Tuesday, July 29, 2008

Skull of Large Extinct Primate Reconstructed

lemur skullAn extinct giant lemur has just gotten a high-tech makeover.

Researchers have virtually glued together newly discovered skull fragments from a species of the rare primate into a nearly complete computer rendering of the skull.

And a new study of this virtual reconstruction of Hadropithecus stenognathus suggests the animal boasted a body size rivaling a large male baboon. A red-ruffed lemur living in Madagascar today weighs about 9 pounds (4 kg). The extinct lemur would have tipped the scales at about 65 pounds (29 kg).

The nearly complete virtual skull, described this week in the journal Proceedings of the National Academy of Sciences, is one of only two known skulls of the species.

"This was an extremely rare lemur," said Ian Tattersall of the American Museum of Natural History in New York, who wrote a commentary on the study in the same issue of PNAS. "It was only known from one adult cranium, apart from the one that's been reconstructed now."

The new research builds on skull fragments from H. stenognathus discovered in 1899 by a professional fossil collector, Franz Sikora, in the Andrahomana Cave in Madagascar. In 2003, anthropologist Natalie Vasey, now at Portland State University, led a team that returned to the cave, where they excavated new cranial fragments and limb bones of the elusive creature.

Back at their home institution of Penn State, Vasey's colleagues Timothy Ryan and Alan Walker imaged the new fossils using computed tomography scanning. Along with CT scans from the past specimens, the team developed a 3-D picture of the lemur's skull. The images showed H. stenognathus sported one of the largest brains relative to body size of any known prosimian (a primitive primate group comprising lorises, lemurs and bushbabies, all of whom have wet, sensitive noses).

Its skull had a large, bony crest similar to that seen in gorillas, where powerful chewing muscles attached. The evidence, the researchers say, suggests this lemur ate hard foods, such as seeds and nuts.

The research sheds light not only on a rare lemur, but also on a batch of lemur species on Madagascar.

"It's important to understanding the full spectrum of diversity among the lemurs," Tattersall told LiveScience. "When you go to Madagascar today you only see the tip of the iceberg, as it were, of the entire fauna as it would've been before humans got to Madagascar."

Some 160 million years ago, Madagascar began to split off from the supercontinent known as Gondwanaland. By about 124 million years ago, the island took up its current spot on the globe. Secluded geographically from other lands, Madagascar developed its own unique flora and fauna.

The lemurs' original ancestor popped up on Madagascar and diversified ultimately into eight families, of which three are now extinct. When humans reached Madagascar some 2,300 years ago, several lemur species got wiped out.

The big ones went first.

"There was a huge range in size of lemurs and all the big ones were driven to extinction by human beings," Tattersall said. "They were easier to hunt, I think. They were slower moving; they were easier to find; they were more desirable to hunt; they had lower reproductive turnovers, more vulnerable."

Several lemur species are still endangered today, mostly due to deforestation, but also because of hunting and trapping, according to the National Museum of Natural History.


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