Stalked crinoids (Echinodermata) collected by the R/V Polarstern and Meteor in the south Atlantic and in Antarctica

During the last decades, R/V Meteor and R/V Polarstern deep-sea investigations in the south Atlantic and neighbouring Southern Ocean collected new samples of stalked crinoids belonging to the families Bathycrinidae, Phrynocrinidae and Hyocrinidae which are herein described. The species found are Bathycrinus australis A.H. Clark, 1907b (the most abundant), Dumetocrinus aff. antarcticus (Bather, 1908), Hyocrinus bethellianus Thomson, 1876, Feracrinus heinzelleri new species, and Porphyrocrinus cf. incrassatus (Gislén, 1933). As only stalk fragments of bathycrinids were frequently collected, a distinction between the two Atlantic species B. australis and B. aldrichianus is proposed using characters of columnal articulations. A few specimens attributed to Porphyrocrinus cf. incrassatus, Hyocrinus bethellianus and Hyocrinus sp. collected by the N/O Jean Charcot on the Walvis Ridge are also described, plus a new specimen of Porphyrocrinus incrassatus collected in the central mid-Atlantic. Biogeography and close affinities between species in the genera Bathycrinus and Porphyrocrinus suggest an Antarctic origin of some stalked crinoids among the north Atlantic deep-sea fauna. The presence of B. australis in both the Angola and Cape basins suggests that the Walvis Ridge is not a bio-geographical barrier for this relatively eurybathic species, which can attach to hard substrates as well as anchor in sediment. The genus Dumetocrinus seems to be an example of colonization of the west Antarctic platform from deeper environment where its ancestor lived.