Petrodus
sp.
dermal denticle (oscicle)
#4
General abundance: Common
Reference:
Hand book of Paleoichthyology Volume 3A, Chondrichthys I
These denticles formed an overlapping skin armor
that protected the sharks. These denticles are called
Petrodus. At one time they were assumed to be from
a single species of shark, but they have been found
associated with a number of different species.
"Petrodus patelliformis" is no longer considered
correct.
The above is a quote from the Kansas Fossils web site
Pennsylvanian
Fossils of Missouri