Fig. 192.—Right manus of †entelodont (†Archæotherium ingens) from lower White River beds. Princeton University Museum.
Fig. 193.—Skull of White River †entelodont (†Archæotherium mortoni). Princeton University Museum. For restoration, see [Fig. 137, p. 260].
In the upper Oligocene were very large species of another, but closely similar, genus (†Boöchœrus) though somewhat smaller than those of †Dinohyus, and the species of the upper White River beds (†Archæotherium) were little, if at all, smaller than those of the John Day. A number of specimens in the museum of Princeton University throw a welcome light upon the habits of these strange creatures. In one, the external, or third, upper incisor tooth has a deep, triangular notch worn in its postero-external face, and the lower canine has a well-defined groove worn on the posterior side at the base of the crown; other individuals show less distinct marks of similar kind. (See [Fig. 194].) It is out of the question to suppose that these grooves and notches could have been produced by abrasion with other teeth, for no other teeth could reach the worn areas, and it is altogether probable that they were made in digging up roots. The root, held firmly in the ground at both ends and looped over the teeth which pulled until it broke, and being covered with abrasive grit, would wear just such marks as the teeth actually display.[7] While the †entelodonts were thus rooters, they were doubtless omnivorous, like other pigs, and did not disdain a meal of carrion when they could get it. It is likely that the heavy canine tusks were also used as weapons, both in defence against the attacks of carnivores and in fighting between the males of the same species. It must have been in some such encounter that the animal represented by a complete skeleton in the Princeton Museum received its broken rib; that the fracture was made during life is demonstrated by the large callus growths on the broken ends, but the pieces did not knit.
Fig. 194.—Specimen showing characteristic grooves of wear in the anterior teeth of †entelodont (†Archæotherium) from upper White River beds. Princeton University Museum.
In the middle and lower substages of the White River the genus (†Archæotherium) was the same as in the upper substage of these beds, but the species were all smaller and some of them very much so, not exceeding an ordinary pig in size. Throughout the series, as we now have it, from the lower Oligocene into the lower Miocene, there is very little change except in size, all the essential features of structure remaining the same; the genera are therefore distinguished by modifications of very secondary importance, and it is a question whether all the species should not be included in a single genus. The European genus †Entelodon, which gives its name to the family, is so like the American forms that by most writers the White River species are referred to it. It is of interest to note that the †giant pigs have also been found in the marine Miocene of New Jersey, one of the few records of the Tertiary land mammals of the Atlantic seaboard.
At present, the †entelodonts proper cannot be traced back of the lower White River beds, nor are they found in any more ancient formations in Europe. It is, therefore, probable that they were immigrants in both of these continents, presumably from Asia.
Fig. 195.—Skull of †short-faced pig (†Achænodon robustus) from the Bridger Eocene. Princeton University Museum.