Pachycynodon sp. 2

(Fig. 2D)

NEW MATERIAL. — UM VD18, right d4.

REMARKS

Specimen UP MGB9 (Fig. 2B 1-B 3) is a small left d4 with elongate crown and low trigonid. thre is a small height difference between the trigonid cuspids, and distal wall of the protoconid gently sloping distally. The inflated metaconid is looking larger than the paraconid in lingual view and almost as high as the protoconid, and gently sloping distally. The thinner paraconid is less inflated than in other species of Pachycynodon, and projected up and mesially. The contact between paraconid and metaconid is at the base of the crown, and thus the trigonid valley is open lingually. The talonid is long and broad with a flat bottom. The hypoconid is developed as a small cuspid connected to the protoconid by a very low and non-oblique cristid obliqua. The buccolingually compressed entoconid is connected without interruption to the metaconid by a low preentocristid. There is a small hypoconulid distally. Specimen UM VD16 is a small right d4 similar to MGB9 (Fig. 2C 1-C 3). The third d4, UM VD18 (Pachycynodon sp. 2), is slightly different in its more swollen cuspids, exaggerating the characters of Pachycynodon, but the overall pattern is the same (Fig. 2D 1-D 3). The low trigonid with swollen cuspids, amongst which the heights are similar, is a character of Pachycynodon. The talonid differs by the higher and more robust hypoconid (size: MGB9 = 6.5 × 3 mm; VD16 = 5.4 × 2.7; VD18 = 8 × 4.2 mm).

These d4s differ from all m1 of Pachycynodon by their smaller size (Table 2), the shape of the paraconid, the low contact between paraconid and metaconid and the shape of the broad talonid. Compared to the d4 LPL13 (Fig. 2A 4, A 5) they display the same pattern but are smaller (MGB9 and VD16) and relatively thicker (VD18). It is at present not possible to identify the species of Pachycynodon corresponding to these milk teeth.