The Hegetotheriidae (Mammalia, Notoungulata) assemblage from the late Oligocene of Mendoza, central-western Argentina

ABSTRACT—This study describes new remains of Hegetotheriidae (Notoungulata), including a new species, from the Deseadan (late Oligocene) of Quebrada Fiera, Mendoza Province, Argentina. The assemblage is composed of four hegetotheriines, <i>Prohegetotherium</i> cf. <i>P. sculptum</i>, <i>Prohegetotherium</i> sp., <i>Prohegetotherium schiaffinoi</i>, and <i>Prohegetotherium malalhuense</i>, sp. nov., and the pachyrukhine <i>Propachyrucos</i> cf. <i>P. simpsoni</i>. The presence of <i>Prosotherium</i> cannot be totally discounted because lower molariforms are rather similar between the two pachyrukhine genera. The new species <i>Prohegetotherium malalhuense</i>, sp. nov., differs from all previously described hegetotheriines by having a lingually projecting, sharp parastyle and marked parastyle groove on the ectoloph of M2–3; talonid of m1–2 posterolabially projected; talonid of m3 with marked posterolabial groove; and the smaller size. Its phylogenetic affinities are not well resolved. <i>Prohegetotherium</i> is paraphyletic, with <i>P. sculptum</i> sister taxon to the remaining hegetotheres, and the new taxon more closely related to <i>Hegetotherium mirabile</i> than to <i>P. schiaffinoi</i>. The recognition of <i>P. schiaffinoi</i> and <i>Prohegetotherium</i> cf. <i>P. sculptum</i> emphasizes that the fauna from Quebrada Fiera shares elements with roughly contemporaneous Deseadan faunas from northern and southern latitudes, but important faunal particularities distinguish the region as well. The record of pachyrukhines at Quebrada Fiera more closely resembles Deseadan faunas in Patagonia than temporally correlative faunas from Bolivia and Uruguay, and indicates the presence of suitable habitats in mid-latitudes of Argentina for this hypselodont clade. Faunal affinities together with particular taxa from Quebrada Fiera appear to support a significant faunal provinciality in South America during the late Oligocene. http://zoobank.org/urn:lsid:zoobank.org:pub:9DF1C9A9-92ED-4C50-BB5A-738D075E5F54SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP