Massive New Meat-Eating Dino Had "Steak Knife" Teeth

James Owen
for National Geographic News
December 12, 2007
A new species of meat-eating dinosaur larger than Tyrannosaurus rex has been identified from remains found in North Africa, fossil experts say.

The previously unknown dinosaur, dubbed Carcharodontosaurus iguidensis, grew up to 45 feet (14 meters) long and used huge "steak knife" teeth for slashing through prey, according to paleontologists.

"It was just a completely ferocious animal," said lead study author Steve Brusatte, a student at the University of Bristol in the United Kingdom.

"The teeth of this guy were enormous. They were the size of bananas, but they were very thin teeth."

The dinosaur's skull was about 5.5 feet (1.7 meters) long and was relatively lightweight given the animal's size.

This suggests that C. iguidensis relied on speed and used its teeth like hatchets to strike at the neck or flanks of its prey, Brusatte said.

T. rex, on the other hand, had a much stronger skull and teeth adapted "not just to taking down prey but actually crunching through bone," the researcher noted.

According to Brusatte, the new dino is one of "the largest carnivores we know of that lived on land."

The main rival for the title is the closely related Giganotosaurus from South America. (Related: "Meat-Eating Dinosaur Was Bigger Than T. Rex" [April 17, 2006].)

Rare Fossil Find

Brusatte's study, which appears today in the Journal of Vertebrate Paleontology, is based on 95-million-year-old skull, jaw, and neck fossils found in Niger in 1997.

The remains were unearthed during an expedition led by study co-author Paul Sereno, a National Geographic Society Explorer-in-Residence and a paleontologist at the University of Chicago. (National Geographic News is part of the National Geographic Society.)

At the time of the discovery, Sereno's team had identified the fossils as belonging to the genus Carcharodontosaurus.

This group of predatory, two-legged theropod dinosaurs was first described based on two fossil teeth recovered in the 1920s that have since been lost.

The only previously named species from the genus, C. saharicus, was described from a single fossil skull found by Sereno in Morocco in 1996.

Subtle differences in the new Niger skull suggested that it belonged to a distinct species—a suspicion now confirmed following detailed examination, Brusatte said.

"There are five or six key differences in the skull, the snout, and the bones that surround the brain," the researcher said.

Jerry Harris, a paleontologist at Dixie State College in Utah, agrees with the classification of the Niger fossil as a new species.

C. iguidensis appears to have been built for "running in and slashing at things with its teeth and waiting for the crippled animal to topple over," he added.

Evolution in Action

The study suggests that the newly described species is evidence for rapid evolution after shallow prehistoric seas inundated North Africa, separating Carcharodontosaurus populations in what is now Morocco and Niger.

The mid-Cretaceous period when these dinosaurs lived was marked by some of the warmest temperatures and highest sea levels in Earth's history, lead author Brusatte said.

"It looks like we're seeing evolution in action," he added. "We see it not only in Carcharodontosaurus but with other dinosaurs from Morocco and Niger from the same time period."

The find could also help researchers understand how the massive Carcharodontosaurus was able to share its watery territory with a variety of other huge, two-legged carnivores.

Researchers know, for example, that theropods from the Abelisaurid family and spinosaurs—sail-backed meat-eaters that may have grown up to 60 feet (18 meters) long—also prowled the ancient ecosystem.

"It seems there are a number of different very large theropods milling about. That's been an interesting puzzle," Dixie State's Harris said.

These top predators may have coexisted because they weren't in direct competition. Spinosaurs, for example, had crocodilelike heads that were loaded with teeth.

"That's the kind of snout you see in organisms that eat fish a lot," Harris said.

"Things like Carcharodontosaurus had much taller, more robust skulls, with teeth that are not nearly as tightly packed," he added.

"That's an adaptation you see in things which are hunting and tracking down land animals."

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