Out of Africa Come Fascinating Fossils ; Finds from Africa's Vastness Will Help Fill in Biology's History of the Dinosaurs' Demise

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As paleontology moves into the 21st century, its newest story may well turn out to be a cross between "Out of Africa" and "Land Before Time."

From Malawi, Niger, Morocco, Cameroon, and Egypt to Madagascar, Tanzania, and South Africa, dinosaur and mammal fossils emerging from layers of ancient sediments are giving researchers new insights into the variety and evolutionary history of earth's menagerie more than 65 million years ago.

The continent is probably best known for what many anthropologists see as its place as the cradle of human evolution, a story told through fossil finds unearthed in southern and eastern Africa since the mid-1920s and dating back at least 3.5 million years.

Yet paleontologists have been digging at many far older sites in Africa on and off at least since the early 1900s. Within the

past decade, as political stability has increased in many African nations, expeditions have returned with increasing frequency, turning the continent into a growing hotbed of research.

In particular, many paleontologists are interested in creatures from the Cretaceous period, which ranged from about 146 million to 65 million years ago. During this time, the sun was setting on the age of dinosaurs, and the supercontinent Pangea had split.

To the north lay what was to become Asia, Europe, and North America. To the south, today's Africa, India, Madagascar, South America, Australia, and Antarctica formed an enormous land mass.

Finds from Africa promise to fill important gaps in earth's biological history book, notes Paul Sereno, a paleontologist at the University of Chicago. Two weeks ago, he and colleagues described the life and times of a large fresh-water crocodile from the Cretaceous period, found in Niger.

The species was first discovered there by French paleontologist Philippe Taquet in the 1960s, who unearthed a skull. Dr. Sereno's group pulled out a largely intact skeleton, giving researchers more insights into the creature's place in its family tree and in its local ecological setting.

"We know so much about North American dinosaurs," Sereno says. "Western North America is particularly rich, richer probably than any other single continent," although Asia, particularly China and Mongolia, is providing stiff competition.

Yet, he continues, Asia and North America were connected during the Cretaceous period, so their fossils "are pretty similar. You end up with a very lopsided view of fossil history."

By contrast, he continues, "Africa is a tabula rasa." When he and his research team began working in a section of Niger a few years ago, he says, "there were two named things from this area. Yet from the expeditions we've led, there's an entire menagerie of animals we'll ultimately name and describe."

Nor is he alone. A team led by David Krause at the State University of New York in Stony Brook has been working in Madagascar since 1993 and has uncovered a variety of dinosaurs, birds, turtles, snakes, fish, lizards, mammals, and crocodiles.

"We're trying to get a snapshot of life at that time and in that place," says Catherine Forster, a SUNY-Stony Brook colleague who three years ago reported the discovery of a prehistoric bird whose skeleton blended birdlike features with those of theropod ground- dwellers, thus strengthening the evolutionary link between birds and their dinosaurian ancestors. "We're trying to develop a complete environmental picture of the area."

Earlier this year, an international team led by University of Pennsylvania paleontologist Joshua Smith reported the discovery of an enormous plant-eating titanosaurid at the Bahariya Oasis in Egypt, an area that paleontologists have not explored since 1935.

Drawn to scale, the new creature gives an African elephant all the presence of a toy poodle standing next to Michael Jordan. The area is so rich in fossils that Mr. …