Thylacoleo (Greek for "marsupial lion"); pronounced THIGH-lah-co-LEE-oh
Plains of Australia
Pleistocene-Modern (2 million-40,000 years ago)
Size and Weight:
About five feet long and 200 pounds
Leopard-like body; powerful jaws with sharp teeth
About Thylacoleo (the Marsupial Lion)
It's a commonly held misconception that that the giant wombats, kangaroos and koala bears of Pleistocene Australia were only able to prosper thanks to the lack of any natural predators. However, a quick glance at Thylacoleo (also known as the Marsupial Lion) puts the lie to this myth; this nimble, large-fanged, heavily built carnivore was every bit as dangerous as a modern lion or leopard, and pound-for-pound it possessed the most powerful bite of any animal in its weigh class--whether bird, dinosaur, crocodile or mammal. (By the way, Thylacoleo occupied a different evolutionary branch from saber-toothed cats, exemplified by the North American Smilodon.) See a slideshow of 10 Recently Extinct Lions and Tigers
As the largest mammalian predator in an Australian landscape teeming with oversized, plant-eating marsupials, the 200-pound Marsupial Lion must have lived high on the hog (if you'll forgive the mixed metaphor). Some paleontologists believe that Thylacoleo's unique anatomy--including its long, retractable claws, semi-opposable thumbs and heavily muscled forelimbs--enabled it to pounce on its victims, quickly disembowel them, and then drag their bloody carcasses high up into the branches of trees, where it could feast at its leisure unmolested by smaller, peskier scavengers.
One odd feature of Thylacoleo, albeit one that makes perfect sense given its Australian habitat, was its unusually powerful tail, as evidenced by the shape and arrangement of its caudal vertebrae (and, presumably, the muscles attached to them). The ancestral kangaroos that coexisted with the Marsupial Lion also possessed strong tails, which they could use to balance themselves on their hind feet while warding off predators--so it's not inconceivable that Thylacoleo could tussle for short periods on its two hind feet, like an oversized tabby cat, especially if a tasty dinner was at stake.
As intimidating as it was, Thylacoleo may not have been the apex predator of Pleistocene Australia--some paleontologists claim that honor belongs to Megalania, the Giant Monitor Lizard, or even the plus-sized crocodile Quinkana, both of which may have occasionally hunted (or been hunted by) the Marsupial Lion. In any case, Thylacoleo exited the history books about 40,000 years ago, when the earliest human settlers of Australia hunted its gentle, unsuspecting, herbivorous prey to extinction, and even sometimes targeted this powerful predator directly when they were especially hungry or aggravated (a scenario attested to by recently discovered cave paintings).