364 The oldest known crinoids and a new crinoid plate homology system

The oldest known crinoids (Early Ordovician, Utah) and a new crinoid plate homology system - BAP #364 Six new primitive genera from the Early Ordovician of western Utah significantly advance our understanding of early crinoid history. Two of the new genera are the oldest crinoids (early Ibexian- early Tremadoc) and represent a previously unknown protocrinoid evolutionary grade, differing from other crinoids in having a nonstandardized dorsal cup and arms bearing ambulacral floor plates. Titanocrinus sumralli, new genus and species, has hundreds of unorganized mid-cup and interbrachial plates separating the cup-base basal circlet and the ray plates. Glenocrinus globularis, new genus and species, has similar plating with a more compact globular cup and fewer mid-cup plates, and is near the origin of diplobathrid camerates. A third taxon, Eknomocrinus wahwahensis, new genus and species, from the same lower stratigraphic interval, is a stem-group monocyclic camerate crinoid with stan