Pachycynodon cf. boriei or curvirostris ( Filhol, 1876 ), Schlosser, 1888
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publication ID |
https://doi.org/ 10.5252/geodiversitas2019v41a15 |
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publication LSID |
urn:lsid:zoobank.org:pub:9DD3CC29-3AEA-44B8-8E8F-6AD882DF5B1C |
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DOI |
https://doi.org/10.5281/zenodo.3703509 |
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persistent identifier |
https://treatment.plazi.org/id/03A48799-1A67-FF97-FF0B-FE7A6C26FB1E |
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treatment provided by |
Valdenar |
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scientific name |
Pachycynodon cf. boriei or curvirostris ( Filhol, 1876 ) |
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Pachycynodon cf. boriei or curvirostris ( Filhol, 1876)
( Fig. 2A View FIG )
NEW MATERIAL. — d3-m1 (UP LPL13).
DIAGNOSIS. — Large species of Pachycynodon (length of m1 = 12 to 13.5 mm), m1 with slightly open trigonid basin. The very robust p4 and high and spaced premolars seem to be characteristic of the species. Another specimen, smaller but with the same characters, figured under the name Cynodictis leymeriei ( Filhol 1876: figs 55-57) could be a female of P. boriei. The occurrence of P. boriei in the new collections of the Quercy was indicated in La Plante2 ( Cirot 1992) and definitively in Valbro ( Peigné et al. 2014) from a fragment of an M1. The new specimens do not firmly verify the occurrence of this species in one of the new localities in the Quercy insofar as another species of Pachycynodon , P. curvirostris ( Filhol, 1876), slightly smaller than P. boriei, differs in its elongated and constricted lower premolars, and smaller p4 relative to m1 (holotype, MNHN.F.QU9208; Filhol 1876: figs 52-54). Two other mandibles (MNHN.F.QU9210 and MNHN.F.QU9216) may be related to the same species.
REMARK
Pachycynodon boriei (Filhol, 1874) was named and later figured ( Filhol 1876: figs 33, 40) as “one of the largest Carnivora ever found into the phosphate localities“(LdeB translation). Filhol 1876: 72) chose as type a mandible ( Filhol 1876: fig. 40) with an associated cranium (1876: fig. 34) that is probably from the same individual.
DESCRIPTION
The d3 ( Fig. 2A View FIG 4 View FIG , A 5 View FIG ) is single-cusped but two-rooted; the crown is slightly dissymmetric, the distal part being larger than the mesial one. It is slightly longer than high with a small medial edge (“protostylid”) and a medium high, lingually situated pacd not along the sagittal cristid as is normally the case in premolars; both mesial and distal cristids are sharp and there is a small, flat and slightly upturned talonid around the distal crown (size: 6.3 × 2.9 mm).
The d4 ( Fig. 2A View FIG 4 View FIG , A 5 View FIG ) is thin with a high protoconid that is clearly buccally convex but slightly lingually convex and moderately sloping distally. The very oblique paraconid appears smaller than the metaconid in lingual view; the latter is slightly distally located and has a triangular horizontal section. The metalophid is acute as are the premetaconid and postmetaconid cristid. The lingual face of the metaconid is slightly convex but the mesial and distal ones are almost flat. The talonid basin has a wide and flat bottom. The cristid obliqua joins the buccal part of the base of the protoconid to the moderately high and bucco-lingually compressed hypoconid. The postmetaconid cristid joins the preentoconid cristid without a notch; postentoconid and posthypoconid cristids reach a small hypoconulid distally. A d4 from Valbro was previously described by Peigné et al. (2014). It is smaller and differs in its less pointed trigonid cuspids, lower protoconid and less transverse paraconid (size: 8 × 35 mm)
The m1 is a germ out of its crypt. Despite a fissure, the crown is very well preserved ( Fig. 2A View FIG 1-A View FIG 3 View FIG ). The grouped cuspids of the trigonid are massive, with the protoconid slightly higher than the other cuspids and a part of the metaconid slightly visible in buccal view. The disto-lingual face of the metaconid is triangular and flat. The distal faces of both protoconid and metaconid are in almost the same plane, sloping distally at an angle of about 45°. There is a large hypoconid occupying the entire talonid basin and gently sloping to the base of the entocristid, the latter being a series of buds in which it is impossible to distinguish an entoconid (size: 12.3 × 5.8).
Judging by the size and morphology, the m1 of the mandible, UP LPL13 could be a small specimen of P. boriei but we cannot exclude, without more complete specimens and knowledge of the premolars, a large P. curvirostris.
SMALL SPECIES AND SUB- SPECIES OF PACHYCYNODON Several taxa of quite small size (length of m1 between about 7 and 9 mm) of Pachycynodon have been described, all from the old collections of the Quercy phosphorites:
Pachycynodon dubius ( Filhol, 1882);
Pachycynodon filholi Schlosser, 1888 ;
Pachycynodon vulpinus Schlosser, 1899;
Pachycynodon tenuis Teilhard, 1915;
Pachycynodon aff. tenuis Teilhard, 1915;
Pachycynodon tenuis ‘ amphictoÏde ’ Teilhard, 1915;
Pachycynodon filholi var. amphictina Teilhard, 1915 ;
All these taxa constitute a homogeneous group in which it is easy to recognize the genus characters but difficult to interpret the tenuous differences between the component species, with size playing a role in the distinctions. The above list of taxa represents almost half of the small Pachycynodon specimens housed in the MNHN. Pachycynodon tenuis is considered by Teilhard (1915: 36) as a model for the origin of the group because of its small size, p4 higher than m1 and the thinness of the latter despite the swollen cuspids of the trigonid. Nevertheless we believe that the narrow m1 is due to the small size of the specimen, since other m1s, although larger, have the same or lower breadth/length index of m1. Other features are cited by Teilhard, such as the sharp-edged cuspids, the hollow talonid of m1, the m2 beginning to be rounded and with a distinct paraconid, but these features also are present in other species (see below), more especially as the paraconid is not all that distinct. To this we may add an entoconid that is less enlarged than the hypoconid but high, and a reduced mesial fovea in m2. Pachycynodon aff. tenuis ( Teilhard 1915: pl. 4, fig. 5), where the tips of the p4 and p3 cuspids are broken off, is characterized by a high and pointed p2 separated from p3 by a short diastema. Pachycynodon tenuis ‘ amphictoÏde’ ( Teilhard 1915: pl. IV, fig. 6) is a poorly preserved hemi-mandible with m1 and alveoli of m2. There is no m3, like in Amphictis, but we cannot say anything else with so a poor material. Pachycynodon dubius was established on a hemi-mandible from the Quercy phosphorites with p2-m2 and part of the ascending ramus. According to Teilhard (1915) it is principally characterized by a very low m1, even taking into account the wear on the trigonid cuspids, and the diastemata between the premolars. The holotype of P. vulpinus comes, like the other species, from the phosphorites of Quercy. Its size is close to that of P. dubius, the m1 is low the premolars have diastemata between them. The p3 and the p2 are smaller than the p4. Comparing a cast of P. vulpinus with P. dubius no significant difference between the specimens can be seen, except that the size difference between p4 and the other premolars is more marked in the former. We believe them to be conspecific, as noted by Teilhard (1915: 39), with P. dubius ( Filhol, 1882) having priority.
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