Rhagasostoma (Bryozoa) from the late cretaceous of eurasia: Taxonomic revision, stratigraphy and palaeobiogeography

Abstract

Species commonly assigned to the cheilostome bryozoan genus Onychocella Jullien, 1882 are numerous in deposits of Late Cretaceous age. Among these are 15 species with wide stratigraphical and geographical distributions that are better placed in the genus Rhagasostoma Koschinsky, 1885. These are used here to show similarities between Late Cretaceous bryozoan associations from Western Europe and Central Asia. Type and additional material was examined of several species from the Turonian to the Maastrichtian of Western Europe, including material studied by R.M. Brydone, E. Voigt and T.A. Favorskaya and undescribed material from the Campanian and Maastrichtian of several localities in Eastern Europe and Central Asia. The new species Rhagasostoma brydonei sp. nov., R. aralense sp. nov. and R. operculatum sp. nov. are introduced. New and published data on the morphology and the stratigraphical and geographical distributions of R. inelegans (Lonsdale, 1850), R. gibbosum (Marsson, 1887), R. gibbosulum Brydone, 1936, R. rowei (Brydone, 1906) and R. mimosa (Brydone, 1930) is presented.