Pleurocystites squamosus
Phylum Echinodermata, Class Cystoidea, Order Rhombifera
Geological Time: Middle Ordovician
Size: Pleurocystites Cystoid is 30 mm long overall; Theca: 20 mm by 15 mm; Matrix: 80 mm by 60 mm.
Fossil Site: Galena Formation, Goodhue County, Minnesota, USA
Code: AW80
Price: $125
 Description:
This plate displays an example of the rhombiferan cystoid known as
Pleurocystites. Cystoids are relatives of the crinoids that have oval
rather than rounded calyces. They were either stalkless or attached
to a stalk much like crinoids. Their triangular pores distinguish
them from all other echinoderms. They arose during the Late Cambrian
and became extinct during the Late Devonian (~500-375 million years
ago). Like all other echinoderms they typically would disarticulate
shortly after death. This one must have been buried soon after death
to be preserved in such a near complete state. |
