Crawfordsville Crinoid with Archimedes Section
Echinodermata; Class Crinoidea; Order: Cladida; Family Staphylinocrinidae
Time: Lower Mississippian Osagean Stage
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
Site: Crawfordsville, Indiana
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.
crinoid pictures to enlarge