A bizarre type of giant land turtle thought to have gone extinct 50,000 years ago survived until recently on at least one small Pacific island.

Dozens of bones found in a 3,000-year-old archaeological site on Vanuatu belong to a previously undescribed species of meiolaniid, a turtle family that evolved 50 million years ago and resembled walking fortresses.

"This group of turtles is not known to have survived into the presence of humans. Now we can say that they met," said paleontologist Trevor Worthy of Australia's University of New South Wales.

The shell of one early meiolaniid species, known from fossils recovered in South America and named Stupendemys for its size, was 11 feet long and seven feet wide. The more modern Meiolania platyceps, found in Australia and Melanesia, had a relatively small five-foot-diameter shell, and weighed an estimated half-ton. All had armored club tails and horned heads.

(One species is even named Ninjemys, in honor of the Teenage Mutant Ninja Turtles, though M. platyceps looks much more like Super Mario Brothers 3-vintage Bowser, the King Koopa).

For 50 million years these defenses sufficed, but they weren't much use against humans – or so researchers suspected, lacking more than the scientific equivalent of hearsay. "In Australia, these turtles survived from the time of dinosaurs, through the Pleistocene. Then humans arrived. And then there weren't turtles anymore. I'd have thought humans had something to do with it, but there was no evidence," said Worthy.

The bones of the newly discovered species, named Meiolania damelipi and described Aug. 16 in Proceedings of the National Academy of Sciences, tell a clear story. They were found in a mound of animal bones discarded near a village of Lapita, a seafaring culture that 3,500 years ago spread east across Polynesia, Melanesia and Micronesia. The bottom layer of the garbage pile, dated to 3,000 years ago, had many meiolaniid bones. The top layer, dated to 2,800 years ago, had none.

The Lapita would have hunted the slow-moving turtles, burned forests to clear cropland, and brought pigs and rats that ate their eggs. Worthy estimates that Vanuatu could have supported tens of thousands of M. damelipi, but in just 200 years they were gone. And if giant land turtles were on Vanuatu, they were likely found on other Pacific islands, and hunted into oblivion.

This fits a pattern of human-preceded extinction recorded worldwide in large animals – collectively known as Pleistocene megafauna – but especially pronounced in the South Pacific, where every populated island lost between 30 and 50 percent of all animal species. These included giant iguanas, terrestrial crocodiles and dozens of birds. Bones of other now-extinct avian species were also found in the Vanuatu heap.

In tandem with these extinctions, the Lapitan culture seems to have vanished. Their distinctive ornate pottery, found across the western Pacific, disappears from the archaeological record.

As for whether there's a lesson to be learned, "I would have thought the lessons would have been learned already," said Worthy. "But people seem to be kind of slow catching on."

Images: 1) Meiolania platyceps at the American Museum of Natura History./Wikimedia Commons. 2) M. damelipi scapula bones./PNAS.

See Also:

Citation: Megafaunal meiolaniid horned turtles survived until early human settlement in Vanuatu, Southwest Pacific. By Arthur W. White, Trevor H. Worthy, Stuart Hawkins, Stuart Bedford, and Matthew Spriggs. Proceedings of the National Academy of Sciences, published online, August 16, 2010.

Brandon Keim's Twitter stream and reportorial outtakes; Wired Science on Twitter. Brandon is currently working on a book about ecological tipping points.