A new Leontiniidae (Notoungulata) from the Late Oligocene beds of Mendoza Province, Argentina

Abstract

The present paper deals with the leontiniid remains recovered from the Late Oligocene (Deseadan) levels of Quebrada Fiera, Mendoza Province, central-western Argentina. The material consists of an almost complete skull associated with 11 vertebrae, as well as some maxillary and mandibular fragments and postcranial elements of different individuals, enabling a life reconstruction. The comparative study allows morphological differences with respect to other Deseadan taxa to be established, such as Scarrittia, Leontinia, Ancylocoelus, Anayatherium and Elmerriggsia, leading to the proposal of the new taxon Gualta cuyana gen. et sp. nov. The new genus and species is close to Scarrittia canquelensis in having upper I1 more developed than I2-3, mainly by its greater crown-height, and the canine overlapping the P1; it differs from this species by the longer, narrower nasals, longer rostrum, I2 not reduced, P3-4 with shallow lingual sulcus, shorter cervical vertebrae, and shorter calcaneum, lacking navicular facet. The complete dentition and/or the larger I1 differentiate Gualta cuyana from Leontinia, Ancylocoelus and Anayatherium ekecoa, as well as from the Miocene Colpodon. The lingual sulcus on P3-4 is much shallower than in Scarrittia barranquensis, Leontinia, Anayatherium and Elmerriggsia. The phylogenetic analysis shows poorly resolved relationships among leontiniids; when using equal weights, the analysis shows that Gualta cuyana is more related to the species of Anayatherium and Scarrittia canquelensis, whereas under implied weights, the new taxon is basal to other Palaeogene taxa. Gualta cuyana adds to other endemic taxa of the peculiar Deseadan assemblage from Quebrada Fiera. The new leontiniid constitutes a low percentage of fossil mammals within the Quebrada Fiera fauna, as is also true for this family in Salla (Bolivia), but in contrast with some Patagonian localities or the Brazilian Tremembé Formation where leontiniids are the best-represented mammal group.