Baby tyrannosaurs were just about the size of Border Collies when they took their first steps — despite being able to grow up to 40 feet, according to a study published Monday.
A team of paleontologist made the discovery by examining the first-known fossils of tyrannosaur embryos.
“These bones are the first window into the early lives of tyrannosaurs and they teach us about the size and appearance of baby tyrannosaurs,” said University of Edinburgh paleontologist Greg Funston in a statement.
The researchers, led by Funston, used the fossilized remains of a tiny jaw bone and claw, unearthed in Montana and Alberta, Canada, and created 3D scans to analyze the bones.
Their findings suggest that the meat-eating creatures — cousins of the T-Rex dinosaurs who lived more than 70 million years ago — were only about 3 feet long when they hatched.
That would make them about the size of the common dog breed — and much larger than the baby dinos seen hatching in movies like “Jurassic Park.”
“Hatchling tyrannosaurs would have been among the largest animals ever to hatch from an egg,” Funston wrote in a blog post about the research.
His team also estimated that tyrannosaur eggs would have been about 17 inches long — a finding the researchers said could help to identify such eggs more easily in the future and gain greater insight into the nesting habits of the creatures.
Further analysis showed that the tyrannosaurs were born with distinct physical traits, including “a pronounced chin” — making them look “remarkably like their parents,” who could weigh up to 8 tons as adults, the researchers said.
“These are just the first clues to understanding baby tyrannosaurs,” Funston wrote, “but now we know where to look, and what we’re looking for.”
The study was published in the Canadian Journal of Earth Sciences and included researchers from the universities of Alberta, Calgary, Montana State and Chapman in California.