A study led by a Florida State University professor suggests that the time it took for baby dinosaurs to hatch from its shell also contributed to their extinction. Apparently, it took dinosaurs between three to six months to fully emerge from their shells, which gave them the disadvantage to survive the extinction event.

In the study now published in the Proceedings of the National Academy of Sciences, this would also mean that dinosaurs needed substantial resources to reach adult size, which put them at risk from predators and ultimately pushed them toward extinction. The incubation length for a dinosaur egg depends on the type of dinosaur.

Actually, some scientists have speculated that it only took a shorter amount of time for dinosaur eggs to incubate completely due to its size, just like birds, which usually need 11 to 85 days. However, FSU Professor of Biological Science Gregory Erickson,  FSU graduate student David Kay and researchers from the University of Calgary and the American Museum of Natural History wanted to find out if this theory is true.

So they studied some rare dinosaur embryos. The two dinosaurs included in the study were Protoceratops and Hypacrosaurus. Protoceratops was dinosaur that grew to the size comparable to sheep and whose eggs only weighed 194 grams while Hypacrosaurus was a huge duck-billed dinosaur whose egg weighed over four kilograms.

The research team analyzed the embryos with a CT scanner. They observed the teeth to look for growth lines that showed them how long the dinosaurs had been growing inside the eggs.

“These are the lines that are laid down when any animal’s teeth develops,” explained Erickson. “They’re kind of like tree rings, but they’re put down daily. We could literally count them to see how long each dinosaur had been developing.”

Overall, the analysis reveals that incubation for Protoceratops embryos took three months while it took six months for Hypacrosaurus. This length put the eggs and their parents at risk from predators, starvation as well as other environmental factors, the researchers stated.

Due to this, the dinosaurs ultimately disappeared from Earth while other animal species survived. Apart from this, the findings also suggest that the theory of some dinosaurs migrating from more temperate lower latitude of Canada to the Arctic during summer could be false considering the time it took for babies to hatch would not have made it possible.