Dinosaur eggs may have had a lot in common with reptile eggs, in the sense that it may have taken months for them to hatch, instead of mere weeks.
A team of researchers from Florida State University sought to find out how long it takes for baby dinosaurs to emerge from their eggs, and carried out this study by analyzing their fossilized teeth. A report from NPR states that this is possible because teeth, just like tree rings, have so-called “lines of von Ebner,” which are growth lines that are used to estimate a living creature’s age.
Before the release of the findings, researchers believed that dinosaur eggs took about a week and a half to three months to hatch, making them similar to bird eggs in that regard. However, based on the FSU study, it takes much longer, as dinosaurs could take three to six months to hatch, depending on how small or large they are.
Study lead author Greg Erickson, a professor of anatomy and vertebrate paleontology at Florida State University, compared the determination of a dinosaur’s age through their teeth to layers of paint. Dentine, in liquid form, fills in a tooth’s inner portion each day, and as it hardens into mineral form, it leaves growth lines on a dinosaur’s tooth, allowing researchers to study the fossilized teeth to glean their data.
For the purpose of the study, the FSU team looked at Protoceratops andrewsi and Hypacrosaurus stebingeri, two dinosaurs of varying sizes that produced eggs that, as NPR noted, range from being among the smallest to among the largest.
A report from Business Insider included some information on the two dinosaurs whose eggs, with intact skeletons inside, were studied by the FSU team. Protoceratops andrewsi was a smaller, lesser-known relative of Triceratops, while Hypacrosaurus stebingeri was a duck-billed dinosaur; both were plant-eating animals, with Protoceratops eggs being smaller than those of Hypacrosaurus.
Dinosaur eggs belonging to Hypacrosaurus weighed in at four kilograms, or about four times heavier than the average ostrich egg — putting things in context, Erickson compared them to “volleyballs” in terms of appearance.
After analyzing both eggs, the researchers concluded that it could take as short as three months for smaller eggs to hatch, or as long as six months for the larger ones to hatch. When compared to bird eggs, the Protoceratops egg would have taken more than twice as long to incubate and would have hatched a little sooner than a comparable reptile would have. The Hypacrosaurus egg, on the other hand, would have required considerably more time to hatch than a comparable modern reptile egg, wrote Business Insider.
It’s that long timeframe that makes Erickson believe that that may have helped drive dinosaurs extinct, in conjunction with the mass extinction event from about 66 million years ago. This catastrophic event would have wreaked so much damage — about 75 percent of all life on Earth — that the long incubation periods made it extremely hard for new life to replace the old.
“You can imagine after the asteroid hit all of a sudden the resources went to nothing. Even when they did reproduce, they had extremely long incubation periods on top of it.”
According to NPR, the study did come with its share of limitations, primarily the lack of specimens with corresponding dinosaur eggs with a skeleton inside. Although the eggs themselves are common, it’s quite hard to find those with a fossilized baby dinosaur inside, and with that limitation in mind, Erickson hopes to study more dinosaurs, including carnivorous species, to see if their theory on incubation times would still hold up, regardless of the type or species.
[Featured Image by Tim Boyle/Getty Images]