New record of the wood-associated sea star Caymanostella, with notes on the phylogenetic position of the family Caymanostellidae (Asteroidea)

In 2016, three specimens of Caymanostella were collected from the Kuril-Kamchatka Trench area at depths of 5101–5134 m. Comparative morphological analysis revealed that the new specimens are similar to Caymanostella spinimarginata, the most geographically distant species (Atlantic Ocean). The new specimens were identified as C. cf. spinimarginata. Multilocus genetic data were obtained for the family Caymanostellidae for the first time in this study. Molecular evidence based on the analyses of three mitochondrial and two nuclear markers recovers the family Caymanostellidae as a sister-taxon to Ophidiasteridae (order Valvatida). Phylogenetic data indicate that morphological features, which were previously used to imply asterinid, xyloplacid or korethrasterid affinities for the family Caymanostellidae, emerged independently. It is suggested that the family Caymanostellidae should be placed within the order Valvatida.