New edrioasterine and astrocystitid (Echinodermata: Edrioasteroidea) from the Ninemile Shale (Lower Ordovician), central Nevada

Abstract

AbstractThe new edrioasterinePseudedriophus guensburgin. gen. n. sp., is described from the Lower Ordovician Ninemile Shale of central Nevada based on three complete to partial small specimens, a well-preserved large ambulacrum, and an isolated ambulacral floor plate. The weathered-out holotype of this edrioasterine exposes the bottom surface of the theca that bears an aboral collar, peduncular stalk, and attachment disk, features that are poorly known in this clade. These specimens were found with a single specimen of a new edrioblastoid,Porosublastus inexpectusn. gen. n. sp., only the second edrioblastoid ever found in the Early Ordovician. Some of the ambulacral cover plates are stripped off one of the ambulacal grooves, revealing new information about how the ambulacra are built in this rare group of bud-shaped edrioasteroids.