New craniodental material of the typotherian notoungulates from the upper Oligocene of Mendoza, central-western Argentina and their taxonomical importance

Among the great diversity of Oligocene mammals from Quebrada Fiera (Mendoza Province, Argentina), three families of typotherian notoungulates are very abundant. Since the first paper on archaeohyracids in 2010 until the last fieldwork in 2016, numerous unpublished remains were added to the collection. The study of all these remains, together with some revised materials, allows us to provide new anatomical data and some taxonomic decisions on these groups. Within Hegetotheriidae, we present one of the most complete skulls of Prohegetotherium schiaffinoi known to date, providing descriptions of certain previously unknown features of the caudal cranium; MCNAM-PV 3984 is discarded as belonging to Hegetotheriopsis sulcatus, as recently suggested, and is considered as Hegetotheriinae indet., like other isolated large specimens and some teeth previously determined as Prohegetotherium sp.; and several well-preserved specimens add to the sample of the pachyrukhine Prosotherium garzoni, including a partial maxilla with erupting P2. Concerning Archaeohyracidae, Archaeohyrax suniensis is now better represented, recording several ontogenetic stages previously observed in the Bolivian sample of this species. Finally, within Interatheriidae, most new dental material belongs to Argyrohyrax proavus, but an isolated upper molar suggests the presence of a different Interatheriinae at Quebrada Fiera, more similar to the Bolivian Brucemacfaddenia boliviensis than to other Deseadan (late Oligocene) taxa.

Automated summary

This study focuses on the Oligocene mammals from Quebrada Fiera in Argentina and provides new anatomical data and taxonomic decisions on three families of typotherian notoungulates. The researchers present a detailed description of the skulls of Prohegetotherium schiaffinoi, provide new information on other species within Hegetotheriidae, record several ontogenetic stages of Archaeohyrax suniensis, and suggest the presence of a new Interatheriinae species at Quebrada Fiera.