The first cranial remains of the Pleistocene proterotheriid Neolicaphrium Frenguelli, 1921 (Mammalia, Litopterna): A comparative approach

Abstract

The first cranial and upper dental remains of a proterotheriid referred to Neolicaphrium cf. N. recens Frenguelli, 1921, are described from the late Pleistocene of northern Uruguay (Sopas Formation). An isolated molariform from the Pleistocene of northeastern Pampean Argentina is considered as Neolicaphrium sp. It is the last surviving Pleistocene Proterotheriidae. An expanded diagnosis of this genusbased until now only on mandibular charactersis provided. The following combination of characters distinguish it from other genera of proterotheriids for which characters of the skull have been described: dorsal surface of skull almost parallel to the occlusal surface of the cheek teeth series; relatively large orbits and diastema; very large caniniform upper incisors; upper premolars and molars relatively low crowned; P2 nearly quadrangular; molariforms (at least P4 and M1-3) with anterolingual cingulae; anteroposteriorly short upper molar series; M1-3 with metaconule reduced to a small transverse crest connecting the hypocone to the metacone; hypocone reduced (or nearly absent), particularly in M3; M3 located below the orbit. A principal component analysis places it near the smallest species of proterotheriids, which were separated very well along the second component, usually related to shape.