"It was one of the greatest last chapters of an expedition," Sereno said.
Team member Hans Larsson, now an assistant professor at McGill University in Montreal, spotted a jawbone and then, about 2 feet (0.6 meter) away, the rest of the skull of the Rugops.
"It was hard to see which end was the front, but we quickly realized we were looking at a braincase, and that it was probably an abelisaur—a huge find," Sereno said. "I knew minutes after we had discovered it that we had got the final crown of this lineage."
The 30-foot-long (9-meter-long) Rugops primus had a short and round snout, tiny teeth, and a permanent smile on its jaw. The small, wrinkle-faced head—the name means "first wrinkle face"—was covered with scales or surfaced armor, and riddled with arteries and veins. Sereno believes it's not the kind of head designed for fighting or bone crushing but for scavenging.
"It's a dinosaurian version of a vulture," Sereno said. "You have an animal that's sticking its short, blunt snout into things and gnawing and pulling with its big, strong neck."
The dino species also has two neat rows of seven holes along its snout. Sereno speculates the holes anchored something ornamental, used by the animal for display. "This is really distinctive," Sereno said. "I've never seen that in any other carnivore."
Continental Drift
During an expedition in 1997, Sereno and colleagues found the neck, trunk, ribs, and spine of Spinostropheus gautieri, a 15-foot-long (4.6-meter-long) dinosaur that represents an ancient relative of Rugops and other abelisaurids.
"This is a group of worldwide distribution that for reasons we don't know, went extinct in the north," Sereno said.
Together, the finds provide fresh evidence about when Africa, Madagascar, South America, and India finally split from each other as a result of continental drift.
Dinosaurs were the only large-bodied animals that lived, evolved, and died at a time when all continents were united. As such, they are excellent organisms through which to study the effects of continental drift, as the animals covered continent-scale distances.
"Until the continents fully separated, dinosaurs like Rugops and other animals used narrow land bridges to colonize adjacent continents and roam within a few degrees of the South Pole," Jeffrey Wilson said. An assistant professor at the University of Michigan in Ann Arbor, Wilson served as one of Sereno's team members and a co-author of the new study.
The Great Frontier
In Argentina in 1988 Sereno unearthed the first complete skeleton of the Herrerasaurus, the oldest dinosaur ever found. In the early 1990s, his focus shifted to West Africa. There, Sereno has excavated several other dinosaurs, including Jobaria and Afrovenator, and has also found a fossil of the 40-foot-long (12-meter-long) crocodilian Sarchosuchus, also known as SuperCroc.
Sereno is now working on cleaning and casting two other species that he found during his 2000 expedition. Next year the paleontologist plans to excavate a new Saharan site that may yield discoveries of dinosaurs that lived in Africa after the Rugops.
"Africa has been like the great frontier," Sereno said. "There has been so little work there, but it holds so many of the answers."
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