Prehistoric 'Tasmanian Tiger' was a Tiny Killer

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Nimbacinus dicksoni, a thalycine-like marsupial from the mid-Miocene.
Anne Musser

An extinct marsupial hunter only the size of a fox may have hunted prey larger than itself, researchers say.

Kasey-Dee Gardner gets a behind-the-scenes look at how information is extracted from ancient fossils.
Junchang Lü

This predatory ability makes the ancient creature different from its most recent living relative, the also-extinct thylacine, or "Tasmanian tiger." The last known wild thylacine was shot in 1930, and the last captive member of the species died in a zoo in 1936.

Hunting apparently helped drive the species to extinction. People targeted the dog-like Tasmanian tigers because they believed that the animals killed sheep; in fact, a 2011 study published in the Journal of Zoology found that the creatures' jaws were too weak to take down large prey, and that they would have only killed animals smaller than themselves.

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The new study analyzed an exceptionally well-preserved whole skeleton of an extinct relative of these last thylacines, known as Nimbacinus dicksoni; the specimen dates to about 11.6 million to 16 million years old.

"The discovery of an entire skeleton of Nimbacinus was a truly amazing finding, particularly as it is was in such good condition," said study author Stephen Wroe, a zoologist and paleontologist at the University of New England in Australia.

Tiny lions and carnivorous kangaroos

The marsupial carnivore was about the size of a very large housecat or a small fox, weighing about 11 pounds (5 kilograms). "Its face looked like a cross between a cat and an opossum," said study lead author Marie Attard, a zoologist at the University of New England in Australia. [Marsupial Gallery: A Pouchful of Cute]

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The modern thylacine (Thylacinus cynocephalus)was larger, comparable in size to a medium-sized or large dog. Modern thylacines weighed in at between 40 and 70 lbs. (20 to 30 kg).

Paleontologists discovered the fossil in the mid-1990s in the Riversleigh World Heritage Area in Australia. In ancient times, warm, humid, lowland rainforests covered this region — then, about 10 million to 15 million years ago, it became progressively cooler and drier, transforming into dry open woodlands and grasslands.

Nimbacinus belonged to an extinct family of marsupial carnivores known as the thylacinids, consisting of at least 12 known species. Nimbacinus may have lived in ancient Riversleigh with several other thylacinid species, along with marsupial lions smaller than a housecat and small carnivorous kangaroos, potentially competing with them all for prey.

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"As a medium-sized carnivore, Nimbacinus was likely hunted by larger meat-eaters, including snakes, ground-dwelling crocodiles and larger species of marsupial lions," Wroe told Live Science.

Aside from studies of the recently extinct thylacine, most knowledge about thylacinids comes from skull fragments, limiting what scientists could deduce about the animals. The newly unearthed Nimbacinus skull, however, helped Attard and her colleagues reconstruct how this creature may have lived.