SALT LAKE CITY - For years, paleontologists have puzzled over strange markings etched into dinosaur fossils.

Now Brigham Young University scientists have identified the insects that left some of these "traces." They are bone-eating beetle larvae, whose descendants scavenge carcasses today, according to findings published last week in Ichnos, a journal devoted to ichnology, the study of plant and animal traces.

"As students we noticed these marks and thought it might be due to algae or insects and we started calling them 'bug bites,' just for fun," said Brooks Britt, a geology professor who led the research.

Most of the marks are believed to be the work of termites, which are known to be capable of eating an entire human skeleton except the enamel crowns of the teeth.

But after investigating unique pits and burrows discovered in a Wyoming dinosaur specimen, Britt determined some were gnawed by an ancient beetle species belonging to the modern family Dermestidae, commonly known as skin beetles.

"Dr. Britt's work … delves into unique aspects of paleobiology that few scientists have yet explored," said Eric Roberts, an expert in dinosaur decomposition at South Africa's University of the Witwatersrand. "We know next to nothing about the fossil record of insects because of their extremely limited preservation potential."

Britt tapped graduate student Anne Dangerfield to examine the traces on 5,000 bone specimens. Most appeared to be termite burrows. But she came across traces that looked completely different in a set of 120 bones at BYU's Earth Science Museum. The fossils were from the 148 million-year-old articulated skeleton of a camptosaurus, a beaked plant eater that roamed what is now the Northern Rockies. The specimen had been excavated near Medicine Bow 13 years ago.

The fossils had been preserved in soft clay that was easily removed to expose pristine insect traces - elliptical clustered pits and shallow bores - on nearly all the bones, Britt said. Like forensic specialists examining crime-scene evidence, the researchers compared the camptosaurus traces with those left by modern insects that eat bone.

"Many insects eat soft tissue but not many eat bone," said Dangerfield, who co-authored the study. "We narrowed them down to dermestid beetles, termites, mayflies and one type of moth."

The beetle, whose paired mandibles leave parallel traces that match the widths on the fossils, was fingered as the likely culprit, the Ichnos paper reported.

The research concluded that dermestids were living 50 million years earlier than when they first appeared in the fossil record and offered proof that Wyoming was a humid, warm place in the late Jurassic period. But the traces also tell a great deal about the habits of these beetles in their larval state.

"The adults fly off to a carcass, deposit eggs, the eggs hatch and the larvae molt multiple times," Britt said. "They prefer eating soft tissue. When that's gone they go for the bone. They like the most fat-laden parts, they mine off the ends of the bones, go into the shafts and mine out the marrow."