Ophiomyxidae Ljungman, 1867

Goharimanesh, Mona, Stöhr, Sabine, Mirshamsi, Omid, Ghassemzadeh, Fereshteh & Adriaens, Dominique, 2021, Interactive identification key to all brittle star families (Echinodermata; Ophiuroidea) leads to revised morphological descriptions, European Journal of Taxonomy 766 (1), pp. 1-63 : 36

Family Ophiomyxidae Ljungman, 1867

Type genus

Ophiomyxa Müller & Troschel, 1842 .

Other genera

Neoplax Bell, 1884 ; Ophiarachna Müller & Troschel, 1842 ; Ophioconis Lütken, 1869 ; Ophiostiba Matsumoto, 1915 ; Ophiurochaeta Matsumoto, 1915 .

Description

ARM. Arm shape unbranched; length 3–4× disc diameter; covering without granules/spines/tubercles. Arm combs absent. Dorsal arm plate present.Accessory dorsal arm plate absent. Ventral arm plate present. Accessory ventral arm plate absent. Girdle of tiny hooks on the arms absent. Spines all similar in shape. Arm spine cross section round. The ratio of thickness of distal ⅓ of arm spine to maximum thickness (in a given cross-sectional plane) 0.6–0.9. Arm spines pointed; mainly lateral; predominantly erect, standing perpendicular to arm axis. Longest arm spines shorter than half a segment, or longer than two segments ( Ophiarachna ). Tentacle scales present; pores visible along most of the arm; slightly longer than wide, or more than two times as long as wide; shorter than the spine nearby; cross section oval. Position of lateral arm plate (LAP) arched (wrapped around the arm). Dorsal and/or ventral edge(s) of LAPs without constriction. Ventral position of LAP projecting ventro-proximalwards. Ventro-distal tip of LAP projecting ventralwards. Arm spine articulation with dorsal and ventral lobes; without or with a weakly developed sigmoidal fold; arranged over entire distal LAP edge; ventralwards increasing in size. Distance between spine articulations equal. Nerve and muscle openings separated by small ridge if at all. Nerve opening approximately as large as muscle opening.

DORSAL DISC. Disc pentagonal; flat (about same level as arms). Integument not obscuring plates. Dorsal disc with granules ( Ophiarachna ) or without granules; with concealed primary plates; with scales; without spines. Dorsal disc scale/plate without tubercles. Radial shield present; without granules/spines; length less than one third of the disc radius; isosceles (mirror-symmetric) triangular to pear-shaped.

VENTRAL DISC. Gonads restricted to the disc. Ventral interradii without granules/spines, or with granules ( Ophiarachna ). Scales on ventral interradii absent. Ventral teeth single or with several tooth papillae ( Ophiarachna ). Infradental papillae on oral plate present. Buccal scales on OP absent. Accessory oral papillae on OP absent. Lateral oral papillae on OP present; single row of lateral papillae; paddle-shaped. Adoral shield spine present. Lyman’s ossicle present. Oral shield covering less than one third of interradius; about as long as wide. Madreporite one; with one pore. Adoral shield separated.Abradial genital plate not twisted. Number of genital slits one per bursa. Genital slit longer than half the length of an interradius. Genital papillae absent. Dental plate ventral half widest; fragmented. Dental sockets slit-shaped and circular; less than 50% of the width or equal to or more than 50% of the width. At least one socket on DP as perforation with septum. Teeth block-like (with square tip). Teeth on DP arranged as single row.

VERTEBRAE. Vertebrae zygospondylous; beyond segment 5 with short keel; without oral bridge.