Abstract

A Lagerstätte of Glyptocrinus decadactylus collected from the Upper Fairview Formation at Maysville, Kentucky, USA, yields new insights into the paleoautecology of camerate crinoids of the Late Ordovician. The Lagerstätte represents an autochthonous community composed of a single siltstone bed representing an obrution event and containing over 400 individual glyptocrinids that had colonized a slight topographic rise of relatively high energy within the deep subtidal zone. The high density of the crinoid community was accommodated by tiering, in which the crinoids presumably employed macroalgae (not preserved), occasionally bryozoans, and the columns of earlier-settled specimens as attachment sites; differing column lengths positioned the crinoids at various levels within the community. A further strategy for crowded conditions may have been small body size. Storm-induced turbidity flows led to the suspension of silts by a lofting plume that smothered the crinoids in their habitat. The densely packed crinoid-macroalgae assemblage may have baffled the sediment plume and induced deposition, facilitating burial. Some specimens apparently died shortly prior to burial, suggesting more than one earlier killing event, likely related to the storm that ultimately caused the obrution. Other specimens were killed by the obrution event and subjected to little or no subsequent scavenging or decay after burial, leading to excellent preservation.

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