Pitkin Formation

[4] This formation was first named the "Archimedes Limestone" by David Dale Owen in 1858, but was replaced in 1904.

[3] The Pitkin conformably overlies the Fayetteville Shale and unconformably underlies the Pennsylvanian-age Hale Formation.

More recently, others have considered the Imo to be informal member of the Pitkin Formation.

Early work aimed at creating a comprehensive list for all fossils found in the Pitkin Formation was done by Easton in 1943.

[1] Previous studies have grouped these diverse animals into a single, obsolete taxon: Vermes.

A modern Cliona from the coastal waters of northern France .
Pentremites godoni from the Lower Carboniferous of Illinois .
An upper Carboniferous species of Archaeocidaris .
A Devonian Fenestella from Belgium .