Emergence and early radiation of cyrtocrinids, with new species from a Lower to Middle Jurassic rock reef of Feuguerolles (Normandy, France)

Abstract

Cyrtocrinids are morphologically diverse crinoids of the Mesozoic, yet their origin and early evolution are still poorly understood. Here, we attempt to disentangle the early evolutionary history of the cyrtocrinids taking into account phylogenetic, palaeobiogeographic, and palaeoecological evidences. In addition, we describe new finds of cyrtocrinids from an upper Pliensbachian to lower Aalenian rock reef section of Feuguerolles, Calvados, France. The material includes the new species Tetracrinus solidus n. sp. and Sacariacrinus amadei n. sp. The common Cotylederma docens, Eudesicrinus mayalis, and Praetetracrinus inornatus are represented by ossicles of all growth stages, complementing previous descriptions. A single ossicle is ascribed to Cotylederma miliaris. Columnals of P. inornatus and primibrachials of C. docens bear yet unknown ichnological traces. In terms of faunal spectrum, the Feuguerolles assemblage is more closely related to Lower Jurassic faunas of northeastern Europe than to Tethyan faunas from Switzerland, Italy and Turkey. Finally, several lines of evidence suggest that the cyrtocrinids originated in the deep sea and invaded the shelf seas in the course of the Early Jurassic.