Discovery changes view of plant-eating dinos

WASHINGTON — Could an elephant-size dinosaur with a skull so thin that a karate chop would have split it in two, teeth that lasted only a month and a brain that, yes, was the size of a walnut, ever be considered one of evolution's success stories?

Paul Sereno thinks so. The University of Chicago paleontologist on Thursday unveiled Nigersaurus taqueti, a strange creature that is helping rewrite theories about what long-necked, plant-eating dinosaurs looked like and how they behaved.

Nigersaurus appears to have spent a lifetime with its head in a hangdog position. Using a broad, tooth-filled mouth, it vacuumed through ferns and other ground cover growing, at most, a couple of feet off the ground. It couldn't even hold its head horizontal; getting leaves off trees was out of the question.

Many other dinosaurs — including the more famous and less bizarre Diplodocus — probably behaved similarly, using their long necks as ground-mowing booms, not treetop cherry-pickers, Sereno said.

"It took an extreme dinosaur to open our eyes to this cowlike behavior," he said Thursday at the National Geographic Society's headquarters in Washington, where a Nigersaurus replica was installed. "It is sort of silly to think that something wasn't doing this. But we had missed the cows of the Mesozoic."

Sereno and teams he headed recovered fossilized bones of the beast on expeditions in 1997 and 1999 to a remote region of the Sahara Desert in the West African nation of Niger. It took eight years for scientists to piece together bones of many specimens in Sereno's Chicago lab to get a nearly complete skeleton.

The skeleton puts a face and body on an animal that science previously knew only from a few scattered bones found elsewhere in the 1950s.

"Putting the whole thing together is a sort of a real eye-opener for paleontology," said Thomas Holtz, a University of Maryland vertebrate paleontologist not associated with Sereno's Niger expeditions. "This is a case of, after putting all the pieces of the puzzle together, the puzzle is more confusing than ever."

Other paleontologists said the new dinosaur will further dispel the notion that long-necked dinosaurs were the prehistoric equivalent of giraffes, holding their heads high overhead.

"It would be hard to imagine a more compelling argument against" that view, said Kent Stevens, a computer scientist at the University of Oregon who has done extensive research on dinosaur posture.

The dinosaur has several physical features that are extreme versions of adaptations seen in other grazing animals.

For example, many grazers have broad faces and prominent teeth at the front of the jaw so each bite can take in large amounts of food. This is needed because grass and other ground cover is low in nutritional value.

Nigersaurus' mouth is wider than its skull, and it is the only terrestrial animal with that feature. Furthermore, all of its teeth are incisors, lined up to form a single clipping mechanism just under its lips.

Material from the Chicago Tribune and Reuters is included in this report.