Pliolophus Owen, 1858

Bronnert, Constance & Métais, Grégoire, 2023, Early Eocene hippomorph perissodactyls (Mammalia) from the Paris Basin, Geodiversitas 45 (9), pp. 277-326 : 281

Genus Pliolophus Owen, 1858

Pliolophus Owen, 1858: 54-70 .

TYPE SPECIES. — Pliolophus vulpiceps Owen, 1858 by original designation.

INCLUDED SPECIES. — Pliolophus barnesi Hooker, 2010 ; P. quesnoyensis Bronnert, Gheerbrant, Godinot & Métais, 2018 .

EMENDED DIAGNOSIS (based on Hooker 2010). — Upper molar paraconule more mesial than protocone. No mesostyle. Twinned lower molar metaconid. Notched protolophid. Cristid obliqua joining the protolophid in the middle. Lower molar hypoconulid generally linked to the hypoconid. Post-p1 diastema absent or reduced.

DIFFERENTIAL DIAGNOSIS. — Differs from Cymbalophus , which displays a small hypoconulid closely appressed to the hypolophid by a lower molar hypoconid-hypoconulid junction on m1-2. Differs from Hyracotherium by the absence of mesostyle. Differs from Orolophus and Propalaeotherium gaudryi by a straight centrocrista and a less developed lophodonty.

NOTES

The genus Pliolophus was established by Owen (1858), who considered that P. vulpiceps differs from Hyracotherium by more developed conules, more developed cingulae on upper teeth, and a P1-P2 diastema longer. P. vulpiceps displays a well-developed entoconid on p4. Cope (1884) includes the American species with the same character within the genus Pliolophus . Wortman (1896) judged this character variable, and classified Pliolophus as a sub-genus of Hyracotherium . Type specimens of Pliolophus and Hyracotherium possess several common features, and Forster-Cooper (1932b) and Simpson (1952) synonymized the two genera. Hooker (1994) resurrected the genus based on a phylogenetic analysis. The phylogenetic analysis ofFroehlich (2002) supported this result, and indicated that Pliolophus might be the only European species belonging to the Equidae .