Fossils of the Owl Creek Formation
The Owl Creek deposit dates to the end of the Cretaceous,
and was first identified
in southeastern Missouri near a town named Ardeola by Lloyd Stephenson in
1955
in a paper entitled "Owl Creek (upper Cretaceous) Fossils from Crowley's
Ridge
Southeastern Missouri" Geologic Survey Professional Paper 274-E. The
deposit is
a mudstone, featuring a diverse fauna preserved generally as molds and casts
in the
soil. It represents an oceanic environment of an extension of the Gulf of
Mexico,
known as the Mississippi Embayment.
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Large clam Pholadomya tippana
3
small shark tooth
4
Section of a gonatitic ammonite Sphenodiscus sp.
5 
6
Ammonite Discoscaphites iris
7
5" razor clam Pinna laqueta