By Guy Gugliotta
The Washington Post
The crocodile was a silent stalker, as long as a school bus and weighing almost 18,000 pounds. It cruised the rivers of what is now Saharan Africa looking for unwary dinosaurs to snatch.
"It was absolutely enormous," said University of Chicago paleontologist Paul Sereno. "There’s nothing that would be able to handle that animal. It’s like a torpedo of muscle 5 feet in diameter. The skull of the world’s largest living crocodile looks like an hors d’oeuvre by comparison."
Sarcosuchus imperator, or "flesh-eating crocodile emperor," lived 110 million years ago, and in an age of giants was a top-of-the-food-chain predator with 4-foot jaws that could gobble fish 12 feet long and probably scooted ashore to bring down dinosaurs weighing tons.
Reporting in the journal Science’s Web site, the Sereno-led team of paleontologists for the first time described the size and habits of this beast, whose remains were found in central Africa’s bone-dry Tenere Desert in an area of Niger called Gadoufaou — "the place where camels fear to tread" in the Tuareg language.
Sereno explained that the existence of Sarcosuchus has been known since bones were first unearthed by French geologists in 1964, but scientists could not estimate the animal’s size because they did not have an intact skull.
The Sereno team’s discovery included several skulls and other bones, and since "there is a well-documented relationship between head and body size in crocodilians," Sereno said, the researchers were able to figure out what Sarcosuchus looked like.
What they found was an animal easily recognizable as a crocodile, but almost unimaginably larger than any modern-day descendant. Sarcosuchus was 37 to 40 feet long, with a 5 1/2-foot-long head and 4-foot jaws. It weighed at least 17,600 pounds — about 1.5 times as much as an African elephant.
By contrast, the largest Australian crocodiles are 21 feet long and weigh a bit over a ton. American alligators, the most familiar species in North America, grow to 15 feet and weigh up to 1,300 pounds.
Sarcosuchus was covered from head to tail with overlapping bony plates called scutes, each one etched with growth rings. Extrapolating from the scute of a young adult, the Sereno team estimated that the giant crocodiles probably attained their great size because they grew throughout their 50- to 60-year life span.
"Living conditions were good," said Columbus State University paleontologist David Schwimmer.
Schwimmer studies Dinosuchus, a giant North American crocodile about the same size as the earlier Sarcosuchus. Both creatures lived during the Cretaceous Period, a time of global warming when vegetation was lush enough to support large numbers of enormous dinosaurs and other creatures.
The Sereno-led expedition, funded principally by National Geographic and the David and Lucile Packard Foundation, found quite different conditions in 1997 and 2000 — a windblown, sandy wilderness where the only water was the supply brought in by the excavators.
Sarcosuchus dominated its habitat. It was a fish-eater, but with nostrils and eyes vertically placed, it could, like modern crocodiles, cruise the riverside almost imperceptibly, keeping a sharp lookout for shore-based prey while its enormous body remained invisible below the surface.
"It was built for ambush," Sereno said.
Noting that modern Nile crocodiles can attack wildebeests and cattle, "it is easy to imagine this one taking down iguanodons and duckbills" weighing up to 2 tons, he said. "For months, life is easy and good, then one day he wakes up and thinks ‘I’m hungry today.’ "
Sarcosuchus’ teeth were short, fat and cylindrical, and the jaws had an overbite, Sereno said. It was a mouth built for "puncture-crushing" of large vertebrates, and not exclusively for eating fish.
Sarcosuchus’ only possible competitor was the dinosaur Spinosaurus, a vicious terrestrial carnivore that gained notoriety as the archvillain in the movie "Jurassic Park III." Sereno said his team found Spinosaurus remains in the same area as Sarcosuchus. "There would have been some really interesting interaction," Sereno said.
But the crocodiles may have had the advantage: "We’re talking about amazingly nasty animals," Schwimmer said. "Unlike (land-based predators), they would be coming out of nowhere. You would be crossing a river, and all of a sudden this thing would swim up and bite you in half."