Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: FRIDAY, October 14, 1994 TAG: 9410140100
SECTION: NATIONAL/INTERNATIONAL PAGE: A-9 EDITION: METRO
SOURCE: Associated Press
DATELINE: LENGTH: Medium
One, for example, is a meat-eating predator that looked like a scaled-up version of Velociraptor, the fictionalized villain of the movie ``Jurassic Park,'' or a scaled-down version of Tyrannosaurus rex. The other new dinosaur was a four-legged, plant-eating sauropod.
When the dinosaurs were alive, the region that is now arid desert was a lush, tropical habitat near the equator with conifer trees, streams and ponds.
The discoveries are leading scientists to question a long-standing assumption about how the breakup of the ancient supercontinent Pangaea affected dinosaur evolution. This is because the new African dinosaurs seem to have resembled their North American cousins, whose continent broke away long ago, more closely than they resembled the dinosaurs of South America, which was linked to Africa until more recent times.
``That was a surprise,'' said Paul C. Sereno, a University of Chicago paleontologist who led the group that found the skeletons. Sereno and colleagues published their findings in this week's issue of the journal Science.
When dinosaur evolution began, around 225 million years ago, there was just one land mass - Pangaea - and the great beasts are thought to have inhabited much of it. Then about 170 million years ago, Pangaea split in two, a northern section called Laurasia (including the future North America, Europe and Asia) and a southern portion called Gondwana (comprising the crustal plates that would become South America, Africa, India, Antarctica and Australia).
This event, according to the old assumption, split the dinosaur world into two parts, each of which would go on evolving independently and, therefore, gradually losing their resemblances to one another.
Then, about 40 million years later, Gondwana began to break up, and South America parted from Africa. The dinosaurs that Sereno found date from shortly after this time - the early Cretaceous, around 130 million years ago. This is why it was expected that African dinosaurs - relatively few of which have been found until now - would resemble South American types.
``Instead, we find that the ancestry of these two African dinosaurs can be traced to more ancient species in North America and elsewhere,'' Sereno said.
Sereno speculated that even though Pangaea had split, dinosaurs still were able to migrate between Laurasia and Gondwana over a land bridge that remained near the area of today's Gibraltar. If so, this would have allowed new evolutionary changes to spread throughout both land masses, keeping the forms of dinosaurs more or less similar everywhere. Sereno said there is some evidence that such a connection may have persisted until about the time South America parted from Africa.
As a result of the land bridge, Sereno said, all continents probably had representatives of the same major dinosaur groups. The differences that appeared in later times, then, would have been the result of some groups dying out in one place but not another.
Sereno has named the new predatory dinosaur Afrovenator abakensis, which he said means ``African hunter from In Abaka,'' the region of Niger where the bones were found. It stood seven feet tall at the hip and stretched 27 feet from head to tail.
The herbivorous dinosaur has not been named but is unusual because it represents a form - typified by broad teeth - that was thought to have become extinct more than 20 million years earlier. It was about 55 feet long. Its thigh bone is six feet long.
The expedition that found the bones took place last fall when Sereno and 11 team members outfitted six Land Rovers in London, ferried to France, drove to Marseilles, ferried to Algiers and then drove 1,500 miles into the Sahara, crossing from Algeria into Niger. In 29 days of digging, they turned up nearly six tons of dinosaur bones.
Sereno said he knew about the area because a French priest and paleontologist had spotted dinosaur bones in the region 50 years ago. In 1990, Sereno and a British Museum expedition relocated the old site and discovered, just 12 miles away, an even richer site - the one that yielded the new finds.
A television documentary about the expedition is to be broadcast Wednesday on PBS.
by CNB