(CNN) – Tyrannosaurs were fearsome predators in the dinosaur kingdom, but new research shows that their creatures were as large as a medium-sized dog.
According to a study from the University of Edinburgh, published on Monday, researchers studying the first known fossils of tyrannosaurus embryos suggest that the dinosaurs were about three meters long when they hatched.
A team of paleontologists studied the fossilized remains of a tyrannosaurus embryo, that is, a jaw bone and a claw found in Canada and the United States, respectively.
After producing 3D scans of the remains, the researchers were able to predict that the dinosaurs would have emerged from the eggs about 17 inches long.
Tyrannosaurus egg remains have never been found, but this finding could help paleontologists detect them in the future.
“Dinosaur babies are very rare,” lead author Greg Funston, a paleontologist at the University of Edinburgh, told CNN, explaining that larger specimens are better represented in the fossil record because their bones were more durable.
“Most dinosaurs don’t nest in an area where eggs could be easily buried,” Funston added, making conservation of such finds even rarer. “It’s a big deal,” he said.
The claw is of an Albertosaurus and the jaw bone of a Daspletosaurus, both of which would have grown to about 35 feet in length.
They were slightly smaller than their more famous cousin, Tyrannosaurus rex, which grew to 40 feet in length, Funston said.
The researchers found that the jawbone, which was just over an inch long, had distinctive features of the tyrannosaurus group, including a pronounced chin.
While tyrannosaurs are known to have undergone many changes throughout their lives, this shows that embryos already had certain physical traits before they hatched, Funston said.
The discovery could help resolve debates about whether other specimens in the fossil record come from new species or younger specimens of known species, he added.
Tyrannosaurs lived more than 70 million years ago. Little is known about their early development, as most of the specimens studied come from older animals, according to Funston, but now researchers know they were born with a complete set of teeth and could hunt on their own, yet than in smaller prey than adults.
“These were animals that hatched and were probably quite active relatively soon after picking,” Funston said.
The study was published in the Canadian Journal of Earth Sciences.
Funston said he plans to try to produce scans of the remains at a higher resolution, to allow for the study of tooth development, which could reveal how long the tyrannosaurs spent inside the eggs before hatching.
This story was first published on CNN.com According to new research, tyrannosaurus babies were the same size as a dog