(Ceriantharia: Anthozoa: Cnidaria): New Status and New Perspectives.

Subclass Ceriantharia is a well-defined and probably ancient group of marine benthic organisms renowned for their bilateral symmetry, which is reflected in the arrangement of tentacles and mesenteries. Four species of Ceriantharia have been reported in the Arctic, including Gosse, 1859, also known from the Northern Atlantic and Northern Pacific. The integrity of this species was questioned in the literature, so we performed a molecular study of from several geographically distant locations using 18S and COI genes. The phylogenetic reconstructions show that specimens of form a single group with high support (>0.98), subdivided into distinctive clades: (1) specimens from Northern Europe, the Black and Barents seas, and (2) specimens from the White, Kara, Laptev, and Bering seas and also the Canadian Arctic and the Labrador Sea available via the BOLD database. There are several BOLD COI sequences of (Verrill, 1873), which form a third clade of the group, sister to the European and Arctic clades. Based on low similarity (COI 86-87%) between and the type species of the genus Delle Chiaje, 1841- (Gmelin, 1791), we propose a new status for the genus Carlgren, 1924, and a new family Synarachnactidae to accommodate .