5 "Oddball" Crocs Discovered, Including Dinosaur-EaterA "saber-toothed cat in armor" and a pancake-shaped predator are among the strange crocodile cousins whose bones have been found beneath the windswept dunes of the Sahara, archaeologists say. (See pictures of BoarCroc, PancakeCroc, DuckCroc, RatCroc, and DogCroc.)The diverse menagerie of reptiles ruled Gondwana—a landmass that later broke up into the southern continents—about a hundred million years ago, during the Cretaceous period. (See a prehistoric time line.)
"There's an entire croc world brewing in Africa that we really had only an inkling about before," said Paul Sereno, a paleontologist at the University of Chicago and leader of a new study.
"We knew about SuperCroc, the titan of all crocs, but we didn't have quite an idea of what existed in the shadows of the Cretaceous," he said.
Ancient crocodile cousins—called crocodilyforms—were not widespread in the Northern Hemisphere. But the south blossomed with bizarre riffs on the croc theme, added Sereno, also a National Geographic explorer-in-residence.
The team found three new species, nicknamed PancakeCroc, BoarCroc, and RatCroc, as well as new skeletons of the previously named DuckCroc and DogCroc. (Meet the strange crocs of the Sahara.)
"There's more to a croc than meets the eye of a living person," Sereno said. "We have crocs here [in what was once Gondwana] that ate plants and galloped and ate dinosaurs and were flat as a board."
Dino-Era Crocs Were "Real Oddballs"Sereno and colleagues have been scouring the harsh deserts of northern Africa since 2000 for evidence of a "lost world" of crocodilian ancestors.
Crocodilians are a living group that includes crocodiles, alligators, caimans, and more. (See alligator and crocodile pictures.)
Each ancient species evolved unique adaptations to reign over its own corner of the lush, river-carved plains of present-day Niger and Morocco, the study says.
For instance, the rodent-like RatCroc had buckteeth for rooting through the ground after tubers or simple animals.
The flat-bodied PancakeCroc was the "ultimate sit-and-wait predator," Sereno said. The animal would lie motionless and "wait for something stupid" to swim into its rail-thin, 3-foot-long (0.9-meter-long) jaws, which were lined with rows of spiky teeth.
DuckCroc had a long, smooth, sensitive nose to poke through vegetation as well as hook-shaped teeth to snag frogs and small fish in shallow water.
And the plant-eating DogCroc had lanky legs that meant it was likely spry enough to run into the water if threatened.
By far the mightiest of the lot, BoarCroc was a 20-foot-long (6.1-meter-long) "saber-toothed cat in armor" that ate dinosaurs for dinner.
Three sets of fangs—so long they jutted above and below the jaw when shut—handily sliced meat, while a snout reinforced with bonelike armor boosted the animal's ramming power.
"Gondwana had lots of real oddballs," said Hans Dieter-Sues, a paleontologist at the National Museum of Natural History in Washington, D.C., who was not involved in the research.
"For somebody who has studied a lot of fossil crocodilyforms, I'm fascinated by these creatures," Sues said.
Croc SurvivorsSkeletal analysis reveals that many of the Gondwana crocs were surprisingly limber, and some may have been able to gallop like modern saltwater crocodiles in Australia, said study leader Sereno, who has studied crocodile movement.
That crocodilian ancestors could run and swim with equal dexterity may have given them a leg-up on escaping predators—and extinction, Sereno added.
Some ancient crocs must have survived the mass extinction event that wiped out the dinosaurs about 65 million years ago. Being nimble on land and in water suggests the crocodile cousins may have taken refuge from environmental catastrophe in bodies of fresh water, where modern crocodilians still thrive, said Sereno, whose study appears today in the journal ZooKeys.
Christopher Brochu, a paleontologist at the University of Iowa, said that it's hard to tell if the ancient crocs really galloped.
Only a small number of modern-day crocodilians gallop, so it's possible the gait evolved among true crocodilians, said Brochu, who was not involved in the study.
"We need to be cautious," he said, "when extending behavior seen in a subgroup of crocodilians to more distant relatives."
He added the new species "are truly beautiful animals" that "really are going to be critical in understanding how the group was so diverse and dominant in the southern continents."
No matter how the ancient crocs moved, there's no denying that some of their traits—passed down via evolution—have helped crocodilyforms as a whole outmaneuver extinction, Sereno said.
"They were a really successful group—they are survivors."
http://news.nationalgeographic.com/news/2009/11/091119-dinosaurs-crocodiles-missions.html
