Research Training Program

Jonathan Mitchell
Appalachian State University
Boone, North Carolina

Matthew T. Carrano, Ph.D.
Supervising Scientist
Department of Paleobiology

"This was one of the better
experiences that I have had
- many new things to see,
do and, above all, learn."

Dinosaur Eggs from the Jurassic of Wyoming

This research focuses on identifying what kind of dinosaur laid a large number of eggs that were found at a site in the Morrison Formation (a group of rocks that formed in ancient streams and floodplains during the Late Jurassic Period, 150 million years ago). The eggs of many dinosaurs, including birds, are surrounded by a hard shell of tiny interlocking crystals. By looking at the fractured surfaces of the eggshells under a powerful microscope, and then comparing the way the crystals interlock, it is possible to identify the basic type of dinosaur that laid these particular eggs. But how is it possible to know which particular dinosaurs laid which eggs? Eggs are occasionally found with embryos still inside, allowing us to match the type of dinosaur with the type of eggshell crystal. By comparing the eggshell's crystals with those of known dinosaurs, we can make a specific hypothesis about the origin of the eggs. These eggshells are most similar to those of the two-legged, meat-eating theropod dinosaurs, such as Allosaurus. This site also produced many bones that looked like those of embryos (tiny and with an unfinished texture). Finding embryonic dinosaur bones is rare, much more so than eggshell. Finding a large amount of both together, in a deposit where the fossils were not moved before being buried, suggests that the embryos probably came from the eggs. Examining the bones reveals several features that diagnose them as theropod. Among the bones were teeth that show features of coelurosaurs, a specific kind of theropod. This is a well-known group, as it contains everything from Tyrannosaurus rex to Velociraptor and Deinonychus, all the way to the only surviving dinosaurs: the birds. By understanding this site, including the embryos, eggshells, and the surrounding environment, a better understanding of the biology and evolution of an early member of the important, and highly successful, coelurosaurs can be gained.

This research was supported by the Dick Benson Internship Endowment.