The Cambridge Natural History Part 21

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FIG. 143.--Wart Hog. _Phacoch.o.e.rus aethiopicus._ 1/6.

The African Wart Hog, genus _Phacoch.o.e.rus_, is usually regarded as the type of a distinct genus of Pigs. This animal, "superlatively ugly" with its huge tusks and great protuberances upon the face, is chiefly to be distinguished from the genus _Sus_ by these characters, and by the complexity of the last molar, which, with the tusks, are sometimes in aged animals the only teeth left. The complete formula is Pm 2/2 M 3/3. There are two species of this genus, _P. aethiopicus_ and _P. africa.n.u.s_. When enraged the Wart Hog is said to carry its tail directly up, and to present a ludicrous as well as ferocious appearance.

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FIG. 144.--Head of Wart Hog.

The Celebesian Babyroussa, genus _Babirusa_, is an almost hairless hog with enormously upturned tusks in both jaws of the {278} male. In the Wild Boar there is a hint of this, which is carried still further in _Phacoch.o.e.rus_; but in _Babirusa_ the upper tusks turn upwards before they leave the substance of the jaw, for which reason they appear to arise on its dorsal surface; the lower tusks are nearly as long. It has been found that the young of this Pig are not striped as are those of other Pigs. By means of the curved upper tusks this animal has been said by old writers to suspend itself to branches of trees, just as does by his downwardly-projecting tusks the male Chevrotain! There is but one species, _B. alfurus_.

From _Sus_ proper the African and Malagasy _Potamoch.o.e.rus_, including the Red River Hog, is barely separable generically. Their princ.i.p.al claim to generic distinction lies in the existence of a h.o.r.n.y outgrowth arising from a bony apophysis above the canine in the male. These have been compared to the osseous "horn cores" in the extinct Dinocerata. But the Javan _Sus verrucosus_ shows at least the beginning of a similar modification. The popular name of the animal is derived from the fine rufous colour of its pelage, not seen, however, in all the species. Dr. Forsyth Major[187]

recognises five species, of which only one is from Madagascar.

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FIG. 145.--Peccary. _Dicotyles tajacu._ 1/6.

FAM. 3. DICOTYLIDAE.--The Peccaries are generally placed in a different family from that of the other Pigs. This family, {279} Dicotylidae, contains but one genus, _Dicotyles_, with at most two species. The name of the animal is connected with the dorsal gland; the animal thus appeared to possess two navels. The Peccaries, exclusively confined to the New World, differ from the Old-World Pigs in one or more important characters. They have only three toes on the hind-feet, and the stomach is complicated.

Though the Peccaries have but small tusks they hunt in packs and are very dangerous animals to meet with. They owe, too, their safety from many foes to their sociable habits. Being nocturnal animals they are liable to the attacks of the Jaguar, which will speedily overpower and devour a Peccary that has strayed from its herd.

FOSSIL SWINE.--The existing genera of the Pig tribe are also known in a fossil condition. _Sus_ itself goes back as far as the Upper Miocene. _Sus erymanthius_, the Erymanthine Boar, is known from beds of that age in Greece, England, and Germany. This genus is not known to have had a wider distribution in the past than it has in the present. _Dicotyles_ occurs in the Pleistocene of both North and South America, the regions which it inhabits at the present day. The genus _Listriodon_, also Miocene, is remarkable for having lophodont instead of bunodont teeth, that is so far as concerns the molars, which resemble those of the Tapir. It was European and Indian in range. A number of genera, more remote from the existing Pigs than those which have just been dealt with, are placed together in a special sub-family, Achaenodontinae. The type genus, _Achaenodon_, had a somewhat short skull for a Pig; and it is in general aspect and in the characters of the canine teeth highly suggestive of that of a Carnivore.

The bunodont molars, however, are Suine, as is the form of the lower jaw with a rounded angle. This is an Eocene animal found in Wyoming.

_Elotherium_[188] occurs chiefly in the Miocene of both North America and Europe; but _E. uintense_ is Eocene. The orbits are completely encircled by bone in the more modern forms; this is not the case in the last-described genus, with which _E. uintense_ agrees. The skull is also longer and more Pig-like. The zygomatic arch is powerful, with sometimes a large descending process, such as is found in _Diprotodon_, more faintly in Kangaroos, and in Sloths and certain extinct Edentates. The lower jaw has a pair {280} of dependent processes near the symphysis, which suggest processes occupying a corresponding position in _Dinoceras_. The skull and body are heavy, but the two-toed limbs are slender. There is a smaller pair of toes behind these. The dent.i.tion is complete, and the canines are not inordinately developed. The brain is very diminutive. Perhaps _E. uintense_ should be separated as a distinct genus, _Protelotherium_.[189]

_Hyotherium_ (which is regarded as identical with _Palaeoch.o.e.rus_) has a sharp sagittal crest; the orbit is nearly but not quite closed. The canines are not strongly developed. The upper canines have double fangs as in _Triconodon_ among extinct mammals, and as in the Hedgehog and other forms among living Mammalia. The premolars have the cutting and serrated edge of those of some other Pigs, a feature which gives them a curious resemblance to the "grinding" teeth of Seals. The molars are tuberculate, and like those of living Pigs. It is European and Indian in range, and Miocene.

The genus _Ch.o.e.ropotamus_ has a complete dental formula save for the loss of a premolar in the lower jaw. Though it has lost this tooth, it is from an older stratum than some of those forms which have retained that premolar; it has been found in the Upper Eocene of the Isle of Wight and of the neighbourhood of Paris.

The American and Miocene _Chaenohyus_ has lost the corresponding teeth of the upper jaw.

_Homacodon_[190] is a genus consisting of several species, which has a bunodont and complete dent.i.tion. The molars are s.e.xtubercular in the upper jaw. _H. vagans_ was of about the size of a Rabbit, and it appears to have had a curved neck. The limbs had five digits, as is so generally the case with Eocene Ungulates. It is known from the Middle Eocene of Wyoming.

GROUP II.--_RUMINANTIA._

The Selenodontia or Ruminantia form the second division of existing Artiodactyles. The characters of the teeth, which give them their name, have already been referred to. They also differ in that there are never more than a single pair of incisors {281} in the upper jaw, and very usually there are none. As a general rule the third and fourth metacarpals and metatarsals become united to form a cannon bone. To this there is but one exception, the African _Hyomoschus_. Moreover, the second and fifth digits are nearly always rudimentary, and may practically disappear altogether. Here again the Tragulidae are an exception. The Ruminantia are so-called on account of the fact that they "ruminate," that is, after the food has been rapidly swallowed, it is forced back up the gullet and more thoroughly masticated. a.s.sociated with this is a complex stomach, which is divided into several compartments. This stomach has at least three compartments, as in the Tragulidae; but it has usually four. Its characters are ill.u.s.trated in Fig. 146. The majority of the Selenodontia possess horns, which are partly formed of solid protuberances of the frontal bones.

In the Giraffe they are somewhat different.

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FIG. 146.--Stomach of Ruminant opened to show the internal structure. _a_, Oesophagus; _b_, rumen; _c_, reticulum; _d_, psalterium; _e_, abomasum; _f_, duodenum. (After Flower and Lydekker.)

This group may be divided into--A. TRAGULINA, Chevrotains; B. TYLOPODA, Camels, Lamas; and C. PECORA, Deer, Antelopes, Oxen, Giraffes, Goats, Sheep.

A. TRAGULINA.

As the Tragulina are undoubtedly the most ancient of the Selenodontia it will be logical to commence with an account of them. {282}

FAM. 4. TRAGULIDAE.--This family comprises a number of small Deer-like animals, which are really in many points more related to the Pigs than to the true Deer. They are known as Chevrotains; and the term "Deerlet,"

introduced by Professor Garrod, is certainly appropriate, since they have the aspect of very small and hornless Deer. If it were not for their Artiodactyle feet one might at a glance confuse these creatures with some Marsupial type. The family is Oriental and West African in range. The two genera (whose individual peculiarities will be considered later) differ from other Artiodactyles in a number of rather important characters.

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FIG. 147.--Indian Chevrotain. _Tragulus meminna._ .

They are absolutely hornless in both s.e.xes. The canines are present in both jaws, and are especially well developed in the upper jaw. The dental formula is I 0/3 C 1/1 Pm 3/3 M 3/3. In the skull the tympanic bulla is usually, as in the non-ruminating Artiodactyles, filled with loose bony tissue. The feet (usually) have the four toes of the Suina, and are therefore in a more primitive condition than in Deer and Antelopes. But as the middle metacarpals are fused in _Tragulus_ (though separate in _Hyomoschus_) they are a stage further than are the Pigs, in the direction of the typical Ruminants.

The stomach is comparatively simple, thus offering {283} intermediate characters between the Pigs and the Ruminants; there are but three separate compartments. A highly-interesting character is afforded by the placenta.

This is in the present family of the diffuse kind, not presenting the separated and tufted cotyledons of the Ruminant placenta. This we may fairly a.s.sume is a further proof of the less-specialised characters of this group[191] as compared with the Ruminantia, a view, however, which is not universally accepted. While the molars have the selenodont character of other Pecora, the premolars are more adapted for cutting, with sharp edges.

The genus _Tragulus_ consists of several species (e.g. _T. stanleya.n.u.s_, _T. napu_, etc.), which have been aptly compared in external appearance to certain Rodents such as the Agoutis. The legs are delicate and slender, hardly "thicker than an ordinary cedar pencil." These creatures have got among the Malays a considerable reputation for astuteness, embodied in the saying, "Cunning as a _kanchil_." The male has tusks, which greatly contributed to the confusion of this creature with the totally different Musk Deer, _Moschus moschiferus_. It is even said to suspend itself by their aid to the branches of trees, and so avoid danger.

_Hyomoschus_ (or _Dorcatherium_ as it should properly be called) is West African. Its rich brown colour, with spots and stripes, is much like that of the Chevrotains, but it has shorter limbs. The only species is _D.

aquatic.u.m_, which is sometimes called, on account of its frequenting the banks of streams, the Water Chevrotain. Remains of this genus occur in Miocene and Pliocene strata of Europe.

The separate metacarpals, comparatively simple stomach, absence of horns, diffuse placenta, and spotted pelage are features which argue the primitive position of these animals among existing Artiodactyles.

Besides the two existing genera which have just been treated of, there are a number of extinct genera undoubtedly belonging to the same group.

_Gelocus_ (Eocene and Oligocene in range) is a European genus known from France. It differs from the living members of the group by the fact that the second and fifth toes on both hind- and fore-feet are represented, as in certain Deer, {284} by rudiments at the upper and at the lower end only; they are deficient in the middle. The middle large metacarpals, though closely applied, are not fused. The metatarsals, on the other hand, are, or are not fused, according to the species. A later form is the genus _Leptomeryx_ from the Miocene of North America. This genus departs from the typical Traguline structure in more than one point. The tympanic bulla is hollow instead of being filled with cancellated bone; the cuneiform is not fused with the cuboid and navicular, though the latter are with each other; the lateral digits of the hind-feet are rudimentary. The magnum and trapezoid, however, are fused. In the fore-feet the middle metacarpals are separate, and the lateral less perfect metacarpals have toes. The metatarsals are fused.

Not definitely referable to the Tragulidae, but coming near to them, are the PROTOCERATIDAE. Of this family there is but one well-known genus, _Protoceras_,[192] from the Miocene of North America.

The skull is singularly reminiscent of _Dinoceras_, with which this quite Artiodactyle genus has, of course, nothing to do. It merely exemplifies the phenomenon of "parallelism." In general form it is peculiarly long and low.

There are three pairs of bony protuberances: one, the largest, pair are situated on the maxillae rising up just behind the implantation of the canine teeth; the parietals have a second pair; and a third much more diminutive pair of bosses are upon the frontals, near their junction with the nasals. This description refers to the male; the female has only traces of the parietal bosses. These were all possibly tipped or sheathed with horn or roughened skin. The dent.i.tion of this genus is precisely that of the Tragulidae, _i.e._ I 0/3 C 1/1 Pm 4/4 M 3/3. The orbit is completely encircled by bone; the auditory bulla is not swollen; the premaxillae are small.

The nasal cavity is very large and open, the end of the nasal bones anteriorly being situated at about the middle of the skull; this would seem to indicate at least a flexible and long nose like that of the Saiga Antelope, if not a trunk.

The brain was of good size, and quite well convoluted.

The limbs are const.i.tuted on the Traguline plan; in the fore-limbs the middle metacarpals are quite free from each other, and the more diminutive lateral digits are complete. The {285} metatarsals are free, but with a tendency to fusion; the lateral toes are only represented at the upper extremity. The carpal bones are separated.

This animal, which was about the size of a Sheep, though of more delicate proportions, was allied not only to the Tragulidae but to the Giraffidae; it is impossible to refer it definitely to either family.

B. TYLOPODA.

FAM. 5. CAMELIDAE.--This small group of Selenodonts includes only the Camels and Lamas. The limbs are long and have no traces of the second and fifth toes. The fused metacarpals and metatarsals diverge somewhat at their distal ends. In the upper jaw is a single pair of incisors. The stomach differs from that of the typical Ruminants. The rumen has smooth and not papillose walls, and from it are developed the "water cells," diverticula with narrow mouths provided with a closing sphincter muscle. The psalterium is reduced to a mere vestige, and so the stomach has, as in the Tragulina, but three chambers. This, so far ancient, character in the structure of the Camel tribe is a.s.sociated with another, also seen in the more primitive Ungulates, viz. the diffuse character of the placenta. A very singular peculiarity of this group is the fact that the blood corpuscles instead of showing the ordinary mammalian round contours are elliptical.

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FIG. 148.--Bactrian Camel. _Camelus bactria.n.u.s._ 1/30.

The genus _Camelus_, confined to the Old World, is made up of two quite distinct species, the Bactrian Camel, _C. bactria.n.u.s_, with two humps, and the Dromedary, _C. dromedarius_, with only one. The former species is Asiatic. It is a singular fact that neither of the species is known to occur in a genuinely wild condition. The so-called "wild" Camels appear to be invariably feral. The two species will interbreed; and there is at the Zoological Society's Gardens such a hybrid, which has the general appearance and s.h.a.ggy brown hair[193] of the Bactrian animal, but the one hump of the Dromedary. It may be that the Bactrian Camels of Lob-nor are really wild; but the desert contains so many remains of cities destroyed by sand-storms that these reputed wild {286} Camels may be the descendants of animals belonging to the inhabitants of those cities. A strayed herd of Camels has established itself in a feral state in Spain. Otherwise the genus does not occur in Europe. The Camels are also represented in the New World. The genus _Lama_ (_Auchenia_ of many authors) belongs to this family. These Camels differ from their allies in the Old World by their smaller size, by the absence of the characteristic hump, and by the dropping of one premolar, the dental formula being otherwise similar. A variety of names, Lama, Alpaca, Huanaco, Vicuna, have been applied to these animals; but it appears that the names are in excess of the number of the species. Mr. Thomas, who has lately inquired into the matter, will only allow two, the Huanaco, _Lama huanacos_, of which there are two domestic races, the Llama and the Alpaca, and the Vicuna, _Lama vicugna_. They are both South American in range. Not only is there a herd of escaped Camels in Spain, but the Spaniards attempted to introduce and acclimatise the useful Lama. The first Lama ever seen in Europe was brought in the year 1558 to {287} the town of Middelburg in Holland; it was purchased and presented to the Emperor of Germany. Gesner gives a curious figure of it, representing the animal as a comparatively colossal beast submitting itself to the guidance of a dwarfish man. The habit of "spitting" of the Lama is well known. Augustin de Zarate and Buffon speak of the Lama as having no protection save this habit, which is more than a mere ejection of saliva: the contents of the stomach are forcibly shot at the object of its annoyance. It can also kick and bite. In the intestines (as in those of some other mammals) are found Bezoar stones, or Bezards as they are variously spelt. These were once valued in medicine, and even so lately as 1847 were, according to Gay, the historian of Chili, in vogue; these concretions, comparable to the ambergris of the Whales, were supposed to be an antidote to poison.

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FIG. 149.--Lama. _Lama huanacos._ 1/12.