Don't call them perverts, but when two New Mexico paleontologists found a spiked opening on a fossilized 210 million-year-old animal — in a place the sun doesn't generally shine — they realized they had discovered something exciting.

The creature, called a Typothorax, appears to have had a protective cover over its naughty bits, although the actual purpose of the spikes hasn't quite been determined, they said.

"Is it an ancient chastity belt? Is it a clasper-type adaptation used in sexual activity? We just don't know yet," said Andy Heckert, an assistant geology professor at Appalachian State University in North Carolina and former geosciences collection manager at the New Mexico Museum of Natural History and Science.

Volunteers from the museum found the fossil near Tucumcari, and Heckert collected it in 2006. But until this summer, preparation work revealing its spiky undersides wasn't complete.

In June and July, Heckert and Spencer Lucas, interim director of the museum, took a closer look at the creature — which has a well-preserved chest, belly, nether region and tail, but no head — and realized the unusual-looking opening was something nobody had discovered before in a Typothorax.

"These animals, they're sort of like big reptilian armadillos," Lucas said. "The plating also makes them sort of like medieval knights in armor. You have to ask, how did medieval knights use the bathroom? Here we have an animal that solved this problem millions of years before knights came along."

After realizing that the plated hole was an indication of protected sex organs, Heckert and Lucas looked at another squashed sample of a Typothorax, also found near Tucumcari, and found similarly shaped spikes mashed together in generally the same area that indicate it had the same sort of protected opening, Lucas said.

"These armor plates raise some questions, though," Lucas said. "We don't know whether this indicates a male or a female or if it's present on all Typothorax."

Modern male crocodiles seem to have similar biology, but Typothorax is a different type of animal that went extinct about 200 million years ago, Lucas added.

"If we can find more fossils with different features than these two, we might be able to determine gender," Lucas said. "If they are sexually dimorphic (different), then it implies some sort of social interaction. That would be very interesting if animals of that age did that."

The other interesting thing about the spiked hole — technically called a vent — is that it indicates where soft internal organs might have been. That's something extremely rare in the fossil record, because generally only bones and hard areas fossilize, Heckert said.

"We're going to learn a lot more about its anatomy because of this," Heckert said.

Typothorax adults grew to somewhere between 5 and 7 feet long, and weighed upward of 300 pounds. They were vegetarians that lived in New Mexico at a time when much of the state was a forested flood plain, Lucas said.

"They were probably fairly harmless unless you cornered one," he said. "I like to think of these animals as more serene, more laid back than any predators that might have been around."

The spikes and plates on the animal would have protected it from just about all the predators of that age, although giant crocodilelike creatures called phytosaurs might have chomped down one or two, Lucas said.

But knowing its environment and eating habits still leaves a lot of questions about what the strange vent might have been for, Lucas and Heckert said.

Heckert speculated a bit about the area's possible function and how it might relate to the creature's gender.

"If it's male that area might act like a clasper," Heckert said. "It might hold things together until sexual interactions are complete. If it's female, maybe those spikes are how she gets the final say as to whether she likes that male or not."

If the creatures are female the opening could possibly have something to do with egg laying, but because the animal had sharp claws, it wouldn't have needed the spikes to dig a nest, Heckert said.

"I suppose it could also be for straight defense," he said.

Whatever the area's purpose, visitors to the museum will soon get a chance to examine and speculate about the creature themselves. Lucas said the fossil will be on display in the atrium starting sometime in October.

"I suppose it's sort of an odd back alley of paleontology to think about ancient latrine behavior and anatomy, but it's really a remarkable find," Lucas said.

The find also appears to be the oldest such area found on any animal discovered in New Mexico, although an older specimen from a different type of creature found in Texas appears to have had a similar vent, Lucas said.

"We can certainly say this is the oldest you-know-what in New Mexico, at least for a reptile," Lucas said.

Contact Sue Vorenberg at svorenberg@sfnewmexican.com.