Abstract
We present an integrative study with molecular phylogenetic reconstructions and morphological assessment across the three Ceriantharia families: Arachnactidae, Botrucnidiferidae and Cerianthidae. The Arachnactidae specimens (Isarachnanthus spp.) form a well-supported lade, whereas Cerianthidae and Botrucnidiferidae are not recovered as monophyletic. Consequently, the validity of the suborder Spirularia is questioned. Cerianthus was recovered as polyphyletic and Ceriantheomorphe may prove to be a junior synonym of Cerianthus. The taxonomic position of Cerianthus d mortenseni is also discussed. All specimens identified on morphology as belonging to Pachycerianthus are recovered as a lade. Further revision of taxa within Ceriantharia is necessary. Molecular phylogenetic analyses based on six mitochondrial or nuclear loci place Ceriantharia as sister to Hexacorallia s.s., but with no significant support relative to an alternative hypothesis that it is the sister taxon to Octocorallia. Further molecular sequence data and taxon sampling will be needed to resolve the position of Ceriantharia.