Baby tyrannosaurs were 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 paleontologists made the discovery by examining the first known fossils of tyrannosaurus embryos.
“These bones are the first window into the early lives of tyrannosaurs and they teach us about the size and appearance of tyrannosaurs,” University of Edinburgh paleontologist Greg Funston said in a statement.
The researchers, led by Funston, used the fossilized remains of a small jaw and claw excavated in Montana and Alberta, Canada, and made 3D scans to analyze the bones.
Their findings suggest that the carnivorous creatures – cousins of the T-Rex dinosaurs that lived more than 70 million years ago – were only about 3 feet long when they hatched.
This would make them as big as the usual dog breed – and much larger than the baby dinosaurs seen in movies like ‘Jurassic Park’.
“Hatching tyrannosaurs would have hatched one of the largest animals ever from an egg,” Funston wrote in a blog post about the research.
His team also estimated that tyrannosaur eggs would have been about 17 centimeters long – a finding that the researchers said could help 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 different physical characteristics, including an ‘pronounced chin’, which made them look “remarkably like their parents”, which 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 are 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.