Ophioscolecidae Lütken, 1869

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 : 28

Family Ophioscolecidae Lütken, 1869

Type genus

Ophioscolex Müller & Troschel, 1842 .

Other genera

Ophiocymbium Lyman, 1880 ; Ophiogeron Lyman, 1878 ; Ophiohyalus Matsumoto, 1915 ; Ophiohymen H.L. Clark, 1911 ; Ophioleptoplax H.L. Clark, 1911 ; Ophiologimus H.L. Clark, 1911 ; Ophiolycus Mortensen, 1933 ; Ophiophrura H.L. Clark, 1911 ; Ophioplexa Martynov, 2010 ; Ophioprium H.L. Clark, 1915 ; Ophiorupta Martynov, 2010 ; Ophiosyzygus H.L. Clark, 1911 ; Ophiuroconis 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, or not all similar in shape ( Ophiolycus ). The atypical spines are hook-shaped. Arm spine cross section round. The ratio of thickness of distal ⅓ of arm spine to maximum thickness (in a given cross-sectional plane) 0.2–0.6, or 0.9–1 ( Ophiolycus ). Arm spines cylindrical ( Ophiolycus ) or tapering (conical); mainly lateral; predominantly erect, standing perpendicular to arm axis. Longest arm spines between one and two segments long. Tentacle scales present ( Ophiolycus ) or absent; pores visible along most of the arm; 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 with constriction. Ventral position of LAP projecting ventro-proximalwards. Ventro-distal tip of LAP projecting ventralwards. Arm spine articulation with dorsal and ventral lobes; without sigmoidal fold; arranged over entire distal LAP edge; dorsalwards increasing in size. Distance between spine articulations dorsalwards increasing. Nerve and muscle openings separated by small ridge if at all. Nerve opening smaller than muscle opening.

DORSAL DISC. Disc circular; flat (about same level as arms). Integument obscuring plates. Dorsal disc without granules; with concealed primary plates; with or without scales; without spines. However, in some species with granules and spines ( O’Hara et al. 2018). Dorsal disc scale/plate without tubercles. Radial shield absent.

VENTRAL DISC. Gonads restricted to the disc. Ventral interradii without granules/spines. Scales on ventral interradii covering the whole area of an interradius. The number of scales on H line of an interradius about 14–21. Ventral teeth several (tooth papillae). Infradental papillae on oral plate present. Buccal scales on OP absent.Accessory oral papillae on OP present. Lateral oral papillae on OP absent. Adoral shield spine present. Lyman’s ossicle absent. Oral shield covering less than one third of interradius; much wider than long. Madreporite one or multiple; with one pore or with numerous pores. Adoral shield meeting in front of the oral shield. 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; entire (single plate). Dental sockets circular; equal to or more than 50% of the width. At least one socket on DP as depression or perforation without septum. Teeth spine-shaped. Teeth on DP arranged as a single row on half of dental plate and other half with a cluster of tooth papillae (ventral cluster), or a single row on ⅔ and a cluster of tooth papillae on ⅓ of dental plate ( Ophiolycus ).

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