A panda-like diprotodontid? Assessing the diet of Hulitherium tomasettii using dental complexity (Orientation Patch Count Rotated) and dental microwear texture analysis

Several groups of marsupial mammals have been cited as examples of functional convergence with placental mammals (e.g. Thylacinus cynocephalus (thylacine) and Canis lupis (gray wolf)), though detailed quantitative analyses have often revealed subtle differences between such groups. A less-well known purported case of convergence is that between the extant Ailuropoda melanoleuca (giant panda) and the extinct diprotodontid marsupial, Hulitherium tomasettii from the montane rainforest of Papua New Guinea. Because of its body weight and bizarre panda-like post-cranial morphology, H. tomasettii has been depicted as a specialist bamboo feeder. Here, we test this dietary hypothesis by using a multi-proxy approach that includes Orientation Patch Count Rotated (OPCR) and dental microwear texture analysis (DMTA). Specifically, we compare the dental complexity and DMTA of H. tomasettii to other diprotodontids and extant herbivores with similar cranio-dental features and/or post-cranial features, including extant bamboo feeders. We show that H. tomasettii does not display the high dental complexity or DMTA attributes exhibited in extant bamboo feeding taxa. Instead, low dental complexity and DMTA data suggest that H. tomasettii was neither adapted for consuming mechanically challenging food nor did it consume particularly tough or hard foods like the culm of bamboo, and was more akin to other diprotodontids and/or bilophodont browsers (e.g. browsing tapirs). Our results suggest that H. tomasettii was likely a generalised browser and not a specialised bamboo feeder. Collectively, the post-cranial morphology and diet of H. tomasettii may indicate a browser that was able to take advantage of vegetation higher up in trees and/or softer bamboo leaves.