Hi all! My son found this fossil in Pease Park, Austin ,TX, Travis County limestone. He wants to use it for our Christmas card! But we need to know what it is, so we can adjust the text on the card. It looks like an coilopoceras ammonite (see image below) , they are common in the region and the number of lines seems right, but someone in a fossil forum thought it was an echinoid, like a star fish? What could it be? Does anyone have an idea? Thank you!!
Ammonites in the region: