A fossilized Mussaurus egg that was the subject of one of two new studies documenting soft-shelled eggs at the time of the dinosaurs. Mussaurus was a long-necked, plant-eating dinosaur that grew to 20 feet in length and lived in modern-day Argentina between 227 and 208.5 million years ago. (Diego Pol)
A side view of the fossil of the giant soft-shelled egg found in Antarctica. (Legendre et al. 2020)
Smithsonian Magazine has a story about dinosaur eggs. Nature had two articles that found evidence that dinosaur eggs were soft-shelled. The first study found evidence of soft-shelled eggs by analyzing fossilized Protoceratops and Mussaurus egg shells. The evidence suggests eggs similar to those of turtles. The second paper identified an enigmatic fossil, commonly referred to as "The Thing", as a soft-shelled egg from a mosasaur.
The new evidence that some dinosaurs and their extinct reptilian contemporaries laid eggs without hard shells helps explain the rarity of eggs in the first half of the fossil record, according to the Times. Soft shells tend to rot away quickly, which would have made it less likely for them to fossilize. Both finds may have implications for the reproductive evolution of dinosaurs and ancient reptiles.
Chilean paleontologists found “The Thing” in Antarctica in 2011. It was a fossil the size of a football that had a crinkled exterior that made it look deflated. The researchers who had collected The Thing couldn’t tell what it was, reports Nell Greenfieldboyce of NPR. But when paleontologist Julia Clarke of the University of Texas at Austin saw its rumpled surface, she knew just what she was looking at.
