Newly discovered fossils from Oklahoma and Morocco support recent revision of cyclocystoid (Echinodermata) morphology and evolution

Abstract Bromidocycloides sprinklei new genus new species (Echinodermata) from the Upper Ordovician, Bromide Formation, Oklahoma, is a cyclocystoid distinguished by having a thin dome-shaped stereomic plate covering each epispire on the aboral surface of the central disk. The tube foot basin side walls are distinctively straight, intersecting at angles of 25–35°, all forming a unique zigzag pattern in lateral view. Also described are new specimens of Moroccodiscus smithi Reich et al., 2017 from the Middle Ordovician Taddrist Formation, Morocco, revealing how floor plates and the associated water vascular system developed sequentially according to the Ocular Plate Rule. These findings support the view that cyclocystoids had an upward facing central disk composed of perforate extraxial plates housing epispires and a peripheral ring of stout ambulacral plates bearing tube feet that projected downward toward the substratum. UUID: https://zoobank.org/35fcd4b8-49c8-41b2-9058-1ed56251c2c2