Pliolophus barnesi Hooker, 2010

Bronnert, Constance & Métais, Grégoire, 2023, Early Eocene hippomorph perissodactyls (Mammalia) from the Paris Basin, Geodiversitas 45 (9), pp. 277-326 : 283-284

Pliolophus barnesi Hooker, 2010

( Fig. 4 )

Pliolophus barnesi Hooker, 2010: 117 , 119, figs 52, 53.

Hyracotherium sp. – White 1931: 18, 25. — Simpson 1952: pl. 40, figs b-d. — Kühne 1969: 199.

Hyracotherium [sic] – Forster-Cooper 1932a: 458. — Savage et al. 1965: 8-10, figs 3c, e, f.

Hyracotherium (Pliolophus) vulpiceps – Forster-Cooper 1932b: 437- 438, pl 51, figs 4-5.

Hyracotherium aff. vulpiceps – Hooker 1980: 106-107, fig. 2; 1984: 234-235, figs 6, 13, 17, 20; 1989: 83-84, figs 6.3L, 6.4I-K, Q.

Pliolophus aff. vulpiceps – Hooker 1994: 54, fig 16.

Pliolophus vulpiceps – Hooker 1994: 52-54. — Hooker & Dashzeveg 2003: 493-494; 2004, fig. 6G, H. — Hooker et al. 2005: 85.

HOLOTYPE. — BMHN M44910 , right mandible with p3-m3 .

PARATYPES. — See Hooker (2010) .

MATERIAL. — Abbey Wood: see Hooker (2010).

Soissons: m2 (R: MNHN-SN34-BN); m3 (L: MNHN unnumbered).

Pourcy: P2 (L: MNHN-PY15715), P4 (L: PY cast), M1 (L: MNHN-PY133-L), M1/2 (R: PY unnumbered, MNHN-PY42-L [broken], PY72-L [broken]), PY146-Lx (cast); L: PY-2-Cn (cast), PY-16-Cn (broken, cast); M3 (R: MNHN-PY40-L; L: MNHN-PY39-L, PY41- L); p3 (L: MNHN-PY45-L, PY34-CN); p4 (L: MNHN-PY20-Ph); m1/2 (R: MNHN-PY9-L [broken], PY143-L [broken]; L: MNHN-PY10-L [broken], PY11-L [broken]); m3 (L: MNHN-PY43-L) .

TYPE LOCALITY. — Abbey Wood (London, United-Kingdom), MP8-9.

DISTRIBUTION. — Abbey Wood (London, United-Kingdom); Soissons, Pourcy (Marne, France), MP8-9.

EMENDED DIAGNOSIS. — Large upper molar metaconule. Labially flexed centrocrista. Large P3 paraconule. Lower molar hypoconulid joining the hypoconid (mostly) or to the hypolophid.

DIFFERENTIAL DIAGNOSIS. — Upper molar centrocrista slightly more flexed than P. quesnoyensis and less flexed than P. vulpiceps . Upper molar and premolar conules less developed than P. vulpiceps .

DESCRIPTION

Teeth

The P2 ( Fig. 4A ) is triangular in occlusal view, and the posterior part is transversally wider than the anterior part. The paracone is developed. The metacone is very reduced and closely appressed to the paracone. The protocone is absent but a cingular bulge is present lingually. Elsewhere, the cingulum is poorly developed or absent. The parastyle is absent. The P4 parastyle is very small and low ( Fig. 4B ). The paraconule is large, slightly smaller than the paracone. The preparaconule crista is interrupted by a notch close to the center of the preparacrista. The metaconule is small, and slightly elongated. The cingulum is continuous, slightly reduced close to the protocone. The M3 parastyle is developed but low ( Fig. 4 C-E). The cingula are well-developed. The centrocrista is slightly flexed. The paraconule is high and merged with the loph. The metaconule varies in size but is generally small, sometimes indistinguishable. The protoloph joins the preparacrista. The metaloph is interrupted at the base of the metacone. The p3 protoconid is larger than the metaconid ( Fig. 4F, G ). The metaconid and protoconid are close on MNHN-PY45 and more separated on MNHN-PY34-Cn. A small paraconid is present. A crest runs from the protoconid and joins a low but well-developed hypoconid. The metaconid of p4 is twinned ( Fig. 4H ). The protoconid and metaconid are about the same height. The protolophid is low. The cristid obliqua is directed toward the center of the protolophid. The entoconid is developed but smaller than the hypoconid. A crest joins the hypoconid and the entoconid. A more developed crest runs disto-lingually to the hypoconulid. The lower molar cristid obliqua joins the protolophid in the middle ( Fig. 4 I-K). The hypolophid is low. The metaconid is twinned. The hypoconulid is linked to the hypoconid by a postcristid. The hypoconulid is small on m1-2. The hypoconulid is large on m3 but the hypoconulid lobe is narrower than the rest of the tooth.

COMPARISONS

The upper molar centrocrista in P. barnesi is slightly more flexed than that in P. quesnoyensis , but less flexed than that in P. vulpiceps . The m3 display more intraspecific variability on the hypoconulid junction (with hypoconid or hypolophid) than P. quesnoyensis . The p4 entoconid is more developed than in P. quesnoyensis . Compared with P. vulpiceps , the upper molar and premolar conules and p1 are less developed in P. barnesi .

COMMENT

Hooker (1994) described P. vulpiceps in Pourcy. However, our revision of the material indicates that the specimens discovered in Pourcy belong to P. barnesi rather than P. vulpiceps . These fossils, as for P. barnesi , notably display less developed conules on upper molars than P. vulpiceps .

Figures

FIG. 4. — Teeth of Pliolophus barnesi from Pourcy and Soissons in occlusal view: A, left P2 (MNHN-PY75715); B, left P4, cast, unnumbered; C, left M3 (MNHN- PY41-L); D, left M3 (MNHN-PY39-L); E, right M3 (MNHN-PY40-L [reversed]); F, left p3 (MNHN-PY45-L [reversed]); G, left p3 (MNHN-PY34-Cn [reversed]); H, left p4 (MNHN-PY20-Ph [reversed]); I, right m1/2 (MNHN-SN34-BN); J, left m3 (MNHN-PY43-L [reversed]); K, left m3 (unnumbered [reversed]). Coated with magnesium. Scale bar: 5 mm.