.7" Blastoid (Pentremites) Fossil - Illinois

This is a Pentremites blastoid fossil, from Ridenhower, St. Clair County, Illinois. These fossils are Upper Mississipian in age or approximately 325 million years old. The fossil has been remounted on the rock.

Blastoids are an extinct type of filter feeding, stemmed echinoderm that resembles a small hickory nut. They thrived during the Mississippian period before going extinct during the great Permian extinction. While not as diverse as their crinoid relatives, they were equally as common in rocks around the world. Blastoids were protected by a set of interlocking plates that formed the main body, or theca. In life, a typical blastoid's theca was attached to a stalk or column made up of stacked disc-shaped plates.
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DETAILS
SPECIES
Pentremites sp.
LOCATION
St. Clair County, Illinois
FORMATION
Ridenhower Formation
SIZE
.7" blastoid, 2.6 x 2" rock
CATEGORY
SUB CATEGORY
ITEM
#102267
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