Ophiacanthidae 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 : 33-34

Family Ophiacanthidae Ljungman, 1867

Type genus

Ophiacantha Müller & Troschel, 1842 .

Other genera

Ophialcaea Verrill, 1899 ; Ophientrema Verrill, 1899 ; Ophiocanops Koehler, 1922 ; Ophiochondrus Lyman, 1869 ; Ophiohamus O’Hara & Stöhr, 2006 ; Ophiolebes Lyman, 1878 ; Ophiolimna Verrill, 1899 ; Ophiomitrella Verrill, 1899 ; Ophiomoeris Koehler, 1904 ; ‘ Ophiophthalmus ’ Matsumoto, 1917; Ophioplinthaca Verrill, 1899 ; Ophioripa Koehler, 1922 ; Ophiosemnotes Matsumoto, 1917 ; Ophiurothamnus Matsumoto, 1917 .

Description

ARM. Arm shape unbranched; length 3× disc diameter, or length 3– 4× disc diameter, or length more than 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, or 0.9–1 ( Ophiochondrus ). Arm spines pointed; mainly lateral; predominantly erect, standing perpendicular to arm axis. Longest arm spines between one and two segments long ( Ophiolimna ), or longer than two segments. Tentacle scales present; pores visible along most of the arm; nearly 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 not projecting ventro-proximalwards. Ventro-distal tip of LAP not projecting ventralwards. Arm spine articulation with dorsal and ventral lobes; with a fully developed sigmoidal fold; arranged over entire distal LAP edge; dorsalwards increasing in size ( Ophiacantha bidentata (Bruzelius, 1805) , Ophiolimna ), or all similar ( Ophiacantha abyssicola G.O. Sars, 1872 , Ophioplinthaca ). 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) or high (above arm level) ( Ophiochondrus ). Integument obscuring plates. Dorsal disc with granules ( Ophioplinthaca , Ophiolimna ); with concealed primary plates; with scales; with spines ( Ophiacantha , Ophiolimna ) or without spines. Dorsal disc scale/plate without tubercles. Radial shield present; with spines and with granules; length between one third and half of the disc radius ( O. bidentata , Ophioplinthaca ), or length more than half of the disc radius ( O. abyssicola , Ophiochondrus ); isosceles (mirror-symmetric) triangular to pear-shaped, or bar-like.

VENTRAL DISC. Gonads restricted to the disc or not restricted to the disc ( Ophiocanops ). Ventral interradii with spines ( O. abyssicola ) or with granules ( O. bidentata , Ophiochondrus , with spine and granules in Ophiolimna ). Scales on ventral interradii covering the whole area of an interradius. The number of scales on H line of an interradius about 7–14. Ventral teeth single. 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; spiniform. Adoral shield spine present. Lyman’s ossicle present. 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 of equal width all over, or dorsal half widest ( Ophiolimna ); entire (single plate). Dental sockets slit-shaped; equal to or more than 50% of the width. At least one socket on DP as depression or perforation without septum. Teeth flat (with round or slightly pointed tip, but never spine-like). Teeth on DP arranged as single row.

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