My grandson is extremely interested in fossil and gemstone hunting. He has found a couple of i interesting fossils in the last month. This one was found at Trammel fossil park near Cincinnati. It is marine of some kind but when you ZOOM in it appears to have a covering/maybe skin or indentations of some sort. It has depth and perhaps the look of a vertebrate remnant which doesn’t make sense with the rest of the fossils found with it - of course i am guessing at all this being a novice. We have purchased multiple books for help but cant find anything like this. Any suggestions would be greatly appreciated #fossil