The Celebesian Babyroussa, genus Babirusa, is an almost hairless hog with enormously upturned tusks in both jaws of the
male. In the Wild Boar there is a hint of this, which is carried still further in Phacochoerus; 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 Potamochoerus, including the Red River Hog, is barely separable generically. Their principal claim to generic distinction lies in the existence of a horny 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[[179]] recognises five species, of which only one is from Madagascar.
Fig. 145.—Peccary. Dicotyles tajaçu. × 1⁄6.
Fam. 3. Dicotylidae.—The Peccaries are generally placed in a different family from that of the other Pigs. This family,
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[[180]] 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
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 dentition 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.[[181]]