SUCHOMIMUS TENERENSIS

An enormous predatory dinosaur with a skull like a crocodile’s and foot-long thumb claws has been discovered in the Sahara by an international team led by Paul Sereno of the University of Chicago. Measuring 36 feet in length and 12 feet high at the hip, the specimen is the most complete known of a peculiar group of fish-eating predators called spinosaurs, animals that grew to the size of Tyrannosaurus rex. In a paper in the Nov. 13 issue of Science, Sereno and his colleagues name the new species Suchomimus tenerensis, meaning “crocodile mimic from Tènèrè,” a remote and forbidding, dune-covered region of the Sahara in the Republic of Niger in West Africa.

Sereno, and his 15-member expedition spent more than two months in the fall of 1997 scouring the desert in temperatures that climbed to 120 degrees. They unearthed 25 tons of bone and rock that included the remains of Suchomimus.

Team member David Varricchio spotted the huge, sickle-shaped thumb claw. “It was lying on the surface of the desert, completely exposed by wind and sand, and would have been visible like that for centuries to anyone who walked by,” Sereno said. The claw led the team to 400 pieces of the skeleton, buried just inches under the desert plain.

Sereno said that the discovery reveals new information about the peculiar anatomy of spinosaurs, which he called “a dinosaur trying hard to be a crocodile.” Its four-foot-long skull has an extremely long and narrow snout with large teeth near its end, as in specialized fish-eating crocodiles. The jaws were studded with more than 100 conical teeth that functioned like hooks rather than slicing blades.

The foot-long thumb claws and powerfully built forelimbs were used to snare fish and other prey as the dinosaur waded in rivers; the thin, bony sail along its back, which reached a height of two feet over the hips, may have been brightly colored for display. Suchomimus lived in Africa about 100 million years ago in what was then a forested region dissected by broad rivers and home to other dinosaurs, huge crocodiles, turtles, pterosaurs and many kinds of fish. It would not have been a friendly place, Sereno said. “If you weren’t grabbed by a spinosaur, you’d likely run into a 50-foot crocodile.”

Suchomimus was the largest and most common predator of its day, judging from the numerous bones Sereno’s team recovered. Its closest cousin is Baryonyx from Europe rather than the tall, sail-backed north African spinosaurid Spinosaurus. This far-reaching link suggests that, on at least one occasion, spinosaurs crossed the broad Tethyan seaway that separated northern and southern land masses at that time. Spinosaur fossils were first discovered in Niger’s Tènèrè Desert some 50 years ago and were collected in earnest 25 years ago by French paleontologists. The region’s fossil-rich rock provides the best opportunity to unearth clues to plants and animals that thrived in Africa 100 million years ago, as the continent was drifting into geographic isolation.