Australogale leptognathus, gen. et sp. nov., a Second Species of Small Sparassodont (Mammalia: Metatheria) from the Middle Miocene Locality of Quebrada Honda, Bolivia

Abstract

The Sparassodonta (Mammalia: Metatheria) were the principal group of carnivorous mammals in Cenozoic South America and an important component of this continent’s terrestrial predator guild for nearly 60 million years. However, knowledge of the evolutionary history of this group is biased towards species larger than 1.5 kg from extra-tropical latitudes. Here, we describe a new, small sparassodont from the late middle Miocene (Serravallian) of Quebrada Honda, Bolivia, a locality in the middle latitudes (southern tropics) of South America (~ 22° S). This species, Australogale leptognathus, gen. et sp. nov., is represented by a partial, well-preserved dentary and can be distinguished from other sparassodonts by a combination of features including a p3 that is much smaller than p2, absence of a posterobasal heel on p2, a conical entoconid, absence of an entocristid on m1, and an entocristid on m2 that is lingual to the trigonid. This new species is among the smallest Neogene sparassodonts, with an estimated body mass of ~840 g. Australogale leptognathus expands the known taxonomic and morphological diversity of late middle Miocene sparassodonts and provides evidence that the group may have been as diverse during the late middle Miocene as during the late Oligocene and early Miocene.