Slow hatch may be tied to dinosaur extinction

LONDON — The mystery of why the dinosaurs became extinct after the Cretaceous meteor strike, while birds and mammals flourished, may finally have been solved.

University of Calgary and Florida State University paleontologists have discovered that dinosaur young took so long to hatch and grow into adulthood that populations failed to recover quickly enough after the devastating impact 65 million years ago.

In contrast, birds and small mammals only took a few weeks for their offspring to emerge giving them a distinct advantage.

“Some of the greatest riddles about dinosaurs pertain to their embryology” — Gregory Erickson

The discovery was made by scientists who realized it was possible to calculate how long it took for dinosaurs to hatch based on marks on the teeth of embryos and babies.

Just like tree rings growing a new layer each year, teeth grow a new layer each day, which can be seen in microscopic lines in the dentine. By counting the lines, scientists found that it took dinosaurs between three and six months to hatch.

The lengthy incubation period — in comparison to small mammals — made the hatchlings, and their parents, vulnerable to predators and left them struggling to re-establish their species.

“Some of the greatest riddles about dinosaurs pertain to their embryology, virtually nothing is known,” Gregory Erickson, professor of biological science at Florida said.

“We suspect our findings have implications for understanding why dinosaurs went extinct at the end of the Cretaceous period, whereas amphibians, birds, mammals and other reptiles made it through and prospered.”

To find out where dinosaurs fitted in, the team studied the fossils of dinosaur embryos.

Their results showed nearly three months for tiny protoceratops embryos and six months for those from the giant hypacrosaurus.

The study was published in Proceedings of the National Academy of Sciences.