Investigations
A dinosaur's worst nightmare
In the punishing heat of the African Sahara, paleontologist Paul Sereno has uncovered the remains of a giant prehistoric crocodile that dwarfs its modern counterparts.

Living during the Cretaceous period, Sarcosuchus imperator ("flesh crocodile emperor") grew to a length of 40 feet and weighed eight tons, twice as much as a full-grown elephant. In contrast, modern crocodiles rarely exceed 14 feet and weigh no more than half a ton.

"This crocodile was probably capable of pulling down just about any dinosaur under the right circumstances," says Sereno, professor of organismal biology & anatomy. "It would have been a force to be reckoned with on the shoreline. It would have been a dinosaur's nightmare."

Fossilized teeth and armored plates of Sarcosuchus were first discovered by French paleontologist Albert-Felix de Lapparent in the 1940s and 1950s. During expeditions to the Tènèrè Desert of Niger in 1997 and 2000, Sereno and his research team recovered several partial skeletons of Sarcosuchus, including vertebrae, limb bones, armor plates, jaws, and a nearly complete six-foot skull. Working from those remains-about 50 percent of the whole skeleton-Sereno and coauthors Hans Larsson, SM'96, PhD'00, Christian Sidor, SM'96, PhD'00, and Niger paleontologist Boubè Gado published a detailed description of the animal's anatomy on the October 25 Science Web site and in print November 16.

Sereno found the remains of Sarcosuchus in the same 110-million-year-old sediment layer where in 1997 he discovered Suchomimus, a two-legged, fish-eating predator measuring 36 feet long and 12 feet high at the hips. But even that large beast, Sereno notes, would have had to be on the alert for surprise attacks from the stealthy Sarcosuchus. Sarcosuchus's jaws were studded with more than 100 bone-crushing teeth and an enormous, bowl-shaped snout that may have aided the animal's sense of smell or been used to make sounds. India's modern-day gharials, for example, are highly communicative. "They're vibrating and belching and growling and hissing all the time, sometimes even in the water," says Sereno.

Despite certain similarities to the much smaller gharial, Sarcosuchus is not directly related to modern crocodiles. Nevertheless, measuring living crocodiles in India and Costa Rica helped Sereno estimate the size of a full-grown Sarcosuchus.

He also studied the growth layers in the armored plates along the back of Sarcosuchus. Examination of thin slices under the microscope revealed that the animals lived to be 50 to 60 years old, about twice the life span of modern crocodiles.

As on three previous expeditions to Africa, Sereno's team probed remote areas of the continent in temperatures reaching 125 degrees Fahrenheit for its fossil treasures. Funded by the National Geographic Society and the David and Lucille Packard Foundation on the 2000 expedition, the team found that Sarcosuchus had plenty of crocodilian company in the broad rivers that flowed across lush plains. Plying the same rivers were the doglike Araripesuchus and a newly discovered species, yet to be named, that attained a full-grown length of only two feet. -Steve Koppes

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