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 example of a nematode, or round worm. Nematodes today vary from a few millimeters to several centimeters in length, and have conquered both freshwater and marine habitats. Due to the lack of hard parts, preservation as a fossil is a chancy occurrence with the oldest known examples coming from the Carboniferous. Because other relatives have left fossils from as early as the Cambrian, some researchers think they may also have arisen then as well.