Bizarre Bear Gulch Fish Fossil Echinochimaera

"Female Part and Counterpart"

Echinochimaera meltoni

Class Chondrichthyes, Subclass Holocephali, Order Chimaeriformes, Family Echinochimaeridae

Geological Time: Mississippian (~320 m.y.a.)

Size: Fish fossil is 76 mm long by 35 mm tall

Fossil Site: Heath Shale Formation, Bear Gulch Limestone, Fergus County, Montana

Echinochimaera meltoniDescription: 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 Echinochimaera30 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 Modern chimaerasenvironment. 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 female as demonstrated by the smaller dorsal and spine and less flamboyant ornamentation than a male Echinochimaera. See the artist’s rendering that differentiates Echinochimaera sexes. Also see a male Echinochimaera.

click fossil images to enlarge


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