Abstract

Iocrinus trentonensis Walcott, 1883 is characterized by the widest food grooves and the largest covering plates of any of the Walcott-Rust Quarry crinoids, which indicates that the animal captured relatively large food particles with large and widely separated tubefeet. Although iocrinids are generally considered as primitive disparids, their anal sac is unique. The holdfasts of I. trentonensis consist of distal stem coils that are tightly wrapped around the columns of other crinoids. The relatively long column of Ectenocrinus simplex (Hall, 1847) was attached to a wide range of shelly substrates by a small irregular and somewhat lobate holdfast. Ectenocrinids ate much smaller food items that were collected by smaller and more tightly packed tubefeet. The ontogeny of E. simplex illustrates the differences between the food gathering systems of conspecific crinoids from shallow and deep water habitats. The calceocrinid Calceocrinus barrandii Walcott, 1883 lived with its long stem forming a runner along the seafloor. The crown was movably hinged to the basal circlet and the stem. Moderately wide food grooves were probably present.

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