Ancient croc slideshow (Flash). Credit: Monterey Bay Aquarium Research Institute.
Darwin's finches have nothing on these crocodiles. Paleontologists Paul Sereno of the University of Chicago in Illinois and Hans Larsson of McGill University in Montreal, Canada, have discovered the 100-million-year-old remains of five monstrous and surprisingly diverse species of crocodile relatives in Niger and Morocco. Despite their differences, the crocs shared an unexpected characteristic: They ran high-up on all fours like mammals.
In another time and place, each of the five ancient animals could have answered a casting call for Star Trek. Take the newly discovered BoarCroc (Kaprosuchus saharicus), one of the four fossilized species found in Niger. The 6-meter-long carnivore evolved an armored snout for ramming its prey and three sets of tusks for ripping flesh. Then there's RatCroc (Araripesuchus rattoides). A new species found in Morocco, it was only 1 meter long and had a buck-toothed lower jaw, which it used to dig up plants and grubs.
The team also found five new fossils of the previously known DogCroc (Araripesuchus wegeneri) embedded within a single chunk of rock. The 1-meter-long plant-and-grub eater sported a soft nose like a dog's and a powerful tail for swimming. DuckCroc (Anatosuchus minor), also previously known, was the same length and ate fish, frogs, and grubs. Sereno says he almost named it PinocchioCroc because of its long nose, which allowed it to root out prey.
Possibly the oddest find of all is the enormous PancakeCroc (Laganosuchus thaumastos). At more than 6 meters long, it boasted a flat, 1-meter-long head bristling with spiked teeth on slender jaws. The scientists think it would probably lie still for hours, waiting for unsuspecting fish to swim through its wide-open maw.
As Sereno and Larsson report in an upcoming issue of the journal ZooKeys, the crocs' walk and paddlelike tails represented a huge advantage over many competing predators. The animals would have been as swift on land legs as they were in the water, giving them great versatility in hunting and escaping. That may be why crocodilians still remain among us, even though, these days, they tend to drag their bellies.
The original version of this story stated that these ancient crocodiles walked upright on their hind legs. The text has been changed to reflect the fact that these creatures instead sometimes walked high-up on all fours like mammals.