Phylogenetic relationships within the Class Anthozoa (Phylum Cnidaria) based on nuclear 18S rDNA sequences

Taxonomic relationships within the corals and anemones (Phylum Cnidaria: Cl ass Anthozoa) are based upon few morphological characters. The significance of any given character is debatable, and there is little fossil record ava ilable for deriving evolutionary relationships. We analyzed complete 18S ri bosomal sequences to examine subclass-level and ordinal-level organization within the Anthozoa. We suggest that the Subclass Ceriantipatharia is not a n evolutionarily relevant grouping. The Order Corallimorpharia appears para phyletic and closely related to the Order scleractinia. The 18S rRNA gene m ay be insufficient for establishing robust phylogenetic hypotheses concerni ng the specific relationships of the Corallimorpharia and the Ceriantharia and the branching sequence for the orders within the Hexacorallia. The 18S rRNA gene has sufficient phylogenetic signal, however, to distinguish among the major groupings within the Class Anthozoa, and we use this information to suggest relationships for the enigmatic taxa Dactylanthus and Dendrobra chia. (C) 1999 Academic Press.