May 8, 2008 -- New findings explain why most dinosaur skeletons exhibit pits, grooves, furrows and even entire gnawed-off sections: Flesh- and bone-eating insects were the culprits.
The evidence comes from dinosaur bones that were buried under soft mud 148 million years ago after a nearby river overflowed. Utah's Western Paleontological Laboratories recovered the bones and turned them over to Brigham Young University scientists, who recently pieced together what happened.
Precise recreations of dinosaur-era events are rare, but the scientists now know the following: A Camptosaurus adolescent dinosaur died in what is now Wyoming, lying down for its final rest. Flying low over a floodplain a few days later, dermestid beetles used their antennae to detect the odor of the decaying carcass, where they laid their larvae that consumed the dinosaur's bones.
"Bone consumption by dermestids is a last resort," said Brooks Britt, lead author of a remarkably vivid report about the dinosaur bones published today in the journal Ichnos. "They prefer juicy tissues."
"However, larvae, lacking wings, cannot fly off to another carcass when food -- soft tissues -- becomes scarce," added Britt, assistant professor of geology at BYU. "In order to become large enough to pupate and therefore survive to the adult stage, the larvae will resort to consuming the soft, greasy ends of bones and the marrow-filled interiors."
He and colleagues Rodney Scheetz and Anne Dangerfield began their investigation after first noticing that tiny teeth marks accompanied the missing parts of their Camptosaurus skeleton. Meaning bent lizard, due to its hunched over appearance, Camptosaurus was a beaked, early Jurassic plant-eater.
The teeth marks on its bones showed that the gnawers were very small and possessed two pointy teeth set on symmetrical jaws. The scientists first tried to match this pattern with an extremely tiny mammal from the period, the Fruitafossor, but its skull and body diameter were still too large.
The researchers then narrowed down the suspects to four groups of insects known to eat bone. These include mayflies, moths, beetles and termites.
"Although it is not commonly known, termites can consume bone, both fresh and weathered, and can completely consume a human skeleton," the team wrote.
Only dermestid beetles, which are still in existence today, matched the dinosaur bone marks, which Britt molded using materials obtained from his dentist, and then viewed under an electron microscope.
"As with undertakers today, the dermestids will always have a job, and that job has remained relatively unchanged for at least 150 million years," Britt said. "A carcass is a carcass and the tissues, including bone, muscle and ligament, have not changed much through time."
Under the microscope, the researchers even detected signs of dermestid feces -- called frass -- within the bones. The frass, together with the bites, constitute the oldest known evidence for dermestid beetles, predating the prior earliest evidence by 48 million years.
The scientists further determined that the climate at the time of the Camptosaurus' death must have had 60 to 80 percent humidity and a temperature of 77 to 86 F, because those match the beetle's typical habitat. The area today has an average yearly temperature of 43.5 F.
"Dr. Britt's work is really exciting and delves into unique aspects of paleobiology that few scientists have yet explored," said Eric Roberts, a dinosaur decomposition expert at South Africa's University of the Witwatersrand.
"Insects are among the most diverse and abundant organisms on the planet, yet we know next to nothing about the fossil record of insects because of their extremely limited preservation potential," Roberts added.
Britt and his team continue to study bug bites on dinosaur bones and have found that beetles did most of the damage during the Cretaceous, while termites dominated the dino-feasting during the Jurassic.
Related Links:
Discovery News blog: Born Animal
Natural History Museum: Camptosaurus