Ancient Crocodile Fossil Defies Dinosaur Label

Parker wasn't even looking for fossils when he was roaming through part of the park, known as the Painted Desert, with several geologists. They were looking for clues to the geological history of the region.

"I saw this very promising outcrop," Parker says, which he immediately recognized as an ancient flood plain.

"That's the best place to find this stuff," he says of the fossils that now threaten to consume his life.

"This was a huge river system," he says. "During the Triassic a lot of things died along the river channels. And during periods of heavy rain the rivers would flood and there would be a lot of sediments, so there was a quick burial. That's pretty much the key to preserving fossils."

Uncovering the Tiny Croc

Parker returned to the same site the next day with a colleague, and "sure enough, within minutes after I got there, I found all these armor plates, crocodilian type plates" that helped protect some early animal from predators, he says.

Minutes later they found a piece of a jaw.

"This was the first time anyone had actually picked up jaw material, or any material other than just isolated teeth that were laying on the ground," he adds.

They kept digging and soon hit the jackpot.

"There was a skull there, and it had Revueltosaurus teeth in it," he says. "So light bulbs went off and I realized that Revueltosaurus was not an ornithischian dinosaur. Instead, it was this little armored, crocodile ancestor."

More digging revealed more evidence. The animal had an ankle like a crocodile, not a dinosaur.

"Dinosaurs have kind of a bird-like ankle that allows for a more upright posture, whereas the crocodile ankle is weaker, and it causes the animal to be sprawling," Parker says.

Paleontological Puzzle

As is so often the case, the discovery has precipitated more questions than answers because it clouds the origin of an entire line of dinosaurs.

"Now we don't know where the ornithischian came from," Parker says. "Where do they fit in?"

It was thought they may have originated in South America, then extended their range across continents that have long since separated. But the evidence for early ornithischian in South America is also largely dental, so who knows?

The researchers say their discovery makes it clear, however, that ornithischian diversified much later than saurischian, and many animals thought to be dinosaurs probably aren't.

Not a bad contribution from a strange little animal that probably ended up on the food chain for an expanding population of meat-eating dinosaurs.

Lee Dye's column appears weekly on A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.

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