Eocene and Oligocene ceriantharian tubes

Abstract Three fossil tube fragments from middle Eocene to late Oligocene strata in western Washington State, USA, are here interpreted as those of ancient Ceriantharia (Hexacorallia, Cnidaria). The tube fragments are 3–6 mm in diameter, up to 60 mm long, and the surfaces show an overlapping, fibrous knitted pattern. This surface pattern resembles that of the extant ceriantharid Cerianthus membranaceus. One specimen has numerous benthic foraminiferans associated with, and apparently even embedded in, the tube wall, analogous to some extant Ceriantharia. These fossils likely represent the first fossil Ceriantharia and indicate that their present-day mode of tube construction using ptychocysts was established at latest by the middle Eocene.