Article: Cupuladria canariensis (Busk)—portrait of a bryozoan

The lunulitiform bryozoan Cupuladria canariensis (Busk) is a benthonic marine organism, whose calcareous colonies can easily be recognized with a hand-lens or under the microscope.This species is eurybenthic (2->300 fathoms), eurythermal (12-31° C.), reasonably euryhaline (28-37%), and requires a stable quartz and/or carbonate sand bottom. It is at present widely distributed over the continental shelves of the Atlantic and East Pacific between the 14° C. surface isocrymes and had an equally wide distribution during the Late Tertiary and Quaternary.The occurrence of C. canariensis in Miocene and Pliocene marine sediments of the southern part of the North Sea basin calls for sea-water surface temperatures at least 9° C. higher than those obtaining at present in this area. Its occurrence in the Miocene, Pliocene, and Early Pleistocene marine sediments of Spain, Italy, and Rhodes suggests that the Mediterranean was somewhat less saline in the geological past than it is at present.Although lunulitiform Bryozoa range from the Upper Cretaceous to Recent, C. canariensis first appears in the Lower Miocene (Aquitanian). Its presence or absence among lunulitiform bryozoan assemblages may serve as a criterion for establishing the Oligocene-Miocene boundary in sequences of ancient tropical and subtropical shelf sediments on both sides of the Atlantic. On this criterion a large part of the 'Caribbean Oligocene' is to be considered as Lower Miocene.