The skeleton of a prehistoric monster crocodile almost 12 meters long was discovered last year by a National Geographic expedition in the African country of Niger and is now on display in Washington.

It could be a creature out of nightmare, but with its 100 teeth, its armor plating and its size the length of a bus, the skeleton on display at the National Geographic Society in Washington DC is clearly ultra-real.

The technical name for this beast, which was discovered in the Sahara Desert, is Sarcosuchus imperator, a Latin phrase meaning "flesh crocodile emperor." But University of Chicago paleontologist Paul Sereno and his discovery team prefer to call it simply "SuperCroc."

"SuperCroc is the nickname for perhaps the largest crocodile that ever evolved, and it evolved about halfway through the Dinosaur Era, about 110 million years ago," says Mr. Sereno. "It lived for only about two million years before it passed into oblivion by going extinct. The crocodile, like living crocodiles, would have lived in large rivers. It has eyes rotated to the top of its skull so it would have been cruising down rivers with not much showing and then, with a weight of about eight tons burst onto the scene to drag animals into the water."

Professor Sereno and his team had known this species existed because some bones from it were found by French paleontologists back in the 1950s. "We didn't realize how common it was. It was the most common animal of its day. And it was a fateful day that first time in the desert when a student walked up to the beautiful skull, just tipped on its side and diving into the ground," he says. "[It was] just an incredible discovery. We knew it the first time we set eyes on it. So you are looking at something that had weight greater than an elephant, jaws as tall as a human that would be capable of dragging just about anything into the river."

Discovering what this ancient animal ate, and therefore how it lived, has been important in Mr. Sereno's detective work. "The key for figuring out what a crocodile is eating is the shape of its snout and, even more importantly, the shape of its teeth," he says. "If it has long slender teeth, finger-shaped teeth that interact with one another up and down, that is the kind of teeth you want for catching fish. The pterodactyls, they had these long teeth, and the living crocodiles today [also]."

But the Supercroc had very different teeth. They were stout, short, very strong, and impossible to break, with the biggest up front. This was an animal that was designed to grab very large prey on the bank suddenly and drag them into the river. And crocodiles don't chew their prey. They just let them drown, and then dismember them."

And entire dinosaurs were a big part of SuperCroc's menu. "There was living on the banks of the rivers at this time 110 million years ago bones and an animal that we found alongside those of the SuperCroc, and animal that would call a Spinosaur," he says. "And this Spinosaur was a two legged carnivore, a meat eater, a fierce predator, the greatest of its day, that looked in general form like a Tyrannosaur, but was very different in the shape of its skull and the fact that it had a sail on its back. It also had 30-40 centimeter long claws. Now this ponderous animal, 12 meters long as well, was living in the same environment, fishing in the same rivers as the SuperCroc Sarcosurus. And I think [that] undoubtedly they would have encountered each other. And that would have been something to see!"

Professor Sereno led the team that discovered Sarcosuchus imperator or "SuperCroc," in the Saharan region of Niger last year.