Dinosaur egg bonanza gives vital clues about prehistoric parenting

X Scalper

Perhaps the most amazing thing about fossils is that they don’t just show us what extinct animals looked like, they can also reveal how those animals lived. Even a fossilized dinosaur egg can provide a wealth of clues about its parents’ behavior.

Dinosaur hunters in the Javkhlant region of the Gobi Desert in Mongolia recently discovered 15 exceptionally well preserved clutches of eggs that came from a species of theropod dinosaur. Through some fantastic detective work, the researchers argue that this fossil site provides the strongest evidence yet that such dinosaurs nested in colonies and protected their eggs.

I’m a behavioral ecologist. I study how animals live their lives and how species fit together in ecosystems. We can uncover the behavioral ecology of past species and ecosystems by using fossils and our knowledge of animals and habitats today. In this case, I suggest that these dinosaurs may have protected their eggs as a community rather than caring solely for their own nests. It is also possible that these dinosaurs didn’t need to care for their young once they had hatched.

The spherically-shaped eggs were found in clutches of between three and 30 eggs in what was a seasonally arid flood plain. They were laid towards the end of the Cretaceous period around 66m years ago, not long before the dinosaurs disappeared.

The eggs are between 10cm and 15cm in diameter, similar in size to those of the largest living bird species, the ostrich. By comparing the eggs with fossilized embryonic remains in other eggs, the scientists identify that these specimens likely came from the Therizinosauroidea family.

The shells of the eggs have a high porosity, meaning they contain lots of tiny holes. The researchers looked at how this compares to the eggs of living species. We know these dinosaurs lived in a dry, arid environment, and animals in these habitats (such as ostriches) typically lay eggs with few pores in order to minimize water loss.

Instead, the high porosity of the Javkhlant eggshells is similar to those of Australasian megapode birds such as the mallee fowl, and crocodilians. These species cover or bury their eggs in organic-rich material, which generates heat as it rots, in order to incubate the eggs. The high porosity of the Javkhlant eggs suggests these dinosaurs did the same because the pores would have made it easier for the developing embryo to breathe in the damp, oxygen-poor environment of rotting vegetation.

The fossils also indicated that all the eggs were laid and hatched in the same nesting season, providing evidence that the dinosaurs nested in colonies. About 60 percent of them hatched successfully, a relatively high hatching rate similar to that of modern birds and crocodilians that protect their eggs. This supports the argument that these dinosaurs also looked after their nests.