USING BURIAL EXPERIMENTS TO UNSCRAMBLE DINOSAUR EGG TAPHONOMY
Experiments involving burial of four egg types and more than 100 eggs were conducted in the lab and at two field sites over a three-month period. Post-exhumation analysis revealed that the preliminary stages in the fossilization of eggs include rapid fracturing, weight change, sand casting, limited decay, and significant egg loss through scavenging. These results suggest that the eggshells tendency to fracture, its architectural strength to withstand collapse, infill by sediment, and internal membranes together elevate fossilization potential. Significantly, holes and depressed fractures on the dorsal side of some buried specimens produced a feature that is similar to "hatching windows," described as evidence that juveniles had emerged from eggs at dinosaur nesting sites. Recent examination of Cretaceous eggs from the Aix-en-Provence basin in France confirms that the gaping holes interpreted to be "hatching windows" resemble those in our experimental eggs. In our study, however, these features formed in infertile eggs as a result of scavengers or brittle fracture, contents seepage, and collapse. Thus similar broken eggs or collapsed eggshell features should be interpreted with caution from fossil egg sites.
Despite the extraordinary paleontological significance of dinosaur eggs, their taphonomy is poorly understood. Ongoing experiments will ensure that egg taphonomy is better understood so that informed interpretations can be made about fossil eggs, preservational conditions, and dinosaur reproductive ecology.