Tree-climbing in search of fruit: an ancient arboreal marsupial megafrugivore from the Miocene of Australia

Abstract

Diprotodontids, a group of large-bodied wombat-like marsupial herbivores, were broadly distributed in Australasian Cenozoic deposits. While most diprotodontids were terrestrial quadrupeds and are often compared to placental herbivores like rhinoceros and hippopotamuses, the zygomaturine diprotodontid Nimbadon lavarackorum, based on its post-cranial morphology, is thought to have occupied the treetops. Understanding the dietary ecology of N. lavarackorum during the Miocene can help clarify potential motivations for an arboreal lifestyle. Here, we conducted dental microwear texture analysis (DMTA) and stable isotope analysis (SIA) of N. lavarackorum specimens from the Riversleigh World Heritage Area and compared them to analogous extant mammals to assess the likelihood that these tree-dwelling marsupials occupied a unique ecological niche during the Miocene in Australia—arboreal megafrugivores. The DMTA of N. lavarackorum (i.e., low anisotropy and high complexity) is most similar to extant mammals that include a high proportion of fruit in their diet and is inconsistent with and statistically distinct from obligate folivores. Stable carbon isotopes of N. lavarackorum also indicate the consumption of C3 food sources, consistent with the consumption of 13C enriched fruit in a C3 forest environment. Fruits may have been a motivation for this ca 70 kg marsupial moving into or staying in the treetops—an ecological niche that is currently unoccupied in Australia today.Larisa DeSantis [larisa.desantis@vanderbilt.edu], Department of Biological Sciences, Vanderbilt University, Nashville, TN 37232, USA; Department of Earth and Environmental Sciences, Vanderbilt University, Nashville, TN 37240, USA; Michael Archer [m.archer@unsw.edu.au], Earth and Sustainability Science Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, 2052, Australia; Karen Black [k.black@unsw.edu.au], Earth and Sustainability Science Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, 2052, Australia; Suzanne Hand [s.hand@unsw.edu.au], Earth and Sustainability Science Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, 2052, Australia; Vera Korasidis [vera.korasidis@unimelb.edu.au], Department of Geography, Earth and Atmospheric Sciences, University of Melbourne, Parkville, VIC, 3010, Australia.