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Artist’s impression of a juvenile tyrannosaurus. Credit: Julius Csotonyi
They are among the largest predators to ever walk on Earth, but experts have found that some baby tyrannosaurs were only the size of a Border Collie dog when they took their first steps.
The first known fossils of tyrannosaur embryos shed light on the early development of the colossal animals, which could grow to 40 feet long and weigh eight tons.
A team of paleontologists, led by a researcher from Edinburgh, made the discovery by examining the fossilized remains of a tiny jaw bone and claw unearthed in Canada and the United States.
Silhouette imagery showing baby tyrannosaurs at scale. Credit: Greg Funston
Baby tyrannosaurus
Production of 3D scans of the delicate fragments revealed that they belonged to baby tyrannosaurs – cousins of T. rex – which, depending on the size of the fossils, were around three feet long when they hatched.
The team’s findings suggest the tyrannosaur eggs – the remains of which have never been found – were about 17 inches long. This could help efforts to recognize these eggs in the future and better understand tyrannosaur nesting habits, the researchers said.
The scan also revealed that the three-centimeter-long jawbone possesses distinctive tyrannosaur characteristics, including a pronounced chin, indicating that these physical traits were present before the animals hatched.
Paleontologists performing fieldwork. Credit: Greg Funston
Vital information
Little is known about the early stages of tyrannosaur development – which lived over 70 million years ago – despite being one of the most studied dinosaur families. Most of the tyrannosaur fossils studied previously were juvenile, adult or old animals.
These bones are the first window into the early lives of tyrannosaurs and they tell us about the size and appearance of baby tyrannosaurs. We now know that they would have been the largest hatchlings to ever emerge from eggs, and they would have looked remarkably like their parents – two good signs for finding more material in the future. – Dr Greg Funston, School of Geosciences
Reference: “Bones and Teeth of a Late Baby Tyrannosaurus Cretaceous of Western North America ”by the authors: Gregory F. Funston [email protected], Mark J. Powers, S. Amber Whitebone, Stephen L. Brusatte, John B. Scannella, John R. Horner and Philip J. Currie, January 25, 2021, Canadian Journal of Earth Sciences.
DOI: 10.1139 / cjes-2020-0169
The study, published in the Canadian Journal of Earth Sciences, has received support from the Royal Society, the Natural Sciences and Engineering Research Council of Canada and the National Science Foundation. It has also involved researchers from the universities of Alberta and Calgary, Canada, and the state universities of Montana and Chapman, United States.
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