Family Amphiuridae Ljungman, 1867 Type genus Amphiura Forbes, 1843 (type species: A. chiajei Forbes, 1843). Other genera Acrocnida Gislén, 1926, Amphichondrius Nielsen, 1932, Amphicontus Hill, 1940, Amphigyptis Nielsen, 1932, Amphiodia Verrill, 1899a, Amphiomya H.L. Clark, 1939, Amphioncus H.L. Clark, 1939, Amphioplus Verrill, 1899a, Amphipholis Ljungman, 1866, Amphipholizona H.L. Clark, 1915a, Amphistigma H.L. Clark, 1938, Dougaloplus A.M. Clark, 1970, Microphiopholis Turner, 1985, Nannophiura Mortensen, 1933 b, Nudamphiura Tommasi, 1965, Ophiocentrus Ljungman, 1867, Ophiocnida Lyman, 1865, Ophiodaphne Koehler, 1930, Ophionephthys Lütken, 1869, Ophiophragmus Lyman, 1865, Ophiosphaera Brock, 1888, Ophiostigma Lütken, 1856, Paracrocnida Mortensen, 1940, Paramphichondrius Guille & Wolff, 1984, Paramphiura Koehler, 1895, Triplodia Turner & Hallan, 2011. Diagnosis Dorsal disc cover variable, often naked scales, but simple spines, granules or tubercles occur in some genera. Large infradental papillae. Buccal scale higher on the oral plate than other oral papillae. Dorsalmost tooth socket a large, heart-shaped fenestration with incomplete septum, other dorsal sockets as fenestrations with septum, ventral sockets shallow, not penetrating. Oral plates with large wingshaped abradial muscle flange, often with branching ribs. Arm spine articulations with two smooth separated, parallel, straight dorsal and ventral lobes. Lateral arm plates commonly sickle-shaped with pointed dorsal tip. Lateral arm plates devoid of ornamentation except for band of more finely meshed stereom in the central part of the proximal edge. Inner side of lateral arm plates with two to three knobs instead of a ridge. Remarks This large family requires revision. Preliminary findings (O’Hara et al. 2017) indicate that there are at least three major clades within the group that fit our criteria for family status. Important genera, including Amphiura, Amphioplus and Amphipholis, are polyphyletic in their current composition.

Published as part of Stöhr, Sabine, Hugall, Andrew F., Thuy, Ben & Martynov, Alexander, 2018, Morphological diagnoses of higher taxa in Ophiuroidea (Echinodermata) in support of a new classification, pp. 1-35 in European Journal of Taxonomy 416 on pages 20-21, DOI: 10.5852/ejt.2018.416, http://zenodo.org/record/3806109