This genus has not been previously reported from the Deseado beds, but we found a tiny lower jaw with three teeth to represent it. The genus is distinguished by premolar 3 being two-rooted, but so small as not to attain the height of premolar 4.
Callomenus praecursor sp. nov.
The type is specimen No. 3020, a fragmentary mandible with premolars 3 and 4 and molar 1 in place. Pm. 3 is two-rooted, but so small as to be entirely overshadowed by the succeeding pm. 4, hardly reaching a half the height of that tooth. On the last premolar and the first molar, the cusps are arranged in a trigonid in front and a talonid behind, the cusps being joined by thick ridges, making two connecting crescents.
Fig. 147. Left mandible with
premolar 3 to molar 2—
4 times natural size.
Fig. 148. Left mandible internal side—
4 times natural size.
| Measurements, Specimen 3020 | |||||
|---|---|---|---|---|---|
| Lower dentition, | premolar 3, | length | 1 mm. | ||
| Lower dentition, | premolar 4, | length | 5 mm., | width | 2 mm. |
| Lower dentition, | molar 1, | length | 4 mm., | width | 2 mm. |
| Lower dentition, | height under pm. 4 | 6.5 mm. | |||