The largest carnivorous mammal that has ever existed in Australia still has many puzzles to solve. It lived in much of the island during the Pleistocene, between 1.6 million years and 46,000 years ago. Among the described species of this genus, Thylacoleo carnifex stands out, whose name means “killer bag lion”, however, it is popularly known as the marsupial lion of Australia. We still have a lot to learn about this species, and this lack of information leads to debates with very different opinions about its behavior.
the strongest bite
As is often the case with Australian fauna, we are dealing with a somewhat strange animal for the common parameters in other continents. In view of the reconstructions carried out and the characteristics that its skeleton shows, it seems to be a mixture between a feline and a kangaroo with special climbing abilities.
It was about 70 centimeters tall at the withers and 150 centimeters long at the end of its tail. They could weigh between 100 and 130 kilos, although some individuals could even reach 160 kilos.
The most striking thing when studying the fossil remains is its jaw, which is exceptionally large for its size. A study was commissioned to compare the bite force in relation to the body mass of both extinct and still living species. The results concluded that the most powerful bite was held by Thylacoleo together with the also extinct Priscileo roskellyae . A 100-kilogram specimen could bite as hard as a 250-kilogram African lion.
In fact, it is in its jaw that we find one of the characteristics that has led it to be considered the most specialized mammalian predator . To its sharp fangs we must add some pointed premolars that would be used to hunt large animals. Unlike a lion, which can bite its prey for more than ten minutes, Thylacoleo could not possibly extend its bite very long. However, with a single attack, its teeth allowed it to pierce flesh, certain bones, and major blood vessels, quickly taking down large prey such as Diprotodon , giant kangaroos, or Megalania, a species of oversized Komodo dragon.
Their forelimbs were more developed than their hindlimbs. It had retractable claws , a feature never seen in other marsupials. In this way, Thylacoleo ‘s claws remained sharp by being protected from wear. It had a semi-possible thumb that had an even larger claw that could have been used to grab and tear its prey.
According to recent studies, the tail could be muscular and rigid like that of kangaroos , which would allow it to rise on its hind legs in the form of a tripod, leaving its front legs free to grab its prey or to start climbing trees.
The biologist and paleontologist Richard Owen was the first to describe this species in 1859 from fossil skull and jaw fragments found in Lake Colongulac, in the Australian state of Victoria. Owen spoke of Thylacoleo as:
“One of the fiercest and most destructive predatory beasts.”
The discovery of new remains has made it possible to increase and complete information on this species. In 2018, a study was published about a new find, an almost complete specimen that has made it possible to investigate novelties such as the tail and the clavicle . The team’s conclusions propose the rigid tail that we have mentioned, however, the clavicle has a morphology that would make this animal a poor runner. Therefore, it has been described as a hunter specialized in ambushes or even that could alternate its predatory activity with a scavenging diet .
An ambush hunter
Although it reminds us of felines, Thylacoleo is a marsupial related to koalas, wombats and kangaroos. In fact, it is suspected that it had ancestry from diprotodont herbivores, but its origin generates debates with theories that do not achieve scientific consensus. Some suggest that the isolation of Australia meant that many of its herbivorous species could evolve into carnivorous animals as an adaptation to survive.
In 2008 rock art was discovered which appears to have depicted a specimen of Thylacoleo . The image shows a quadruped with a large jaw, powerful forelimbs, and prominent eyes, which may indicate a nocturnal hunter.
The painter included striped fur in his work, an attribute that would reinforce the idea that we are dealing with a skilled climber and an ambush hunter who surprised his prey by jumping from the trees. For this they needed such a camouflage , like tigers, which inhabit forested areas, instead of lions, which chase their prey in open spaces.
Therefore, perhaps it would be more accurate to call it the “marsupial tiger of Australia”. All in all, the closest structural and functional analog to Thylacoleo is the Tasmanian devil, Sarcophilus harrisi , precisely another scavenger and hunter.
The skull so specialized for hunting big game could have contributed to its extinction. Ineffective with small prey, the reduction of the Australian megafauna between 40,000 and 50,000 years ago, added to hunting by humans, were the main reasons that led Thylacoleo to disappear.
Wells, R. T. y Camens, A. B. 2018. New skeletal material sheds light on the palaeobiology of the Pleistocene marsupial carnivore, Thylacoleo carnifex. PLoS ONE 13, 12, e0208020. DOI: 10.1371/journal.pone.0208020.
Wroe, S. et al. 2005. Bite club: comparative bite force in big biting mammals and the prediction of predatory behaviour in fossil taxa. Proceedings of the Royal Society B 272, 1563. DOI: 10.1098/rspb.2004.2986.