A surprise find a few days ago in a Brigantian (middle-upper Mississippian) marine shale, Co. Durham, UK.
I've been collecting at this locality for years and it's the first tooth I've found there.
It's fragile, the left hand side and ridge at the base of the enamel was broken into small blocks and flakes, mixed up with a load of shale fragments. I bagged it all up and spent a happy afternoon gluing it and prepping out the rest.
Some knowledgeable friends have helped out with the ID and it's probably Ctenopetalus/Petalodus serratus Owen, depending on which genus is currently in use - I've been told that it may be Owen's original Petalodus again. (It has also been called Ctenoptychius).
42mm across and satisfyingly chunky. (I read that they can be more than 100mm...)
Awkward to photograph, it mostly looks black against the black matrix and doesn't show up well but with certain light the enamel reflects brown.
Finished,:
As found: