Formation: St. Louis Formation
Location: St. Louis, Missouri
Size: Plate is 3.7 inches across
This is a very special find. It is a spiny 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. This urchin has 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 rare. The echinoid displays well on the natural plate of matrix. This is a very large, distinct example of Archaeocidaris illinoisensis from the St. Louis Formation.
A Certificate of Authenticity from EXTINCTIONS is included with this specimen.