Systematics, diversity and paleoecology of cyrtocrinids (Crinoidea, Echinodermata) from the Oxfordian sponge meadows of northeast Spain (Tosos, Zaragoza)

Abstract Jurassic cyrtocrinids from Spain are first documented here as representing relatively diverse assemblages from the western Tethys. The species Ascidicrinus pentagonus , Eugeniacrinites cariophilites , Gammarocrinites compressus , Pilocrinus moussoni , Sclerocrinus cf. S . strambergensis , and Tetracrinus moniliformis are described from Oxfordian marl levels belonging to the Yátova Formation, around Tosos (Zaragoza, NE Spain). Although based on partially disarticulated material, these fossils preserve cups, stem columnals, attachment structures, and brachial plates. Based on the sedimentology and associated invertebrate fauna, cyrtocrinids from this area lived below storm wave action but eventually were affected by storms, as opposed to their modern counterparts that occupy deep water environments. Some specimens preserve traces of interactions with other organisms, such as predation marks or epibiontic colonization during life and post-mortem. Attachment structures suggest cyrtocrinids mostly attached on sponges. We note that diversity of cyrtocrinids changed in step with the abundance of sponge reefs in the Jurassic, suggesting that both groups probably had an important link in that period related with similar ecological requirements.