A history of land mammals in the western hemisphere

by William Berryman Scott

Fig. 6.—Tapirus terrestris, 3 days old. Compare with [Fig. 137, p. 320]. (By permission of W. S. Berridge, London.)

It would, however, be misleading to claim a greater authority for these attempts at restoring a long-vanished life than can fairly be ascribed to them. The general form and proportions of the head, neck, body, tail, limbs and feet may be deduced with a high degree of accuracy from the skeleton, while the external characters of skin, hair and colouration are largely conjectural, but not altogether imaginary. It cannot be doubted that among the extinct mammals were many which, owing to some uncommon growth of subcutaneous fat, or some unusual local development of hair, were much more curious and bizarre in appearance than we can venture to represent them. If, for example, the Camel, the Horse, the Lion and the Right Whale were extinct and known only from their skeletons, such restorations as we could make of them would assuredly go astray in some particulars. The Camel would be pictured without his hump, for there is nothing in the skeleton to suggest it; the forelock, mane and characteristic tail of the Horse and the Lion’s mane would certainly not be recognized; while the immense development of blubber in the head of the Whale gives to it a very different appearance from that which the skull would seem to indicate. Such cases are, however, exceptional and restorations made by competent hands from complete skeletons probably give a fair notion of the appearance of those animals when alive.

It will thus be sufficiently plain that the work of restoration is beset with difficulties, but that there is no good ground for the uncritical scepticism which summarily rejects the results as being purely fanciful, or for the equally uncritical credulity which unhesitatingly accepts them as fully and incontestably accurate. It is altogether likely that one of the main sources of error consists in making the extinct animal too closely resemble some existing species which is selected as a model.

Too much space has perhaps been devoted to the problem of restoring the external form of these extinct mammals, a problem which, after all, is of distinctly subordinate importance. The most valuable results which may be gained from a study of these fossil mammals are the answers which they afford to the great questions of relationship, classification and genetic descent, and the light which they throw upon the processes of evolution and the course of geographical arrangement. The bones and teeth afford admirable means of tracing the gradual steps of modification by which the modern mammals have arisen from very different ancestors and of following their wanderings from region to region and continent to continent. It is to these questions that most of the subsequent chapters are devoted.

CHAPTER III
THE CLASSIFICATION OF THE MAMMALIA

The terminology and nomenclature of science form a great barrier, which only too often shuts out the educated layman from following the course of investigation and keeping abreast of the discoveries in which he may be particularly interested. No more frequent and heartfelt complaint is uttered than that which decries the “scientific jargon,” and one might be tempted to think that this jargon was a superfluous nuisance, deliberately adopted to exclude the uninitiated and guard the secrets of the temple from the curious intruder. As a matter of fact, however, this terminology, though an unquestionable evil from one point of view, is an indispensable implement of investigation and description. Ordinary language has far too few words for the purpose and most of the words that might be used lack the all-important quality of precision. The vernacular names of animals and plants are notoriously inexact and, even when not inaccurately employed, are not sufficiently refined and distinctive for scientific use. This is pre-eminently true of the New World, where the European settlers gave the names of the creatures with which they had been familiar at home to the new animals which they found in the western hemisphere. Some of these names, such as deer, wolf, fox, bear, are accurate enough for ordinary purposes, while others are ludicrously wrong. The bird that we call the Robin is altogether different from his European namesake, and the great stag, or Wapiti, is commonly called “Elk,” a name which properly belongs to the Moose. In short, it is impossible to gain the necessary accuracy and abundance of vocabulary without devising an artificial terminology, drawn chiefly from Greek and Latin.

In dealing with fossils, the difficulty of nomenclature becomes formidable indeed. The larger and more conspicuous mammals of the modern world are more or less familiar to all educated people, and such names as rhinoceros, hippopotamus, elephant, kangaroo, will call up a definite and fairly accurate image of the animal in question. For the strange creatures that vanished from the earth ages before the appearance of Man there are no vernacular names and it serves no good purpose to coin such terms. To the layman names like Uintatherium or Smilodon convey no idea whatever, and all that can be done is to attempt to give them a meaning by illustration and description, using the name merely as a peg upon which to hang the description.

The system of zoölogical classification which is still in use was largely the invention of the Swedish naturalist Linnæus, who published it shortly after the middle of the eighteenth century. As devised by Linnæus, the scheme was intended to express ideal relationships, whereas now it is employed to express real genetic affinities, so far as these can be ascertained. The Linnæan system is an organized hierarchy of groups, arranged in ascending order of comprehensiveness. In this scheme, what may be regarded as the unit is the species, a concept around which many battles have been waged and concerning which there is still much difference of opinion and usage. Originally a term in logic, it first received a definite meaning in Zoölogy and Botany from John Ray (1628-1705) who applied it to indicate a group of animals, or plants, with marked common characters and freely interbreeding. Linnæus, though not always consistent in his expressions on the subject, regarded species as objective realities, concrete and actual things, which it was the naturalist’s business to discover and name, and held that they were fixed entities which had been separately created. This belief in the fixity and objective reality of species was almost universally held, until the publication of Darwin’s “Origin of Species” (1859) converted the biological world to the evolutionary faith, which declares that the only objective reality among living things is the individual animal or plant.

According to this modern conception, a species may be defined as signifying a “grade or rank assigned by systematists to an assemblage of organic forms which they judge to be more closely interrelated by common descent than they are related to forms judged to be outside the species” (P. Chalmers Mitchell). The technical name of a species, which is either in Latin, or in latinized form, is in two words, one of which designates the genus (see below) and the other the particular species of that genus, as, for example, Equus caballus, the species Horse, E. przewalskii, the Asiatic Wild Horse, E. asinus, the species Ass, etc. In order to identify a species, the genus to which it belongs must be stated, hence the term, binomial system of nomenclature, which Linnæus introduced, becoming trinomial when the name of a subspecies is added, a modern refinement on the older method. A very large species (i.e. one which is represented by great numbers of individuals), extending over a very large area, is often divisible into groups of minor rank, as varieties, geographical races or subspecies. Taking the species as the unit in the scheme of classification, the varieties and subspecies may be considered as fractions.