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 is an example of a scale of the fish Sterpsodus, a lobe-finned fish found in North America, Europe, and Australia during the Carboniferous. There is little fossil material known other than the very diagnostic scales and teeth. While little is known about this mysterious fish, due to the dearth of remains one thing is obvious: it was fairly big – scales are known over 40 mm across. Indeed, some rhizondonts approached 7 meters in overall length, making them the largest freshwater fish ever.