4" Fossil Sea Cucumber (Achistrum) (Pos/Neg) - Mazon Creek


This is a very nice fossil sea cucumber (Achistrum sp) from the 300 million year old Mazon Creek fauna. It's preserved inside a ironstone nodule that was split open, over 4" long and highly detailed. Both halves of the nodule are included.

The Mazon Creek fossil beds are a conservation lagerstätte (deposit with exceptional fossil preservation), located in Illinois. This location of late Paleozoic (~307 million years ago) biota, ranks among many of the other great fossil sites around the world. The large variety of fossils collected here, vary between plants and animals, including soft bodied and insect preservation. The fossils from this site are often quite detailed and are preserved within siderite (iron carbonate) nodules.

Over 500 animal and 200 flora species have been described from Mazon Creek. The event that caused this die off and preservation is believed to have started with a catastrophic flood event that buried the biota of the modern day Mazon Creek area. The deposition of river-borne silt and clay, brought on by upland erosion and delta progradation, contributed to the incredible preservation of one of the most complete records of Paleozoic biota.

This site has been collected for more than 100 years, and likely will continue to be collected by both professionals and amateurs for many years to come.

Achistrum sp.
Grundy County, Illinois
Francis Creek Shale, Carbondale Formation
Over 4" long, Nodule 4" long
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