Abrotocrinus Crawfordsville Crinoid with Archimedes Section

Name: Abrotocrinus unicus

Phylum Echinodermata; Class Crinoidea; Order: Cladida; Family Staphylinocrinidae

Geological Time: Lower Mississippian Osagean Stage

Size (25.4 mm = 1 inch): Crown: 38 mm long by 12 mm wide on a 30 mm by 43 mm matrix. Archimedes: 21 mm by 18 mm

Fossil Site: Crawfordsville, Indiana

Abrotocrinus Crawfordsville CrinoidDescription: A fine example of an Inadunate Cladid crinoid (Family Staphylinocrinidae) known as Abrotocrinus unicus from the famous Crawfordsville crinoid beds showing an extensive section of attached stem. Preservation on this specimen is remarkably complete, down to the fine pinnules on the arms. This is fine example of the type, well-positioned on its siltstone matrix. On the reverse is a section of the fenestrate bryozoan Archimedes. Archimedes lived attached to a screw-shaped support structure, and so derives its name from Archimedes’ screw, invented by the ancient Greek during a trip to Egypt to pump water.

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