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This Blastoid is the Pentremites species. The size of the matrix is about 3" across. The actual Blastoid measures from 1/2" to 3/4". There will be one Blastoid per plate. Each specimen will vary slightly; we choose the best specimen available at the time of purchase.
Location: Ridenhower Formation, Millstadt, Illinois
Age: Mississippian, ~350 m.y.o.
The oldest blastoids lived about 425 million years ago. The animals survived until the Permian Period, about 260 million years ago, when they became extinct.
Blastoids look much like small hickory nuts. They most commonly are found in the river cliffs and stream banks of western and southwestern Illinois, especially in Randolph County, and in southern Illinois near the Ohio River.