Fig. 215.—†Syndyoceras cooki, lower Miocene. Restored from a skeleton in the museum of the University of Nebraska.
One of the phyla which persisted into the lower Miocene was there represented by a most fantastic creature (†Syndyoceras) with four horn-like outgrowths from the skull, one pair arising from the anterior part of the face and curving outward away from each other, and the hinder pair, which were placed over the eyes, curved toward each other at the tips and were shaped much like a cow’s horns in miniature. The shape of these bony protuberances makes it unlikely that they were sheathed in horn and probably they were merely covered with skin like the horns of the giraffes. This description applies only to the skull of the male; that of the female is not yet known, but there is good reason to believe that in that sex the horns were much smaller or wanting, as in nearly all existing deer. The skull was long, narrow and low; the orbits were small, completely enclosed in bone and unusually prominent; the nasal bones were exceedingly short, as though indicating the existence of a proboscis, but this can hardly have been the case, for the nasal opening was divided into anterior and posterior portions by the bony bridge which united the bases of the forward pair of horns. In no other known mammal does such a division of the nasal opening occur. The upper incisors had all disappeared, but there was a small upper canine tusk and another formed by the first lower premolar, while the real lower canine had gone over to the incisor series. This exceptional arrangement is a point of resemblance to the †oreodonts (see [p. 372]). The grinding teeth were brachyodont. The fore limb is not known, but the hind limb has been completely recovered; it was stout and not very long in proportion to the length of the head. The fibula was completely reduced, only the ends remaining, and the pes was didactyl, the two metatarsals uniting in a cannon-bone; the hoofs were like those of deer and antelopes.
Fig. 216.—†Protoceras celer, upper White River; males on the right and left, female in the middle. Restored from skeletons in the American Museum and Princeton University.
No representative of this series has yet been found in the upper Oligocene; and it is not yet possible to say whether their absence from the John Day beds, as in several other cases already referred to, was due to an actual geographical difference in contemporary faunas, or whether it is merely one of the accidents of preservation and collecting. In the upper White River, however, was another most curious animal (†Protoceras), a forerunner, if not a direct ancestor, of †Syndyoceras. The exact relationship between the two forms can hardly be determined, until the genera, one or more, which once connected them shall have been recovered, though it is obvious that they belonged to the same series. †Protoceras was a smaller animal and, if anything, an even more bizarre-looking object, for the anterior protuberances were broad, prominent and everted plates of bone, not even suggesting horns in their form, and the posterior pair were short and club-shaped; in the female neither pair was more than indicated. The dentition was very similar to that of †Syndyoceras, except that the upper tusk was considerably larger and scimitar-shaped; the female had no tusks. In the fore-arm the two bones were just beginning to coalesce, but in the lower leg the fibula was completely reduced. The manus had four complete and functional digits, the laterals not very much shorter and thinner than the median pair; but the pes was already didactyl, though the metatarsals were separate, not fused into a cannon-bone; two long and pointed splints were the vestigial remnants of the second and fifth digits.