A team of paleontologists from Lake Forest College, Stellenbosch University, the University of Minnesota and North Carolina State University has described a new assemblage of fossil eggshells from the Mussentuchit Member of the Cedar Mountain Formation, which is a renowned unit amongst scientists studying the early Late Cretaceous epoch.
100-million-year-old dinosaur eggshell fragments from the Mussentuchit Member of the Cedar Mountain Formation. Image credit: Lake Forest College.
The first fossil eggshell from the Mussentuchit Member of the Cedar Mountain Formation was described over fifty years ago.
In the half-century since, the fossil eggshell diversity of this rock unit has been limited to only one egg type.
However, Lake Forest College’s Dr. Josh Hedge and colleagues uncovered an alternative narrative.
“We found new dinosaur egg types here that have previously not been seen from this time or from this location,” Dr. Hedge said.
“We found five different types of eggshells in this area when previously research described one kind.”
“We found three kinds of eggshell fragments belonging to feathered bipedal dinosaurs, two kinds of eggs from ornithopod duck-billed dinosaurs, and also a really funky find: some crocodylomorph eggshells.”
These new discoveries challenge the traditional view of one of each kind of dinosaur living in an ecosystem.
“We can see a pattern of coexisting dinosaurs,” Dr. Hedge said.
“Just as animals like multiple big cats coexist on the African savannas now, we can see the co-occurrence of similar kinds of dinosaurs in one geographic area.”
The researchers hope to uncover information that will lead to a better understanding of the ecosystem 100 million years ago.
They are currently researching ways to better understand these oviraptorosaur eggs.
“We have found so many eggshells that we have a sample size large enough to interpret them at higher resolution, so we can hopefully distinguish not just between species, but individuals sharing a single nest, for example,” Dr. Hedge said.
The team’s paper was published online in the journal PLoS ONE.
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J. Hedge et al. 2025. Fossil eggshell diversity of the Mussentuchit Member, Cedar Mountain Formation, Utah. PLoS ONE 20 (2): e0314689; doi: 10.1371/journal.pone.0314689
