Crinoids (Echinodermata, Articulata) from the Campanian (Upper Cretaceous) rocky shore at Ivö Klack, southern Sweden

Ten species of crinoids are recorded from a rocky shoreline deposit of upper lower Campanian age at Ivö Klack in southern Sweden. These include three comatulids, i.e., Semiometra annulata Rasmussen, 1961, S. impressa (Carpenter, 1881), and Loriolometra retzii (Lundgren, 1875), three isocrinids, i.e., Nielsenicrinus cf. carinatus (Roemer, 1840), and isocrinid sp. 1 and sp. 2, as well as four pelagic roveacrinids, i.e., Stellacrinus lineatus Gale, 2018, Crassicoma suedica sp. nov., Applinocrinus cretaceus forma spinifer Gale, 2018 and Cultellacrinus labyrinthus Gale, 2016. The comatulids and isocrinids coexisted in shallow (<30 m), high-energy coastal environments, whereas the roveacrinids were Chalk Sea dwellers in the upper water column that were washed into the shallows by currents. The presence of isocrinids in such shallow habitats is remarkable given that these environments are characterised by high biodiversity, intense predation pressure, strong currents and wave-agitated waters – conditions typically considered unsuitable for these slow-moving stalked crinoids, and the reason they are thought to be confined to depths in excess of 100 m in present-day oceans. The Ivö Klack specimens presented herein represent the only known occurrence of isocrinids in a rocky shoreline deposit, marking a notable shift in isocrinid ecology and habitat preference. The limited stratigraphical ranges of the roveacrinids in expanded chalk successions elsewhere corroborates other age assignments of the succession at Ivö Klack.