THE SYNECOLOGY AND AUTECOLOGY OF ECHINODERMS FROM THE PARAGON FORMATION (PENNINGTON GROUP, UPPER VISEAN-NAMURIAN A) OF KENTUCKY, USA.
Chesnut, Donald R., Kentucky Geological Survey, Lexington, Kentucky 40506,
USA, and Ettensohn, Frank R., Geology Department, University of Kentucky,
Lexington, Kentucky 40506, USA.

Forty-five species belonging to 38 genera and six classes of the
phyllum Echinodermata were recovered from the highly fossiliferous Sloans
Valley Member of the Upper Mississippian Paragon Formation, Pennington
Group (Upper Visean-Namurian A). The Sloans Valley Member was deposited in
a protected, shallow-water environment leeward of a carbonate shoal.
Oxygenated waters from the seaward direction and land-derived nutrients
promoted a prolific echinoderm fauna in this wave-protected environment.
	The communities on small shoals within the protected area were
dominated by stemmed crinoids and blastoids, probably because the shoals
provided firm substrates for attachment and elevated positions provided the
crinoids access to feeding currents higher in the water column. The
intervening basinal areas were characterized by low energy, and supported a
fauna that lived closer to the substrate and generally adapted to soft
bottom conditions. Tiering apparently existed in these communities.
	Predation upon some echinoderms by durophagous fish may explain the
development of spines on many species. The asteroid Calyptactis may have
also preyed upon bryozoans. The presence of Phosphannulus indicates
parasitism upon crinoids; however, acrothoracic barnacle borings may have
occurred after death. Commensal relationships include the ophiuroid
Onychaster with the crinoid Pulaskicrinus (new genus), the gastropod
Platyceras with the crinoids Pterotocrinus and Acrocrinus, and various
epizoans, such as bryozoans, inarticulate brachiopods (Crania), worm(?)-
tubes (Spirorbis, Cornulites) and small crinoids (Cymbiocrinus, Linocrinus,
and Ramulocrinus) upon living crinoids.
	The feeding mechanisms among the Sloans Valley echinoderm fauna
include suspension feeding, browsing, scavenging, active predation and
deposit feeding. Suspension feeders were the dominant forms. Suspension
feeders fed at different tiers from substrate level (Agassizocrinus,
Pterotocrinus, Lepidodiscus, and Ulrichidiscus) to levels perhaps greater
than 1.5 m high (Onychocrinus). Remaining crinoids and blastoids fed at
intermediate levels. Small crinoids such as Linocrinus, Ramulocrinus, and
Cymbiocrinus may have climbed larger crinoids in order to reach higher
feeding levels. The edrioasteroids (Lepidodiscus, Ulrichidiscus) were able
to change their level by expanding their peduncle. Browsers include the
echinoids Archaeocidaris and Palaechinus. The flexible echinoid
Lepidesthes may have been a deposit feeder. The ophiuroid Onychaster may
have been a scavenger that supplemented scavenging with coprophagous,
carnivorous, and suspension feeding. The asteroid Calyptactis may have
been an active predator upon bryozoans.
	Spines on crinoids protected them from predation by durophagous fish
and in some cases may have served as "outriggers" for bottom dwelling forms
(Pterotocrinus). Zig-zag arms of small crinoids (Linocrinus, Ramulocrinus)
may have provided added flexibility to assist them in climbing upon
elevated surfaces such as crinoids and bryozoan colonies to reach-higher
feeding levels. The coiled stem and V-shaped cirritrough of Camptocrinus
may have been used to hide its small crown from predation. The V-shaped
cirritrough may also have channeled food-bearing currents to the crown.
The largely inflexible recumbent arms of Hyrtanecrinus may have allowed the
crinoid to feed in changing currents. Hypertrophied arms probably served
two purposes: the hypertrophied arms of the stemless crinoid
Agassizocrinus probably served as supportive struts to stabilize it on the
substrate, while the hypertrophied arms of Anartiocrinus may have served as
rudders in the current as well as provided protection.