Cretaceous Fossils


For 79 million years dinosaurs and other reptiles ruled only to be done in by a massive meteor landing in Mexico 65 million years ago. Many other groups of animals shared their demise notably the ammonites. Strangely, closed related nautiloids in the form of the pearly nautilus survived. One theory holds that the difference in larvael ecology was responsible.

There are additional pages for two areas known for Cretaceous fossils, The Pierre Formation in Larimer County, Colorado and the Navesink Formation in Monmouth County, New Jersey:

Rocky Ridge    Big Brook

Mowry Shale, Vernal, Utah


Small fish: Note head on the right, fins on the left, and other bones

Fish vertebra

Fish scale

Fish scale

Rock Springs, WY

Del Rio, TX

Pierre Shale
South Dakota


Mancos Shale
Dolores, CO

This is a stromotolite.

A close view of the layering on the right side of the stromotolite specimen.

Ilymatogyra sp.

Ammonite in which iridescene is preserved

Deformed inoceramus from a shale layer below the Dakota Sandstone that forms the first large hogback west of Fort Collins, CO.

Exogyra make up nearly all of some layers of the Mancus Shale near Dolores, CO. Here is an example and examples of individual valves.