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. Smith dubs it "dinosaur heaven."
Africa's seemingly late appearance as a fertile ground for dinosaur fossil-hunting is traceable largely to its history as a geopolitical football, researchers say. Two world wars, wars for independence, and subsequent civil wars fueled in part by cold-war allegiances allowed for only brief windows of stability through which US and European researchers could peek at the continent's prehistoric treasures.
"Probably the greatest undertaking was in what's now Tanzania," says Hans-Dieter Sues, vice president for collections and research at the Royal Ontario Museum in Toronto and a professor of zoology at the University of Toronto. "They got spectacular material, and it forms one of the most important Jurassic dinosaur assemblages in the world to this present day."
Conducting their digs from 1909 to 1912, the team used slash-and-burn techniques to uncover fossil-bearing formations - literally cutting their way through the rainforest and burning out the undergrowth. The expedition employed hundreds of local tribesmen.
"Every bone had to be carried to the coast hundreds of kilometers away," Dr. Sues says. "It was a real testament to their perseverance."
About the same time, German researchers working in Egypt found the rich trove of fossils at the Bahariya Oasis, only to see the collection largely destroyed during Allied air raids during World War II.
Two French paleontologists moved into North Africa in the late 1940s and early '50s, yielding the first hint "that North Africa has these remarkable resources," Sues continues. They were followed in the 1960s by Dr. Taquet, who began exploring Niger after French mineral companies reported finding large numbers of fossils as they explored for uranium.
Even now, researchers say, they would love to poke around promising formations in Algeria and the Congo. But Islamic militancy in Algeria and the low-level war in the Congo are giving them pause.
Says one paleontologist, "The Congo has excellent prospects.
"We have hints of Cretaceous reptiles and Jurassic fish. I'd love to explore Algeria, but I'm worried about getting my throat cut, especially in rural areas where they don't like foreigners very much."
Still, when combined with those from other parts of the world, Africa's finds to date are helping to tell a story of the diversification of vertebrates, whose changes appear to have been driven as much by plate tectonics as by genetic mutation.
Sues describes an outline that begins in the late Triassic period, some 230 million years ago, when Pangea, driven by the molten heat exchanger beneath earth's crust, begins its inexorable split.
At that time, he says, Pangea was inhabited by early mammals and lizard-like reptiles that appear to be virtually the same throughout the supercontinent. "You see these same little animals in places as far apart as Nova Scotia, South Africa, and China. That's just extraordinary. There was nothing like it before in earth history and has been nothing like it afterwards."
With the breakup came the beginnings of regional variations in species among creatures in the northern and southern segments. Now, researchers in Africa are using Cretaceous creatures to help document the biological and ecological effects of further splitting as the southern segment, known as Gondwanaland, began to break apart.
Large animals are particularly good markers for continental drift, because they are less likely to "raft" their way on fallen trees or other vegetation over oceans thousands of miles wide to new shores, Sues says.
In 1997, for example, Dr. Krause and colleagues from India described finding the same fossil mammals from the late Cretaceous period in Madagascar and India, providing what the team calls the first evidence of a growing "cosmopolitansim" among Gondwanaland mammals from that period. The only other travelers from Gondwanaland had been seen in South America, another cast-off from the larger land mass.
As they work their sites and study the lessons fossils have to teach, several paleontologists also are working to erase the legacy of Indiana Jones-style approaches to collecting fossil specimens.
The shift is driven in no small part by increasingly tight restrictions host countries have placed on shipping evidence of Africa's prehistory heritage to other parts of the world.
In some cases, expedition leaders are looking for local students who have an aptitude for the work, inviting them to come to Western universities for graduate degrees, and then watching as they return to take up the work at home on their own.
"If you can take a person and train them to perform at an international level and they go back, those people will be leaders in their countries - they have abilities and knowledge that that country can use," says Louis Jacobs, a paleontologist at Southern Methodist University in Dallas and director of the university's Shuler Museum of Paleontology.
He has focused his own efforts on Malawi and the hunt for Cretaceous mammals.
Under his tutelage, a Malawian graduate student earned her PhD and returned home to take over work at the sites Jacobs had begun studying there. He and his team trained others to properly care for and display the fossils.
He notes, "Our group from the outset said, 'We're not going to practice scientific colonialism.'"
In other cases, expedition leaders are initiating small-scale aid projects.
In what Jacobs calls a model, SUNY's Krause has established a foundation that has endowed a school and teacher for the village in Madagascar near his team's excavation site.
The group also has sunk a well for the village, to provide clean water.
"We often had kids visit the site in the middle of the day. We had a great time showing them the site, but we wondered why they weren't in school like they should be," says Dr. Forster, who works with Krause. "They didn't have one."
"We thought the best thing we could to to thank these people for letting us come into their community every summer and dig holes in their landscape is at least to hire a teacher," she says.
As efforts to uncover Africa's fossilized flora and fauna expand, researchers note the universal interest in dinosaurs.
"People in Malawi are just as interested in dinosaurs as people in the United States are," Dr. Jacobs says.