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Dinosaur bones reveal ancient bug bites

Paleontologists have long been perplexed by dinosaur fossils with missing pieces – sets of teeth without a jaw bone, bones that are pitted and grooved, even bones that are half gone. Now a Brigham Young University study identifies a culprit: ancient insects that munched on dinosaur bones.

BYU professor Brooks Britt will publish his study of these dinosaur bone-eating bugs in the May 8 issue of the scientific journal Ichnos. Britt’s idea for this study came when he first noticed the unique markings on the bones as an undergraduate at BYU.

“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,” Britt said.

Years later, current BYU student Anne Dangerfield also wondered about the markings and teamed up with Britt to investigate the cause. They studied insect traces on the 148-million-year-old remains of a Camptosaurus, a plant-eating specimen discovered in Medicine Bow, Wyo., in 1995.

“I knew this trace was something different because I had been looking at fossil termite traces all summer, so I knew we needed to check it out,” Dangerfield said.

Their analysis revealed that beetles, from the family entomologists call Dermestidae, left the markings on the Camptosaurus. Dermestid beetles still exist today and are typically brown or black, oval-shaped and feed on flesh, hair, skin or horns of carcasses.

Information about the beetle’s typical habitat reveals the climate at the time of the Camptosaurus’ death probably had 60-80 percent relative humidity and a temperature of 77-86 F. By comparison, the average yearly temperature in Medicine Bow is now 43.5 F.

When the dinosaur died near what is now Medicine Bow, the carcass was consumed by other insects. The beetles then infested the Camptosaurus within months of its death.

In addition to shedding light on Wyoming’s ancient climate, Dangerfield and Britt’s work shows dermestid beetles existed much earlier than previously thought. The traces on this Camptosaurus predate the oldest body fossils for dermestid beetles by 48 million years.

“This information gives us an idea of the environment during the Jurassic period and the evolution of insects,” Dangerfield said.

To analyze the markings on the bones, Britt went to his family dentist for molding materials, allowing Britt to more quickly create replicas of the bone traces to work with.

He took the castings back to BYU’s Earth Science Museum where he used an electron microscope to look at the mandible markings in the bone, analyzing eating patterns and the width between the teeth marks. Britt and Dangerfield compared the marks to information about the mandibles of moths, termites, mayflies and dermestid beetles – all known to consume bone – to determine the identity of the insect.

“Other people have thought they have seen dermestid beetle marks, or they have interpreted termite marks as dermestids, but this paper provides a guide to identifying insects from the bone traces,” Britt said.

Britt and Dangerfield continued their research by looking at more than 7,000 bones from various quarries and found that insect traces on dinosaur bones are quite common, but dermestid beetle traces were found only on the Camptosaurus skeleton from Medicine Bow.

“Dr. Britt’s work is really exciting and delves into unique aspects of paleobiology that few scientists have yet explored,” said Eric Roberts, an expert in dinosaur decomposition who teaches 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.”

Dangerfield’s undergraduate and graduate mentored research experience has impressed many potential employers. After finishing her master’s degree in August, she will assume a position with Exxon Mobile as an exploration oil and gas geologist.

“Whenever I show my resume, employers are impressed with the amount of undergraduate research I’ve done,” Dangerfield said.

Britt received his bachelor’s and master’s degrees at BYU and his Ph.D. at the University of Calgary and is an assistant professor. Rodney Scheetz, another author on the study, is the curator at BYU’s Earth Science Museum.


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BYU geology professor Brooks Britt inspects ancient bug bites on a bone from a Camptosaurus. Behind Britt is a Torvosaurus tanneri, whose bones were also munched on by bugs.

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BYU student Anne Dangerfield is a co-author on the study that identified the insects that munched on the Camptosaurus skeleton.

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The groove seen on the tip of this vertebra was excavated by dermestid beetle larvae.

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Dangerfield points to small pits made by beetle larvae on a shoulder blade.

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A pit excavated by the strong mandibles of dermestid beetle larvae while searching for soft, fat-soaked bone.

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The sinuous grooves in this Camptosaurus knee joint were mined by beetle larvae hungry for proteins from the bone.

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Partial set of "dinosaur dentures," a product of insects consuming the jaw bones, leaving behind only teeth, which are much harder than bone. Prior to this study, there was no explanation for boneless sets of articulated teeth.
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