Description: The Bear Gulch Limestone is a deposit of some 70 square km in extent and 30 m in depth that has been a source of one of the most diverse assemblages of fossil fish with some 110 species having been described over the past 30 years. Most were new to science, and provided a unique view of the marine environment of Mississippian times. Fine preservation of both fish and invertebrates is a hallmark of these deposits, presumably due to an anoxic depositional environment. This specimen is an unusual shark known as a petalodont. Most of these sharks are known only from their distinctive teeth, with this being one of two genera known by the body form as well. They have features such as the possession of an operculum (gill cover) that distinguish them from any known group of extant chondrichthyes. This one is seen in ventral view showing the jaws with teeth, pectoral and ventral fin rays as well as the skull and vertebral column.