I’ve found many of these bivalves in some of the Sunniland Limestone Quarries (SWFL). I can’t tell if it’s an oyster, but many have said it is.
It’s from the Tamiami Formation. Anyone have any idea what genus it might belong to? Everytime I find them they are always encrusted with all sorts of bryozoans, sponge-borings, worm tubes, etc. Definitely not like the Hyotissid
The shell is very thin and growth bands are very well preserved on every specimen. They are fairly large; the one in the photo is probably 8 inches long at the most.