LIFE MODE OF PTEROTOCRINUS IN THE LOWER PENNINGTON 
( LOWER CARBONIFEROUS) OF EAST-CENTRAL KENTUCKY.
CHESNUT, Donald R., Jr., Kentucky Geological Survey, Lexington, KY
40506 and ETTENSOHN, Frank R., Department of Geology, University
of Kentucky, Lexington, KY 40506.

In-place specimens of Pterotocrinus from the Lower Pennington Formation
of east-central Kentucky indicate that adults in this genus probably
lived with the calyx sitting on the substrate. This interpretation is
also suggested by an apparently stemless species from western Kentucky
(Gutschick, 1965). One specimen from the Pennington showed a Pterotocrinus 
calyx sitting on an upper bedding plane surface with a 6.3-cm
segment of the stem running below and parallel to the bedding plane at
the level of the basal plates. The stem was only 2 mm in diameter. The
arms flexed outward at the level of the wing plates, one-half the length
of the free arms, which suggests that the calyx may have been embedded
in the sediment to this level in life. The small size of the stem com-
pared to the heavily plated calyx, the orientation and buried nature of
the stem, and the peculiar flexure of the arms suggest that the crinoid
lived partially embedded in the substrate. Although wing plates may
have protected arms near the substrate or formed small eddies that were
helpful in feeding or stabilization in currents, their most important 
function was probably support and stabilization on the substrate. The
wing plates probably functioned much like outriggers.
	The two Pennington specie, P. depressus and P. acutus, lived 
respectively on mud and sand substrates and exhibit calyx and wing-plate
morphologies adaptive for their substrate type. Nonetheless, each
species exhibits many small-scale variations in wing-plate morphology
which are probably ecophenotypic in nature. This suggests that many
species based soley on wing-plate morphology may be invalid.