Nature

A young student seeks for fossils on the beach near Charmouth in Dorset, a rich hunting-ground

Wildlife of Long Ago

MOST MONTHS I TELL YOU ABOUT THE ANIMALS AND PLANTS THAT LIVE IN OUR BEAUTIFUL REGIONAL COUNTRYSIDE. SINCE IT IS JANUARY AND VERY LITTLE WILDLIFE IS STIRRING, I THOUGHT I WOULD GO BACK IN TIME AND HAVE A LOOK AT THE CREATURES THAT LIVED HERE MORE THAN 60 MILLION YEARS AGO.

By Mike George

Mike George is our regular contributor on wildlife and the countryside in France. He is a geologist and naturalist, living in the Jurassic area of the Charente

In the Jurassic period, and into the Cretaceous, our area was a lagoonal sea, very warm and teeming with life – a bit like the Caribbean today. The water was alive with tiny creatures that scavenged calcium and carbon dioxide out of the seawater to build a tiny skeleton to support their tissues. When they died, they fell to the sea floor where their skeletons coalesced into a limy ooze which eventually hardened to form limestone. So, in essence, limestone is in itself a fossil. But what excites folk is to find traces of larger animals. And there were plenty of those, which also sank at the end of their lives and became a part of the limestone. However, it must be said that the preservation of the fossils is not very good except in rare cases, as a lot of recrystallisation has occurred within the rocks, wiping out fine details of the fossils.

What can you find?

Ammonites are the most easily recognised. These relatives of the squid and nautilus lived in coiled, ribbed shells. Many were small, but some grew to 40 cm diameter, and some even larger. Usually, by looking carefully, you will find partial impressions of the shells in stones lying in the fields. When the limestone was being quarried the quarrymen would sometimes find casts of whole ammonites, which they would sell for a premium, as there was a fashion for incorporating one or more in the walls of stone-built houses as display specimens. If you keep your eyes peeled you may spot examples. Occasionally you may see the traces of a bullet-shaped shell, especially in limestone flag-stones. These are the shells of belemnites, also relatives of the squid, who strengthened themselves with this internal skeleton. Very occasionally, one may find a specimen where the belemnite’s ink-sac has been preserved. Some early palaeontologists in the 19th

Our area was a lagoonal sea, very warm and teeming with life – a bit like the Caribbean

century used to reconstitute the ink from these ink-sacs and write letters with it! Another quite common fossil is the socalled “lamp shell”. It has a passing resemblance to a Roman oil-lamp, but is quite small (two or three centimetres long). It is in fact a brachiopod. (I told you a bit about those in the sea-shell article in August). Once these two-shelled creatures lived throughout the sea-floors of the world; now they are extremely rare. Sometimes you find layers of limestone which are full of these shells, and this stone was often chosen to make decorative or functional parts of houses –they often form the structure of old Charentaise sinks and the peculiar “Queue-de-vache” ledge-stones through which these sinks drained. Sometimes you can pick up individual lamp-shells on gravelled roads or in fields, but they are usually somewhat damaged. In the Cretaceous rocks you may find fossil sea-urchins. There are too many different shapes to describe, but a good fossil-book will help. Suffice it to say they look a bit like moderate-sized potatoes, with a star-shaped mark on one side where the rows of tube-feet of the creature emerged to provide locomotion. Vertebrate remains are few and farbetween, but they do occur. The remains of huge, four-legged plant-eating dinosaurs have been found near Angoulême, and the remains of early mammals can be found in the Eocene/Oligocene beds in the south of the area. Marine reptiles such as crocodiles and ichthyosaurs are also represented. There are fossils representing all the phyla of hard-bodied creatures; you even find some soft-bodied ones, as there are very rare occurrences of amber in the Charente, and these contain insects and other arthropods. Certain beds even contain plant remains.

How do you find them?

But where can you go to find all these wonders? Walking over fields is an ageold exercise, but of course it takes an appreciable time to “get your eye in”. When I was a geology student I mapped an area of the Mendips, and I spent hours fruitlessly walking across fields looking for fossils, until suddenly I saw one, and from then on, the fields were full of them! And, of course, be careful not to damage any crops or disturb any animals that may be in the fields! Quarries are of course excellent places to look, but if they are active quarries there will be health and safety formalities to go through even if the management is agreeable to your looking. If they are abandoned quarries then the dangers are very acute, and if you trespass on the land, you have no comeback. Roadside cuttings and cliffs might seem promising, but they are inherently unstable. Geologists follow the rule that A long, bullet-shaped Belemnite, a fossil ancestor of the squid, with some small ammonites

Above - A beautiful ammonite fossil, an extinct member of the cephalopod (octopus) family

Three brachiopod fossils. The ones you are likely to find here will probably be less ribbed, but will display the oil-lamp-like shape.

A fossil sea urchin. You may well find one of these, especially in a field. Please check it isn't a potato Four vertebrae and some rib-fragments of a small Ichthyosaur, an extinct sea-living reptile similar in lifestyle to a dolphin

you never stand at the bottom of a cliff, but always look in the fallen talus a safe distance away. In my early career I had one or two close calls through standing too close to rock-faces, and I have seen amateur fossil collectors on coastal sites in England taking insane risks. If I ever had to stand close to a cliff for any reason, I would be constantly listening for any sound that would indicate movement of material above me, and I always had a safe and rapid exit-route planned.

Where to go for information.

If you want to look for fossils, the first requirement is to become familiar with the geology of the region, then you will know what to look for in any given area. If you want to find trilobites, for example, you will be seriously out of luck in our region, as these creatures were long extinct by the time the Jurassic and Cretaceous rocks were laid down. You will need to study books and geological maps. Local geological maps are best studied in libraries and museums, as they are fiercely expensive in France, although the “Carte geologique de la France à l’échelle du millionième'' is quite reasonably priced (BRGM, ISBN: 2-71592158-6). There is an excellent book, sadly only available in French, called “Fossiles de la Préhistoire charentaise'' by Néraudeau, Mazan & Vullo, ISBN: 978-236199-434-1. This is a gentle and relatively jargon-free introduction to the geology of the region, with explanations of the geography at various stages as the rocks were deposited. It also has superb photographs of a wide range of fossils from the region, which should help you identify your finds. Recently, Guide Delachaux published a useful little book called “Guide des Fossiles” (ISBN ISBN 978-2-603-026724). It is pocket-sized for ease of carrying, but has a useful introduction explaining what fossils are, where and how to collect them, what equipment you will need, and how to protect and study the fossils you do find. There are several hundred different examples, wellillustrated by excellent photographs. So many books pride themselves on using illustrations of museum-quality specimens – this book shows fossils in the state you might well find them! As far as I know it is only published in French, but a photograph can be understood in any language, and the fossils are identified by their Latin names. It is moderately priced at €24. Finally, for the French-readers who want to know more about our local mega-fauna, there is “Dinosaures, les géants du vignoble”, published by Eidola, ISBN 97810-9009-317-4. 979-10-90093-17-1This large-format book introduces the reader to the science of Mesozoic vertebrate palaeontology, then concentrates on the work done in the hundred-Km radius around the Gironde Estuary. It is a demanding read, but well-illustrated, and with a touch of humour rare in such publications. It does not limit itself to dinosaurs either, but includes fish, flying

If you want to look for reptiles, crocodiles, and other vertebrates as well. fossils, the first requirement is to become familiar with If you are serious about your geology, it is always well worth contacting a localthe geology of the region society. Several museums cover local geology and palaeontology. These are good places to spend some productive time, and they will have details of local fossilcollecting societies, where you can learn from other local enthusiasts and get help with identification. They may well have larger-scale geological maps you can study. Above all, be sensible. Have regard to your own and others’ safety. Respect the law. Happy hunting!