U-M researchers study toothy, ground-feeding dinosaur

November 15, 2007
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ANN ARBOR—Two paleontologists from the University of Michigan are members of a team that discovered and spent the past decade making sense of a bizarre dinosaur with a mouth that worked like a vacuum cleaner, hundreds of tiny teeth and a paper-thin spine.

A reconstruction of the dinosaur’s skeleton, along with a fleshed-out model of the head and neck and the actual, 110-million-year-old fossils, will be unveiled Nov. 15 at the National Geographic Society in Washington, D.C. Details of the dinosaur’s anatomy and lifestyle will be published online the same day in the journal PLoS ONE, and will also be featured in a cover article, “Extreme Dinosaurs,” in the December 2007 issue of National Geographic magazine.

“The specimen was found almost exactly 10 years ago,” said Jeff Wilson, an assistant professor of geological sciences who was on the expedition to the Sahara—led by paleontologist Paul Sereno of the University of Chicago—during which the dinosaur was discovered. “We have been actively poring over the bones of this animal for the past decade and we now have the first detailed look at one of the most bizarre-looking dinosaurs. We have made some exciting discoveries about its lifestyle too, but many mysteries remain.”

Originally named by Sereno and his team in 1999 with only a few of its distinctive bones in hand, Nigersaurus taqueti was a plant-eating, younger cousin of the more familiar North American dinosaur Diplodocus. Barely able to lift its head above its back, Nigersaurus grazed more like a cow than a giraffe, mowing down mouthfuls of greenery that consisted largely of ferns and horsetails.

The dinosaur’s oddest feature was a broad, straight-edged muzzle, which allowed its mouth to work close to the ground. Unlike any other plant eater, Nigersaurus had more than 50 columns of teeth, all lined up tightly along the front edge of its squared-off jaw, forming, in effect, a foot-long pair of scissors.

Wilson’s graduate student John Whitlock studied those teeth in detail.

“The teeth are one of our best lines of evidence for figuring out how and what these sauropods ate,” Whitlock said. “The small facets and abrasions on the teeth have a pattern of microscratches and pits that represent the animal’s last few meals, which tells us what caused the teeth to be worn down. In this case, what we see is a pattern consistent with eating soft vegetation.”

The researchers write in the PLoS ONE article that Nigersaurus’ downwardly deflected muzzle may characterize most diplodocoids, such as North America’s Diplodocus. “Some of these unusual sauropods thrived to become the pre-eminent ground-level feeders of the Mesozoic,” Wilson said.

Jaw design was not Nigersaurus’s only odd characteristic: It had a backbone that was more air than bone.

“The vertebrae are so paper-thin that it is difficult to imagine them coping with the stresses of everyday use, but we know they did it, and they did it well,” Wilson said.

The fossil area, in the present-day nation of Niger, was home to the enormous extinct crocodilian nicknamed SuperCroc as well as the likely fish eater Suchomimus, both found by Sereno and both on the prowl for Nigersaurus some 110 million years ago. At that time the African continent was just beginning to free itself of land connections it inherited as a central part of the ancient supercontinent Pangaea. Nigersaurus’ closest relative has been found recently in Spain.

In addition to Sereno, Wilson and Whitlock, coauthors on the PLoS ONE paper include Lawrence M. Witmer of Ohio University, Abdoulaye Maga and Oumarou Ide of the University of Niamey in the Republic of Niger, and Timothy A. Rowe of the University of Texas at Austin. The research was funded by the National Geographic Society, The David and Lucile Packard Foundation, the Pritzker Foundation and the Women’s Board of the University of Chicago. Sereno is a National Geographic Explorer-in-Residence.

 

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