Formation: St. Louis Formation
Location: St. Louis, Missouri
Size: Plate is 3.6 inches across
This is a very distinct echinoderm fossil. It is a plate of two Archaeocidaris illinoisensis from the Mississippian of St. Louis. Fossil echinoids from the St. Louis area are famous around the world and have been extremely sought-after by collectors for decades. These spiny urchins are LARGER than the Lepidocidaris found in the Mississippian Warsaw Formation, and are OLDER than the Pennsylvanian Archaeocidaris from Texas. These two urchins themselves are complete with MANY barbed spines still intact. Most of the types of urchins from this site have smooth spines (there are three species!), and ones with the barbed spines are quite cool. The echinoids display well on the large, squared plate of shale. This is a very nice multiple example of two Mississippian echinoids from the St. Louis Formation.
A Certificate of Authenticity from EXTINCTIONS is included with this specimen.