A year or two ago I visited a swimming creek in Oklahoma with family (I can't tell you which one for the life of me). The first thing I did after stepping out of the SUV was pick up what looked like an impression fossil off of the ground (the shoreline of the creek was all pebbles). It must have been sheer luck, because I couldn't find anything else the whole time I was there. My guess is that it's a chrinoid stem. Am I close?