Dinosaur eggs, at least of one small birdlike genus called Troodon, may have been brooded and hatched just like modern birds. Researchers from Montana State University and the University of Calgary recently published their evidence in Paleobiology.
A lot of reptiles like crocodiles and turtles also lay eggs, but the mother usually just digs a hole, lays the eggs, and buries them in the dirt. After that, the babies are pretty much on their own.
By comparison, most birds sit on their eggs and fuss over them a bit, often turning them to make sure they develop properly. A watchful parent, and often both of them, is almost always on the scene to bring up baby.
The trouble is that both birds and crocodiles are living relatives of dinosaurs, so it has been an open question whether dinosaur eggs were buried or brooded.
The researchers teamed up to study the late Cretaceous era Troodon formosus fossil eggs, which are very roughly 75 million years old. The fast-running meat-eaters had sickle-shaped claws, with very large eyes and also some of the largest known brains relative to body size of any dinosaur. Ever since the link between birds and dinosaurs was established, T. formosus has been singled out as being particularly closely related to primitive birds like Archaeopteryx.
By examining the porosity of the fossil eggshells, the scientists determined that the eggs were brooded, not simply buried and abandoned. Completely buried eggs must be far more porous, to allow the living creature growing inside to breathe properly.
“[T]his dinosaur did not completely bury its eggs in nesting materials like crocodiles do,” said study co-author Darla Zelenitsky.
Lead author David Varrichio agreed, saying that the elongated eggs were only partly buried in mud, laying them almost vertically so that they were poking straight up. An adult dinosaur would then have sat on the eggs to brood them.
The birdlike nesting behavior and the brooding of the dinosaur eggs is more evidence of the evolutionary link between birds and dinosaurs.
[photo Darla Zelenitsky studying Troodon fossil dinosaur eggs by Jay Im (University of Calgary)]
[photo fossil Elangatoolithidae dinosaur eggs by Daderot via Wikipedia Commons]