One of the locations from which
Agaricocrinus americanus is known is the Edwardsville Formation, in the vicinity of
Crawfordsville,
Montgomery County, Indiana, in the United States. In this fossil-rich bed have been found the fossils of sixty species of crinoid, distributed among more than forty genera. It is thought that the various species had different length stalks so that they could capture
plankton drifting past at various heights above the
substrate. The fossil beds were formed at a time when the seabed was much higher than it is today. It is believed that the crinoids were buried in sediment from nearby
deltas during storms. The resulting
siltstone deposits are soft enough for the fossils to be extracted in three-dimensional relief. Other fossils of this species have been found in similar sedimentary rocks in
Whites Creek in
Davidson County, Tennessee, from Osagean rocks in Kentucky, and more recently from the
Fort Payne Formation near the boundary between Tennessee and Kentucky. Certain morphological differences have been found between various specimens from these different locations and new finds have often been claimed as new species. David Meyer and William Ausich studied the genus
Agaricocrinus in 1997 and proposed that
A. arcula,
A. dissimilis,
A. elegans,
A. podagricus,
A. ponderosus,
A. profundus and
A. tugurium should be brought into
synonymy with
Agaricocrinus americanus. A closely related but less common species is
Agaricocrinus crassus. ==Description==