A NEW EXCEPTIONALLY PRESERVED PARACRINOID FROM THE NEUVILLE FORMATION OF QUÉBEC, CANADA

Paracrinoids are a small group of extinct echinoderms that were restricted to the Middle to Late Ordovician of North America. Paracrinoidea is a monophyletic class of blastozoans defined by asymmetry in both the mouth and stem position as well as the ambulacral construction. They are a disparate group of sessile, filter-feeding echinoderms varying in thecal shape and the arrangement of their feeding appendages. A new genus of paracrinoid was recently found in the Neuville Formation of Québec, Canada. This formation consists of interbedded grey limestones and shale deposited on a shallow marine carbonate ramp. This new genus is known from two well preserved and mostly complete specimens showing details of the brachioles, theca, and stem. The new genus has a laterally flattened theca with two well developed ambulacra (BC and DE) similar to the genera Amygdalocystites and Platycystites. The theca is composed of numerous unorganized and unornamented plates with no obvious respiratory structures. The specimens have many thin, widely separated, well preserved brachioles that are twice the height of the theca. The brachioles have preserved cover plates and food grooves such that they are particularly informative in understanding feeding in aberrant paracrinoids in terms of hydrodynamics and diet. Furthermore, one specimen has multiple regenerated brachioles indicating possible predation. Despite the excellent preservation of these specimens, they are preserved in a similar orientation that makes discerning the oral plating difficult. Preliminary phylogenetic analysis indicates this new taxon is grouped with Amygdalocystites and Oklahomacystis based on ambulacral arrangement, thecal plating, and thecal morphology. The large disparity of forms seen within paracrinoids can be attributed to progressive shifts in ambulacral development resulting in the loss of pentameral symmetry paired with adaptations to maximize feeding; this new taxon aids in further elucidating evolutionary trends within this group.