Quaternary research in East Anglia at the Harrison Zoological Museum

QUATERNARY RESEARCH IN EAST ANGLIA AT THE HARRISON ZOOLOGICAL MUSEUM DAVID L.

HARRISON

T h e mainstream of research on mammals in the Harrison Zoological Museum has shifted during the last decade from purely Recent mammalogy to embrace the E u r o p e a n Quaternary mammal fauna. T h e purpose of this article is to outline the reasons for this change in policy and the benefits that are already flowing f r o m it. There seems little d o u b t that in the past mammalogists and palaeontologists have worked in separate disciplines, remaining blinkered to each other's advancing knowledge. A much more balanced view of the entities that we recognise as species is acquired if their zoogeographical history and evolution is studied in addition to the Variation present in their living descendants and their present ecology.

T h e importance of this new approach has already been noted by Corbet (1984).

T h e Q u a t e r n a r y has been a period of profound climatic change. Recent researches outlined by Sutcliffe (1985) have revealed that at least seventeen m a j o r cold-warm fluctuations of climate have occurred during the past two million or so years back to the Pliocene, averaging about one hundred thousand years each. Although we like to deceive ourseives that we are living in the Postglacial H o l o c e n e , there is every reason to believe that we are in fact in the Flandrian 'Interglacial' with further climatic changes yet to come.

It should not be too surprising that the Pleistocene has been a time of extensive changes in mammal faunas, with great fluctuations in the geographica! ranges of many species and complete extinction of others. T h e argument rages on concerning the part played by man in the extinction of Pleistocene mammals. T h e disappearance of so many large mammals has been attributed to the 'Pleistocene Overkill' (Martin & Klein, 1984). It is clear however, that great ränge changes and extinctions also affected small mammals, none of which would have been systematically hunted by man.

Their ranges changed, f u r t h e r m o r e , before the environment began to be severely affected by m a n ' s agricultural, urban and industrial activities during the Flandrian. No doubt hunting by man has been a m a j o r factor in the disappearance of many large Pleistocene mammals, but a much more balanced view of the whole story becomes possible if the small mammal faunas are also taken into account.

T h e f a m o u s Pleistocene deposits of East Anglia provide a unique opportunity to conduct such a study and it is there that much of our research effort in this field is currently directed. It might be thought that such famous deposits as the Cromerian Freshwater Bed at West R u n t o n , Norfolk (type section for the C r o m e r i a n ) could no longer yield any surprises after well over a Century of study (Newton, 1882). Refined m e t h o d s of sieving the deposit, down to a mesh size of 0-5mm has, however, resulted in the recovery of some previously unknown species from the Freshwater B e d , including the Noctule

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Bat ( N y c t a l u s noctula) identified from a Single very characteristic mandibular canine tooth.

Bats a r e very rare in o p e n sites; this Noctule is t h e first bat species to b e f o u n d in t h e deposit a n d , incidentally, the oldest E u r o p e a n record of the species, ( H a r r i s o n & Bates, 1984). It has also been possible to confirm the presence of the extinct vole Pliomys episcopalis in the F r e s h w a t e r B e d . It had been f o u n d in British Middle Pleistocene deposits at Sugworth and W e s t b u r y Sub M e n d i p ( S t u a r t , 1984) but not at West R u n t o n until M r J o h n C l a y d e n , and m o r e recently ourselves, f o u n d teeth t h e r e . It is interesting to n o t e that a closely related relict d e s c e n d a n t , Dinaromys bogdanovi still exists in the m o u n t a i n s of Yugoslavia.

O t h e r small and m e d i u m sized m a m m a l s f o u n d in t h e F r e s h w a t e r Bed a r e also extinct like Pliomys. T h e s e include t h e G i a n t B e a v e r ( T r o g o n t h e r i u m cuvieri) a n d Savin's Shrew (Sorex savini). O t h e r s a r e still existing in Britain today completely or virtually u n c h a n g e d , such as t h e H e d g e h o g (Erinaceus europaeus), Pygmy S h r e w (Sorex minutus) and Noctule Bat ( N y c t a l u s noctula). A m o n g s t the r o d e n t s t h e W o o d M o u s e ( A p o d e m u s sylvaticus), Beaver (Castor fiber) and B a n k Vole (Clethrionomys glareolus) h a v e similarly survived into recent times in E u r o p e .

M a n y species f o u n d have u n d e r g o n e considerable ränge changes. T h e C o m m o n h a m s t e r (Cricetus cricetus) like t h e B e a v e r is now confined to Continental E u r a s i a . P e r h a p s the most surprising species in this class is t h e Russian D e s m a n ( D e s m a n a moschata), an aquatic mole ( F a m . T a l p i d a e ) only existing today in t h e River systems of the D o n , Volga and L o w e r Ural in Russia ( C o r b e t , 1978). T h i s interesting little Insectivore, with a robust rudder-like tail, p r e f e r s t o live in r a t h e r s t a g n a n t m a r s h y t e r r a i n , or slowflowing rivers, (Fig. 1). S o m e of t h e fossil limb b o n e s a r e highly characteristic (Fig. 2). O g n e v (1928) gives an excellent account of its natural history. It is interesting to note that t h e r a t h e r o m n i v o r o u s diet includes p o n d snails, which a r e e a t e n t o g e t h e r with the hard shell. Fossil jaws of the D e s m a n f r o m West R u n t o n s o m e t i m e s exhibit r e m a r k a b l e flat w e a r facets o n t h e cusps suggesting a hard e l e m e n t in the diet. T h e F r e s h w a t e r B e d is c e l e b r a t e d for t h e large n u m b e r of f r e s h w a t e r molluscs c o n t a i n e d in it, o f t e n in amazingly good p r e s e r v a t i o n .

Study of the British Pleistocene small m a m m a l s provides m a n y o t h e r e x a m p l e s of surprising r ä n g e changes. Cold a d a p t e d species such as t h e Arctic L e m m i n g ( D i c r o s t o n y x torquatus) a n d N o r w a y L e m m i n g ( L e m m u s lemmus) have predictably r e t r e a t e d to t h e far n o r t h e r n A r c t i c t u n d r a .

O t h e r s , p e r h a p s b e t t e r a d a p t e d to s t e p p e conditions have r e t r e a t e d eastwards into Asia, including t h e Pika ( O c h o t o n a pusilla), a small relative of the hares and rabbit. It is startling at first to realise that s o m e large p r e d a t o r s , such as t h e Lion (Panthera leo) and the S p o t t e d H y a e n a (Crocuta crocuta) were p r e s e n t h e r e in t h e Pleistocene and evidently well a d a p t e d to cold t u n d r a conditions in the D e v e n s i a n , while t h e H i p p o p o t a m u s ( H i p p o p o t a mus amphibius) r a n g e d as far n o r t h as Y o r k s h i r e during t h e w a r m interglacials. A M a c a q u e m o n k e y , a p p a r e n t l y indistinguishable f r o m t h e N o r t h A f r i c a n B a r b a r y A p e ( M a c a c a sylvana), f o r m s a n o t h e r rare and surprising A f r i c a n e l e m e n t in o u r British Middle Pleistocene. A p a r t f r o m the new

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Fig. 2

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Humerus of fossil Desmana moschata H Z M 31-163600. West R u n t o n , Norfolk. Anterior (above left); posterior (above right) and lateral view of head, showing bicipital groove and foramen (below).

Scale = 3mm. Stereomicroscope drawings by D. L. Harrison.

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Suffolk Natural History, Vol. 22 knowledge of the zoogeographical history of species imparted by Quaternary research there is also the unique opportunity to examine the actual evolutionary lineages in small mammals.

Probably there is no case so well known and documented as the ancestry of the living Water Vole (Arvicola terrestris). Abundant material of fossil Microtine teeth now available has permitted documentation of the gradual change from the low-crowned, rooted cheek teeth of the ancestral Mimomys voles of the Pliocene and Lower Pleistocene to the high-crowned, rootless teeth of the modern Arvicola. Stuart (loc. cit.) has outlined the various changes involved. One particularly interesting feature is the manner in which the 'Mimomys fold' and enamel island present in the anterocone of the first mandibular cheektooth of most of the Lower Pleistocene ancestral species becomes gradually lost (See Fig. 3).

The last British representative of the genus Mimomys is found in the Freshwater Bed (M. savini). In young unrooted teeth of this species the fold is still present in most, and the enamel island in some. By the late Cromerian the descendant species Arvicola cantiana has become virtually rootless and only occasionally exhibits the fold. In the modern species A. terrestris the fold has only been reported as a rare atavistic character reappearing in occasional individuals of an Upper Pleistocene population, (Nadachowski, 1984). It is apparently altogether lost, like the rooting of the teeth in Flandrian populations of the present day. The history of these archaic characters in the Water Vole lineage is reminiscent of Haeckel's Law of Recapitulation which stated that the development of the individual (ontogeny) repeats phylogeny.

Our recent collections from East Anglian and Kentish sites have added greatly to the available material of British Pleistocene shrews and in collaboration with Andrew Currant of the British Museum (Natural History) and John Clayden it is hoped to make a comprehensive review of the known 10

Fig. 3 Loss of archaic characters (Mimomys fold and enamel island) in the first mandibular cheektooth of voles (genera Mimomys and Arvicola) during the Quaternary. (a) Mimomys reidi HZM 3.16393 Lt. ml, subadult, rooting. Lower Pleistocene (Prepastonian), Norfolk. 'Mimomys fold' and enamel island present in the anterocone. (b) Mimomys savini HZM 230.14998 Rt. ml, juvenile, unrooted.

Middle Pleistocene (Cromerian), Norfolk. 'Mimomys fold' and enamel island present in the anterocone. (c) Mimomys savini HZM 220.14981 Rt. ml, subadult, rooting.

Middle Pleistocene (Cromerian), Norfolk. 'Mimomys fold' only present in the anterocone. (d) Mimomys savini HZM 225.14986 Rt. ml, old adult, with long roots. Middle Pleistocene (Cromerian), Norfolk. 'Mimomys fold' and enamel island both absent. (e) Arvicola terrestris HZM 56.13197 Rt ml, old adult, rootless.

(Flandrian), Perthshire. 'Mimomys fold' and enamel island lost.

Scale = 1mm. Stereomicroscope drawings by D. L. Harrison.

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fossil species in comparison with recent material, thereby perhaps clarifying the rather confused taxonomy of Pleistocene British shrews, little studied since Hinton (1911).

For this special research project detailed measurements are being made of the fossil species, including all available teeth, maxillae and mandibles for comparison with one another and with Recent populations. The employment of a Wild Stereomicroscope with eyepiece graticule facilitates the standardised measuring techniques and also permits the making of stereomicroscope drawings of diagnostic features. The results will be analysed statistically and graphically. In addition a special study is being made of the limb bones of the fossil species, which are sometimes found intact.

Chaline et al. (1974) have clearly demonstrated that extant shrew species in France can be identified by their limb bones, both by size and by distinctive morphological features. Our preliminary results indicate that this also applies to some fossil species at least, as suggested by Hinton (loc. cit.). This could well add valuable additional knowledge of the postcranial morphology as well as additional morphometric data. Comparison with Recent species will be facilitated by the fact that limb bones of all recent shrew specimens have been prepared in addition to skins and skulls in the Harrison Zoological Museum for some years, (See Fig. 4).

We believe that collaborative researches between mammalogists and palaeontologists such as we are undertaking, as outlined above can only lead to a better understanding of mammalian evolution. Already it is clear that the 'biological' species of the Recent mammalogist is quite a different concept to the 'temporal' species of the palaeontologist. Given adequate material from a complete fossil record the palaeontologist must choose a convenient point in time to create an artificial species boundary and change the species name. For this purpose he must choose some more or less definable morphological change, such as has been done in the case of the Mimomys to Arvicola lineage referred to above.

It is perhaps pertinent to quote here from the Introduction to the author's Mammals of Arabia (Harrison, 1964): 'No taxonomic system that ever has been or ever will be invented can possibly be perfect. This is because we are endeavouring to divide something which is essentially a continuum into discontinuous, clearly definable parts.' This prophetic remark has returned to haunt its author on numerous occasions. It embodies the essential

Fig. 4

Femur of some fossil and living Sorex species. (a) Sorex araneus H Z M 278.13037. Wells, Somerset. Recent. Rt. femur. (b) Sorex savini H Z M 4.14206. West Runton, Norfolk. Cromerian.

Rt. femur. (c) Sorex runtonensis HZM 17.15623. West Runton, Norfolk.

Cromerian. Lt. femur. (d) Sorex minutus H Z M 80.16427. Itteringham, Norfolk.

Ipswichian. Rt. femur. Scale = 2mm. Stereomicroscope drawing by D. L. Harrison.

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dilemma of the Student of Quaternary mammals, confronted as he is with a mixture of extinct and living species and populations undergoing evolutionary transition. However inconvenient for the taxonomist, we certainly have a unique opportunity to promote better understanding of evolution and extinction. The truth we seek is infinitely more important than the labels we attach to our specimens. What is quite certain is that East Anglia still has a vital part to play in the slow but sure advance of scientific knowledge in this intricate and fascinating field. The modern multidisciplinary approach to Quaternary research is essential for success.

References Chaline, J., Baudvin, H., Jammot, D., and Saint Girons, M.-C. (1974). Les proies des rapaces (petits mammiferes et leur environment). Doin (Eds.) Paris. 141 pp.

Corbet, G . B . (1978). The mammals ofthe Palaearctic Region: a taxonomic review. Brit. Mus. Nat. Hist. Pub. 134pp.

Corbet, G. B. (1984). The mammals ofthe Palaearctic Region: a taxonomic review. Supplement. Brit. Mus. Nat. Hist. Pub. 45pp.

Harrison, D. L. (1964). The Mammals ofArabia I. Insectivora. Chiroptera.

Primates. Benn (London) Pub. 192pp.

Harrison, D. L. and Bates, P. J. J. (1984). Occurrence of Nyctalus noctula Schreber, 1774 (Chiroptera: Vespertilionidae) in the Cromerian Interglacial of England. Mamm. (Paris) 48, 603.

Hinton, M. A. C. (1911). The British fossil shrews. Geol. Mag. 8, 529.

Martin, P. S. and Klein, R. G., (Eds.) (1984). Quaternary Extinctions: a prehistoric revolution. Univ. Arizona Press. 892pp.

Nadachowski, A. (1984). Morphometric variability of dentition of the late Pleistocene Voles (Arvicolidae, Rodentia) from Bacho Kiro Cave (Bulgaria). Acta Zool. Cracoviensia 27, 149.

Newton, E. T. (1882). The vertebrata ofthe Forest BedSeries of Norfolk and Suffolk. Mem. Geol. Surv. UK. Ognev, S. I. (1928). Mammals of Eastern Europe and Northern Asia. 1.

(Insectivora and Chiroptera). 631pp. G L A V N A U K A - MoscowLeningrad.

Stuart, A. J. (1982). Pleistocene vertebrates in the British Isles. Longman Pub. 212pp.

Sutcliffe, A. J. (1985). On the track of Ice Age mammals. Brit. Mus. Nat. Hist. Pub. 224pp.

Acknowledgements I am much indebted to our colleagues in Quaternary research who have introduced Paul Bates and myself to the unfamiliar paths of palaeontology, especially Andrew Currant of the British Museum (Natural History), Department of Palaeontology and Martin Warren, (Cromer Museum). Our field work in East Anglia has been immensely assisted by our friends

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John Clayden, Jonathan Abbs, Michael Ford, H o n . Mrs Jonathan Balcon and Paul Leung. Without their enthusiastic help we could have achieved little.

Dr D. L. Harrison, Harrison Zoological Museum, Bowerwood House, St Botolph's Road, Sevenoaks, Kent TN13 3 A Q

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