What a croc! Scientists discover supersized reptile

It's dubbed SuperCroc - a 110-million-year-old beast that ruled a deep, wide river running through what is now the African country of Niger.

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The croc, formally known as Sarcosuchus imperatur, stretched 40 feet long, tipped the scales at about 8 tons, and regularly dined on dinosaurs. The crocodile hosts a large bony growth the size of a toilet bowl on the end of its snout - a feature that could have played a role in communication or been part of a hypersensitive nose for sniffing out prey.

The enigmatic creature remains "one of the greatest crocodiles the world has ever seen," says Dr. Sereno, whose team has been working in the region for the past decade to answer riddles posed by bits and pieces of SuperCroc that others had found since the early 1950s.

During SuperCroc's heyday, the continents of Africa and South America were still joined at the geophysical hip. The fossils come from a formation in a remote section of the Ténéré Desert that sits atop an ancient rift valley - a zone where the crust tried, but failed, to split in two under the stress of the continents' separation. The valley hosted an expansive river that, as years passed, covered and preserved the creatures who died in and along it in layers of silt.

Unlike many early crocodiles during this period, which were ocean-going, SuperCroc inhabited fresh water, Sereno says. Based on the size, shape, and orientation of teeth and jaws, SuperCroc's salt-water compatriots dined exclusively on seafood. SuperCroc's jaw and teeth arrangement, however, is more suited to puncturing and crushing a wider variety of prey.

Until now, SuperCroc has been known only though "one photo and a couple of pages of notes," says Sereno, a paleontologist at the University of Chicago. During an expedition last year, which he dubs "the most extraordinary expedition I've ever led," his group gathered 20 tons of fossils, including many new species. The team gathered large numbers of SuperCroc remains, including partially assembled skeletons. "We knew in the field that we would be able to put this thing together," he says.

Trying to imagine how SuperCroc would have behaved, he says, is difficult, given the experience most people have seeing crocodiles laying about on concrete at zoos. In the wild, however, today's crocodiles "are hard to track, very cunning, and are capable of bringing down large animals."

Given its immense size, it's unlikely SuperCroc could have risen up on its four legs for quick bursts of speed on land, the way some modern crocs can. But Sereno says he has little doubt that SuperCroc hunted from ambush and was capable of "incredible bursts of speed from the water."

Sereno says SuperCroc would have stood at the top of the food chain. But it would have shared that position with the large sail-backed spinosaur that his team found in the same sandstone formation. Looking a bit like Velociraptor, that land-based creature was 36 feet long and stood 12 feet high. To see them heading for the same prey "would make for a spectacular meeting ," Sereno says.

Technicians are working on a model skeleton and "flesh" model "at size" of SuperCroc to allow viewers "to really come to grips with an 8- to 10-ton animal," he says.

It's the type of model that might give T-rex a run for its money as the preferred location for unrolling sleeping bags during Scouting sleepovers at the local museum.