Wally Windscheffel doesn't recall whether he or his pal Charles Safris saw the gray, fist-sized rock first. It might have just been a rock, after all; only the black speck on one end suggested it was something more.

	Mark A. Klingler, Carnegie Museum of Natural History Life reconstruction of Fruitafossor windscheffelia as a digging mammal feeding on termites and other small invertebrates. Click photo for larger image.

But once he got back to his home in Grand Junction, Colo., and began picking off the gray bentonite, Windscheffel, 78, realized that black speck was a fossil jaw. And a black speck on the other side of the rock turned out to be a tail bone.

As more of the rock gave way, he realized he had something very rare: an almost complete skeleton of a mammal that lived among the dinosaurs 150 million years ago during the Late Jurassic period.

And this mouse-size critter was a strange one. Its small head, tapered body and particularly its massive forearms reminded the retired Navy submariner of a favorite cartoon character. So he nicknamed it Popeye.

"We'd never seen anything like Popeye before," said John Wible, curator of mammals at the Carnegie Museum of Natural History, recalling the day in 1999 when Windscheffel showed the fossil to him and his colleague Zhe-Xi Luo. "We were just totally blown away."

As he and Luo report in today's issue of the journal Science, this Popeye didn't use its mighty forearms to bust open cans of spinach, but likely used them to dig up colonies of termites to gobble up. Its arms and peg-like teeth are similar to those of the armadillo and the aardvark, but the now-extinct Popeye was a very different animal.

Scientists have previously found fossils of mammals that co-existed with dinosaurs -- the so-called Mesozoic Era -- but those mammals are more alike than not: small, insect-eating animals that lived on the ground or in trees. It was believed that a great diversity of mammals did not appear until the dinosaurs died off.

	Mark A. Klingler, Carnegie Museum of Natural History Skeletal reconstruction of Fruitafossor windscheffelia with a primitive and robust forelimb for digging. Click photo for larger image.

None of these previous mammals have displayed the same degree of specialization as Popeye, said Luo, curator of vertebrate paleontology at the museum. "It's more than just 'gee whiz,'" he insisted; rather, the existence of Popeye suggests Mesozoic mammal life was highly diverse and that lots of mammal species remain to be discovered from that era.

"It's not the oldest example of a digging animal [that would be a reptile] but it may be the oldest digging mammal," said Kenneth Rose, a paleontologist and authority on digging mammals at Johns Hopkins University. He agreed that Popeye suggests that Mesozoic mammals were far more diverse than suspected. "It certainly adds a new dimension."

In addition to peg-like teeth and strong arms, Popeye even has a backbone similar to that of armadillos, with vertebrae joints that may help stabilize the back while digging. But Popeye predates the armadillo by about 100 million years. Despite the similarities, Luo said these specialized features evolved independently, an example of what scientists call "convergent adaptation."

Unlike aardvarks and armadillos, which are placental mammals, Popeye has features common to monotremes, or egg-laying mammals, Rose noted.

The quarry near Fruita, Colo., where Windscheffel and Safris found Popeye is part of the Morrison formation, the same geological formation as Dinosaur National Monument, the source of most of the Carnegie's world-famous dinosaur collection.

Windscheffel first visited the site two decades ago, as part of an expedition organized by the group called Earthwatch. He returned again and again, eventually moving from San Diego to Grand Junction. He now regularly visits the Fruita quarry as a volunteer on behalf of the Carnegie museum.

"This is something that's critical to museums in general," Wible said of volunteers such as Windscheffel.

Though nicknamed Popeye, the creature's formal name is Fruitafossor windscheffelia -- giving nods to the location of the find, the animal's propensity for digging (fossor is Latin for digger) and to Windscheffel.