Hi all! Perhaps this is a dumb question, but I' still new to the forum as well as the hobby itself, so I offer a teaching moment -
In round rock, (just north of austin in central texas), I have a location at the base of a limestone cliff where after some gritty mining efforts I've come across an extremely dense pocket of what I've been informed are internal casts of rudists. That ID was great!, but I'm having trouble learning about what the actual organisms were like. I've tried researching quite a bit with no clear picture of what these are that I'm discovering. Also geologic maps of the area have some disagreement, so the exact spot could be Edwards limestone, eagle ford, or buda limestone.
I understand (I think) that these were some variation of a mollusk but the story ends there. Discovering these would be even more magical if I had a proper understanding of what these organisms were like, looked like, and what role they played in their environment while they were living. I know these are a common fossil so many of you will have a wealth of knowledge about these.
Please enlighten me, I'd love to learn!
Below are some examples for reference: