Orbiculoidea Orbiculoidea Orbiculoidea belongs to a small class of brachiopods called inarticulates.
Most brachiopods have their two shell valves held together on a hinge with teeth and sockets.
Inarticulates have no hinge. Their two shell valves are held together by muscles only. The images below are of fossils found in a unit of the Pennsylvanian Kanwaka Shale near Neal in Greenwood, County, Kansas. These are not found weathered out of the shale. They are found by popping apart small concretions found associated with the shale.