Juvenile T. rex was already eating large prey

New research from the University of Wisconsin Oshkosh indicates that even as a teenager the Tyrannosaurus rex showed signs that it would grow up to be a ferocious predator.

In a study published last week in the peer-reviewed journal Peerj, scientists reported evidence that a juvenile T. rex fed on a large plant-eating dinosaur, even though it lacked the bone-crushing abilities it would develop as an adult.

While studying fossils from an Edmontosaurus–a plant-eating Hadrosaurid or duck-billed dinosaur, UWO vertebrate paleontologist Joseph Peterson noticed three large, v-shaped, bite marks on a tail bone and wondered, “Who made these?”

Peterson knew that T. rex–a member of the meat-eating dinosaur suborder known as Theropoda–was “a likely culprit.”

“We suspected that T. rex was responsible for the bit marks, because in the upper Cretaceous rock formation, where the hadrosaur was discovered, there are only a few carnivorous dinosaurs and other reptiles in the fossil record. Crocodile fossils are found there, but such a crocodile would have left tooth marks that are round rather than the elliptical punctures we found on the vertebra,” Peterson explained.

“There also were small Velociraptor-like dinosaurs, but their teeth are too small to have made the marks. Finally, an adult T. rex would have made punctures that would have been too large! That’s when we started considering a juvenile tyrannosaur.”

Joseph Peterson, a vertebrate paleontologist at the University of Wisconsin Oshkosh, demonstrates how a T. rex takes a bite. Credit: Patrick Flood

To test the hypothesis, Peterson and geology student Karsen Daus, of Suamico, coated the fossil with a silicon rubber to make a silicone peel of the puncture marks.

They found that the dimensions of the “teeth” better matched a late-stage juvenile T. rex (11 to 12 years) than an adult (approximately 30 years).

“Although this T. rex was young, it really packed a punch,” Peterson said.

“This is significant to paleontology because it demonstrates how T. rex–the most popular dinosaur of all time–may have developed changes in diet and feeding abilities while growing,” he said. “This is part of a larger, ongoing research initiative by many paleontologists to better understand how T. rex grew and functioned as a living creature over 65 million years ago.”

Research article: Feeding traces attributable to juvenile Tyrannosaurus rex offer insight into ontogenetic dietary trends

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1 Response

  1. Avatar Dave Hone says:

    This headline is quite misleading. The paper in question specificalyl says this is most likely scavening and not to do with predation or killing large prey.

    Quote: the punctures present on BMR P2007.4.1 are likely from postmortem scavenging behaviors of a juvenile tyrannosaur (https://peerj.com/articles/6573/#p-31).

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