Marsupial Lion

Scientific name: Thylacoleo carnifex Scientific classification:

Phylum: Chordata

Class: Mammalia

Order: Diprotodontia

Family: Thylacoleonidae

Thylacoleo Carnifex
Marsupial Lion—The marsupial lion is an Australian oddity. Its grasping thumb and fearsome teeth are clearly visible in this image. (Rod Wells)

When did it become extinct? This marsupial appears to have gone extinct approximately

40,000 years ago. Where did it live? The marsupial lion was found only in Australia.

The word marsupial conjures up images of cuddly creatures like the kangaroo, koala bear, and wombat, but many thousands of years ago, some very different marsupials stalked Australia, and one of these, the marsupial lion—a relative of the wombats and kangaroos—was probably the most bizarre pouched mammal that has ever lived. Sir Richard Owen, the renowned Victorian paleontologist, was first to describe this animal from a small collection of skull fragments, and in a 1859 Royal Society paper he said these bones must have come from "the fellest and most destructive of predatory beasts." He described it as a marsupial "lion." For many years, the deductions of Richard Owen were questioned as this was an extinct marsupial whose closest relatives were vegetarians. However, over time, more remains of this animal came to light, and in 1966, the first almost complete but heavily calcium carbonate-encrusted skeleton was discovered. This reawakened the debate about the feeding habits of this strange animal. The specimen proved difficult to prepare, but then, in 1969, better preserved specimens were discovered in the Naracoorte Caves, which proved beyond any reasonable doubt that Owen's long-extinct marsupial must have been a meat eater, not simply a scavenger either, but, very probably a well-adapted predator.

Since the 1960s, more skeletal remains have come to light, largely from cave deposits, and the marsupial lion has secured its place as one of the most remarkable mammals that has ever lived. In terms of size, the marsupial lion was about the same size as a modern lioness. They were around 75 cm at the shoulder and 150 cm long, and it has been estimated that the heaviest individuals were around 160 kg. Scientists can tell a great deal about where an animal spent its time by looking at its bones, and although it has been suggested that this marsupial was an animal capable of climbing trees, it is now believed that the marsupial lion skulked around on the ground, where it ambushed its prey and perhaps dragged it into caves or up into trees, as leopards do. Not only can we tell where an extinct animal lived, but we can also get a good idea of how it moved by looking at the proportions of the limbs, and it seems that this marsupial lion was no long-distance athlete; instead, it probably ambled about, employing short bursts of speed when the need arose.

The most amazing thing about this animal's skeleton is the skull—it's big and heavy, with some incredible teeth. This marsupial had the most specialized dentition of any carnivorous mammal. Carnivorous placental mammals have enlarged canine teeth for stabbing their prey, but the marsupial lion's canines are small and probably close to useless. The two pairs of incisors, on the other hand, are big and pointy, giving the skull an appearance that is reminiscent of a large rodent. Further down the mouth are enormous premolars that can be as much as 60 mm long. These incredible cheek teeth must have worked like a pair of bolt cutters—slicing through the flesh of prey—powered by the big jaw muscles. The marsupial lion's other intriguing weapon was the clawed thumb on each of its forepaws. Although this digit wasn't a true opposable thumb like ours, it could still be used to exert a very powerful grip, driving the sharp, retractable claw into whatever unfortunate victim the marsupial lion had captured. The presence of this thumb is another reason for the belief that the marsupial lion was a tree-dwelling creature as it would have enabled a good grip on branches and tree trunks; however, it is now widely believed that the thumb was primarily for grabbing and subduing prey. Once the prey was immobilized, the fearsome teeth could be brought into action to deliver the killer bite. The pointy incisors were probably used to break the neck and sever the spinal cord, before the heavy-duty premolars were used to bite chunks of flesh from the dead body of the prey.

Bones can provide us with a sketch of how an animal lived, but for the fine detail, we must resort to deduction. For example, we can never know for sure what animals the marsupial lion preyed on or how it hunted them, but its size and teeth lead us to the conclusion that it must have killed and eaten fairly large animals. In the same cave deposits that have yielded the remains of the marsupial lion, paleontologists have found the hind leg bones of kangaroos and wombats bearing large, opposing, V-shaped cuts that perfectly match the cheek teeth of the marsupial lion, suggesting that they were the victims of this predator. We can be fairly certain that the marsupial lion was a specialist predator because it possessed so many unique features that bear no resemblance to any other predatory marsupials we know, alive or dead. We do know that the marsupial lion shared its home with that other great antipodean predator, the thylacine, and for two top predators to have coexisted in space and time, they must have lived in quite different ways. It's plausible to think of the thylacine as a wolflike predator, using its stamina to chase down prey, and the marsupial lion as more of an ambusher, taking its prey unaware and dispatching it with its battery of weapons.

Along with many of the other unusual mammals that once roamed Australia, the marsupial lion became extinct around 40,000 years ago. This date coincides with a period of increasing aridity in Australia, which reached a climax some 20,000 years ago and an increase in the abundance of charcoal in the fossil record, suggesting a change in the frequency of fires. We also know that humans reached Australia around 60,000 years ago. Humans undoubtedly hunted the prey of the marsupial lion, and it could have been a combination of competition with humans and a fire-induced vegetation change brought about by humans as well as climate change that forced these remarkable Australian mammals into extinction.

♦ The mammals are divided into three groups: the monotremes (duck-billed platypus and echidnas), marsupials, and placentals. The latter have become the most widespread and successful of all the mammals, while the marsupials are at their most diverse in Australia and South America. As marsupial females give birth to an embryo that spends the rest of its early development locked onto a teat in a pouch (marsupium), the evolution of wholly aquatic forms was impossible.

♦ Some recent scientific research showed that, pound for pound, the marsupial lion had one of the strongest bites of any predatory, land-living mammal. The bite of a 100-kg marsupial lion was at least as powerful as that of a 250-kg lion.

♦ The Nullarbor Plain in Australia is riddled with cave systems, some of which are connected to the surface by sinkholes. In 2002, a group of cavers exploring one of these tunnels found a chamber containing the bones of numerous, long-dead beasts spanning a period of time from 195,000 to 790,000 years ago (see the "Extinction Insight" in this chapter). These animals had been roaming around on the plains and had tumbled to their deaths through the cave entrance. The cavers' torches illuminated the finest marsupial lion skeletons that have ever been found—lying on the cave floor in the same position in which they had died thousands of years previously.

Further Reading: Wroe, S., C. McHenry, and J. Thomason. "Bite Club: Comparative Bite Force in Big Biting Mammals and the Prediction of Predatory Behaviour in Fossil Taxa." Proceedings of the Royal Society B: Biological Sciences 272 (2005): 619-25; Prideaux, G.J., J. A. Long, L. K. Ayliffe, J. C. Hellstrom, B. Pillans, W. E. Boles, M. N. Hutchinson, R. G. Roberts, M. L. Cupper, L.J. Arnolds, P. D. Devine, and N. M. Warburton. "An Arid-Adapted Middle Pleistocene Vertebrate Fauna from South-Central Australia." Nature 445 (2007): 422-25.

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    Why did the marsupial lion became extinct?
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    Where did Thylacoleo live south australia?
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