Dining on dino delite
POSTED 15 NOV 2001 It was big, and it was nasty. The giant fossil crocodile, 110 million years old, looked, in the drawing, like a regular movie monster. Long as a school bus, it was almost as heavy, 8 metric tons.

Sarcosuchus (SARK-oh-SOOK-us) imperator boasted a massive snout would make kiddies at a bus stop think twice before boarding a bus -- even before they saw little details like big teeth...

Those teeth show that Sarky, which lived along riverbanks during the hey-day of the dinosaurs, was a carnivore. But unlike modern crocs, which tend to order turtle soup and sushi from the menu, this mayhem-meaning-monster was a regular at the dino-diner.

Yup. It apparently ate dinosaurs. You can deduce that preference because its teeth did not interlock, as did the teeth of a typical fish-flaying dino.

Food fighter
As protection against food that might want to fight back, Sarky had armor plates called bony scutes embedded in its skin. Since the scutes added one growth ring per year, researchers examined an immature skeleton and concluded that the giant croc needed 50 to 60 years to reach full size. That's much slower growth than the average big dinosaur.

The detailed picture of Sarcosuchus imperator emerges from new research by Paul Sereno, of the University of Chicago, and colleagues.

When the first Sarky was found in the desert in Niger, West Africa in 1964, the bits and pieces gave only a sketchy picture of the giant carnivore.

Further fossils and research (see "Giant Crocodyliform..." in the bibliography) have fleshed out the image of a creature with all the hallmarks of a 1950s Hollywood monster: Teeth. Attitude. Size.

Champion chomper
The body, for example, probably reached 11 to 12 meters -- 37 to 40 feet -- in length. Sarky's teeth met with a substantial overbite (orthodontists being rare in the Cretaceous Era). This was a critter that took dining seriously. Fully 75 percent of its skull was devoted to a pair of pointy ("needle-nosed") jaws. The toothy snout terminated in a peculiar, bowl-shaped structure that may have detected odor (crocs being stiff-necked, and have a tough time turning toward interesting scents). This bowl may also have resonated the croc's "voice" -- present-day crocs are highly loquacious reptiles, Sereno noted.

The new find also helps place Sarky in evolution. "This new material gives us a good look at hyper giant crocodiles -- there's been rampant speculation about what they looked like and where they fit in the croc family tree, but no one had enough of the skull and skeleton to really nail any of the true croc giants down until now," Sereno told Science Online.

About 110 million years ago, six species of crocodiles lived at the Niger site, Sereno continued, including one midget that Sarky might have considered an appetizer. Sereno observed that crocodiles have evolved toward the golden mean -- the midgets and the giants have largely gone extinct, leaving only the mid-size units.

That comment got us to wondering. Large size is good, in that big critters can push bitty ones around (although in the long run microbes rule).

But if being big is such an advantage, why did giant crocs go extinct?

And why did large mammals disappear after people reached Australia and North America?