Slow-cooking dinosaur eggs may have contributed to extinction

A joint research team from the University of Calgary, American Museum of Natural History, and Florida State University announced Monday that the eggs of non-avian dinosaurs such as the duck-billed dinosaur took as long as six months to hatch, far longer than had previously been believed.

Hypacrosaurus stebingeri nest with eggs. Image: Roland Tanglao/Wikimedia Commons (CC BY 2.0)

Bird eggs incubate for 11 to 85 days, about half the time of most other egg-laying vertebrates. Scientists had thought dinosaur eggs were more like those of modern birds than modern reptiles, but this long hatch time is far more reminiscent of monitor lizard than magpie.

The scientists reached this conclusion by comparing CT scans of the teeth of dinosaur embryos of two different species, the Protoceratops andrewsi, which has eggs weighing under 200 grams, and Hypacrosaurus stebingeri, a type of duck-billed dinosaur that has eggs twenty times that size.

They observed the von Ebner lines, patterns that form in vertebrate teeth as they grow, to determine how long the overall developmental process was taking.

"They're kind of like tree rings, but they're put down daily," said Florida State University co-author Gregory Erickson. "And so we could literally count them to see how long each dinosaur had been developing." They found the Protoceratops embryo was about three months old and the Hypacrosaurus about six months.

According to the research team, this may be one reason why dinosaurs did not recover after the Cretaceous-Paleogene extinction event 65 million years ago.

Both the eggs and any parents guarding them would have drawn the attention of predators and been unable to flee floods or other problems. Guardians might not have been able to move far to find food. This, researchers say, would have put dinosaurs at a disadvantage over animals with quicker-hatching eggs and their mammalian competitors. (Wikinews)

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