.95" Fossil Goniatite (Anthracoceras) - Bear Gulch Limestone, Montana
This is a fossil goniatite of the species Anthracoceras sp. that was collected from the Bear Gulch limestone of Fergus County, Montana. The goniatite is .95" wide on a 1.8 x 1.55" slab of limestone.
Goniatites possessed a shell which was divided internally into chambers filled with gas for buoyancy. An open chamber at the front of the shell provided living space for the animal. The general morphology and habit of goniatites was probably similar to that of their later relatives the ammonites, being free swimming and possessing a head with two well developed eyes and arms.