Carthage biology professor Thomas Carr stands in the Carnegie Museum of Natural History with a cast of a sub-adult T.rex skull.

Carthage biology professor Thomas Carr stands in the Carnegie Museum of Natural History with a cast of a sub-adult T.rex skull.

Dinosaurs Decoded

Professor featured in National Geographic Channel documentary

Carthage biology professor Thomas Carr was featured in a National Geographic Channel documentary exploring evidence that has paleontologists questioning whether many dinosaur species ever existed.

"Dinosaurs Decoded” premiered Oct. 11, 2009, on the National Geographic Channel. The documentary features Prof. Carr, a vertebrate paleontologist and expert on tyrannosaurid dinosaurs, along with other famed paleontologists. The scientists compare how juvenile dinosaur skeletons differ from those of their adult counterparts.

"It is about how Triceratops and T. rex grew up," says Prof. Carr. "The differences between little dinosaurs when they're young and big ones when they're grown up are so great that they’re often mistaken for different species. But as new fossils are found, the gaps get filled in, and it becomes clear that there's an unbroken transition from the little ones to the big ones in terms of how their faces change."

The findings challenge long-held beliefs that baby dinosaurs were smaller versions of their parents. "Baby dinosaurs looked utterly unlike adults, and they go through a lot of changes while they grow," Prof. Carr says. "Because we knew so little about dinosaurs, we thought the babies were really a different species from the grown-ups."

That means that "there are a lot of misidentified dinosaurs out there in museums," Prof. Carr says.

Answers lead to more questions

In recent years, paleontologists including Prof. Carr have uncovered skeletons of baby and sub-adult dinosaurs that prove dinosaurs underwent a tremendous transition to adulthood.

"T. rex, like most dinosaurs, went through dramatic changes as it grew up, just like people do," Prof. Carr says. "Baby T. rex skulls are pretty sleek, long and low. As they grow up, the skulls get really big and deepen. They lose teeth and the teeth get big and fat. They look like completely different animals."

Only a handful of baby T. rex skeletons have been found. The first baby T. rex skull discovered is on display at the Cleveland Museum of Natural History, where Prof. Carr was interviewed for "Dinosaurs Decoded."

"That skull is important because it has baby features of tyrannosaurs in general and core T. rex features that identify it as that species," Prof. Carr says.

Prof. Carr is excavating another baby Tyrannosaurus rex in Montana — "the only active quarry digging up a baby T. rex," he says. That skeleton is of a dinosaur that was probably 3 years old. "It's a little big deal," Prof. Carr says.

The key to dinosaur evolution

Now that paleontologists are beginning to understand how species changed from baby to adult, they may be able to show that some dinosaurs species are actually juveniles of other dinosaurs. It's also key to understanding how dinosaurs evolved.

"If we have unrecognized babies, then we don't know anything about dinosaur biology," Prof. Carr says. "If we can understand how to recognize what a baby looks like, we can then know what their growth is, and answer questions about how dinosaurs evolved."

For Prof. Carr, a senior scientific advisor for the Dinosaur Discovery Museum in Kenosha, it's an exciting discovery.

"We're at a time in history when we can actually answer the question, 'How do dinosaurs grow up?'" he says. "It opens up a whole new way of looking at dinosaur evolution."

 

Related article: Prof. Carr helps discover new dinosaur species