This Specimen has been sold.
1.9" Carboniferous Fossil Goniatite (Muensteroceras) - Indiana
This is 1.9" wide fossil goniatite (Muensteroceras parallelum) from the Rockford Limestone of Jackson County, Indiana. The outer shell is gone leaving the intricate patterns of the inner shell sutures. This specimen is from an old collection.
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.