Anthracoceras sp.
Class Cephalopoda, Order Goniatida, Family Anthracoceratidae
Geological Time: Mississippian (~320 m.y.a.)
Size (25.4 mm = 1 inch): Fossils are 10 mm - 25 mm; Matrix: 100 mm by 135 mm
Fossil Site: Heath Shale Formation, Bear Gulch Limestone, Fergus County, Montana
Fossil Code: BGF218
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 death assemblage of no fewer than SEVEN goniatitic
ammonites 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 death assemblage most unusual. |
