Northernmost record of Crypthelia medioatlantica (Hydrozoa: Stylasteridae) in Icelandic deep waters

Abstract The stylasterid coral Crypthelia medioatlantica Zibrowius & Cairns, 1992, previously reported only from the Mid-Atlantic Ridge (~ 23–37° N), is newly documented from Icelandic waters based on material collected by the BIOICE programme. Six dry, subfossil skeletal fragments were recovered at 1539 m depth west of Iceland in 1996, extending the known range of the species by ~ 28° latitude into sub-Arctic environments and representing its northernmost record. Detailed morphological analysis of coenosteal texture and cyclosystem structure confirms the identification. This discovery adds a fifth stylasterid coral species to the high-latitude North Atlantic fauna and demonstrates that C. medioatlantica has occurred in deep sub-Arctic benthic communities at least historically. It also highlights overlooked stylasterid diversity in under-explored regions and the value of historical collections. Combining re-examination of archived material with targeted, molecularly suitable collections will be essential to clarify the biogeographic history and conservation status of C. medioatlantica in the North Atlantic and to determine whether the Icelandic fragments represent an extant but unsampled population or the remnants of a past local population.