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Discoveries From the Land Down Under

Spanish Translation

By, Claudia Atticot

Australia's unique animals are among the most fascinating creatures on the planet. Roly-poly wallabies, duck-billed platypuses, cuddly koalas, flightless emus and prickly echidnas can be found only on that continent. But a recent fossil discovery reveals that Australia's ancient creatures were even more bizarre than their modern cousins.

About 500,000 years ago, kangaroos as tall as trucks, wombats weighing more than 400 pounds and fierce marsupial lions roamed the Land Down Under. Scientists call the animals "megamarsupials" for their giant size. A marsupial is a mammal whose infants develop in an external pouch.

Until a few years ago, scientists had assembled only bits and pieces of megamarsupial skeletons. The poor fossil record did not give researchers a clear idea of what the animals looked like or why they became extinct. In January, Australian scientists announced that they had found a treasure trove of fossils, including the first-ever complete skeletons of marsupial lions.

Locked Up In Caves

In 2002, a team of cave explorers were soaking up the sights on the Nullarbor Plain, in southern Australia. They came across several small openings in the ground. The group found that the holes led to a series of extensive caves.

The explorers were the first humans to set foot in the caves. They found "heaps of bones and complete skeletons of unusual animals that looked as fresh as if they had died yesterday," Gavin Prideaux told TFK. Prideaux, the lead scientist, examined the bones. He believes the animals accidentally fell through holes into the caves and died there.

In all, the scientists unearthed 69 well-preserved fossils of birds, mammals and reptiles. "Those animals had died a half-million years ago, but the caves had been locked up tight for so long that the fossils were barely covered in a layer of dust," Richard Roberts told TFK. Roberts, a scientist at the University of Wollongong, helped determine how old the bones were.

A giant wombat, two new species of parrots and eight new species of ancient kangaroos, including two tree-climbing varieties, were found. But scientists are most excited about finding complete skeletons of the marsupial lion, or Thylacoleo carnifex (thy-lack-oh-lee-oh car-nee-fex).

Eleven marsupial lion fossils were discovered. The lion was the largest carnivorous, or meat-eating, marsupial ever to roam Australia. The 220-pound prehistoric predator has fascinated scientists for more than a century. It had retractable thumb claws and a stronger jaw than any other animal its size.

Why Did They go Extinct?

Researchers had long believed that a drastic change in climate was responsible for the extinction of Australia's megamarsupials. But after studying the fossils found in Thylacoleo Cave, a team of scientists has developed a new theory. They believe that climate change alone cannot account for the animals' disappearance. "Current evidence tells us that the extinctions happened soon after people arrived, probably within a few thousand years. That points to humans as the cause," says Christopher Johnson, a scientist who consulted with the team. He argues that a low birth rate and human hunting led to the animals' decline.

More Digging, More Species

For now, scientists are keeping the exact location of the caves a secret. They are eager to explore the area to find out more about what happened to Australia's megamarsupials and learn more about how they lived. "(Before this find), very little was known about the species that lived in very dry areas," says Johnson. "No doubt, exploration of other sites will come up with even more species."

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