New Fossil Platyrrhine from Argentina

Abstract

A new fossil primate was found in the Pinturas Formation, south-western Patagonia, at the type locality of the rare Soriacebus ameghinorum. It is a mandibular fragment with two molars that strongly resemble those of S. ameghinorum in their high and closed trigonid, distal expansion of the talonid, small hypoconulid, buccal expansion of the enamel and similar cusp development. But the type of S. ameghinorum differs by having mesiodistally longer trigonids, long premetacristids and more oblique distal trigonid walls, with the metaconid more lingually placed and the postmetacristid distolingually oriented and with the talonid being buccolingually smaller than the trigonid with a more restricted basin. M2 is slightly smaller than in the new specimen, and the buccal enamel is less flared. Although it is difficult to determine if this new specimen represents an individual variation of S. ameghinorum or a new species of Soriacebus, its morphology appears to be less derived than that of the type mandible, and it is, therefore, of systematic significance.