Phylogeny and biogeography of the deep-sea goniasterid Circeaster (Echinodermata, Asteroidea, Goniasteridae) including descriptions of six new species

A phylogenetic analysis of 13 taxa and 32 characters resulted in a single most parsimonious tree that supports monophyly of the goniasterid (Echinodermata, Asteroidea) genus Circeaster Koehler, 1909 and supports re-establishment of the genus Lydiaster Koehler, 1909. The phylogeny supports monophyly of the ingroup, including 10 species, six of which, C. kristinae n. sp., C. helenae n. sp., C. arandae n. sp., C. loisetteae n. sp., C. sandrae n. sp., and C. pullus n. sp., are new. Phylogenetic results support diversification into the Indian, Pacific, and Atlantic ocean basins. The phylogeny is constrained by a sister taxon with a Cretaceous fossil occurrence and two geologic events, including the closure of the Indonesian seaway and formation of the Panamanian isthmus. These events formed barriers limiting or preventing larval dispersal between the Indian/Pacific and the Pacific/Atlantic oceans. Larval dispersal through a deep-sea environment was a significant consideration for estimating timing constraints from paleoenvironments. Based on fossil constraints, ancestry for the lineage is suggested as early as the Late Cretaceous with subsequent diversification in the Cenozoic. In situ observations of Circeaster perched on bare deep-sea coral skeletons and morphological similarities with other known corallivorous goniasterids suggest important ecological roles in the deep-sea.