Frankie Jackson is a dinosaur egg specialist from Montana State University in Bozeman, where she also teaches Vertebrate Paleontology. She has also participated in several expeditions to Auca Mahuevo and conducted extensive field work at Jack Horner's dinosaur nesting site in Montana called Egg Mountain.

The past three field seasons working in Patagonia have offered an unparalleled opportunity for studying the reproductive biology of sauropod dinosaurs. Few localities in the world provide the essential components found at Auca Mahuevo: eggs containing identifiable embryonic remains, exposure of extensive egg-bearing rock layers, and nest structures excavated by dinosaurs. These characteristics allow comparisons to living animals that lay hard shelled eggs such as turtles, crocodilians and birds. These studies provide information about the type of nests constructed by sauropods and the distribution of eggs and clutches in a nesting locality.

The study of eggshell microstructure also provides information about this extinct group of animals. Hard shelled eggs of both extinct and living animals are comprised of organic and mineral components. Eggshell structure is under genetic control and therefore the internal arrangement or microstructure of the calcite mineral is distinctive for different animals. Fossil eggshell, however, can change over geologic time and therefore it is important to differentiate structure, which results from egg formation from eggshell altered by geologic processes. For example, the original eggshell calcite may also be replaced by minerals that occur in the ground water. Identification of the minerals may provide clues to the paleo-environoment. For example, the zeolite mineral analcime occurs in eggs at Auca Mahuevo and is typically associated with volcanic ash and alkaline conditions.



High magnification under scanning electron microscopy also reveals eggshell structural features not otherwise visible. Unusually thick eggshell from this locality consists of two or more layers, often separated by mineralization of the original protein eggshell membrane. Auca Mahuevo is one of the rare localities in the world where eggs of this abnormality occur in clutches rather than as isolated eggshell fragments. This abnormal eggshell condition occurs in modern eggs as a result of egg retention by the female, often in response to physiological or environmental stress. The second shell layer blocks the pores that allow the embryo to take in oxygen and death usually occurs. Comparison of eggshell abnormalities that occur at this site with those found in living “reptiles” and birds may eventually provide a better understanding of the reproductive anatomy of sauropods.