Baby tyrannosaurs were about the size of Border Collies when they took their first steps – despite growing as long as 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 baby tyrannosaurs,” paleontologist Greg Funston of the University of Edinburgh said in a statement.
The researchers, led by Funston, used the fossilized remains of a small jaw bone and claw, excavated in Montana and Alberta, Canada, and performed 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 1 meter long when they hatched.
That would make them about the size of the common dog breed – and much bigger than the baby dinosaurs that came out in movies like “Jurassic Park.”
“Newborn tyrannosaurs are said to have been among the largest animals to ever hatch from an egg,” Funston wrote in a blog post about the study.
His team also estimated that tyrannosaur eggs would have been about 17 inches long – a finding the researchers say could help identify such eggs more easily and gain a better understanding of the creatures’ nesting habits.
Further analysis showed that the tyrannosaurs were born with several physical characteristics, including “a pronounced chin,” making them “remarkably similar to their parents,” who could weigh as much as 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 to look 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.