Wednesday, February 24, 2010

Ancient Man-eating Crocodiles

Researcher: horned, man-eating crocodiles once roamed Africa

A University of Iowa researcher and his colleagues have found evidence in existing fossil collections that horned crocodiles lived in the Olduvai Gorge region of Tanzania, Africa, about two million years ago.

"Olduvai Gorge is the location of many key discoveries of early human ancestors, and these crocodiles appear to have dined on them," said Chris Brochu, associate professor of geoscience in the UI College of Liberal Arts and Sciences. Brochu is the co-author of an article published in the Feb. 24 issue of the journal PLoS ONE (Public Library of Science) that describes a new species of crocodile.

"So, what I've got is a horned, man-eating crocodile," said Brochu. "In fact, its name is Crocodylus anthropophagus, and 'anthropophagus' literally means 'eater of people.'"

Crocodylus anthropophagus would have been about as large as its living cousin, the Nile crocodile, which can reach lengths of almost 20 feet and weigh up to a ton. The early humans walking along the lake and stream margins that used to exist at Olduvai Gorge were smaller than people of today and would have been in grave danger if they got too close to the water, according to Brochu.

"The bones of early humans have been found in rocks of the same age in Olduvai Gorge showing bite marks made by crocodiles," he said.

A crocodile that ate humans would have been frightening enough, but this variety also had horns.

"Not antlers or anything, but the back of the skull was somewhat fancier than in most living crocs," he said. "Two living crocodiles -- the Cuban and Siamese crocodiles -- also have horns, but those of the Olduvai crocodile were more prominent." Of course, horns probably would have given the crocodile a devilish appearance, as if that were needed on a man-eating crocodile.

Brochu and his colleagues based their conclusions on fossils collected over many decades. Some were collected in 2007 by a team led by Robert Blumenschine of Rutgers University and Jackson Njau, then of the National Natural History Museum of Tanzania. But others were collected as long ago as the 1930's and kept in museums in Kenya and the United Kingdom. Most of these fossils, by themselves, are fragmentary and not very impressive, but together, they reveal a crocodile different from any of its living relatives.

"It would have looked more or less like a Nile crocodile except for a deeper snout and, of course, the horns," Brochu said.

Apart from the very scary image projected by the beast, Brochu said that the discovery of Crocodylus anthropophagus teaches us something new about the variety of crocodiles to be found in pre-historic Africa.

"The fossil evidence is geologically fairly young, at just under two million years. We knew crocodiles were more diverse in the geological past, but we assumed their diversity was much lower as recently as 2 million years ago. Crocodile diversity in Africa remained higher than at present for longer than we had thought," he said.

Brochu's co-authors are Njau, Blumenschine and Llewellyn Densmore of Texas Tech University.

STORY SOURCE: University of Iowa News Services, 300 Plaza Centre One, Iowa City, Iowa 52242-2500