Searching an approximately 70-mile area north the Niger river, the scientists came away with half a dozen skulls and numerous other bones belonging to the 40-foot-long, 16,000-pound Sarchosuchus(SARK' oh SOOK' us)imperator, said team member Hans Larsson, a post-doctoral fellow in evolutionary biology at Yale University. The find is described in the Oct 25 issue of the journal Science.

The crocodiles grew to such an enormous size in a different way than dinosaurs achieved their massive size, said Paul Sereno, a paleontologist at the University of Chicago, and the leader of the team.

"It seems they did it by simply growing longer," he said. "The dinosaurs that were living alongside the river were building their bodies in a very different way. They achieved gigantism by increasing the speed at which they grew. This is apparent in looking at bones from different dinosaurs. They grew faster than mammals, most of them.

"But the crocodile was doing it differently," he said. "It simply prolonged its growing phase. We estimate the full size would have not been reached till 50 or 60 years," based on analysis of bones.

Sereno's work is the first to provide an adequate understanding of how this animal grew to its enormous size, said Jason Head, a Ph.D. candidate in vertebrate paleontology at Southern Methodist University. He is not part of the research team.

By analyzing their teeth, Sereno concluded these giant crocodiles also preyed on small dinosaurs.

"The teeth did not interlock, as they would in a dedicated fish eater," Sereno said. "The teeth are cylindrical, and they don't interact with each other and that seems to indicate a more generalized diet as if they were adapted for pulling down large things."

That, analysis, said Wann Langston Jr., emeritus professor of geological sciences at the University of Texas, marks a new way of looking at the niche these animals occupied in the environment.

"Previously it was assumed to have been a fish catcher. Sereno has reasonable arguments that it fed on dinosaurs because of it huge size, and because the snout is not really suited for fish catching," said Langston, who was not part of the research team. "It may have lurked in the shadows and waited for its prey to come close and spring on it."

Understanding Sarchosuchus' predatory behavior helps paleontologists paint a better picture of the nature of the "animal community," said Donald Brinkman, a paleontologist at the Royal Tyrrell Museum in Alberta, Canada.

"As we understand each animal that was part of the community, we can understand the community better," he said. "If you have a crocodilian that big, that suggests that carnivorous dinosaurs weren't doing all the predation. So that complicates the picture a little bit; you have to take these critters into account," said James Farlow, professor of geology at Indiana-Purdue University, Fort Wayne.

(Reported by Harvey Black, UPI Science News)