The cranial endocast of the early Miocene marsupial, Wynyardia bassiana: an assessment of taxonomic relationships based upon comparisons with recent forms.

Wynyardia bassiana, a possum-like marsupial from the early Miocene of Tasmania has long been considered to display skeletal features intermediate between the relatively primitive polyprotodont and the advanced diprotodont marsupials. Our examination of the latex endocast of the nearly intact neurocranium reveals that Wynyardia's brain is clearly phalangeroid in external morphology, resembling closely that of the extant phalangerid, Trichosurus vulpecula. These findings indicate that an unambigously phalangerid brain had evolved within the Diprotodonta, by 21 million years ago.