The diet of Thylacoleo, the so-called ‘marsupial lion,’
has been a puzzle for decades. The jaws and teeth look dangerous and carnivorous, but Thylacoleo nests in the middle of an herbivorous clade of wombat-like marsupials.
That’s the problem.
Morphology and phylogeny provide the problem… and the answer to the diet of Thylacoleo. This answer could have been known decades earlier, but alas… the same taxon exclusion issue that pervades paleo was also present here.
One look at the palate of Thylacoleo documents a very different sort of mammal palate:
- The jawline curves laterally near the premolars
- Several molars seem to have fused to become one giant tooth
- There is an asymmetry in the lineup of the posterior teeth
In the large reptile tree (LRT, 1250 taxa) the closest living sisters to Thylacoleo, the sugar gliders, like Petaurus, should provide some sort of natural guidance as to what the giant sugar glider ate. And they do.
Sugar glider diet
From the Wikipedia page on sugar gliders: “Sugar gliders are seasonally adaptive omnivores with a wide variety of foods in their diet… In summer they are primarily insectivorous, and in the winter when insects (and other arthropods) are scarce, they are mostly exudativorous (feeding on acacia gum, eucalyptus sap, manna, honeydew or lerp). Sugar gliders have an enlarged caecum to assist in digestion of complex carbohydrates obtained from gum and sap.
To obtain sap and nectar from plants, sugar gliders will strip the bark off trees or open bore holes with their teeth to access stored liquid gum. Little time is spent foraging for insects, as it is an energetically expensive process, and sugar gliders will wait until insects fly into their habitat, or stop to feed on flowers. They are opportunistic feeders and can be carnivorous, preying mostly on lizards and small birds. They eat many other foods when available, such as nectar, acacia seeds, bird eggs, pollen, fungi and native fruits. Pollen can make up a large portion of their diet, therefore sugar gliders are likely to be important pollinators of Banksia species.”
Well, there you have it.
Little sugar gliders can be carnivorous. They can also strip bark off trees to get at the gum inside. That’s a rare diet. As sister taxa, giant sugar gliders, like Thylacoleo, were therefore likely also carnivorous and/or stripped bark off trees to get at the gum. For the latter odd reason the odd skull of Thylacoleo was likely adapted, and predation, if you insist, but predators don’t have the odd palate and teeth that Thylacoleo has.
We don’t have to provide a narrow dietary answer for Thylacoleo
because the diet of living sugar gliders is diverse. AND sugar gliders provide the long-sought carnivorous exception to this herbivorous clade.
Petaurus breviceps (Waterhouse 1839; Early Miocene to present; up to 30cm) is the extant sugar glider, a nocturnal squirrel-like marsupial able to climb trees and glide with furry membranes between the fore and hind limbs. An opposable toe is present on each hind foot. Sharp claws tip every digit.
Thylacoleo carnifex (Owen 1859; Pliocene-Pleistocene; 1.14 m long) was a giant sugar glider like Petaurus. Thylacoleo had the strongest bite of any mammal with the largest, sharpest molars of any mammal. It had fewer but larger teeth than Petaurus. The manus included retractable claws. The pes had a very large heel bone (calcaneum). This supposedly carnivorous ‘marsupial lion’ nests with herbivores. Pedal digit 1 likely had a phalanx and claw, but it has not been shown. Sugar gliders strip bark off of trees and the very odd teeth of Thylacoleo could have done the same on a larger scale.
Owen R 1859. On the fossil mammals of Australia. Part II. Description of a mutilated skull of the large marsupial carnivore (Thylacoleo carnifex Owen), from a calcareous conglomerate stratum, eighty miles S. W. of Melbourne, Victoria. Philosophical Transactions of the Royal Society 149, 309-322.
Waterhouse GR 1838. Observations on certain modifications observed in the dentition of the Flying Opossums (the genus Petaurus of authors). Proceedings of the Zoological Society of London. 4: 149–153.