Chew on this! The diet of an extinct "panda-like" marsupial from New Guinea

What did the “Beast of Huli" eat? The diet of this bizarre extinct marsupial, which had similarities to both giant wombats and pandas, has remained a mystery. PhD student Joshua White, with coauthors, examined the teeth of this species to help answer these questions.

More than 30 years ago, the Australian Museum’s Professor Tim Flannery discovered a bizarre extinct marsupial from the remote highlands of Papua New Guinea. He named it Hulitherium, meaning “Beast of Huli” after the indigenous people who lived in the area where the remains of this unusual beast were discovered. Hulitherium belonged to an extinct group of wombat-like marsupials, called Diprotodontidae, which roamed the rainforests of New Guinea during the Pleistocene period¹. Like most fossil discoveries, there wasn’t an abundance of remains from this animal, but the fossils described include various teeth, skull fragments, forelimbs and hindlimbs. Fortunately, the remains discovered were enough to identify this fossil as a new and unique genus and species, Hulitherium tomasettii.

The family Diprotodontidae were large quadrupedal, herbivorous marsupials of Australia and New Guinea that looked perhaps like overgrown or giant wombats. The largest of which was Diprotodon optatum of Australia, weighing in at approximately 3 tonnes and 1.6 metres tall at the shoulders, the largest marsupial that ever lived. The fossil record of New Guinea includes a variety of diprotodontids, classified in the genera Kolopsis, Kolopsoides, Maokopia, and Hulitherium. When originally described, Hulitherium was proposed to be a possible bamboo feeder because it shared similar traits to the giant panda (Ailuropoda melanoleuca), including its post-cranial morphology, weight, and habitat¹. Based on its joints, Hulitherium was also capable of rearing up on its hind legs, enabling it to grasp at food that was out of reach for other herbivores.

To test whether Hulitherium was a bamboo specialist feeder, my research included two different methods to evaluate the diet of Hulitherium - and included assessing the fossil molars of the species, in the Australian Museum Palaeontology Collection. One of these methods is called dental complexity analysis, which is a type of topographical analysis used to map out teeth and assess how many features are available to grind plant material². In our recent study, my co-authors and I applied this principle to the chewing surfaces of molars, and measured regions of low areas and high areas to calculate how ‘complex’ the chewing surfaces are². The more complex the chewing surfaces of the tooth are, the more likely that the organisms consumed fibrous vegetation because processing this type of food required sophisticated molars. Previous studies that used this same method indicated living species that consumed bamboo have a much higher level of molar complexity than other diet categories (herbivores, omnivores and carnivores)³. Our results show that Hulitherium did not possess the same complexity as modern-day bamboo feeding specialists, such as the giant panda, therefore we concluded that it most likely did not primarily consume tough fibrous vegetation like bamboo.

The second method we applied was dental microwear texture analysis (DMTA), which examines the scratches caused by chewing food and tooth-on-tooth interactions. DMTA has previously been applied to studying other species of diprotodontids, including Diprotodon and Zygomaturus⁴. We examined the scratches on the molar rows of Hulitherium specimens and compared these to other extinct diprotodontids from previous studies; we also compared them to bamboo feeding taxa, including the giant panda and the Andean bear (Tremarctos ornatus). Our results demonstrated that microwear seen on the teeth of Hulitherium is completely different to that seen in the giant panda.

Using a combination of dental complexity and dental microwear analysis, we were able to reconstruct the diet of this ancient and misunderstood giant wombat. Our research shows that Hulitherium most likely did not eat bamboo like giant pandas, and instead likely fed on softer plants like grasses and leaves. This study also shows the importance of applying quantitative methods to test for assumed convergence between distantly related taxonomic groups, such as marsupials and placentals.

Joshua White, PhD candidate, Australian National University and Australian Museum Research Institute.