Palaeontology

PALÆONTOLOGY

Among many other claims to the best attention of the student of vertebrate palæontology, Somerset has a special pre-eminence on account of having yielded the earliest known evidence in Britain of the existence of mammals. Indeed, there are no earlier representatives of the group known from any part of the world. In referring the remains in question to the Mammalia it must however be borne in mind that they may prove to belong to creatures intermediate between reptiles and the living duckbill (Ornithorhynchus anatinus) of Australia, which is one of the two lowest existing mammals. These presumed mammals are known only by teeth and are assigned to a genus (Microlestes) originally described from the Trias of the continent, but to species different from the continental. Certain of these teeth, now in the Bath Museum, were obtained from a fissure in the Rhætic strata of Frome, and named by Sir R. Owen Microlestes moorei, in honour of Mr. C. Moore, the well known collector of Somerset fossil vertebrates. Another tooth, preserved in the museum at Oxford, was collected by Professor W. B. Dawkins in the Rhætic of Watchet, and named by him Hypsiprymnopsis rhæticus, on the supposition that it indicated a creature allied to the modern rat-kangaroos of Australia. It appears however to be undoubtedly referable to the same genus as the Frome specimens, if indeed it be specifically distinct. If, as is stated to be the case, it was found in undisturbed Rhætic strata it is of the highest importance as definitely fixing the Triassic age of the former. For as the Frome teeth were obtained from a fissure in the Rhætic, it is obvious that they might perfectly well be of post-Triassic origin.

Leaving then these highly interesting teeth, we pass on to the consideration of the fossil fish of Somerset, among which several are peculiar to the county. The oldest of these occur in the Carboniferous strata of the county, (fn. 1) where they are represented by Cladodus mirabilis, a primitive shark of the group Ichthyotomi. Among the true sharks (Selachii) a tooth from Clevedon in the British Museum belongs to the well known Psammodus rugosus, whose large pavement-like crushing teeth are common in Carboniferous strata. Other teeth from Clevedon have curved and elevated crowns, and belong to Delto ptychius gibberulus, a member of the family Cochliodontidæ. The Carboniferous strata of the same locality have likewise yielded numerous teeth referable to Orodus ramosus, a pavement-toothed shark belonging to the family (Cestraciontidæ) typified by the existing Port Jackson shark.

The formations newer than the Carboniferous have yielded a large number of peculiar fishes, one of the most interesting being Diplodus moorei (fn. 2) from the Keuper, which is only known from Somerset, and indicates the survival in the early Secondary of the Palæozoic cladodont type (Ichthyotomi). Specimens from the Rhætic strata of the county indicate the occurrence of Hybodus minor, a fairly common cestraciont shark. Among species of uncertain affinity described on the evidence of fin-spines, the one known as Nemacanthus monilifer is indicated by a small spine from the Rhætic of the county. Other Rhætic fishes are the ganoid Sargodon tomicus and Saurichthys acuminatus, both of which have a wide distribution.

From the lower Lias three species are known, namely the pavement-toothed shark Acrodus nobilis, of which teeth (termed by quarrymen in some parts of the country fossil leeches) and fin-spines are met with at Weston and Keynsham near Bath ; the ganoid Pholidophorus stricklandi, of which remains occur at Glastonbury (the only other locality for the species being Leicestershire); and another ganoid, Mesodon liassicus, which is known from Langport.

Special interest attaches to the Upper Liassic fishes of Ilminster, a fine series of which, now in the Bath Royal Literary and Scientific Institution, were collected by the late Mr. C. Moore. These specimens have been described by Dr. A. Smith Woodward in a paper contributed to the Proceedings of the Bath Club. (fn. 3) They belong to a zone in the Lias represented elsewhere in Würtemberg, Bavaria, Calvados and Vassy in France, and Whitby in Yorkshire.

The first is a ganoid, Lepidotus elvensis, originally described from Würtemberg, and belonging to a well known genus in which the crushing teeth are button-shaped and the polished scales large and rhomboidal. Fragments too imperfect to admit of specific determination indicate the occurrence of a representative of another ganoid genus, Dapedius; but of much more interest is a fine and apparently unique specimen of an unnamed species of the genus Caturus, which occurs typically in the lithographic limestones of Bavaria. The special interest of Caturus, as remarked by Dr. Woodward, consists in its being almost identical in regard to the structure of the head, skeleton and fins with the rhombic-scaled Eugnathus, although its whole body is invested with thin overlapping scales. The most numerous of the Ilminster fishes belong however to the Mesozoic ganoid genus Pachycormus, which represents a family whose members present a curious superficial resemblance to the modern sword-fishes; the Cretaceous Protosphyræna being one of the Pachycormidæ in which a true sword was developed. The Ilminster species apparently include the typical Pachycormus macropterus, the smaller P. curtus, P. esocinus, and an unnamed small-scaled form. Other remains suggest a species which may belong either to Pachycormus or the allied genus Saurostomus, while a head in the British Museum belongs to a species of Pholidophorus, perhaps identical with P. germanicus of Würtemberg and Whitby. Leptolepis bronni, a more modern type of ganoid, is also met with at Ilminster.

From the Great Oolite of the county teeth of two common Mesozoic sharks, Strophodus magnus and Hybodus grossiconus, have been obtained, both belonging to the family Cestraciontidæ; and also the ganoid Lepidotus tuberculatus. In the Upper Greensand of Kilmerton we have a more modern type of shark represented by a tooth in the British Museum referable to the common Cretaceous Oxyrhina mantelli. (fn. 4)

Of the fossil reptiles of Somerset, one of the earliest appears to be the small carnivorous dinosaur Thecodontosaurus platyodon, of which there are two teeth in the British Museum from the upper Trias of the county. This species is typically from the Trias of Bristol, but other dinosaurian remains from the Rhætic of Wedmore near Glastonbury have been considered to represent two genera and species peculiar to the county. These have been named (fn. 5) Avalonia sanfordi and Picrodon harveyi, but further evidence seems desirable to show their distinctness from one another and also from the widely spread Triassic genus Zanclodon.

Remains of large marine saurians belonging to the genera Ichthyosaurus, Plesiosaurus, etc., are exceedingly abundant in the lower Liassic strata of Bath, Glastonbury, Street and Watchet, where many more or less nearly entire skeletons have been obtained. A fine series of such specimens are exhibited in the British Museum, several of which are the types of the species they represent. Ichthyosaurs, it may be mentioned, have very large heads, short necks, paddles composed of a number of polygonal bones articulated together to form a pavement, and the bodies of the vertebræ very short, deeply cupped, and quite separate from the arches protecting the spinal cord. Some of them reach thirty feet in length, and all have a ring of bones in the white of the eye. Most of the species from the county belong to the group with broad paddles, among them being Ichthyosaurus communis from Bath and Street, I. conybeari from Saltford near Bath, and I. intermedius from Street. The very distinct and gigantic I. platyodon is common in the county, and there are certain bones from Watchet in the Boulogne Museum which may indicate yet another species of the genus.

The Liassic plesiosaurs differ from the ichthyosaurs not only by their elongated necks and small heads, but likewise by the structure of their paddles, the bones of which are of normal form and do not make a pavement. The bodies of the vertebræ too are relatively longer, less deeply cupped, and more firmly articulated to the arches, while there are no ossifications in the ball of the eye. Plesiosaurus compressus has been met with in the lower Lias of at least one locality in the county. P. dolichodirus occurs at Bath and Watchet, P. hawkinsi at Street, and P. macrocephalus at Street and at Weston near Bath. The species Plesiosaurus eleutheraxon was named from remains found at Street, and vertebræ from the same locality have been made the type of a nominal species under the name of P. subconcavus, while others from Weston have been described as a second nominal species with the title of P. subtrigonus. Of the allied genus Thaumatosaurus, distinguished by the proportionately larger head, two species occur in the lower Lias of the county, namely T. arcuatus and T. megacephalus. Part of a lower jaw in the British Museum, which is probably from Street, forms one of the types of the former species, of which remains also occur at Bath. The second species is typified by an entire skeleton in the British Museum from some locality in the county.

Reptilian remains from other Mesozoic deposits appear to be rare in Somerset. A peculiar species of long-nosed crocodile of the genus Steneosaurus is typified by a skull from the Great Oolite of Bath described by Sir R. Owen as S. temporalis. The common Cretaceous Ichthyosaurus campylodon is represented in the county by teeth and vertebræ from the Upper Greensand of Kilmerton; (fn. 6) and a large-headed representative of the pliosaurs occurs in the lower Chalk of Frome in the form of the widely spread Polyptychodon continuus.

As regards Tertiary Mammalia, Somerset is celebrated on account of the large number of remains obtained from the limestone caves of the Mendips, of which a magnificent series are preserved in the Museum of the Somerset Archæological and Natural History Society at Taunton. (fn. 7) The earliest of these caves to be explored was that of Hutton near Weston-super-Mare, which was known to contain bones so long ago as the middle of the eighteenth century. This cave, together with the neighbouring ones of Banwell, Bleadon, Goat's Hole in Barrington Combe, Sandford Hill and Uphill were explored by Messrs. Beard and Williams between 1821 and 1860, while the so-called hyæna den of Wookey Hole, on the south side of the Mendips near Wells, was worked in 1859 and following years by Professor W. B. Dawkins and others. It was one of the first caverns in England where articles of human manufacture were found in association with the remains of extinct mammals. In addition to the abundance of hyænas at Wookey Hole, the Mendip mammalian fauna is especially characterized by the number of remains of lions, as it likewise is by a few indications of the presence of the wolverine, or glutton, an animal scarce in British Pleistocene deposits.

Among the Carnivora from the Mendip caverns may be mentioned the Pleistocene lion (Felis leo spelæ), which occurs at Banwell, Bleadon, Sandford and Wookey, the leopard (F. pardus) from Banwell and Bleadon or Hutton, the wild cat (F. catus) at Bleadon, the Egyptian cat (F. maniculata), the Pleistocene variety of the spotted hyæna (Hyæna crocuta spelæa) from Banwell, Bleadon and Wookey, the wolf (Canis lupus) and fox (C. vulpes) from Banwell, Bleadon and Sandford, the otter (Lutra lutra) from Banwell and Bleadon, the badger (Meles meles) from Banwell and Wookey, the marten (Mustela martes) from Bleadon, the wolverine (Gulo luscus) from Banwell and Bleadon, the brown bear (Ursus arctus), including the so-called grizzly, and the great cave-bear (U. spelæus).

The Somerset cave rodents, according to Mr. W. A. Sanford, (fn. 8) include the common hare (Lepus europæus), mountain hare (L. timidus), Pleistocene hare (L. diluvianus), Siberian hamster (Cricetus songarus), water-vole (Microtus amphibius), field-vole (M. agrestis), bank-vole (Evotomys glareolus), Norwegian lemming (Lemmus lemmus), banded lemming (Dicrostonyx torquatus), an apparently extinct species of suslik (Spermophilus erythrogenoides), and the common pica (Ochotona pusilla).

Another vole, Microtus ratticeps, has also been recorded from the caves of Somerset ; this being apparently the only known instance of the occurrence of this continental species in Britain.

Among the hoofed mammals may be mentioned the Pleistocene bison (Bos priscus), the wild ox (B. taurus primigenius), the red deer (Cervus elaphus), giant fallow deer, commonly called 'Irish elk' (C. giganteus), roe (Capreolus capreolus), reindeer (Rangifer tarandus), wild boar (Sus scrofa), woolly rhinoceros (Rhinoceros antiquitatis), leptorhine rhinoceros (R. leptorhinus), wild horse (Equus caballus fossilis), mammoth (Elephas primigenius), and straight-tusked elephant (E. antiquus).

Remains of bats are rare in British caves, but bones provisionally assigned to White's bat (Pipistrellus noctula) have been recorded from Banwell and Hutton caves.

There are also certain Pleistocene deposits other than those in caverns from which mammalian remains have been obtained in the county. Teeth or bones of the horse have, for instance, been found in a raised beach at Weston-super-Mare, as well as in superficial deposits at Bath and Larkhall. The mammoth also occurs at the two localities last-mentioned, while the straight-tusked elephant, woolly rhinoceros and reindeer are recorded from Larkhall, and the wild boar from both Larkhall and Ilminster.