St. Louis County, Missouri
Click on pictures to Magnify
This unusual specimen was found weathered free of matrix
and the only preparation was the use of a toothbrush and water.
The crinoid is a species of Dorycrinus, probably Dorycrinus cf.
mississippiensis. Dorycrinus mississippiensis is one of the
diagnostic crinoids found in the Keokuk Formation. I have
never seen this crinoid in any of the Warsaw sites in Illinois
that I have collected, but the line between the Warsaw and
Keokuk is hazy at best. A couple of years ago, someone did a
paper (I will have to look it up, probably Ausich and Kammer)
saying that D. mississippiensis (from the Western side of the
Illinois Basin) was the same as Dorycrinus gouldi from the
Crawfordsville, Indiana area (east side of the Illinois Basin).
I am not sure if I buy it or not. The plates are much more
protuberant than the Dorycrinus from Crawfordsville - this
may be an environmental factor, I don't know. The authorities
always said that the Crawfordsville crinoids were Keokuk in
age. Will be doing more research and will let you know.
Mississippian Fossils of Missouri