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 a chimaeroid known as Echinochimaera meltoni, related to the modern day chimaeras that are known as ghost sharks or ratfishes (see life drawing of Chimaera monstrosa). Most chimaeras of today possess a poisonous spine forward of the dorsal fin. Echinochimaera also displays such a spine, and it possibly served the same defensive purpose. Note the exceptional detail to this fine specimen. This one is a male as demonstrated by the taller spine and presence of claspers. See the artist’s rendering that differentiates Echinochimaera sexes. Also see a female Echinochimaera fossil.