A STRANGE EXTINCT BEAST

The terraces of gravel deposited by existing rivers and the deposits in caverns in the limestone regions of Western Europe—the so-called "Pleistocene" strata—contain, besides the flint weapons of man and rare specimens of his bones, the remains of animals which are either identical with those living at the present day (though many of them are not living now in Europe) or of animals very closely similar to living species. Thus we find the bones of horses like the wild horse of Mongolia, of the great bull (the Urus of CÆsar), of the bison, of deer and goats, of the Siberian big-nosed antelope, of the musk-ox (now living within the Arctic circle), of the wild boar, of the hippopotamus (like that of the Nile), and of lions, hyenas, bears, and wolves. The most noteworthy of the animals like to, but not identical with, any living species are the mammoth, which is very close to the Indian elephant, but has a hairy coat; the hairy rhinoceros, like, but not quite the same as, the African square-mouthed rhinoceros; and the great Irish deer, which is like a giant fallow-deer. These three animals are really extinct kinds or species, but are not very far from living kinds. In fact, the most recent geological deposits do not contain any animals so peculiar, when compared with living animals, as to necessitate a wide separation of the fossil animal from living "congeners" by the naturalist who classifies animals and tries to exhibit their degrees of likeness and relationship to one another by the names he adopts for them. The mammoth is a distinct "species" of elephant. It requires, it is true, a "specific" or "second" name of its own; but it belongs to the genus elephant. Hence we call it Elephas primigenius, whilst the living Indian elephant is Elephas Indicus. The reader is referred to the preceding chapter for further notes about elephants.

The strata next below the Pleistocene gravels and cave deposits are ascribed to the "Pliocene age"—older than these are the "Miocene" and the "Eocene," and then you come to the Chalk, a good white landmark separating newer from older strata.

We know now in great detail the skeletons and jaws of some hundreds of kinds of extinct animals of very different groups found in the Eocene, the Miocene, the Pliocene, and the Pleistocene layers of clays, sands, and gravels of this part of the world. Nothing very strange or unlike what is now living is found in the Pleistocene—the latest deposits—but when we go further back strange creatures are discovered, becoming stranger and less like living things as we pass through Pliocene to Miocene, and on—downwards in layers, backwards in time—to the Eocene.

Though the past history of the Mediterranean sea shows that it was formerly not so extensive as it is now, and that there were junctions between Europe and Africa across its waters, yet the deeper parts of that sea are very ancient, and some of the islands have long been isolated. In Malta the remains of extraordinary species of minute elephants have been found, one no larger than a small donkey, and in the island of Cyprus an English lady, Miss Dorothea Bate, has discovered the bones of a pigmy hippopotamus (like that still living in Liberia) no larger than a sheep. Miss Bate some three years ago heard of the existence of a bone-containing deposit of Pleistocene age in limestone caverns and fissures in the island of Majorca, and with the true enthusiasm of an explorer determined to carry on some "digging" there and see what might turn up. In the following spring she was there, and obtained a number of bones, jaws, and portions of skulls, which appeared at first sight to be those of a small goat. Its size may be gathered from the fact that its skull is six inches long. These and the bones of a few small finches were all that rewarded her pains. The bones of fossil goats (of living species) are found in caves at Gibraltar and in Spain; so at first the result seemed disappointing. But on carefully clearing out the specimens and examining them in London, Miss Bate found that the supposed goat bones obtained by her in Majorca were really those of a new and most extraordinary animal, to which (in a paper published in the "Geological Magazine" in September, 1910) she has given the name "Myotragus balearicus."

I must ask the reader now to look at the figures here given (Figs. 16 and 17) of the skull and the lower jaw of a goat. The lower jaw might (except for size) pass for that of a sheep, ox, antelope or deer. They are all alike. There are on each side six grinding cheek-teeth (molars), and then as we pass to the front we find a long toothless gap until we come to the middle line where the two halves of the jaw unite. There we see a little semicircular group of eight chisel-like teeth, which work against the toothless pad of the upper jaw opposed to them, and are the instruments by which these animals, with an upward jerk of the head, "crop" the grass and other herbage on which they feed, to be afterwards triturated by the grinding cheek teeth. A vast series of living and of fossil animals, called the Ruminants—including the giraffes, the antler-bearing forms called deer, the cavicorn or sheath-horned bovines, ovines and caprines, and the large series of antelopes of Africa and India—all have precisely this form of jaw, this number and shape and grouping of the teeth. Now let me call to mind the lower jaw of a hare or rabbit or rat (Figs. 18 and 19). There we find on each side the group of grinding cheek-teeth, with transverse ridges on their crowns, and a long, toothless gap before we arrive at the front teeth. But the front teeth are only two in number, one on each side, close to each other, very large, and each with a tremendously long, deeply set root. They meet a similar pair of teeth in the upper jaw, and give the hare, rabbit, rats, mice, beavers, and porcupines the power of "gnawing" tough substances. These animals are hence called Rodents, or gnawers, and the two great front teeth are called "rodent-teeth." No two arrangements of teeth could be much more unlike than are the group of eight little chisel-like teeth of the lower jaw of the Ruminants and the two enormous gnawing teeth of the Rodents. Apparently the two rodent incisors, or front teeth, of the lower jaw of the rat correspond to the two middle incisors of the Ruminant's lower jaw; the other front teeth of the Ruminant have atrophied, disappeared altogether. The rodent condition has been developed from that of an ancestor which had several front teeth and not two large ones only; but we have not at present found the intermediate steps.

The reader should compare the teeth of the goat and the large rat here pictured with the more typical and complete series of the pig, given in Fig. 10, p. 84. The pig's teeth are the same in number as those of the ancestral primitive typidentate mammal, and their form is near to that of the ancestor's teeth.

Now I come to the extraordinary interest of Miss Bate's goat-like or antelope-like animal from Majorca. Although it is shown by its skull (Fig. 20) and other bones to be distinctly one of the sheath-horned Ruminants, very like a small goat or antelope, the lower jaw, of which there are several specimens, does not present in front the little group of eight small chisel-like "cropping" teeth, but, instead, two enormous rodent teeth placed side by side, very deeply fixed in the jaw, and quite like those of some rat-like animals in shape. Hence the name given to this little marvel by Miss Bate—"Myotragus," "the rat-goat." This strange little animal also differs from goats and antelopes in having proportionately much thicker and shorter "feet" (cannon-bones) than they have.

If the remains of this strange little creature had turned up in more ancient strata—in Pliocene or Miocene—it would have not been quite so astonishing. But it would be still very remarkable, since it has all the characters of a goat-like creature in the shape of its skull, its bony horn-cores, its limb-bones, and its cheek-teeth; and yet, as it were monstrously and in a most disconcerting way, protrudes from its lower jaw two great rats' teeth. Nothing like it or approaching it or suggesting it, is known among recent or fossil Ruminants. They all without exception have a lower jaw with the teeth of the exact number and grouping which you may see in a sheep's lower jaw. We know hundreds of them, both living and fossil, many from the Pleistocene, others from Pliocene deposits, and even from the still older Miocene, but all keep to the one pattern of lower jaw and lower jaw teeth. It is only in this little island of Majorca, surrounded by very deep water and not known to have nurtured any other animal so large in size either in recent or geologic times, that we come upon a Ruminant with horns like a goat's, but with great rat-like front teeth in place of the semicircle of eight little cropping toothlets. The wonderful thing is that the bones found by Miss Bate are light and well preserved, evidently not very ancient—probably late Pleistocene in age.

The questions that arise are: Where did the rat-goat come from? How did this utterly peculiar change in a Ruminant's teeth come about? With regard to the second question, it is a matter of importance that although we have hitherto not discovered any Ruminants with this modification of the teeth, still less any cavicorn or sheath-horned Ruminant so altered, yet it is by no means rare amongst herbivorous mammals to find such rat-like teeth making their appearance, whilst the smaller side-teeth of the incisor group or front teeth disappear. The Australian kangaroos and wombats are a case in point—so is the lemur-like aye-aye of Madagascar (an insect eater). So is the Hyrax or "damian" of the Cape, and also the very ancient Plagiaulax from the prÆ-chalk Purbeck clay. But perhaps the best case for comparison with the ruminants is that of the rhinoceroses. There are a great many species and even genera of fossil and recent rhinoceroses. An old Miocene kind (called Hyracodon) has eight little teeth in the front of the lower jaw. In a Pliocene kind of rhinoceros (called R. incisivus) these are reduced to two, the middle two, which are of great size and project far forward—like those of the rat-goat of Majorca. Among living rhinoceroses the Indian species have these two front teeth, but smaller, whilst the square-mouthed African rhinoceros has none at all! This helps us, as a parallel, to understand "the strange case" of Myotragus. But, of course, the rhinoceroses are a distinct line of animal descent—remote from Ruminants. They are (like horses and tapirs) odd-toed hoofed beasts—not even-toed ones, as are pigs, camels, and ruminants.

On first considering the question of the origin of the rat-goat of Majorca, some naturalists will, no doubt, be tempted to suggest that it is a case of a sudden "sport," a "mutation" as they now call it, and not a result of gradual slowly developed reduction of the now lost teeth and correspondingly gradual enlargement of the two middle ones, taking many thousand generations to bring about. The fact that the rat-goat is found on an island cut off from competition with other animals will favour this view. On the other hand, there is the important and really remarkable fact that familiar as man has been for ages with Ruminants of many kinds—such as sheep, goats, cattle, deer—there is absolutely no case on record of an "oddity" or "monstrosity" resembling the rat-goat's condition occurring in the teeth of any of the hundreds of thousands of these animals killed and eaten by man, and therefore closely examined. Professor Bateson, who a few years ago ransacked the museums of Europe for instances of "discontinuous variation," or "sports," and wrote a valuable book on the subject, did not discover any example of the kind. Apart from the view, which is very generally held, that such sudden "mutations" as "rat-teeth in a ruminant" are—even should they occur—not perpetuated, we are not really in any way driven to suppose that the rat-goat of Majorca originated in that island. It is true that we know nothing like it in the Pliocene and Miocene of the Mediterranean region which could have been its immediate ancestor. But probably the ancestors of the rat-goat were slowly developed from a Miocene sheath-horned ruminant, a primitive sort of antelope in some part of North-west Africa, or in an extension of it now submerged in the Atlantic, and stragglers of this curious and now lost Ruminant stock were left in Majorca when in Miocene or early Pliocene times that island became detached from its Hispano-African connection.