The Tyrannosaurus rex is known as a fearsome predator and is among the biggest animals that have ever lived on Earth. Now scientists have determined that as babies that were just beginning to walk, these massive dinosaurs were probably about as big as a Border Collie-sized dog.
Researchers came to this conclusion after studying the fossilized remains of a claw and a little jaw bone about three centimeters in size, which belonged to baby tyrannosaurs that were found in Canada and the United States. The jaw bone has features that typically distinguish tyrannosaurs from other dinosaurs, like a prominent chin. This shows that these characteristics developed very early on.
Tyrannosaurs are cousins of the T. rex. This study has provided insight into the early developmental stages of these gargantuan animals, some of which grew to be forty feet long and weigh eight tons.
This study suggested that when the baby tyrannosaurs hatched they were about three feet long. Tyrannosaur egg remains have never been found, but this study indicates they might have been around 17 inches long. The researchers are hopeful that this information will help scientists find more.
While fossils from the tyrannosaur family are among the most studied, we still don't know much about the early phases of their development. Most fossils that researchers have assessed have belonged to juveniles or adults.
"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 the study leader Dr. Greg Funston of the University of Edinburgh's School of GeoSciences. "We now know that they would have been the largest hatchlings to ever emerge from eggs, and they would have looked remarkably like their parents; both good signs for finding more material in the future."