First Crania and Assessment of Species Boundaries in Nimbadon (Marsupialia: Diprotodontidae) from the Middle Miocene of Australia

A comprehensive analysis of fossilized cranial material from Nimbadon lavarackorum, a middle Miocene marsupial, reveals significant intraspecific morphological variation within the species. This challenges previous distinctions between N. lavarackorum and its junior synonym, N. whitelawi, demonstrating that such variations likely fall within natural species boundaries rather than representing distinct taxa. The study employs both quantitative and qualitative analyses to assess cranial and dental dimensions, providing a benchmark for determining species boundaries in extinct marsupials. Findings suggest that N. lavarackorum was a relatively small (75–120 kg), possibly gregarious browsing species adapted to closed-forest habitats, with lower overall morphological variation compared to its contemporary Neohelos stirtoni, reflecting differences in body size, home range, and habitat preference.

Black, K. H., & Hand, S. J. (2010). First Crania and Assessment of Species Boundaries in Nimbadon (Marsupialia: Diprotodontidae) from the Middle Miocene of Australia. American Museum Novitates, 3678, 1–60. https://doi.org/10.1206/666.1