Pachycynodon amphictina Teilhard, 1915

Bonis, Louis de, Gardin, Axelle & Blondel, Cécile, 2019, Carnivora from the early Oligocene of the ‘ Phosphorites du Quercy’ in southwestern France, Geodiversitas 41 (15), pp. 601-621 : 610

Pachycynodon amphictina Teilhard, 1915 n. stat.

Pachycynodon filholi var. amphictina Teilhard, 1915: 38 , pl. IV, fig. 8.

Pachycynodon crassirostris Schlosser, 1888: 253 . — Peigné et al. 2014: 33, fig. 20a.

REMARK

Teilhard (1915: pl. IV, fig. 10) figured a mandible from the phosphorites of Quercy (MNHN.F.QU9224) as Pachycynodon filholi Schlosser, 1888 var. amphictina . It is a small Pachycynodon (m1 = 8.8/ 4.5 mm; m2 = 4.3/ 4.1 mm) with p1-p2, p4-m3, the three first premolars being spaced in the mandible. The p1 is single-rooted and asymmetric, the complete mesial half of the crown being projected forward out of the root.

After a short diastema p2 is less asymmetric although the mesial face is almost vertical while the distal face is oblique and, distally, a faint cingulid forms a minute talonid. The p3 is broken off. The p4 is higher than the protoconid of m1 and less asymmetric than p2. A faint cingulid produces a minute mesial basin and a larger one around the distal border. A pacd is situated at midheight of the crown. The low trigonid of m1, with a small height difference between the cuspids, displays a vertical wear facet along the para- and protoconids. The distal face is oblique, with a small notch between metaconid and entocristid and a large one between protoconid and prehypocristid. The m2 is rectangular with a distinct paraconid on the mesio-lingual corner, and a mesially open trigonid basin. The protoconid slightly larger than the metaconid, both with wear facets to the dentine at the tip, but not in contact together, thus leaving an aperture between trigonid and talonid basins. There are wear facets on the mesio-buccal faces of the hypo- and entoconid. The m3 is small and rounded. The two posterior molars, especially m3, are implanted in the ascending ramus of the mandible. We may observe these characters in the mandible with p1-m3 from Valbro (UM VBO 456) figured in Peigné et al. (2014: 32, 33, fig. 20a), in which the m3 is located higher than the protoconid of m1. There is an original shortening of the mandible by the distal part, re-enforcing the pressure on m1 because there is no pressure in m2 and m3 Thus, m1 is worn down while m3 is still unworn. The two specimens differ from the type of P. filholi , which has less a globular metaconid of m1, more symmetrical p3 and p4, a shorter and more pointed p4 with a pacd located lower, and we consider that they belong to a separate species with the name originally given by Teilhard for a variant.