Abstract

We describe Numbigilga ernielundeliusi new genus and species, a highly unusual marsupial represented by a partial right mandible with p2–m4 and a left upper molar from early Pliocene deposits at Bluff Downs, Queensland, northeastern Australia. Numbigilga n. gen. is characterized by a bunodont dentition with a number of striking specializations, and we refer it to Numbigilgidae new family. This taxon shares a range of dental apomorphies with various bunodont marsupial groups from the Late Cretaceous of North America and Paleogene of Gondwana. However, many of these features are most likely highly homoplastic within marsupials, reflecting convergent adaptations to a frugivorous-omnivorous diet. Other dental characters suggest possible affinities to the Australian order Peramelemorphia (bandicoots). Alternatively, Numbigilga may be a representative of an entirely new order of Australian marsupials. In the absence of more nearly complete specimens that might clarify its relationships, we refer Numbigilga to Marsupialia incertae sedis. We consider the distributions of a number of dental characters in bunodont marsupials and argue that no North American Late Cretaceous taxa can be convincingly referred to the order Polydolopimorphia. Thus, polydolopimorphians continue to be known only from the Cenozoic of Gondwana, with no fossil evidence that their initial divergences occurred in North America.

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