Hi @thomas-williams & @matthew-gramling – Do you all think it could be a rudist clam? Here is a link: https://en.wikipedia.org/wiki/Rudists
They were colonial reef building animals in the Cretaceous… so there could be fragments of several here. It’s hard to tell but that’s a guess, anyway!

Hi, @thomas-williams – It’s a little hard for me to see the sutures in these images. They vaguely look more Ceratitida-like to me than ammonitic but it’s hard to tell. You should be able to minimally update the taxonomy to include Animalia > Mollusca > Cephalopoda

Hi, @Thomas-Williams! I think this is the internal mold of a Gryphaea oyster. https://macrostrat.org/map/#/z=1.5/x=16/y=23/bedrock/lines/ might help, as it can help you figure out which geological unit and what age it is.

Hi, @thomas-williams, could you upload more photos of different sides of this fossil?

Hey@thomas-williams ! This looks like a possible fossil, but its hard to tell because of the matrix on it. Depending on where you found it, there a lot of Early Cretaceous marine or deltaic strata near Copperas Cove.