Description

Anthracoceras
Ammonite
Late Mississippian
Bear Gulch Limestone
Fergus County, Montana, USA

Two 25mm goniatites on 72mm slab, both showing aptychus and evidence of soft anatomy. Rare.

Cephalopod. Goniatite.

Anthracoceras is a goniatite ammonite genus that lived during the Carboniferous Period.  It’s known from sites in North America and Europe.  The preservation allowed by the Bear Gulch Limestone sometimes reveals parts of the internal anatomy where other sites would leave you looking at just a broken shell.

An interesting alternative preservation of two goniatites in matrix.