Ophiernidae 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 : 37-38

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

Type genus

Ophiernus Lyman, 1878 . (No other genera)

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 not all similar in shape. The atypical spines are bristles ( Fig. 2H ). Arm spine cross section oval. 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 between half and one segment long. Tentacle scales present; pores visible along most of the arm; slightly longer than wide; shorter than the spine nearby; cross section oval. Position of lateral arm plate (LAP) only lateral. Dorsal and/or ventral edge(s) of LAPs with constriction. Ventral position of LAP not projecting ventro-proximalwards. Ventro-distal tip of LAP projecting ventralwards. Arm spine articulation without dorsal and ventral lobes or with weak lobes ( O’Hara et al. 2018); arranged over entire distal LAP edge; dorsalwards 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 to circular; flat (about same level as arms). Integument obscuring plates. Dorsal disc with 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 with granules. 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 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; about as long as wide. Madreporite one; with one pore. 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; 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 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. 2. SEM images of various brittle star ossicles. A–E. Disc structures.A. Dorsal disc, radial shield with tubercles (Ophiomusa lymani (Wyville-Thomson, 1873)). B. Dorsal disc (Ophiolimna bairdi (Lyman, 1883)). C. Ventral disc (Ophionereis porrecta Lyman, 1860), the interradius is assumed as a triangle and H gives its height. D. Dorsal disc, triangular radial shield (Ophiactis savignyi (Müller & Troschel, 1842)). E. Ventral disc, mouth (Ophioderma sp.). – F–H. Atypical arm spines. F. Umbrella-shaped arm spine (Ophiotholia spathifer (Lyman, 1879)). G. Hook-shaped arm spine (Asteronyx loveni Müller & Troschel, 1842).H. Bristle spines (Ophiernus vallincola Lyman, 1878). – I–L. Lateral arm plates (LAP). I. LAP with constriction (Ophioscolex glacialis Müller & Troschel, 1842). J. Dorsal and ventral part of LAP without constriction (Ophiura ophiura (Linneaus, 1758)). K. Ventral part of LAP projecting ventro-proximalwards (Ophiopallas paradoxa Koehler, 1904). L. Ventral part of LAP not projecting ventro-proximalwards (Ophiosphalma fimbriatum (Koehler, 1922)).