The skull of what may be the biggest meat-eating dinosaur ever found confirms that the southern continents were once a single huge stomping ground for dinosaurs. The skull, reconstructed from new fossils collected in Patagonia, was unveiled today at The Academy of Natural Sciences in Philadelphia. Its 100-million-year-old features look much like those of a Tyrannosaurus rex-sized predator from North Africa--except that the South American skull is even bigger, say paleontologists. The similarities between the two titans, they say, mirror ancient geography.
About 175 million years ago, when the supercontinent Pangaea first began to break in half, dinosaurs in the northern regions started evolving separately from their southern comrades. Then, some 90 million years ago, the southern landmass split into pieces. Paleontologists had suspected that dinosaurs living in South America and Africa before that date would be similar, but until a few years ago, they simply didn't have enough bones to study.
In 1993, Rodolfo Coria, director of the Carmen Funes Museum in Plaza Huincul, Argentina, unearthed the bones of a large predator, which he named Giganotosaurus carolinii. Three years later, Paul Sereno of the University of Chicago reported finding Carcharodontosaurus, another 100-million-year-old predator, in Morocco. But the relationship was blurry because parts of Giganotosaurus's skull were missing. Last year, Coria went back to the site and found the lower jaw and parts of the nose. He now knows what 90% of the skull looks like--enough to peg its length at 180 centimeters, at least 20 centimeters longer than the skulls of Carcharodontosaurus and the largest T. rex, a North American beast. "It is certainly the largest meat-eating dinosaur skull I have ever seen," says Jack Horner, a dinosaur expert at the Museum of the Rockies in Montana. It's also clear, Coria says, that the South American and African forms were closely related.
The similarities imply that the land connections between the two continents must have still been intact 97 million years ago, the age of pollen associated with Giganotosaurus, says Coria. He and his colleagues have also found a frog, two types of turtles, and three kinds of crocodiles--all with counterparts in east Africa--to back up the link. And within the last few years, Coria and other paleontologists have found another seven kinds of cosmopolitan dinosaurs, including a plant-eating sauropod called Rebbachisaurus and a predator in the spinosaurid group.
These discoveries suggest that, even though North American dinosaurs are better known than those of Africa and South America, the vast southern landmass may have been a more important center of dinosaur evolution. "It was an extremely productive environment," says Dale Russell, a paleontologist at North Carolina State University in Raleigh and the Museum of Natural Sciences. "I'm really impressed."