The artist’s impression of a youthful tyrannosaurus. Credit: Julius Csotonyi
They are one of the largest predators ever to walk the earth, but experts have discovered that some baby tyrannosaurs were only the size of a Border Collie when they took their first steps.
The most famous fossils of tyrannosaurus embryos shed light on the early development of the colossal animals, which can grow up to 40 feet long and weigh eight tons.
A team of paleontologists, led by an Edinburgh researcher, made the discovery by examining the fossilized remains of a small jawbone and claw in Canada and the USA.
Silhouette image showing tyrannosaurs on baby. Credit: Greg Funston
Baba tirannosourusse
The production of 3D scans of the delicate fragments revealed that they were tyrannosaurs – cousins of T. rex – which, based on the size of the fossils, were about three feet long when they hatched.
The team’s findings suggest that tyrannosaur eggs – the remains of which have never been found – were about 17 centimeters long. This could help efforts to recognize such eggs in the future and gain greater insight into the nesting habits of tyrannosaurs, researchers say.
The analysis also revealed that the three-centimeter-long jaw contained characteristic tyrannosaurus traits, including a pronounced chin, indicating that these physical traits were present before the animals hatched.
Paleontologists doing fieldwork. Credit: Greg Funston
Important insights
Little is known about the earliest stages of evolution of tyrannosaurs – which lived more than 70 million years ago – despite being one of the most studied dinosaur families. Most tyrannosaurus fossils previously studied are from adult or older juvenile animals.
These bones are the first window in the early lives of tyrannosaurs and they teach us about the size and appearance of tyrannosaurs. We now know that they would have been the largest hatcheries ever hatched from eggs, and that they would look strikingly like their parents – both good signs of finding more material in the future. – Dr Greg Funston, School of Geosciences
Reference: “Baby tyrannosaurid bones and teeth from the late Chalk of Western North America ”by 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, was supported by the Royal Society, Natural Sciences and Engineering Research Council of Canada, and the National Science Foundation. It also involved researchers from the universities of Alberta and Calgary, Canada, and the Montana State and Chapman universities, USA.