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Utah dig site reveals increased diversity of fossilized eggshells

A team of biological, Earth and environmental scientists from North Carolina State University, Stellenbosch University and the University of Minnesota has found new types of ancient eggshells in the Mussentuchit Member in Utah. Their is published in the open-access journal PLOS ONE.

The Mussentuchit Member is a sedimentary rock layer that is part of Utah's Cedar Mountain Formation. Researchers have been digging at the site for more than half a century. It was also the site of the first fossilized egg find from the Cenomanian age. Because of work conducted at places like the Mussentuchit Member, a new branch of science called "oodiversity" has evolved, which is the study of the diversity of fossilized eggs.

The researchers examined the range of ancient eggshells recovered from the Mussentuchit Member over the years to learn more about the creatures that laid them. Their work involved studying more than 4,000 fossilized eggshell fragments and attempting to categorize them based on their features and data found at the dig site, such as fossilized bones that might have been associated with the eggs and their shells.

They also put them under microscopes to learn about their structure and to differentiate them from one another. In some cases, they went even further, using scanning electron microscopes to better understand some of the details in the fossils.

Their task was difficult, to say the least, but they still managed to find a category for most of the samples they studied. They also found some eggshell types that had not been identified before and were able to confirm that at least six egg-laying species lived in the area approximately 100 million years ago—three that had been laid by oviraptorosaur dinosaurs, two by ornithopod dinosaurs and one by a crocodylomorph, a type of ancient reptile.

The research team notes that several of their findings mark the first time that these eggshells have been identified in North America. They suggest that Cretaceous North America was more complex than has been thought.