / F o r t e y tree, 133-5

bacteria, 27-8,68-70,125,215

B r i t i s h C o l u m b i a , 57,123

B a i t a l - H i k m a ( B a g h d a d ) , 158

B r i t i s h I s l e s , 20, 80 see also individual place names

Balizoma, 243 Balnibarbi erugata F o r t e y , 257

B r o g g e r , W . C , 247

Baltica, 202-3,206,209

B r o n g n i a r t , A l e x a n d r e , 49, 76

B a r r a n d e , J o a c h i m , 54,221-6

B r i i n n i c h , M. T., 49 B r u t o n , D a v i d , 44,130, 248

contributions to science,

B u d d , G r a h a m , 138

256-7

B u i l t h W e l l s , 172-5

s p e c i e s d i s c o v e r e d by, 77, 238,

Bumastus, 78

250 Bathyurellus,

Burgess Shale, 57,123-35, 4°

200

2

see also e v o l u t i o n

B a t h y u r i d a e f a m i l y , 200 B e e c h e r , P r o f . , 64-8

B u r s n a l l , J o h n , 35, 36

B e e n y Cliff, 3,13-19, 81 b e e t l e s , 74,149 B i l l i n g s , E l k a n a h , 200

C a e r f a i Bay, 20

b i o l o g i c a l c l a s s i f i c a t i o n , 51

calcite, 61,107-8,197-8 o p t i c a l p r o p e r t i e s of, 92-7

c l a d i s t i c s , 132-5

s h e l l s c o m p o s e d of, 28

p h y l a , 123

c a l c i u m p h o s p h a t e , 140

b i r a m o u s limbs, 65,137-8

C a l e d o n i d e s , 209

see also l e g s

Calymene,

b i r d s , 149 b l i n d n e s s , 7 5 - 6 , 1 1 6 - 1 7 , 73Âť x

2 1

31,78-9,173

C. blumenbachii, 78-9

4'

C. senaria, 61

238-9

S i l u r i a n p e r i o d , 243

see also e y e s

c a l y m e n i d s , 241-2

B o d m i n , 9-10

272

Index Cambrian/Ordovician boundary,

cephalon, 28-9,32,114 m o u l t i n g p r o c e s s , 220

247

i n v a r i o u s s p e c i e s , 74-83

C a m b r i a n p e r i o d , 20,42, 5 2 - 3 ,

Ceraurus, 62

236-41

C. pleurexanthemus, 59-60

Burgess Shale, 57,123-35, 4 째 2

C e r a u r u s layer, 60

Cambrian/Ordovician bound-

c h a l k , 93

ary, 247

C h a t t e r t o n , B r i a n , 221,228

evolutionary evidence from,

c h e e k s , see f i x e d c h e e k s ; free

166-8

cheeks

evolutionary "explosion,"

Cheirurus,

121-45

185-6

e x t i n c t i o n e v e n t s , 183

C h e n g j i a n g f a u n a , 135-6

L o w e r (early), 88-9,177-80,

C h e n J u n - y u a n , 135-6 Chiens aboient, Les ( W i l d ) , 252-3

237-8

China, 34,88,118,123,137

M i d d l e , 238-40

C h a n g s h a n , 247-9

Olenus, 69-71 t r a c k s , 233-6

C h e n g j i a n g f a u n a , 135-6

U p p e r (late), 240-1

Mucronaspis,

v a r i o u s s p e c i e s , 74-6

U p p e r (late) C a m b r i a n p e r i o d ,

185

240

C a m b r i d g e , E n g l a n d , 35 C a m b r i d g e U n i v e r s i t y , 42

c h i t i n , 55

c a m o u f l a g e , 88, 212

c l a d i s t i c s , 1 3 2 - 5 , 1 3 8 , 235n

C a n a d a , 57,103,121-2,123

c l a d o c e r a n s , 228 c l a m s , 45, 70,183

see also individual place names Canadaspis,

C l a r k s o n , E u a n , 99-101,106-7,

130

109,168

carapace, 37,51,60, 80-3,176

c l a s s i f i c a t i o n , see b i o l o g i c a l c l a s s i -

p o l y p h y l e t i c o r i g i n , 129

fication

p r e s e r v a t i o n o f f o s s i l s , 56,198

c l i m a t e , 189,197, 2 0 5 - 6 , 2 4 2 - 3 ,

s o f t - s h e l l e d f o s s i l s , 221

246

see also s h e l l s

see also e n v i r o n m e n t ; h a b i t a t

Carboniferous period, 7-8,186-7,

Cloacaspis,

245-7

69

C o r n w a l l r o c k s , 17

Cnemidopyge,

sea-floor, 10-11

C o c k s , R o b i n , 205

Carolinites,

173,175,213

C o l e r i d g e , S a m u e l Taylor,

111,242-3

118-19

c a r t o g r a p h y , 191-2 c a u d a l f u r c a , 126

colour, 28,88

c e l l s , s t u d y of, 8 6 , 9 0

C o l u m b i a College, 64

c e n t i p e d e s , 50,55

Comma,

273

81

Index Conjectures and Refutations

Darwin, Charles, 1 1 8 , 1 2 5 - 6 , 1 2 8 ,

(Pop-

131,152

per), 24

see also e v o l u t i o n

c o n t i n e n t a l drift, see p l a t e t e c t o n -

Dawkins, Richard, 141,142, i43n

ics

D e a n , W.T., 1 4 7

c o n t i n e n t s , f o r m a t i o n of,

Deanaspis goldfussi, 2 5 0 , 2 5 2

199-211

d e f e n s e m e c h a n i s m s , see c a m o u -

see also p l a t e t e c t o n i c s

flage; enrolment

Conway Morris, Simon, 123,129,

Deprat, Jacques, 249-54

130,142-5 c o p e p o d s , 139

Descartes, Rene, 108

Cornwall, 3-19

Deuterostome animals, 91

c o r r e l a t i o n , see r o c k c o r r e l a t i o n

Devonian period, 1 0 2 - 3 , 1 6 2 - 6 ,

Corynexochus,

244-5

240

c h a r a c t e r i s t i c s o f fossils, 186

crabs, 3 7 , 1 2 1 cranidium, 37, 2 2 0

Hunsriick Slate, 7 1 - 3

creation theory, 1 5 9 - 6 2 , 1 6 6

soft-shelled fossils, 221 tracks from, 236

Cretaceous period, 12 Cross, Frank, 54

D e w e l , Bill, 2 5 5 - 6

Crotalocephalus,

Dewel, Ruth, 255-6

81,212

d i a s t r o p h i s m , see p l a t e t e c t o n i c s

Crucible of Creation, The ( C o n w a y

Dicranurus, 8 0 , 2 4 4

Morris), 143-5

dinosaurs, 7 - 8 , 1 3 6 , 1 4 0 , 2 6 1 - 2

crustaceans, 5 0 , 6 3 , 1 3 7 , 2 3 5 n

Dionide formosa, 2 5 0

blindness, 117

Ditomopyge,

enrolment, 55

188

divergence time, 8 6 , 8 9 - 9 2

Cruziana, 1 2 8 - 9

DNA, 90,153

C. semiplicata, 2 3 6 22J

see also g e n e t i c s

Cyclopyge, 7 7 - 8 , 1 1 2 , 2 4 2

doublure, 3 3 - 4 , 1 1 4

cyclopygids, 112-14

Drepanura, 2 4 0 , 2 4 3

Czech Republic, 221

Drosophilia,

Cybelurus,

86,160

Dryden, John, 66 Dudley, Worcestershire, 79 D a l m a n , J . W., 7 0

Durand-Delga, M., 252

dalmanitids, 241-2

Durness, 177-8

Dalmanites,

Dynefor Park, 4 8 - 9

81,245

Dalmanitina socialis, 2 5 0 Dalziel, Pamela, 15 Damesella, 2 4 0

e c h i n o d e r m s , 9 m , 122

Dartmoor, 10

Edgecombe, Greg, 135-6

274

Index E d i a c a r a f a u n a , 125

homology, 124,187

Edinburg Limestone, 38-9

H O X genes, 8 5 - 7 , 1 3 1 , 1 6 0

see also l i m e s t o n e

Kaufmann, Rudolf, 166-71 polyphyletic origin, 129

Eldredge, Niles, 162-6 E l i o t , T. S., 1 3 9

punctuated equilibrium, 162-6

Elrathia, 2 1 2 , 2 4 3

t h e o r y of, 2 5

E. kingi, 2 3 9

see also e v o l u t i o n ; g e n e t i c s exoskeleton, 4 1 - 2 , 5 0 , 1 2 7 , 1 8 6

embryology, 86, 90

see also m o u l t i n g p r o c e s s

Emergence of Animals, The ( M c M e -

extinction, 1 2 0 - 4 5 , 1 8 1 - 9 , i 8 ~ 5 4

n a m i n a n d M c M e n a m i n ) , 141

2

at end of Devonian period,

encrinurids, 185, 2 4 1 - 2

245-6

e n d u r a n c e o f s p e c i e s , 165

mass, 185,242-3

England, 3 - 1 0 , 5 5 - 6

see also individual place names

eyes, 3 2 , 8 4 - 1 1 9

enrolment, 5 5 - 6 , 6 0 - 1 , 1 0 2 , 245

B r i g g s / F o r t e y tree, 1 3 3 - 5

environment, 1 1 8 , 1 7 5 , 1 8 7 , 1 8 9 ,

calcite, 9 2 - 6 compound, 96,97,102

211-17

corneal surface, 101-2

see also c l i m a t e ; h a b i t a t

d e v e l o p m e n t of, 8 7

erosion, 8 , 1 3 7 , 1 9 4

evolutionary evidence, 9 1 , 1 6 2 - 6

see also p l a t e t e c t o n i c s Escher, M . C , 8 7

field o f v i e w , 9 9 - 1 0 0 , 1 1 0 - 1 6

Estonia, 56

genetic origin, 8 9 , 1 1 6 - 1 7

evolution, 159-90

and habitat, 1 1 3 - 1 9

allopatry, 1 6 4 - 5 , 1 6 8 , 1 7 5

holochroal, i 0 3 n

anatomical adaptation, 187,

lenses, 9 6 - 9 , 1 0 1 - 4 , 1 0 6 - 8 magnesium, 107-8

211-17 of arthropods, 2 3 4 - 6

moulting process, 3 7 , 1 0 1 - 2

Cambrian "explosion," 121-45

phacopid (schizochroal), 103-9, 186,244

cladistics, 1 3 2 - 5 , 1 3 8 , 235n

progressive illumination, 1 1 8 - 1 9

c r e a t i o n theory, 1 5 9 - 6 2 , 1 6 6 divergence time, 8 6 , 8 9 - 9 2

"soft," 94

environmental adaptation, 175,

spherical aberration, 106-8

189

of swimmers, 110-19

e v i d e n c e of, 1 6 2 - 8 , 1 7 2 - 5

in various species, 7 4 - 8 3

and extinction, 1 8 1 - 9

see also s e n s e s

"failed designs," 1 2 9 - 3 0 , 1 3 8 geographical influences on, 164-5,194-211

Face of the Earth, The ( S u e s s ) , 112-13

homoeomorphy, 208

275

Index Fallotaspis, 88

" F u n e s the M e m o r i o u s " (Borges), 219

felspar, 10

Fuxhianshuia,

filter f e e d e r s , 2 1 3 - 1 5

89

fish e v o l u t i o n of, 1 5 6 - 7 "flatfish," 4 7 - 9 , 6 5 , 1 7 3 , 1 8 7

gender distinction, 229

genetic similarities to, 8 5 - 7

genetics, 8 5 - 7 , 1 3 2 - 5 , 1 7 6 - 9 , 230

protection from, 245

eyes, 8 7 , 1 1 6 - 1 7

fixed cheeks, 37

fruit flies (Drosophilia), 8 6 , 1 6 0

"flatfish," 4 7 - 9 , 6 5 , 1 7 3 , 1 8 7

homology, 124,187

flatworms, 8 7 - 8

H O X genes, 8 5 - 7 , 1 3 1 , 1 6 0

foraminiferans, 161, 215

Mendel, Gregor, 167-8

Forteyops, 1 5 4

see also e v o l u t i o n g e o g r a p h i c a l f o r m a t i o n of conti-

fossils, 2 1 , 221

nents and oceans, 6 - 9 , 1 9 4 - 2 1 1

b a c t e r i a , 125

geographical isolation, 1 6 4 - 5 , 째 8

Burgess Shale, 1 2 3 - 3 5 , 4 째

2

2

Homo, 1 6 0

see also e v o l u t i o n

Hunsriick Slate, 7 1 - 3

Geological Society of London, 53

m a g n e t i z a t i o n of, 1 9 6

geological time, i4(table), 237-49 Cambrian/Ordovician bound-

missing species, 139-40

ary, 2 4 7

p l a n t s , 125 preserved in amber, 1 3 9 - 4 0 , 1 6 0

e v i d e n c e of, 1 7 2

preserved in iron pyrite, 6 4 - 9

r a d i o a c t i v e c l o c k s , 10

protaspides, 228

rock correlation, 5 2 - 4 , 1 7 2

rock correlation, 5 2 - 4 , 1 7 2 , 1 7 7 ,

Gerastos, 1 8 6 , 1 8 8

247

Germany, 43, 71-3, 80,103

shells, 2 7 - 5 1 , 1 6 1

Gifford, E m m a , 16

silica, 3 8 - 9

G i l b e r t , W i l l i a m , 195

soft-bodied animals, 123,125

gills, 6 3 , 6 6 , 7 1

specimen collections, 152-3

glabella, 3 2 , 4 1 , 1 1 4

tracks, 2 3 3 - 6

gender distinction, 229

x - r a y p h o t o g r a p h s of, 7 2 - 3

during larval stage, 226

France, 80,128, 238

in various species, 60, 7 4 - 8 3 ,

Frasnian-Famennian event, 186,

118,173

245-6

Gondwana, 202, 206-8 Gould, Stephen J.

free cheeks, 37, 7 7 - 8 3 , 1 1 0 , 2 2 0 fresh water, 211

Burgess Shale, 123-4

fruit flies, 8 6 , 1 6 0

c r e a t i o n theory, r e s p o n s e t o , 166

276

Index d i s p u t i n g t h e o r i e s of, 132,138,

H e n r y , J e a n - L o u i s , 251

140-5

Hercynian mountains and ocean

" e x p l o s i o n " t h e o r y , 130

8 - 9 , 1 1 - 1 2 , 71, 210 h e t e r o c h r o n y , 1 7 5 - 6 , 1 7 9 , 247

on e y e s , 108 on h e t e r o c h r o n y , I79.n

H i c k s , H e n r y , 53

on p u n c t u a t e d e q u i l i b r i u m , 165

H i n l o p e n S t r a i t , 46

G r a b a u , Prof., 34

Hirnantia f a u n a , 184

g r a d u a l i s m theory, 165

H i t l e r , A d o l f , 168-71 h o l a s p i s s t a g e , 226

see also e v o l u t i o n G r a n d Canyon, 57

H o l o c a u s t , 168-71

granite, 9-10,12

H o l t e d a h l , Olaf, 46

G r e a t B a s i n , 240-1

h o m i n i d s , 160

Green, J . , 60

Homo, 160 H. sapiens, 42

G r e e n l a n d , 123 Griffithides,

h o m o e o m o r p h y , 208

81,246

see also e v o l u t i o n

G r o s M o r n e N a t i o n a l P a r k , 122

h o m o l o g y , 124,187

G r o t t e du Trilobite, 128 g r o w t h s t a g e s , 224-9

see also g e n e t i c s

G u n n , T h o r n , 217

h o r s e s h o e c r a b s , 137, 229-30 trilobite " l a r v a , " 180,235-6 Walcott, Charles Doolittle,

h a b i t a t , 1 1 3 - 1 9 , 1 7 8 - 9 , 211-17, 2 4

63 n

1

see also c l i m a t e ; e n v i r o n m e n t

H o u , Dr., 135-6

H a h n , G e r h a r d , 245-6

H o u s m a n , A . E . , 78-9

H a h n , R e n a t e , 245-6

H O X genes, 85-7,131,160

H a l d a n e , J. B. S., 190

H u g h e s , C h r i s , 130

Halkieria, 123

H u g h e s , N i g e l , 229

H a l l , J a m e s , 54, 74

H u n s r i i c k S l a t e , 71-3

Hallucigenia,

H u y g e n s , C h r i s t i a n , 108

124,138

H a r d w i c k , D a v i d , 115

h y d r o c h l o r i c a c i d , 38-9

Hardy, Thomas, 4,8,128

hypostome, 41-2,126-7,

c r u s t a c e a n s , 63 Pair of Blue Eyes, A, 1 3 - 1 9 , 2 5 3 - 4 H a r t e , Bret, 144

I a p e t u s O c e a n , 200, 205

H a r v a r d U n i v e r s i t y , 42,129n, 164

i c e a g e s , 1 2 2 , 1 8 3 - 4 , 242-3

H a r v e y , W i l l i a m , 29

I c e l a n d s p a r , 94

h e a d , see c e p h a l o n

Illaenus, 78 /. katzeri B a r r a n d e , 257

Henningsmoen, Gunnar, 44

277

2 2 0

Index Ceraurus pleurexanthemus, 6 0 , 61

Illustrations of the Geology of York-

d i s c o v e r y of, 5 4 - 6 4

shire ( P h i l l i p s ) , 81

evidence of polyphyletic origin,

Imperial College of Science and

129

Technology, 114-16

jointed, 50-1

India, i 3 8 n

Olenoides, 1 2 6 - 7

Indochina, 249-52 insects, 50

Lena River, 137

Iowa, 162

lenses, 1 6 2 - 6 see also e y e s

iron, 6 4 - 9 , 7 1 - 3

Letna Formation, 250

i r o n o r e m a g n e t i t e , 195

L e v e r h u l m e Trust, 113

Island of Dr. Moreau, The ( W e l l s ) ,

Levi-Setti, Riccardo, 1 0 6 - 8

260 isopods, 55

Lewontin, R. C, 143-4

Isotelus, 7 6 , 1 8 3 , 2 1 2 , 2 4 2

L h w y d , E d w a r d , 27, 4 7 - 9 , 6 5 , 1 7 3 , 187 l i b r i g e n a , see free c h e e k s

J a a n u s s o n , Valdar, 170

Lichas, 2 4 5

jointed legs, 5 0 - 1

lichids, 2 4 1 - 2 light, 8 5 , 8 8

see also a r t h r o p o d s ; l e g s

and habitat, 1 1 3 - 1 9 o p t i c a l p r o p e r t i e s o f calcite, 9 2 - 7 Kaiser, Reinhard, 1 6 8 - 9 , 7 1

see also e y e s

1

Kaufmann, Rudolf, 8 2 , 1 6 6 - 7 1

l i m b s , see l e g s

Kazakhstan, 82-3

limestone, 35, 7 6 , 9 2 , 1 9 7

Keswick M u s e u m , 157

Carboniferous Limestone, 186-7

Kettneraspis,

C e r a u r u s layer, 6 0

264

Kdnigskinder ( K a i s e r ) , 1 6 9

Edinburg Limestone, 38-9

Ktenoura, 2 4 3

Trenton Falls, N e w York, 58 Wales, 27 Wenlock Limestone, 78-9 see also c a l c i t e

Lane, Phil, 36 Lantenois, Honore, 2 5 0 - 4

Limulus, see h o r s e s h o e c r a b s

Lapworth, Charles, 178

Linnaean system, 51,151 see also b i o l o g i c a l c l a s s i f i c a t i o n ;

larval stage, 1 7 5 - 6 , 2 2 4 - 8

nomenclature

Laurentia, 4 6 , 1 9 9 - 2 0 2

Linnaeus, Carolus (Linne, Karl

legs, 5 2 - 8 3

von), 51,151

biramous limbs, 137-8 of Burgess Shale fossils, 1 2 3 - 4

Lister, M a r t i n , 2 7 , 4 7

C e r a u r u s layer, 6 0

Llandeilo, 2 7 , 4 8 - 9

278

Index L l a n d r i n d o d W e l l s , 172-5

Mucronaspis,

l o b s t e r s , 37, 5 0 - 1 , 1 2 1

m u d - g r u b b e r s , 212-15

184,242

L u Y e n - h a o , 249

m u d s t o n e s , 172

Lyell, C h a r l e s , 125

M u r c h i s o n , S i r R o d e r i c k , 49, 53, 77

magnesium,

m u s e u m s , 146-9,157-8

107-8

see also individual names

m a g n e t i t e , 195 M a g n u s s o n , I n g e b o r g , 168-71 M a n s u y , H e n r i , 251-2

N a r o d n y M u s e u m , 224

M a p p a M u n d i , 191

n a t a t o r y a p p e n d a g e s , 61,63 see also l e g s

mating, 220,228-9 M a t t h e w , G . R , 247

N a t i o n a l M u s e u m o f W a l e s , 117, 186

M a t t h e w , W. D . , 64 M a y r , E r n s t , 164

Natural History,

M c C o r m i c k , T i m , 113-14

Natural History M u s e u m , Lon-

108,144

d o n , 9 5 , 1 4 6 - 9 , 1 5 1 - 2 , 221

M c M e n a m i n , D i a n n a , 141-2 M c M e n a m i n , M a r k , 141-2

Nature, 1 3 2 , 1 3 4 - 5 , 7 4

M c N a m a r a , K e n , 177-80

n a u t i l o i d s , 191

Megistaspis,

Nautilus, 45

x

203

N a z i s m , 168-71

M e n d e l , G r e g o r , 167-8

N e v a d a , 246-7

see also g e n e t i c s Meneviella,

N e w f o u n d l a n d , 121-2,139

238

N e w Y o r k S t a t e , 54, 57, 6 4 - 7 1 ,

m e r a s p i d e s , 231 Merlinia,

102-3,162

204-6

m i c a , 10

N i n e W e l l s , 20-1

M i d w e s t e r n U n i t e d S t a t e s , 162-3

n o m e n c l a t u r e , 29-30, 50, 53-4, 151-6

M i l l e r , J i m , 248 Mines and Minerals of the Lake District ( P o s t l e t h w a i t e ) , 157

Norasaphus, 241

M i s s i s s i p p i a n p e r i o d , see C a r -

see also individual place names

boniferous period M o i n e T h r u s t , 177

N o r w a y , 69-71,185 see also S p i t s b e r g e n

M o n g o l i a , 121 Monograph of the Trilobites of North

208

N o r t h A m e r i c a , 57, 80,162, 239,

Norwegian A c a d e m y of Sciences, 46

America, A ( G r e e n ) , 60 M o r o c c o , 80, 88,103, 244

N o v a y a Z e m y l a , 46-7

moulting process, 37,101-2,

Novum Organum ( B a c o n ) , 254 N u i - N g a - M a , 251

175-6, 219-20

279

Index O a k l e y , K e n n e t h , 128

e n r o l e d f o s s i l s , 56

o c e a n s , f o r m a t i o n of, 194-9

evolutionary evidence from,

172-5

see also p l a t e t e c t o n i c s

Odontochile rugosa, 224

e x t i n c t i o n e v e n t s , 183, 241-3

o d o n t o p l e u r i d s , 79-80, 241-2, 245

geography, 45,191-2,194-211

Oenone, 154

i n d i g e n o u s s p e c i e s , 241-3

Oenonella, 154

i r o n p y r i t e , 68

Ogyginus, 204

L e t n a F o r m a t i o n , 250

O g y g i o c a r e l l a , 242-3

Ogygiocarella, 173-5,

l i m e s t o n e , 58

^7'

ยง

s w i m m e r s , 110-19

22

e x t i n c t i o n of, 183, 242-3

Origin of Species ( D a r w i n ) , 126,128

O. debuchii, 4 8 - 5 0 , 1 7 4

O w e n s , B o b , 5 4 , 1 1 7 , 1 8 6 , 233,245

O h i o , 81,102-3 O k l a h o m a , 162

Olenelloides,

178

p a e d o m o r p h o s i s , I79n

Olenellus, 7 4 , 1 2 1 - 2 , 1 2 7 , 1 5 9 , 2 3 7 - 8 O. armatus, 178-81

Pair of Blue Eyes, A ( H a r d y ) , 13-19,

O. lapworthi, 178-81

2

a n d Paradoxides, 246-7

196-8, 206

e x t i n c t i o n of, 183

Palaeontological Society of Amer-

h a b i t a t of, 241

i c a , 145

O l e n i d S e a , 166-8

P a l a e o z o i c e r a , 24, 78-9,128,

126,133-4

194-211

Olenus, 6 9 - 7 1 , 1 6 8

see also individual geological

O m a n , 233

periods

O n t a r i o , 103

P a l m e r , A l l i s o n R., 240

ontogeny, 176-7,178-9,230

P a n g a e a , 194-211

see also g e n e t i c s

Onychophora,

53-4

palaeomagnetic measurements,

olenids, 69-71,166-8

Olenoides,

Pagetia, 238

Parabadiella,

138

Parabarrandia,

O p e n U n i v e r s i t y , 174

137 114-15,116

Paradoxides, 21-2, 23, 33, 75-6, 222

O p i k , A l e x a n d e r A r m i n , 170,240

as c h r o n o m e t e r s , 238

Opipeuter inconnivus, 45,110-13

a n d Olenellus, 246-7

o p t i c s , see e y e s

P. davidis, 224

Ordovician period, 35,178,183-4

P. hicksi Salter, 53

Cambrian/Ordovician bound-

P. oelandicus, 155

ary, 247

P. paradoxissimus, 33

c l i m a t e , 46

Paralbertella bosworthi, 239

E d i n b u r g L i m e s t o n e , 38-9

Parapilekia jacquelinae Fortey, 155

280

Index Prague, 2 2 3 - 4 , 2 5 0

Pattern of Evolution, The

Precambrian era, 86, 8 9 - 9 0 , 1 2 5

(Eldredge), 162-3

p r e d a t o r s , 127, 2 1 2 - 1 5

PAUP (Phylogenetic Analysis

Pricyclopyge,

U s i n g P a r s i m o n y ) , 133

105,113

P r i m o r i a l S y s t e m , see C a m b r i a n

P A X 6 g e n e , 8711

period

P e e l , J o h n , 123 p e l a g i c s , 183

proetids, 1 7 5 - 6 , 1 8 6 - 7 , 4 2

P e n t a r g o n Bay, 5 - 1 2

Proetus, 1 8 6 , 2 4 3 , 2 4 5

p e r a m o r p h o s i s , 17cm

Profallotaspis,

Permian period, 1 8 7 - 9 , 9 1

2

121,137

Protocystites walcotti,

phacopids, 186

Protostome animals, 9 m

Phacops, 7 3 , 1 6 2 - 6 , 2 2 0 , 2 4 4 - 5

Ptychoparia striata, 2 3 9 see also e v o l u t i o n pygidium, 29, 31-2, 36-7, 6 5 , 1 1 4 evolutionary evidence, 168,

Phillips, John, 81 Phillipsia, 8 1 - 2 Philosophical

122

punctuated equilibrium, 162-6

P. rana, 8 0 , 1 6 3 - 6 pharmacopoeia, 240

174-5,177

Transactions of the

moulting process, 220

Royal Society, 4 7 - 9

spines protruding from, 39

p h o t o s e n s i t i v i t y , see light

in various species, 6 0 , 7 4 - 8 3 , 1 7 3

Phylogenetic Analysis Using

pyrite, 6 4 - 9 , 7 1 - 3

P a r s i m o n y ( P A U P ) , 133 phylogeny, 8 6 , 1 3 2 - 5 , 1 7 6 - 9 , 2 3 0 see also g e n e t i c s

quartz, 6 - 7 , 9

plankton, 139,161,175, 226-8 plants, 1 2 5 , 1 6 7 - 8 , 2 2 6 - 7 plate tectonics, 6 - 9 , 1 9 0 - 2 1 7

Radiaspis,

pleural lobes, 31

radioactive clocks, 10

Poe, Edgar Allan, 2 5 9 - 6 1

Ray, J o h n , 151

P o l a n d , 185

R a y m o n d , P e r c y E., i 2 9 n

p o l y p h y l e t i c o r i g i n , 129

Redlichia, 2 3 8

see also g e n e t i c s

3

protaspis stage, 175-6, 2 2 4 - 8

Petigurus, 2 0 0

eyes, 103-9

1 _

79-80

Remopleurides,

228

research

Popper, Karl, 24 Porth-y-rhaw, 2 0 - 1

f u n d i n g of, 2 6 1 - 2

Possible Worlds ( H a l d a n e ) , 1 9 0

f u t u r e of, 1 5 3 , 2 6 3 - 5

P o s t l e t h w a i t e , J . , 157

grants, 113

potassium, 10

t o o l s of, 2 0 8 - 9

Potsdam Sandstone, 246-7

see also s c i e n t i s t s

281

Index respiration, 6 3 , 6 6

S e l w o o d , E. B . , 9

ribonucleic acid (RNA), 90

senses, 41, 6 4 , 1 0 0 see also e y e s

ribosomes, 90 r i b s , see p y g i d i u m

Serolis, 1 5 2

rock correlation, 5 2 - 4 , 1 7 2 , 1 7 7 ,

Service Geologique de lTndochine, 2 4 9 - 5 2

247

Rules of Zoological Nomenclature, 154

sexual maturation, 177 Shakespeare, 96 shale, 7 , 9 - 1 0 , 1 9 - 2 0 , 1 9 8

Rushton, A d r i a n , 157

B u r g e s s S h a l e , 123

Rusophycus, 1 2 8

r o c k c o r r e l a t i o n , 177 Silica S h a l e , 8 1 Utica Shale, 6 4 - 7 1

Salter, J o h n , 5 3 , 8 2

Sanctacaris, 1 3 0

S h e l d o n , Peter, 1 7 2 - 5 , 1 8 3

s a n d s t o n e , 195

shells, 1 0 - 1 1 , 2 7 - 5 1 , 5 6 , 1 4 0 , 1 6 1

Sao hirsuta, 2 2 4 , 2 2 5

calcite, 28

Scandinavia, 166-8, 241, 242

L o w e r C a m b r i a n period, 126

schizochroal eyes, 1 0 3 - 9 , 160,

m o u l t i n g of, 3 7 , 1 0 1 - 2 , 1 7 5 - 6 , 219-20

162-6

see also c a r a p a c e

see also e y e s ; Phacops

Shergold, John, 206

S c h r o e t e r , J . S., 5 3

Science, 1 3 5

shrimps, 55

scientists, 2 5 5 - 8

Shropshire, 4 9 , 1 1 8 Shumardia,

disputes among, 249-54

81,118,177

S. crossi F o r t e y & O w e n s , 54

nomenclature usage, 29-30, 50,

t h o r a c i c s e g m e n t s of, 2 3 1 , 232

53-4/151-6 r e s e a r c h by, 1 3 4 - 5 , 2 0 8 - 9 , 2 6 1 - 5

Siberia, 121,139

rivalry a m o n g , 1 3 5 - 6 , 1 4 0 - 5

Sicily, 2 4 6 silica, 3 8 - 9 , 8 1

s t e r e o t y p e s of, 2 5 8 - 6 1 scorpions, 234-5

Silica Shale, 81

Scotland, 177

Silurian period, 4 9 , 5 3 , 209-10, 242-4

Scutellum, 82

British L o w e r Palaeozoic rocks,

Sedgwick, Revd. Adam, 42, 52-3

78-9

Sedgwick Museum, 35,130

c h a r a c t e r i s t i c s o f fossils, 1 8 5 - 6

segmentation, 22, 2 9 - 3 2 , 5 0 - 1 ,

confused with other geological

131

periods, i28n, 2 2 m

see also a r t h r o p o d s ; t h o r a c i c

enroled fossils, 56

segments

fish e v o l u t i o n , 1 5 6 - 7

Seilacher, Dolf, 2 3 4 - 6

282

Index S t u b b l e f i e l d , S i r J a m e s , 177,231-2

Silurian System, The ( M u r c h i s o n ) ,

S t u n n e r , W i l h e l m , 72-3

49

S u e s s , E d u a r d , 112-13,

slate

2

H u n s r i i c k S l a t e , 71-3

s u l p h u r , 68-9

vertical slabs, 5

s u l p h u r b a c t e r i a , 70,166

0

2

S m i t h s o n i a n I n s t i t u t i o n , 106,141

S w e d e n , 56, 78,168

s n a i l s , 10-11,45, 59

S w e d i s h N a t i o n a l M u s e u m , 170

S n o w , C. P., 258

s w i m m e r s , 77-8,110-19,183, 242-3

S o c i e t e G e o l o g i q u e d e F r a n c e , 252

S w o f f o r d , D a v i d , 133

soft b o d i e d a n i m a l s , 71, 88-9 E d i a c a r a f a u n a , 125

s y m b i o s i s , 70-1,166

fossils, 123

Symphysurus,

55,188

Systeme Silurien de la Boheme ( B a r -

s o f t - s h e l l e d s t a g e , 221

r a n d e ) , 221-3

see also m o u l t i n g p r o c e s s S o u t h A f r i c a , 185 S p a i n , 238

tail, see p y g i d i u m

"Spandrels of San Marco and the

t a r d i g r a d e s , 256

Panglossian Paradigm, T h e "

t a x o n o m y , see n o m e n c l a t u r e

( G o u l d a n d L e w o n t i n ) , 143-4 s p e c i a t i o n , 149-56,160,164-5, ^

t e c t o n i s m , see p l a t e t e c t o n i c s

2

Tempest, The ( S h a k e s p e a r e ) , 96

see also b i o l o g i c a l c l a s s i f i c a t i o n ;

T e r m i e r , Prof., 252

evolution; nomenclature s p i d e r s , 50

t e t r a p o d s , 133

s p i n e s , 37, 39-41

T h a i l a n d , 185, 237, 242 t h o r a c i c s e g m e n t s , 29-32, 36-7,65,

m o u l t i n g p r o c e s s , 220

131

Olenoides, 126

e n r o l m e n t , 55-6

i n v a r i o u s s p e c i e s , 74-83,178-9

e v o l u t i o n a r y e v i d e n c e in, 175-7

S p i t s b e r g e n , 35, 43-6 fossils of p r o t a s p i d e s , 228

m o u l t i n g p r o c e s s , 220, 224-6

Olenidae, 69-71

r e l e a s e d i n t o t h o r a x , 231

s w i m m e r s , 110

s p i n e s p r o t r u d i n g f r o m , 39

St. D a v i d ' s P e n i n s u l a , 19-20, 35, 53

in v a r i o u s s p e c i e s , 71, 74-83, 118,173,178-9

S t e v e n s o n , R o b e r t L o u i s , 24,156

t h o r a x , see t h o r a c i c s e g m e n t s

s t o m a c h , 41 S t o r m e r , Lief, I29n

Time Frames ( E l d r e d g e ) , 165

s t r a t i g r a p h y , see fossils; g e o l o g i c a l

T i m o r , 246

t i m e ; individual geological time

T o r n q u i s t ' s S e a , 205-6

periods

T o w e , K e n n e t h M . , 106 t r a c k s , 233-6

s t r e a m l i n i n g t h e o r y , 115-16

283

Index T r e n t o n F a l l s , N e w Y o r k , 57,58 Triarthus,

62,64-71,111,166

Trilobites, Les ( B r o n g n i a r t ) , 49

W a l c o t t , L u r a , 58 Walcottaspis,

154

W a l e s , 238

t r i n u c l e i d s , 173, 242-3

n o r t h , 5 2 - 3 , 1 8 4 , 236

Trinucleus,

s o u t h , 19-20, 2 7 , 4 8 - 9 , 1 1 7

77,116-17,213,228

s w i m m e r s , 113

e x t i n c t i o n of, 242

Trinucleus, 77

T. fimbriatus, 53

U p p e r (late) C a m b r i a n p e r i o d ,

t u b e r c l e s , 41

241

Two Cultures, The ( S n o w ) , 258

see also individual place names w a t e r fleas, 228 United States Geological Survey, 57 U n i v e r s i t y o f C h i c a g o , 107 U n i v e r s i t y of E d i n b u r g h , 99

W e l l s , H. G . , 260 W e n l o c k E d g e , 78-9 W h i t t i n g t o n , D o r o t h y , 42-3 W h i t t i n g t o n , H a r r y B., 34,38-44, 228,231

U n i v e r s i t y of E x e t e r , 9

B u r g e s s S h a l e , 129,130

University of Gottingen, 43

excavation of pyritized limbs,

U n i v e r s i t y o f G r e i f s w a l d , 166,167, 169

65-6

u r a n i u m , 10

Olenoides, Whittingtonia,

U t i c a S h a l e , 64-71

126 154

W i l d , H e r b e r t , 253-4 see also D e p r a t , J a c q u e s v e l v e t w o r m s , 138

W i l s o n , E. O . , 216

V e n d i a n s t r a t a , 125

W i t h e r s , T . H , 147

v e n t r a l c u t i c l e , 220

Wonderful Life ( G o u l d ) , 123,130, 132,144

v e r t e b r a t e s , 42, 86, 91 V i e t n a m , 249-52

w o o d l i c e , 55

V i n i c e F o r m a t i o n , 250

W o r c e s t e r s h i r e , 79

V i r g i n i a , 38

W o r l d W a r II, 168-71

v i s i o n , see e y e s v o l c a n o e s , see p l a t e t e c t o n i c s x-ray p h o t o g r a p h s of fossils, 72-3 W a l c h , H e r r , 49 W a l c o t t , C h a r l e s D o o l i t t l e , 57-63, 8 2 , 1 2 6 , 1 3 7 , 246-7

Y o n n e , 128

284

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Richard Fortey is a senior palaeontologist at the N a t u r a l History M u s e u m in London. He is the author of several b o o k s , i n c l u d i n g Fossils:

The Key to

the Past; The Hidden

Landscape, w h i c h w o n t h e N a t u r a l W o r l d B o o k o f t h e Y e a r i n 1993; a n d Life, w h i c h w a s s h o r t - l i s t e d f o r t h e R h o n e P o u l e n c P r i z e i n 1998. H e i s a F e l l o w o f t h e R o y a l S o c i e t y .

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The text of this book was c o m p o s e d in Palatino, a typeface designed by the noted G e r m a n typographer Hermann Zapf. N a m e d after Giovanni Battista Palatino, a writing master of Renaissance Italy, Palatino was the first of Zapf's typefaces to be introduced in America. T h e first designs for the face were m a d e in 1 9 4 8 , and the fonts for the complete face were issued between 1 9 5 0 and 1 9 5 2 .

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