A Fossil Exhibit with Real Teeth: Dinosaur Bones Tell Unique Tale

Article excerpt

A young boy's intense gaze over the exhibit railing at the National Geographic Society's Explorers Hall captured what everyone in the room seemed to feel - a sense of awe.

They were staring at rows of blade-shaped teeth, eye sockets big enough to push a fist through, and the sleek, 5-foot-long jaw of a dinosaur.

"I sure wouldn't want to be caught by one of those if I was roaming the plains 65 million years ago," said Reg Murphy, president of the society, as the "Africa's Dinosaur Castaways" fossil exhibit opened at the Northwest museum. It will run until Sept. 8.

He was referring to the displayed replica of the recently excavated skull of Carcharodontosaurus, or "shark-toothed reptile," one of two major finds uncovered by the team of University of Chicago paleontologist Paul Sereno during an expedition to Saharan Morocco last summer.

"Carcharodontosaurus was the largest predator during the period from 65 million to 100 million years ago in Africa and probably preyed on plant-eating sauropods," Mr. Sereno said.

The dinosaur was discovered at the turn of the century by German scientist Ernst Stromer, Mr. Sereno explained, and "it rivaled Tyrannosaurus rex in both size and ferocity, but had a much smaller brain than its North American counterpart."

Mr. Sereno, 38, said these fossil discoveries shed light on the final chapter of dinosaur evolution on the isolated continent of Africa. "The pieces we found paint a picture of Africa's dinosaurs different from those on any other continent at the time," he said.

The earliest dinosaurs and their Jurassic descendants that lived more than 150 million years ago looked remarkably alike worldwide. But by the time Carcharodontosaurus appeared about 90 million years ago, the Earth's land had become a patchwork of separate continents.

The team's discoveries - bones differing from those of similar species found in other parts of the world - suggest that, once isolated, dinosaurs in Africa and other continents embarked on divergent evolutionary paths.

These finds, once embedded in sandstone, also provide evidence that today's Sahara Desert once was a flood plain similar to the Mississippi Delta, with flowing rivers edged by coniferous trees, said Mr. Sereno, whose team discovered nearly 50 different animal species.

Along with the enormous skull of the largest terrestrial animal ever to roam the Earth, a member of Mr. Sereno's team - a young assistant who was along to record findings and later provide educational outreach - stumbled upon the skeleton of a dinosaur never before known to exist.

Deltadromeus, or "delta runner," coexisted in the same environment as the Carcharodontosaurus, Mr. Sereno said.

Experts believe it was a speedy hunter with extraordinarily delicate and long limbs. (The exhibit reproduction stretches more than 25 feet.) Mr. Sereno declined to estimate how fast the dinosaur would have run, saying only that the beast "could not outrun a horse, but could certainly outrun a human."

Gabrielle Lyon, 24, the discoverer of the set of bones, said she found the fossils when she took a goat path to the bottom of a rough cliff instead of the steeper, more dangerous route taken by other team members. …