Australia’s fearsome marsupial lion

New fossil finds have enabled the first reconstruction of a complete skeleton of the extinct ‘marsupial lion’, Thylacoleo carnifex.

The bones – which include the first full-length tail and collar-bones not previously known to exist – have opened a window into how the prehistoric beast’s bizarre features made it a deadly predator, according to a report on the discoveries published in the open access journal PLOS One.

Much like the Australian platypus (Ornithorhynchus anatinus), the marsupial lion was a weird mash-up of features. Weighing more than 100 kilograms, it was roughly the size of a modern-day jaguar. But unlike the jaguar, or its African lion namesake, Thylacoleo was a pouched marsupial, related to other antipodean icons such as the kangaroo, the koala and the extinct thylacine.

Marsupial lion bones in situ, during a dig in naracoorte in south australia.

Marsupial lion bones in situ, during a dig in Naracoorte in South Australia.

Credit: Steve Bourne

Thylacoleo’s muscular jaw – estimated to be the most powerful of any mammal – bore chisel-like front teeth and fused cheek teeth, reminiscent of a pair of gardening secateurs, the likes of which aren’t seen in any other mammal.

Its muscular forearms were topped off with fearsome hooked first claws. These were retractable – another unique feature not seen in any other marsupial. 

But added to this list of predatory features, are possum-like hind feet.

“Evolution has fashioned a hyper-carnivore from a herbivore ancestry,” explains palaeontologist Rod Wells from Australia’s Flinders University, who conducted the study with Aaron Camens from the South Australian Museum.

Now with the tail, “we’ve completed the jigsaw,” says Wells.

The new fossils were discovered more than a decade ago in limestone caves in Naracoorte in southern Australia, and further west in caves under the Nullarbor plain.

Combined with previously discovered remains, Wells and Camens reconstructed a complete Thylacoleo skeleton.

By measuring how the tail bends and flexes, and comparing it to live species, the researchers have been able to glean information not only about what Thylacoleo looked like, but also how it moved and hunted.

Thylacoleo had a stiff tail and lower back. Nevertheless, the presence of chevron bones, used by kangaroos to protect delicate blood vessels when the tail is bent, suggest that it was able to use its tail as a third leg of a ‘tripod’ when standing on its hind pair.

Armed with the notion that form follows function in biology, Wells and Camens looked to living marsupials for insights into Thylacoleo’s possible behaviour.

The closest analogue, says Wells, is the much smaller Tasmanian Devil (Sarcophilus harrisii), an animal about as distantly related to the marsupial lion as is possible for a marsupial to be. The similarity is therefore in function rather than evolutionary or genetic relatedness. 

“If you could actually see the living animal it would move very much like a Tasmanian Devil, with that strange sort of half-bound walk that they have,” says Wells.

Like the Tasmanian Devil, Thylacoleo was probably an ambush predator, rather than a pursuit hunter. It probably also scavenged dead animals, tearing flesh from their bones rather than crunching them like a dog.

It’s a terrifying thought: a super-sized Tasmanian Devil, lurking by a waterhole, ready to pounce and disembowel an unsuspecting diprotodon.

Even more terrifying: Thylacoleo likely lived alongside the early human inhabitants of Australia.

Like other Australian megafauna, the marsupial lion went extinct around 30,000 years ago, long after humans arrived on the continent at least 65,000 years ago.

A cave painting discovered in 2008 in northern Australia’s remote Kimberley region is thought to be the image of a striped Thylacoleo.

The co-existence of people and the marsupial lion is also preserved in some indigenous histories. There is a suggestion that Thylacoleo could even be the mythical bunyip, a creature that lurks near rivers and billabongs in stories from the Wemba-Wemba or Wergaia peoples of South Eastern Australia. 

When pastoralist William Adney sent Thylacoleo remains to Richard Owen at the British Museum of Natural History in 1843, he noted that “the blacks” referred to the fossils as “old men’s bones and some said they were the remains of the bunyip”.

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