The Cambridge Natural History Part 22

EXTINCT CAMELS.--The earliest cameloid type is the genus _Protylopus_,[194]

of which we are acquainted with an imperfect skull {288} and the greater part of a radius and ulna belonging to one individual, and most portions of the hind-limbs in other specimens. The one species, _P. petersoni_, was about the size of a "jack rabbit," and is late Eocene (Uinta formation) and American in range. The teeth of this mammal are the typical forty-four, and the canines are not p.r.o.nounced, being incisiform in shape. In the skull the nasals overhang, as in the genus _Poebrotherium_. The orbit is not closed by bone. There is in this ancient Camel a trace of the supra-orbital notch so characteristic of the Camel tribe. "The vertebrae resemble those of the modern Lamas closely in their general proportions." The lumbars have the usually Cameloid formula of 7. This genus has but two functional toes on the hind-feet, the second and fifth being reduced to vestiges. It is interesting to note that the radius and ulna appear to remain distinct, except in very old animals, in which they come to be co-ossified in the middle only, thus foreshadowing their complete union in the next genus, _Poebrotherium_. The present genus, moreover, as well as _Poebrotherium_, was distinctly unguligrade; it has not acquired the characteristic phalangigrade mode of progression of the modern types of Camels.

[Ill.u.s.tration]

FIG. 150.--Skull of _Poebrotherium wilsoni_. _i_^1, _i_^2, _i_^3, Incisors 1-3. . (After Wortman.)

The American and Oligocene _Poebrotherium_ has been recently and exhaustively studied by Professor Scott.[195] It was considerably smaller than a Lama. Its neck was long as compared with other Artiodactyles, but still shorter than that of the Lama. It was a lightly-built, graceful creature, with apparently some external likeness to a Lama. It is an important fact to notice that at this {289} period, and for a long time after, there were no types referable to the Camelidae in the Old World.

Though a Camel in many features of its organisation, _Poebrotherium_ was "generalised" in many ways. Thus the metacarpals and metatarsals were not fused to form a cannon bone, and the two lateral digits were represented by splint rudiments of metacarpals and metatarsals. The dent.i.tion was complete. The skull though distinctly Tylopodan, also shows more generalised characters. Thus the orbit is not quite, though nearly, completed by bone. In the Camel it is quite closed. The nasal bones are much longer, reaching nearly to the end of the snout. The odontoid process of the axis vertebra is not spout-like as in existing forms, but cylindrical, though slightly flattened upon the upper surface. The scapula is described as being more like that of the Lama than of the Camel, though variations occur which approximate to the Camel. The brain, judging of course from casts, has those sulci "which are common to the whole series of Ungulates, and closely resemble those of a foetal Sheep."

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FIG. 151.--Anterior surface of axis of Red Deer, 2/3. _o_, Odontoid process; _pz_, posterior zygapophysis; _sn_, foramen for second spinal nerve. (From Flower's _Osteology_.)

Later in historical sequence than _Poebrotherium_, and structurally intermediate between it and _Protolabis_, is the Miocene genus _Gomphotherium_. It shows an advance in structure upon _Poebrotherium_, in that the orbit is completely encircled by bone, though the posterior wall is thin; the lower canines instead of being incisiform are curved back as in later Camels, and separated by a wide diastema from the preceding and the succeeding teeth.

Later in age than _Poebrotherium_ is _Protolabis_, a _Tylopod_ in which the full number of teeth is still retained; its skull presents no particular changes from the Poebrotherine type; the nasals, however, are somewhat shortened.

Later still in point of time is _Procamelus_. In this form we have apparently an ancestral stock, whence both Camels and Lamas were derived.

The upper incisors are as in existing forms, but the first and second persist for a somewhat longer time. The skull shows two well-marked types of structure; in _P. occidentalis_ {290} there are more points of likeness to the Lama, in _P. angustidens_ to the Camel. In both, the orbits are completely encircled by bone. The nasals are much shortened. The odontoid process of the axis is still more concave than in _Poebrotherium_, but not spout-like as in existing forms. This fact shows that the spout-like character of the Camels' odontoid process is not a point of affinity to other Artiodactyles--in fact the occurrence of the same form of odontoid process in Perissodactyles is enough proof of this. We must come to the conclusion that the form is adaptive in all cases. If we were not obliged on palaeontological evidence to come to this conclusion, the structure in question is just one which would be fastened upon as evidence of genetic affinity; for it is a resemblance in a small though distinctive point of structure having no obvious relation to utility. The metacarpals and metatarsals have coalesced to form the cannon bones, though a rudiment of one metacarpal seems to remain. The genera referred to appear to be on the direct line of descent of the modern representatives of the family. But there are other forms which are offshoots of the main stem. Such are _h.o.m.ocamelus_, _Eschatia_, and _Holomeniscus_. The last two are Pliocene and American; the teeth are much reduced.

C. PECORA.

The Pecora are a group which possess so many characters in common that it is not an easy task further to subdivide them.

In all there are but two functional digits on the feet, and the metacarpals and metatarsals of these are fused. There are no upper incisors, and canines in the upper jaw are not universal, and generally small. Horns are confined to this group of the Selenodontia.[196] The premolar teeth are of a simpler form than the molars. The stomach has four chambers, of which two may be regarded as belonging to its cardiac half and two to the pyloric.

The former are, in the first place, a large paunch or rumen, followed by a smaller reticulum, so called on account of the network arrangement of the folds of its lining membrane. Connected with the latter, and const.i.tuting the first part of the pyloric half of the stomach, is the psalterium or "manyplies," so called on account of the longitudinal folds, like the leaves of a {291} book, into which its lining membrane is raised. Finally there is the abomasum, out of which proceeds the small intestine. Garrod has observed that the chamber of the stomach which varies most among the Pecora is the psalterium. This chamber is specially large in _Bos_, and particularly small in the Antelopes _Nannotragus_ and _Cephalophus_. But its variation relates more especially to the folds of its mucous membrane.

These folds are of varying lengths and have a definite arrangement There may be as many as five sets of laminae of regular depths. The most simple psalterium is that of _Cephalophus_, where there are only two sets of laminae of different sizes, a deeper set and a very much shallower set; this form is termed by Garrod "duplicate." Most common is the "quadruplicate" arrangement, with four sets of laminae of differing depths.

In all Pecora the liver is but little divided by fissures.

FAM. 6. CERVIDAE.--The Deer tribe is a very extensive one, and, with the exception of Africa and Australia, world-wide in distribution.[197]

The Deer are absolutely distinguished from all other Ruminant animals by the existence of antlers, which are invariably present in the male s.e.x, save in the aberrant genera _Moschus_ and _Hydropotes_; in the Reindeer alone are antlers present in both s.e.xes. The general characters of these appendages have been dealt with on a former page (p. 200), where they are compared to, or rather contrasted with, the horns of the Bovidae. These antlers, so characteristic of the Cervidae, are very variously developed among the members of the family. Thus in _Elaphodus_ the antlers are very small and entirely unbranched. In the Muntjacs, _Cervulus_, the antlers are hardly larger, but they have a small anterior branch arising from near the pedicel, the "brow tine." In _Cariacus antisiensis_ only one branch, the brow tine, is present, but it is nearly as long as the main stem of the antler, the "beam." In _Capreolus capraea_ the beam bears two tines; in _Cervus sika_ three; in _C. duvauceli_ two of the three tines present bear secondary branches. There are other complications (some of which are ill.u.s.trated in Figs. 152-157) of the simple antler which culminate in the complex antlers with their expanded "palms" of the Elk and the Fallow Deer.

{292}

Another highly-interesting fact concerning these same antlers is their gradual increase in complexity of tines and palm from the Miocene _Cervus matheroni_ to the great Irish Elk of post-Tertiary times.

Beyond the antlers there seems to be no character of universal applicability which distinguishes the Cervidae from the nearly-related Antelopes. There are, however, a number of structural features which are _nearly_ universally characteristic. Excepting _Moschus_ (which Professor Garrod would not allow to be a "Deer"), no Cervine has a gall-bladder[198]

to its liver. All Bovidae (including Antelopes) have, with the exception of _Cephalophus_.

A small but constant character of the Deer is the existence of two orifices to the lachrymal duct. The genus _Tragelaphus_ alone among Antelopes shows this character.

So far as is known the placenta of the Deer has but few cotyledons, that of the Bovidae many. But not many types are known.

The navicular, cuboid and ectocuneiform are often united. This is never the case in the Bovidae.

The first and second phalanges of the lateral (imperfectly developed) digits are always present except in the Muntjacs; they are never found in Bovidae. The Deer always present a light brown to a darker brown coloration. _Elaphodus michia.n.u.s_ is almost black. There is commonly white on the under parts and beneath the short tail. Some Deer, such as the Fallow Deer, are spotted; and the young of others that are uniformly coloured when adult are spotted. In some cases a winter coat, darker than the summer coat, is developed.

Altogether some sixty species of Deer are known, of which the preponderance are Old-World forms. The Deer of the Old World are distributed among the genera[199] _Cervus_ (all Europe and Asia); _Cervulus_, the Muntjacs (India, Burmah, China, etc.); _Hydropotes_ (Eastern China); _Capreolus_ (Europe and Central Asia); _Elaphodus_ (Eastern China); there is one American _Cervus_, the Wapiti. The American genera are _Cariacus_ and _Pudua_. The Elk (_Alces_) and the Reindeer (_Rangifer_) are circ.u.mpolar.

The princ.i.p.al structural modification which occurs within {293} the family Cervidae concerns the rudimentary fifth and second toes. In _Capreolus_, _Hydropotes_, _Moschus_, _Alces_, _Rangifer_, and _Pudua_ there are considerable remains of the lower parts of metacarpals II. and V.; in the other genera smaller traces of the upper ends of the same bones.

The two most abnormal genera are _Moschus_ and _Hydropotes_, more particularly the former, which neither Sir V. Brooke nor Professor Garrod allow to be members of the family at all. _Moschus_ is usually placed in a special sub-family by itself, Moschinae, the remaining Deer being referred to another sub-family, Cervinae.

SUB-FAM. 1. CERVINAE.--The genus _Cervus_ comprises rather over twenty existing species, which, except the Wapiti (_C. canadensis_), are exclusively Old World in distribution. The princ.i.p.al features of variation in the genus, in accordance with which it has been divided up into sub-genera, are (1) palmated (Fallow Deer, _Dama_) or non-palmated antlers; (2) adults spotted with white at all ages and seasons (_Axis_), or in summer only (_Pseudaxis_), or not at all; (3) spotted or unspotted young; (4) existence or absence of rudimentary canines in the upper jaw.

Among the members of this genus, _Cervus (Elaphurus) davidia.n.u.s_ is interesting as having been first observed by the missionary Pere David in a park belonging to the Emperor of China near Pekin. Its horns are remarkable for dividing early into two branches of equal length, of which the anterior again branches into two. Specimens of this Deer were ultimately obtained for the Zoological Society's Gardens.

The species of _Cervus_ are fairly distributed between the Palaearctic and the Indian regions. The Palaearctic species, such as Luhdorff's Deer (Fig.

152), are mainly Asiatic. _Cervus elaphus_ and _Cervus dama_ alone are European and British. The former of course is the Red Deer, the latter the Fallow Deer. The Red Deer is reddish-brown in summer and greyish-brown in winter, with the white patch on the rump so common in the Deer tribe. The Red Deer is genuinely wild in Scotland, in certain parts of Devonshire and Westmoreland, and in the New Forest. At the beginning of the last century, according to Gilbert White, there were 500 head of deer in Wolmer Forest, which were inspected by Queen Anne. The antlers may have as many as forty-eight points; and a stag with more than the three anterior tines is termed a "Royal Hart." The Fallow Deer has {294} palmated antlers, and is usually spotted. It seems to be an introduced species, common report pointing to the Romans as the introducers. It would be more correct to say "re-introduced," for fossil remains of this Deer have been met with.

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FIG. 152.--Luhdorff's Deer. _Cervus luehdorffi._ 1/15. (From _Nature_.)

_Elaphodus_[200] contains probably two species, _E. cephalophus_ of Milne-Edwards and _E michia.n.u.s_ of Swinhoe, both from China. The antlers are small and unbranched; the canines in the male are ma.s.sive; it differs from _Cervulus_, to which it is closely allied, princ.i.p.ally in the absence of frontal glands. The second {295} species has a dark iron-grey pelage, and the late Mr. Consul Swinhoe described it as very Goat-like in aspect.

_Capreolus._--The Roe Deer has fairly complex antlers. It is a small Deer and has spotted young. The common Roe Deer, _C. capraea_, is a native of this country. It is the smallest of our Deer, and its antlers only have three tines in stags of the third year. It is a singular fact about this Deer that though the pairing season is in July and August, the young are not born until the following May or June, a period which does not represent that of gestation. The germ remains dormant for some time before developing.

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FIG. 153.--Mule Deer. _Cariacus macrotis._ 1/15. (From _Nature_.)

The Muntjacs, _Cervulus_, form a distinct generic type confined to the Indian and the South-Eastern Palaearctic region. They are small Deer with spotted young, and short one-branched antlers placed upon pedicels as long as themselves. The canines are strongly developed in the males. There are about half-a-dozen species.

_Cariacus_ is exclusively American in range, and contains about twenty species. There are or are not upper canines. The young {296} are spotted.

The antlers are occasionally very simple; in _C. rufus_ and a few allies (placed in a special sub-genus _Coa.s.sus_) they are simple spikes without branches. In this genus, and in the nearly allied and also New-World _Pudua_, the vomer is prolonged backwards and divides the posterior nares into two. The bulk of the species are South American.

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FIG. 154.--Chilian Deer. _Cariacus chilensis._ 1/12. (From _Nature_.)

_Pudua_, just mentioned, comes from the Chilian Andes. It is a small Deer without canines and with minute antlers. Other generic names have been proposed for various species of American deer.

_Hydropotes inermis_ is a small perfectly hornless Deer, living on the islands of the Yang-tse-kiang. The male has tusks; the young are spotted.

Though, like other deer, _Hydropotes_ has no gall-bladder, both Mr.

Garrod[201] and Mr. Forbes[202] found the {297} rudiments of one in the shape of a white ligamentous cord. Mr. Forbes has especially dwelt upon the likeness of the brain to that of _Capreolus_. The female has four teats, and produces three to six young at a time.

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FIG. 155.--Water Deer. _Hydropotes inermis._ 1/10. (From _Nature_.)

_Alces machlis_, the Elk or Moose, is a circ.u.mpolar species with palmated antlers and is of large size. The young are unspotted. This animal is the largest of the Deer tribe. The aspect of this creature is by no means that of a Deer, the long, thick, and rather prehensile upper lip not by any means suggesting the family to which it belongs; the legs, too, are ungainly through their unusual length. The Moose has a curious method of protecting himself from Wolves. Instead of moving about during heavy snowstorms, and being thus on the heavy ground an easy prey for these agile enemies, the animal forms what is known as a "Moose yard." An area of ground is kept well {298} trampled down, and the animal contents itself with browsing upon the adjacent stems. The well-trampled ground gives an easy footing, and by his powerful horns the great stag is able to keep his enemies at bay.

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FIG. 156.--Moose. _Alces machlis._ 1/20.

_Rangifer tarandus_, the Reindeer, is unique among Deer by reason of the fact that both s.e.xes wear antlers. These antlers are palmated. The brow tine and the next or bez tine are also palmated and are directed forwards and a little downwards. The young are unspotted. The pelage alters in winter. Like the Moose, the Reindeer is circ.u.mpolar. As is well known, during the Pleistocene period the Reindeer extended its range as far as the South of France. Even in the historic period it is said to have been hunted in Caithness.

Reindeer, like so many other particularly Arctic animals, have regular migrations. In Spitzbergen, for instance, the animal migrates in the summer to the inland region of the island, and in {299} the autumn back again to the sea coast to browse upon the seaweed. These migrating herds have been stated to be led by a large female.