Laetmogonidae Ekman, 1926

Rogacheva, Antonina, Cross, Ian A. & Billett, David S. M., 2009, Gebrukothuria profundus, a new genus and species of laetmogonid holothurian (Elasipodida, Laetmogonidae) from around the Crozet Plateau in the Southern Indian Ocean *, Zootaxa 2096 (1), pp. 479-483 : 479-480

Family Laetmogonidae Ekman, 1926

Diagnosis. Deposits wheel-shaped, scattered rods or (in Laetmogone violacea ) spinous crosses or (in Gebrukothuria ) rods only. Tube feet conspicuous, evenly distributed along entire ventrolateral radii, never fused into a brim. Midventral tube feet present or absent. Papillae numerous, placed along dorsal radii or dorsal and ventrolateral radii; papillae on dorsal radii free, on ventrolateral radii (if present) free or fused. Circum-oral papillae present or absent. Calcareous ring reduced or not calcified. Gonad composed of numerous branched ducts and tubules.

Remarks. Hansen (1975) assigned the families Deimatidae and Laetmogonidae to the suborder Deimatina . These families show similarities in the absence of primary cross-shaped deposits and presence of numerous large papillae and tube feet; the latter never form a brim. The family Laetmogonidae differs from Deimatidae by the absence of perforated plates or their derivatives (e.g. spatulated rods) and by gonads composed of numerous branched tubules instead of a single cluster of unbranched tubules. All deimatids possess ventrolateral papillae whereas in the Laetmogonidae only two species have them: Apodogaster alcocki Walsh, 1891 has ventrolateral papillae forming a brim above the ventrolateral tube feet and Pannychia moseleyi Théel, 1882 has free ventrolateral papillae. Almost all known deimatids have 18 – 20 tentacles in mature specimens, except for one specimen of Orphnurgus glaber Walsh, 1891 in which only 15 tentacles were found. Many representatives of the family Laetmogonidae develop 15 tentacles: seven species of Laetmogone , Psychronaetes hanseni and the new genus and species, Gebrukothuria profundus .