Eager beetle.
This close-up image shows the bite marks of a dermestid larva on a fossilized dinosaur bone.

Brooks Britt/Brigham Young University

Blame It on the Beetles

Frustrated that there aren't more dinosaur bones at your local museum? Blame beetles. A team from Brigham Young University (BYU) in Provo, Utah, has examined thousands of dino bones from the Jurassic and Cretaceous periods and found that flesh-eating bugs devoured them by the mouthful, erasing part of the fossil record in the process.

One family of beetles called dermestids--and those related to a species called Dermestes maculatus in particular--did quite a number on overripe dinos. Waiting until the first round of scavengers had eaten their fill, the beetles would lay their eggs on a body days or weeks after it had died. Then, slowly and methodically, their hungry larvae reduced what was left of the carcass to bare bone, and then some.

That's the scenario crafted by paleontologist Brooks Britt of BYU and colleagues in the current issue of the journal Ichnos. Britt first suspected the work of insects when he was in high school and found a fossilized bone that contained strange markings. Back then, he explains, "I said, 'Wait a minute, these bones have been consumed by some type of insect.' " Later, in college, when Britt asked paleontologists about the markings, he just got blank stares. So eventually, he conducted further studies with BYU colleagues, including one on a fossilized bone from a herbivorous dinosaur called Camptosaurus, found near Medicine Bow, Wyoming. The specimen revealed telltale scrapings that matched the work of dermestid beetles on contemporary samples. The team's examination of 5000 more bones produced frequent evidence of degradation by dermestid larvae as well as other species. "About one-eighth of the specimens have been degraded by insects," Britt says. "They're surprisingly common."

Britt says that the findings also confirm that the beetles lived about 150 million years ago, or nearly 50 million years earlier than their own fossils have suggested. He says that he and his colleagues plan to examine even older fossils to see how far back the dermestids lived.

Vertebrate zoologist Edward "Ted" Daeschler of the Academy of Natural Sciences in Philadelphia, Pennsylvania, calls the examinations "a classically simple way to interpret material in the fossil record." He adds that the presence of carrion-feeding insects in the dinosaur age is no surprise because they act as "nature's recyclers," but it's always interesting to see confirmation of modern insects "going back deeper in time."

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