7.2" Multiple Blastoid (Pentremites) Plate - Illinois

This is a 7.2" wide plate with 20 Blastoid (Pentremites sp.) fossils collected from St. Clair County, Illinois. The fossils are Upper Mississipian in age or approximately 325 million years old. Most of the blastoid fossils have been cleaned using air abrasives and remounted on a slab of rock from the locality to create a beautiful display. Some of the blastoids are still within the rock and have only been cleaned, not remounted

The rock also includes various bryozoan fossils, brachiopods and crinoid fossils. Comes with an acrylic 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.
St. Clair County, Illinois
Ridenhower Formation
Largest blastoid .8" long, plate is 7.2 x 6.5"
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