The upper molars are strongly hypsodont, curved teeth. On the upper surface, the basin is subdivided by two strong cristae into three smaller bays. In an early stage of wear, the second crista unites with the posterior lobe, converting bay 3 into a pit. On the posterior margin of the tooth, the cingulum is developed so as to appear like a third crista, which inclosed bay 4, and when the tooth is worn, bay 4 becomes a pit also.
In my lower jaw incisor 3 is developed into a strong caniniform tush. Most of the teeth are lacking, but lower molar 2 is a strongly compressed, hypsodont tooth, surrounded by a thick layer of enamel. This tooth rises 22 mm. above the well-developed roots, and is already considerably worn down. The pillar is prominent as a strong fold in the middle of the posterior crescent. In this specimen there is no trace of the usual pit (3) indicative of the septum, but I should expect to find it in a younger specimen. The mandible broadens in front into a scoop-like anterior end, and the alveoli of the first two incisors would indicate that they were proclivous. The alveoli for the other teeth are arranged as in Adinotherium.
| Measurements | |||||
|---|---|---|---|---|---|
| Skull, width across the zygomatic arches | 148 mm. | ||||
| Skull, width across opposite m. 3 (outside) | 73 mm. | ||||
| Upper dentition, | molar 2, | length | 25 mm., | width | 13 mm. |
| Upper dentition, | molar 3, | length | 23 mm., | width | 12 mm. |
| Lower dentition, | incisor 3, | length | 13 mm., | width | 7 mm. |
| Lower dentition, | molar 2, | length | 20 mm., | width | 7½ mm. |
Proadinotherium angustidens Ameghino
P. angustidens Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 467.
This is based on a single lower tooth, which is considered either pm. 4 or m. 1, and measures 13 mm. long by 4½ mm. wide.
Pronesodon Ameghino
Pronesodon Amegh., 1895, Bol. Inst. Geog. Argen., t. 15, p. 626.
The genus is said to resemble Proadinotherium, but with the caniniform incisors proportionally much shorter. An associated calcaneum is shorter than that of Adinotherium and longer than that of Nesodon.
Two species are described.