American Big Game in Its Haunts: The Book of the Boone and Crockett Club. VariousЧитать онлайн книгу.
border, and these deer have varied little except in size, although three subspecies have lately been set off from the mule deer in the extreme southwest.
The section represented by M. virginiana, with antlers curving forward and tines projecting from its hinder border, takes practically the whole of America in its range, and under the law of variation which has been stated, has proved a veritable gold mine to the makers of names. At present it is utterly useless to attempt to determine which of the forms described will stand the scrutiny of the future, and no more will be attempted here than to state the present gross contents of cervine literature. The sub-genus Dorcelaphus contains all the forms of the United States; of these, the deer belonging east of the Missouri River, those from the great plains to the Pacific, those along the Rio Grande in Texas and Mexico, those of Florida, and those again of Sonora, are each rated as sub-species of virginiana; to which we must add six more, ranging from Mexico to Bolivia. One full species, M. truei, has been described from Central America, and another rather anomalous creature (M. crookii), resembling both white-tail and mule deer, from New Mexico.
The other sub-genera are Blastoceros, with branched antlers and no metatarsal gland; Xenelaphus, smaller in size, with small, simply forked antlers and no metatarsal gland; Mazama, containing the so-called brockets, very small, with minute spike antlers, lacking the metatarsal and sometimes the tarsal gland as well. The last three sub-genera are South American and do not enter the United States. Another genus, Pudua, from Chili, is much like the brockets, but has exceedingly short cannon bones, and some of the tarsal bones are united in a manner unlike other deer. In all, thirty specific and sub-specific names are now carried on the roll of Mazama and its allies.
Attention has already been directed to the parallelism between the course of progress from simple to complex antlers in the development of the deer tribe, and the like progress in the growth of each individual, and to the further fact that all the stages are represented in the mature antlers of existing species. But a curious result follows from a study of the past distribution of deer in America. At a time when the branched stage had been already reached in North America, the isthmus of Panama was under water; deer were then absent from South America and the earliest forms found fossil there had antlers of the type of M. virginiana. The small species with simple antlers only made their appearance in later periods, and it follows that they are descended from those of complex type. This third parallel series, therefore, instead of being direct as are the other two, is reversed, and the degeneration of the antler, which we have seen taking place in the southern deer, has followed backward on the line of previous advance, or, in biological language, appears to be a true case of retrogressive evolution—representing the fossil series, as it were, in a mirror.
The reindeer-caribou type, of the genus Rangifer, agrees with American deer in having the vertical plate of the vomer complete, and in having the lower ends of the lateral metacarpals remaining, but, like Cervus, it has a brow-tine to the antlers. Of its early history we know nothing, for the only related forms which have yet come to light are of no great antiquity, being confined to the Pleistocene of Europe as far south as France, and are not distinguishable from existing species. Until recently it has been supposed that one species was found in northern Europe and Asia, and two others, a northern and a southern, in North America, but lately the last two have been subdivided, and the present practice is to regard the Scandinavian reindeer (Rangifer tarandus) as the type, with eight or nine other species or sub-species, consisting of the two longest known American forms, the northern, or barren-ground caribou (R. arcticus); the southern, or woodland (R. caribou); the three inhabiting respectively Spitzbergen, Greenland and Newfoundland, and still more lately four more from British Columbia and Alaska. The differences between these are not very profound, but they seem on the whole to represent two types: the barren-ground, small of size, with long, slender antlers but little palmated; and the woodland, larger, with shorter and more massive antlers, usually with broad palms. There is some reason to believe that both these types lived in Europe during the interglacial period, the first-named being probably the earlier and confined to western Europe, while the other extended into Asia. The present reindeer of Greenland and Spitzbergen seem to agree most closely with the barren-ground, while the southern forms are nearest to the woodland, and these are said to also resemble the reindeer of Siberia. It is, therefore, not an improbable conjecture that there were two migrations into America, one of the barren-ground type from western Europe, by way of the Spitzbergen land connection, and the other of the woodland, from Siberia, by way of Alaska.
Little more can be said, perhaps even less, of the other circumpolar genus, Alces, known in America as "moose," and across the Atlantic as "elk." It also is of mixed character in relation to the two great divisions we have had in mind, but in a different way from reindeer.
Like American deer it has the lower ends of the lateral metacarpals remaining, and the antlers are without a brow-tine, but like Cervus it has an incomplete vomer, and unlike deer in general, the antlers are set laterally on the frontal bone, instead of more or less vertically, and the nasal bones are excessively short. The animal of northern Europe and Asia is usually considered to be distinct from the American, and lately the Alaskan moose has been christened Alces gigas, marked by greater size, relatively more massive skull, and huge antlers. Of the antecedents of Alces, as in the case of the reindeer, we are ignorant. The earlier Pleistocene of Europe has yielded nearly related fossils,[2] and a peculiar and probably rather later form comes from New Jersey and Kentucky. This last in some respects suggests a resemblance to the wapiti, but it is unlikely that the similarity is more than superficial, and as moose not distinguishable from the existing species are found in the same formation, it is improbable that Cervalces bore to AIces anything more than a collateral relationship.
[Footnote 2: The huge fossil known as "Irish elk" is really a fallow deer and in no way nearly related to the moose.]
Even to an uncritical eye, the differences between ungulates and carnivores of to-day are many and obvious, but as we trace them back into the past we follow on converging lines, and in our search for the prototypes of the carnivora we are led to the Creodonta, contemporary with Condylarthra, which we have seen giving origin to hoofed beasts, but outlasting them into the succeeding age. These two groups of generalized mammals approached each other so nearly in structure, that it is even doubtful to which of them certain outlying fossils should be referred, and the assumption is quite justified that they had a common ancestor in the preceding period, of which no record is yet known.
The most evident points in which Carnivora differ from Ungulata are their possession of at least four and frequently five digits, which always bear claws and never hoofs; all but the sea otter have six small incisor teeth in each jaw; the canines are large; the molars never show flattened, curved crests after the ruminant pattern, but are more or less tubercular, and one tooth in the hinder part of each jaw becomes blade-like, for shearing off lumps of flesh. This tooth is called the sectorial, or carnassial.
Existing carnivores are conveniently divided into three sections: Arctoidea—bears, raccoons, otters, skunks, weasels, etc.; Canoidea—dogs, wolves and foxes; Aeluroidea—cats, civets, ichneumons and hyaenas.
It is highly probable that these three chief types have descended in as many distinct lines from the Creodonta, and that they were differentiated as early as the middle Eocene, but their exact degree of affinity is uncertain; bears and dogs are certainly closer together than either of them are to cats, and it is questionable if otters and weasels—the Mustelidae, as they are termed—and raccoons are really near of kin to bears.
Seals are often regarded as belonging to this order, but their relation to the rest of the carnivores is very doubtful. Many of their characters are suggestive of Arctoidea, but it is an open question if their ancestors were bear or otter-like animals which took to an aquatic life, or whether they may not have had a long and independent descent. At all events, doubt is cast upon the proposition that they are descended from anything nearly like present land forms by the fact that seals of already high development are known as early as the later Miocene.
The difficulty so constantly met with in attempting to state concisely the details of classification,