REVISED CLASSIFICATION AND PALEOECOLOGY OF THE DEVONIAN STEMLESS CRINOID GENUS EDRIOCRINUS HALL, 1858

New morphological observations of Edriocrinus Hall, 1858, enable a more modern, holistic view of this unusual crinoid genus, previously included within the Superorder Flexibilia (Zittel, 1895) Wright et al., 2017. The problematic designation of Edriocrinus as a flexible crinoid was based on a few incompletely preserved arms from one species and ignored more diagnostic characteristics of the cup and arms. Re-analysis of Edriocrinus suggests that the genus should now be assigned to the Order ‘Dendrocrinida’ within the Magnorder Eucladida Wright, 2017. Diagnostic characters include a dorsal cup with firmly bound plates, presence of five, high infrabasals which are visible from the side in unattached forms, lack of patelloid processes in the arms, presence of straight muscular articulation on radial facets, presence of brachials that are rigidly attached to and free above the radials, and presence of muscular articulation between brachials. Moreover, examination of the slight variations separating the current 14 Edriocrinus species indicates that many of these “species” are likely ecophenotypes, which are now included in four species, E. pocilliformis, E. sacculus, E. pyriformis, and E. dispansus. The genus is restricted to an ~25 Myr interval in the Early and Middle Devonian, a time of global eustatic and tectonic disruption, when its stemless nature provided an adaptive advantage in a series of unsettled environments in the Old World and Eastern Americas realms. These realms included adjacent parts of east-central North America, south-central Europe, southern England, and northern Africa that occurred in subtropical to warm temperate climatic zones surrounding the Rheic Ocean between 25°and 35⁰ south latitude. The genus persisted in south-central Europe until the Chotec Event in early Eifelian time and in North America until the Bakoven Event in mid-Eifelian time, when episodes of transgression and anoxia apparently led to genus extinction.