Tyrannosaurus rex is some of the largest carnivores that have ever lived on Earth, but scientists have found that some of the cubs of this species were the size of a border collie dog when they took their first steps.
The first known tyrannosaur embryo fossils shed light on the early development of these colossal animals, which could grow up to 12 meters in length and weigh eight tons.
A group of paleontologists led by a researcher from the University of Edinburgh made the discovery by examining the fossil remains of a tiny jawbone and claw found in Canada and the United States. Three-dimensional scans of the fragile fragments revealed that they belonged to baby Tyrannosaurus – relatives of Tyrannosaurus rex – who, judging by the size of the fossils, were about a meter in length when they first appeared.
An artist’s impression of a young tyrannosaurus. Credit: Julius Csotonyi
The results of the study suggest that the tyrannosaurus eggs – whose remains have never been found – were about half a meter in length. The analysis also showed that the 3-centimeter jawbone possesses the distinctive features of a Tyrannosaurus rex, including a pronounced chin.
Today, little is known about the earliest developmental stages of tyrannosaurs, which lived more than 70 million years ago. And this despite the fact that they were one of the most studied families of dinosaurs. Most of the previously examined tyrannosaur fossils were from adults or older, young animals.
The study, published in the Canadian Journal of Earth Sciences, was supported by the Royal Society, the Science and Engineering Research Council of Canada and the National Science Foundation. It also brought together researchers from the Universities of Alberta and Calgary, Canada, and the Universities of Montana and Chapman, USA.