Fossil eggshell: Fragments from the past
By Laura E. Wilson1,2, Karen Chin1,2, Frankie D. Jackson3, and Emily S. Bray1 1Museum of Natural History, University of Colorado, Boulder, Colorado, USA; 2Department of Geological Sciences, University of Colorado, Boulder, Colorado, USA; 3Department of Earth Sciences, Montana State University, Bozeman, Montana, USA

The study of fossil eggshell is diverse in focus and methodology and sheds light on the paleobiology, systematics, and paleoecology of the organisms that laid them. Eggs provide a unique glimpse into reproductive physiology and behavior, which could not otherwise be explored. The following list summarizes what eggs and eggshell can tell us:

So there really is a lot we can learn from fossil eggshell. Let's take a closer look:

I. Eggshell research Everything you ever wanted to know about the shells of amniote eggs, both past and present. Introduction to eggshells The evolution, components, and physical properties of the amniote egg. Eggshell morphology and structure A quick look at some of the methods used to study fossil eggshell and an examination of the general morphology, crystalline structure, and textures of eggshell. Eggshell identification: Who laid the egg? Fossil eggshell is classified on the basis of external physical characteristics and internal morphology. Comparisons between the internal structure of fossil eggshell (the microstructure) and modern eggshell also helps in this process. Knowing the eggshell type can provide information about the egg-layer. Fossil record of amniote eggs When eggshell appears in the fossil record, where it has been found globally, and the circumstances that can affect its preservation. Paleobiology and eggs What we can discover about the origin, structure, evolution, and behavior of extinct organisms based on studies of eggshell structure, the arrangement and orientation of eggs in nests, embryonic remains, eggshell pathologies, and depositional conditions.

	II. Karl Hirsch and the Hirsch Eggshell Collection About one of the world's foremost researchers and collectors of fossil eggs/eggshell and the collection that bears his name.

III. Case studies Selected research studies of fossil eggs and eggshell and what they have revealed. The Willow Creek Anticline, Two Medicine Formation, Montana The thirty years of research on the eggs and nests — as well as the embryonic, hatchling, juvenile, and adult skeletal material associated with them — of multiple species of dinosaurs from the Two Medicine Formation of Montana provide a superb example of the complex path that scientific exploration can take.

IV. Where eggs and eggshell are found: An interactive map Browse the Hirsch Collection using geographic, taxonomic, age, or other parameters in this database interface. Your selection is Google-mapped, then you can click on any locality on the custom map to see information on the eggshell specimen(s) found at that locality.

This site was funded by the National Science Foundation under award no. 0646420.

 
The authors would like to thank Toni Culver, Vertebrate Collections Manager, University of Colorado Museum of Natural History, for her help with the organization of the Karl Hirsch eggshell collection and accumulating data and images for the website; and Jack Horner, Curator of Paleontology, Museum of the Rockies, for suggestions on how to make the information in the website more accurate and accessible.