name denotes,[1] had also canines and, in one species, six incisors in the lower jaw. This Aceratherium had, moreover, four toes in the fore-feet. In the Miocene and later the Rhinoceros existed in Europe and America. There was even a purely northern form, the Rh. tichorhinus, which possessed a woolly covering and had the same range as the Mammoth. This Rhinoceros was two-horned.
The post-Pliocene and European Elasmotherium was a colossal rhinocerotine creature. This great beast had two horns and a body 15 feet long. Its limbs are not known, and as the teeth are different from those of Rhinoceroses in general, it may not have belonged to this group at all, though Osborn is inclined to derive it from Aceratherium, admitting at the same time that the evidence is "decidedly slender." The teeth in fact are like those of a Horse in being hypselodont and prismatic in form. As to the two horns, they were apparently not exactly like those of typical Rhinoceroses; there was an enormous horn posteriorly, supported on a huge boss of bone, and in front of this a roughened spot suggests a smaller or at least a much more slender horn.
It is important to notice that fossil Rhinoceroses belonging to the restricted genus Rhinoceros were in Europe invariably two-horned; it is only in India, where they still exist, that one-horned forms are met with in a fossil state.
The Rhinoceroses of America were mostly hornless. Diceratherium is an exception; but in many cases it had two parallel not successive horns, and these were, to judge from the slight prominences, but feeble in development, and perhaps hardly exactly comparable with the formidable weapons of the Old-World forms. Aceratherium tridactylum, with indications of paired horns, may be ancestral to Diceratherium. The American forms have weak and slender nasals in correspondence with the absence of horns; the sagittal crest is retained in contradistinction to the great flattened surface of the skull in the horned Rhinoceroses. Aceratherium of both divisions of the globe probably represents the ancestral group of the horned and the hornless forms. This being the case it is highly interesting to note a distinct convergence in the quite
- ↑ Quite recently, however, a species, A. incisivum, preserved at Darmstadt, has been found by Professor Osborn to possess a slight rugosity upon the frontal bones, which probably indicates the presence of a rudimentary horn, and the same author is apparently inclined to place in Aceratherium the horned Teleoceras (see p. 261).
