Update on the above fossil (first addressed here 20 January 2008).

In response to questions about this fossil, I did a little research, consulting with a certified Texas geologist who is quoted below. This fossil is also identified, with pictures, in the publication: Texas Fossils: An amateur collector's handbook, William H. Matthews III, Guidebook 2, Bureau of Economic Geology, The University of Texas, 1960.

This is a fossil of a creature called a protocardia bivalve.

Protocardia bivalve fossils are a genus of pelecypods (symmetrical two-shelled animals like clams, mussels, scallops and oysters) quite common in the limestone Glen Rose formation in northwest Hays County, Texas (just west of Austin) where this specimen was found.

Could this be a triceratops egg? Geologist: “No triceratops lived in the Cretaceous seas where these fossils [including the one in the photograph] are found, [and] their eggs would be found in sandstones not limestones.”

Is it possible it originally had a head and arms and legs? There are thousands of fossils like these that have been found, and there's been no reported evidence of appendages.

The fossil in the photograph was found in a neighborhood between Austin and Dripping Springs that also has fossil oysters, other mollusks, sand worm holes, and little sea urchins (echinoderms). It’s reasonable to assume these creatures died in the sea, not on land. Apparently what is true now was true back then: there are a lot of mollusks in the sea.

This one was alive over 60,000,000 years ago.

It's good to question stuff you read or see on TV, and I appreciate the opportunity to answer questions about stuff I post here.