- Pentremites godoni
- Upper Mississippian
- Ridenhower Formation
- St Clair, Illinois
- This is a very nice composite plate (All fossils are real, the plate is real but some of the blastoids may have been set back onto the matrix) of high quality blastoids… the plate measures approx. 3 5/8″ wide
Blastoids (class Blastoidea) are an extinct type of stemmed echinoderm, often referred to as sea buds. They first appear, along with many other echinoderm classes, in the Ordovician period, and reached their greatest diversity in the Mississippian subperiod of the Carboniferous period. However, blastoids may have originated in the Cambrian. Blastoids persisted until their extinction at the end of Permian, about 250 million years ago. Although never as diverse as their contemporary relatives, the crinoids, blastoids are common fossils, especially in many Mississippian-age rocks.