The type of this species is a calcaneum and astragulus, to which Ameghino later assigned the rear part of a mandible with pm. 4 and the three molars; also a milk dentition, this last I think wrongly, for it is too small. I should interpret this specimen as deciduous inc. 2 to deciduous pm. 4, plus permanent molar 1, in which case the permanent molar corresponds to that of A. scotti and it is not necessary to discuss “the remarkable bicuspid canine,” as Ameghino does. Gaudry had some of this material, upper molars, the lower end of the humerus, the ulna, calcaneum and astragulus, and he referred the genus as the same as Homaladontotherium. With this last, I can not agree. We found the three upper molars, the lower end of the humerus, part of the radius, the tibia, and two phalanges, all on the Chico del Chubut, west of Puerto Visser.
Fig. 92. Molars 1-3 of the left side—
½ natural size.
While brachydont, the external faces of the molars are high, and each has a tiny cingulum along the base of the crown. There is also a strong cingulum around the anterior, internal, and posterior faces of the crown, which on the posterior margin flares out, making a marked and characteristic ridge. The grinding surface, with its external wall and two transverse lobes, is very similar to the molar of a rhinoceros. When the tooth wears down, the inclosed basin becomes a large pit. Between the posterior lobe and the flaring cingulum on the posterior margin, there is also a small posterior bay, which, in an old tooth, will also appear as a pit, but being shallow, it does not last long.
The lower molars, as figured by Ameghino, are of the same type as those of the toxodonts, consisting of two crescents with the pillar in the middle of the posterior crescent, but the crescents and pillar are very plump; so that with wear they form broad grinding surfaces; and the bays, instead of becoming pits, first appear as notches, then disappear entirely. Each premolar and molar has a cingulum on the internal and external sides.
Fig. 93. Premolar 4 to molar 3—
½ natural size, after Ameghino.
| Specimen 3179 | |||||
|---|---|---|---|---|---|
| Upper dentition, | molar 1, | length | 46 mm., | width | 50 mm. |
| Upper dentition, | molar 2, | length | 51 mm., | width | 55 mm. |
| Upper dentition, | molar 3, | length | 50 mm., | width | 51 mm. |
| Lower dentition, from Ameghino’s measurements | |||||
| Lower dentition, | premolar 4, | length | 28 mm., | width | 23 mm. |
| Lower dentition, | molar 1, | length | 34 mm., | width | 24 mm. |
| Lower dentition, | molar 2, | length | 46 mm., | width | 24 mm. |
| Lower dentition, | molar 3, | length | 76 mm., | width | 23 mm. |
Only the distal end of the scapula has been found; and this shows a shallow glenoid cavity, which is much longer in the antero-posterior direction, than in the transverse. The spine rises close above the rim of the glenoid, and is unusually heavy.
