A new deepwater species of Stauromedusae, Lucernaria janetae (Cnidaria, Staurozoa, Lucernariidae), and a preliminary investigation of stauromedusan phylogeny based on nuclear and mitochondrial rDNA data.

The deepwater stauromedusan Lucernaria janetae n. sp is described from adult and juvenile specimens collected from the East Pacific Rise. Lucernaria janetae is the first species in the genus recorded from the Pacific Ocean, and differs from its congeners in size and morphology. Mitochondrial (16S) and nuclear (SSU) ribosomal gene sequences from L. janetae were analyzed with those of representative stauromedusan taxa to evaluate stauromedusan monophyly. Both genes recovered a strongly monophyletic Stauromedusae that is the sister group to all other medusozoans. Support of these hypotheses is robust to method of phylogenetic reconstruction and to outgroup selection, buttressing the argument that Stauromedusae should be recognized as the class Staurozoa. The molecular markers used here favor the same topology of relationships among our samples and clearly distinguished between two species, Haliclystus sanjuanensis and H. octoradiatus, that have been considered synonymous by many workers. A stable systematic framework for Stauromedusae appears achievable through comprehensive study of both morphological and sequence data.