Reticycloceras
sp
Class Cephalopoda,
Subclass Nautiloidea, Order Nautilida, Family Pseudorthoceratidae
Geological
Time: Mississippian (~320 m.y.a.)
Size: Fossil
is 74 mm long
Fossil Site:
Heath Shale Formation, Bear Gulch Limestone, Fergus County, Montana
| 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 an orthocone nautilod
known as Reticycloceras. The orthocones derive their name from
their essentially straight shell; some from the Ordovician and
Silurian reached lengths of 3 meters. The dark spot on the one
side is most likely remains of the ink sac. |
|
