12.1" Blastoid, Rugose Coral and Crinoid Fossil Association - Illinois

This is a beautiful association of rugose coral (Zaphrentis sp.), two partial crinoids (Zeacrinites sp.) and 18 blastoids (Pentremites sp.) from Ridenhower, St. Clair County, Illinois. These fossils are Upper Mississipian in age or approximately 325 million years old.

There are a wide variety of bryozoans, brachiopods and crinoid segments that can be found scattered throughout the rock. Many of the blastoids have been mounted to the shale. Comes with a display stand.

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 relative the crinoid, they were equally as common in rocks around the world. Blastoids were protected by a set of interlocking plates, which formed the main body, or theca. In life, the theca of a typical blastoid was attached to a stalk or column made up of stacked disc-shaped plates.
Pentremites sp. (Blastoids), Zeacrinites sp. (Crinoids) & Zaphrentis sp. (Coral)
St. Clair County, Illinois
Ridenhower Formation
12.1 x 1.6" rock
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