GENERAL RELATIONS OF THE LAND CARNIVORA, RECENT AND FOSSIL.
From very obvious reasons we have been compelled to describe the various forms of Land Carnivora of which we have been able to take account, one by one, beginning with Cats, and ending with the Otters. But the reader will already have discovered that a linear arrangement like this gives no true conception of the relations existing between the various families of which the sub-order is composed, or of the various genera which are included in the families. For cross-relationships of the most puzzling and often complicated description are perpetually turning up: among the Æluroids, forinstance, we found Cryptoprocta to be intermediate between Cats and Civets, and yet, if we had followed the order indicated by this relationship, we should have had to ignore the close connection between Cats and Hyænas, and that between Hyænas and Civets, through the intermediation of the Aard Wolf.
It is necessary, then, to devise some method of writing down the names of the families, other than that of placing them one under the other, if we are to get anything like a clear notion of their mutual relationships. The method adopted by Professor Flower is perhaps the most convenient, and following him, we arrange the groups thus:—
FELIDÆ.HYÆNIDÆ.URSIDÆ.CRYPTOPROCTIDÆ.PROTELIDÆ.CANIDÆ.PROCYONIDÆ.AILURIDÆ.VIVERRIDÆ.MUSTELIDÆ.
FELIDÆ.HYÆNIDÆ.URSIDÆ.CRYPTOPROCTIDÆ.PROTELIDÆ.CANIDÆ.PROCYONIDÆ.AILURIDÆ.VIVERRIDÆ.MUSTELIDÆ.
FELIDÆ.HYÆNIDÆ.URSIDÆ.CRYPTOPROCTIDÆ.PROTELIDÆ.CANIDÆ.PROCYONIDÆ.AILURIDÆ.VIVERRIDÆ.MUSTELIDÆ.
FELIDÆ.HYÆNIDÆ.URSIDÆ.
FELIDÆ.
HYÆNIDÆ.
URSIDÆ.
CRYPTOPROCTIDÆ.PROTELIDÆ.CANIDÆ.PROCYONIDÆ.AILURIDÆ.
CRYPTOPROCTIDÆ.
PROTELIDÆ.
CANIDÆ.
PROCYONIDÆ.
AILURIDÆ.
VIVERRIDÆ.MUSTELIDÆ.
VIVERRIDÆ.
MUSTELIDÆ.
In this scheme we see an expression of the fact that the Dogs (Canidæ) form a central group, from which the families of the Æluroidea—those to the left—diverge in one direction, and the families of the Arctoidea—those to the right—in the other direction. The Civets (Viverridæ) and the Weasel family (Mustelidæ), being the least modified of the Æluroid and Arctoid sections respectively, are placed at the bottom of the table, the Cats (Felidæ) and Bears (Ursidæ), being the most modified, are placed at the top. The two latter families, again, are placed at opposite extremities of the table, as far from one another as possible, to indicate the great gap which separates the digitigrade, short-skulled, active, carnivorous Cats, from the plantigrade, long-skulled, clumsy, herbivorous Bears. To be quite accurate, such a scheme should take account not merely of families, but of genera: in our table, for instance, there is nothing to show the immense amount of specialisation undergone by one section of theMustelidæ—the Otters—to fit them for aquatic life; but such a detailed arrangement is quite beyond the scope of the present work.
In considering the chief forms of Carnivora existing at the present day, we have by no means exhausted this varied and interesting group, for a number of its members, the forerunners of those now living, have vanished from the face of the earth, and are known to us only by their bones, which we find here and there entombed in the strata of which the crust of our earth is composed.
In the newest, that is the most recently deposited, set of strata, those which together form the beds of the Pleistocene period, we find a very curious change in the flesh-eaters inhabiting England. Instead of having nothing but Wild Cats, Wolves, and Bears—the only wild beasts known to have existed in the historical period—we have the enormous Cave Lion (Felis spelæa), besides the Cave Bear (Ursus spelæus), and the Cave Hyæna (Hyæna spelæa), the last being merely a variety of the Spotted Hyæna (Hyæna crocuta) of the present day. The presence of the first and last of these would seem to indicate that the climate of Britain was warmer in the Pleistocene period than it now is; but the presence of the Glutton, as well as of some non-carnivorous Arctic animals, tends to the other opinion, namely, that the climate of England was sub-Arctic. Very probably the Cave Lion and Hyæna were provided with thick woolly fur, and so, like the Mantchurian Tiger and the Northern Leopard (seepp. 34and42), enabled to bear a degree of cold experienced by but few of their relatives at the present day.
SKULL OF MACHÆRODUS. (After Gaudry.)
SKULL OF MACHÆRODUS. (After Gaudry.)
In beds of the same age in South America is found a true Cheetah, a species now confined to the Old World. But the most wonderful animal belonging to this period is the great Sabre-toothed Tiger (Machærodus), a gigantic animal, with canines six or eight inches long, and jagged at their edges like a very fine saw. It would almost seem as if Dame Nature, in producing this terrible beast, had actually got to the end of her tether in the matter of specialisation for carnivorous habits; the caninesof Machærodus were so long that he must have had some difficulty in opening his mouth sufficiently wide to take in anything large, and thus it would seem that he actually overshot the limit of perfection, and died of over-specialisation. The canines of the Sabre-toothed Tiger are, however, not its only peculiarity: there is one less premolar on each side of the upper jaw than in the modern members of the Cat family, so that the total number of teeth is reduced to twenty-eight,[196]the smallest number found in any of the Carnivora.
On descending to the rocks of Pliocene age, we find, amongst many forms existing at the present day, an animal calledGalecynus, about the size of the Fox, and possessing many characters, in its teeth, limbs, &c., intermediate between those of the Dogs and those of the Civets. Another genus,Hyænarctos, is almost exactly half-way between Dogs and Bears; its molars have less of a cutting character than a Dog’s, and less of a grinding character than a Bear’s, and its front premolars, though much smaller than a Dog’s, do not fall out altogether, as in the Bear.
In the Pliocene, or Late Miocene strata, remains have been found of many existing genera, such as Cats, Civets, Hyænas, Dogs, Weasels, Ratels, and Otters; but amongst these are several genera not occurring in any of the more recent strata, and all, or nearly all, tending to bridge over the gaps which separate existing families from one another. For instance, a perfect gradation between the Hyænas and Civets is afforded by two genera,HyænictisandIctitherium; whileLutrictisshows affinities both with Civets and Otters,Hemicyonwith Dogs and Gluttons, andDinictiswith Cats and Weasels. Another very interesting genus,Promephitis, belongs undoubtedly to the Weasel family, but is intermediate between its three sub-families, the Weasels proper, Badgers, and Otters.Simocyon, again, an animal about the size of a Leopard, is described as having the canines of a Cat, the molars of a Dog, and jaws shaped like those of a Bear. Lastly,Amphicyonis a large plantigrade animal, Bear-like for the most part, but with trenchant molars, like a Dog’s, and having a small additional or third molar on each side of the lower jaw, the number of its teeth being thus brought up to that which may be called the typical Mammalian number, namely, forty-four.[197]
SKULL OF ARCTOCYON. (After Gaudry.)
SKULL OF ARCTOCYON. (After Gaudry.)
In the Eocene, or Lower Tertiary, still more remarkable forms occur, along with several genera existing at the present day, such as the Cryptoprocta, Civet, Dog, and Marten, all of which are found in the upper or more recent strata of the Eocene formation. But lower down the genusCynodonalso connects Dogs with Civets; and in the very lowest beds occurs a large plantigrade animal (Arctocyon), with a very small brain-case, wide jugal arches, a complete set of forty-four teeth, and altogether of a generalised character. In the Eocene of North America,LimnocyonandPrototomusoccur low down, and in the Middle Eocene a form as large as a Lion has been discovered, to which the nameLimnofelishas been given, and alsoOrocyon, and some allies of theHyænodon.
LOWER JAW OF HYÆNODON. (After Gaudry.)
LOWER JAW OF HYÆNODON. (After Gaudry.)
But we have not yet learned all that Palæontology can teach us about the history of the Carnivora. In the Eocene and Lower Miocene beds are found animals referred to the generaHyænodon,Pterodon,Palæonictis, andProviverrawhich, not content with trespassing on the boundaries between existing families, actually wander outside the Carnivorous order altogether, and approach so nearly to the Marsupials (Kangaroos, Opossums, &c.) that many competent anatomists have proposed to place them in the latter group. The premolars and molars in these extinct animals have sharp cusps, andincrease gradually in size from before backwards; so that, of the whole grinding series, the first premolar is the smallest, and the last molar the largest. Now we have seen that the rule among existing Carnivora is for the last molar to be a small tooth, and for the largest of the set to be the fourth premolar in the upper jaw, and the first molar in the lower jaw. On the other hand, the regular increase in size is very characteristic of the flesh-eating Marsupials, amongst which the Thylacine, or so-called Tasmanian Wolf, shows a considerable resemblance, as to its teeth, toHyænodonandPterodon, whilePalæonictisandProviverraare more nearly allied to the Opossums and to the Dasyure, or Tasmanian Devil. The brain-case in these forms was very small, and a cast of the interior of the skull of Proviverra, figured by M. Gaudry,[198]shows that the brain must have had an extremely low character.
SKULL OF PROVIVERRA. (After Gaudry.)The roof of the skull is supposed to be cut away to show the form of the brain, as deduced from a natural cast of the interior of the skull.
SKULL OF PROVIVERRA. (After Gaudry.)
The roof of the skull is supposed to be cut away to show the form of the brain, as deduced from a natural cast of the interior of the skull.
We thus see that a considerable number of the existing genera of Carnivora took their origin in the Eocene epoch, where they co-existed with creatures curiously intermediate between the various existing families, and with others intermediate between Carnivora and Marsupials. In the rocks of the Secondary period (chalk, oolite, lias, &c.), none of the Carnivora have as yet appeared, and only Marsupial remains are found.