Anthracoceras sp.
Class Cephalopoda, Order Goniatida, Family Anthracoceratidae
Geological Time: Mississippian (~320 m.y.a.)
Size (25.4 mm = 1 inch): Fossil is 25 mm across on 45 mm by 60 mm matix
Fossil Site: Heath Shale Formation, Bear Gulch Limestone, Fergus County, Montana
Fossil Code: BGF40
Price: Sold
 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 goniatitic
ammonite of the genus Anthracoceras. The Ammonidea have a rich evolutionary
history which began in the Upper Silurian/Lower Devonian. The order
began an extensive radiation in the Triassic and Jurassic, and became
most diverse during the Cretaceous, only to become extinct during
the late Cretaceous extinction event which also saw the demise of
the non-avian dinosaurs. The Goniatite forms became extinct during
the Permian. Specimens from the Mississippian are not often seen,
making this example most unusual. The most unusual feature is that
the jaws are preserved within the shell of this fine example. |
