My cousin has been extracting fossils from a piece of Carlile Shale Formation matrix. It was found in Grant County, South Dakota, USA. He has been slowly breaking it down to reveal the hidden fossil shark teeth. The fossils date to the Cretaceous Period (Turonian). The picture shows Scapanorhynchus raphiodon shark teeth fossils.
Thanks to Kenny for the image.
Info Source:
http://en.wikipedia.org/wiki/Scapanorhynchus
http://www.elasmo.com/frameMe.html?file=genera/cretaceous/scapanorhynchus.html&menu=bin/menu_genera-alt.html
