Large Mississippian Bear Gulch Orthocone Nautiloid Fossil

Nautiloidea indet

Class Cephalopoda, Subclass Nautiloidea

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

Size (25.4 mm = 1 inch): Orthocone fossil is 125 mm long by 20 mm across at living chamber Matrix: 165 mm by 75 mm

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

Fossil Code: BGF281

Price: Sold

Bear Gulch OrthoconeDescription: 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 orthocone nautilod . The orthocones derive their name from their essentially straight shell; some from the Ordovician and Silurian reached lengths of 3 meters. Note the darkened spots near the living chamber. These appear to be related to the jaws and ink sac.

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