Ophiosphalmidae O’Hara, Stöhr, Hugall, Thuy & Martynov, 2018

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 : 22-23

Family Ophiosphalmidae O’Hara, Stöhr, Hugall, Thuy & Martynov, 2018

Type genus

Ophiosphalma H.L. Clark, 1941 .

Other genera

Ophiolipus Lyman, 1878 ; Ophiomusium Lyman, 1869 .

Description

ARM. Arm shape unbranched; length 3–4× disc diameter; covering with spines distal to the genital slit around the disc margin but 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. 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 parallel to arm axis (adpressed). Longest arm spines shorter than half a segment. Tentacle scales present; pores visible only on proximal arm; nearly as long as wide; shorter than the spine nearby; cross section round. Position of lateral arm plate (LAP) arched (wrapped around the arm) ( Fig. 3L ). Dorsal and/or ventral edge(s) of LAPs without constriction. Ventral position of LAP not projecting ventro-proximalwards. Ventro-distal tip of LAP not projecting ventralwards. Arm spine articulation without dorsal and ventral lobes; arranged over entire distal LAP edge; ventralwards increasing in size. Distance between spine articulations dorsalwards increasing. Nerve and muscle openings separated by large, prominent ridge or regular stereom. Nerve opening approximately as large as muscle opening.

DORSAL DISC. Disc pentagonal; flat (about same level as arms). Integument not obscuring plates. Dorsal disc without granules; with obvious primary plates; with scales; without spines. Dorsal disc scale/plate without tubercles. Radial shield present; without granules/spines; length more than half of the disc radius; scalene (oblique) triangular.

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 fewer than 7. Ventral teeth several (tooth papillae). Infradental papillae on oral plate present. Buccal scales on OP present. Accessory oral papillae on OP absent. Lateral oral papillae on OP absent. Adoral shield spine present. Lyman’s ossicle absent. Oral shield covering less than one third of interradius; much longer than wide. Madreporite no data. 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 present. Dental plate of equal width all over; 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.

Figures

Fig. 3. SEM images of various ossicle structures in brittle stars. A. Muscle and nerve opening on LAP separated by small ridge if at all (Amphiura chiajei Forbes, 1843). B. Muscle and nerve opening on LAP separated by large, prominent ridge or regular stereom (Ophiolycus purpureus (Düben & Koren, 1846)). C. Non-keeled vertebra (Amphiura chiajei). D. Keeled vertebra (Ophiothrix fragilis Abildgaard, 1789). E. Vertebra with oral bridge (Euryale aspera Lamarck, 1816). F. Sockets indicate teeth and tooth papillae on dental plate as single row (Amphilepis norvegica (Ljungman, 1865)). G. ½ single row of teeth and ½ tooth papillae (Ophiothrix fragilis). H. ⅔ single row of teeth and ⅓ tooth papillae (Ophiocamax vitrea Lyman, 1878). I. Sockets on dental plate covering evenly (Asteronyx loveni Müller & Troschel, 1842). J–K. LAP not arched = position lateral. L. LAP arched = wrapped around the arm.