Family Hemieuryalidae Verrill, 1899

Type genus

Hemieuryale von Martens, 1867 .

Other genera

Actinozonella Stöhr, 2011; Astrogymnotes H.L. Clark, 1914; Ophioholcus H.L. Clark, 1915; Ophioplocus Lyman, 1861; Ophioplus Verrill, 1899; Ophiozonella Matsumoto, 1915; Ophiozonoida H.L. Clark, 1915; Quironia A.H. Clark, 1934; Sigsbeia Lyman, 1878 .

Description

ARM.Arm shape unbranched; length more than4×disc diameter;covering without granules/spines/tubercles. Arm combs absent. Dorsal arm plate present. Accessory dorsal arm plate present or absent ( Actinozonella). 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 or oval (Sigbeia). The ratio of thickness of distal ⅓ of arm spine to maximum thickness (in a given cross-sectional plane) 0.9–1. Arm spines cylindrical; at proximal segments only on ventral side of arms; predominantly parallel to arm axis (adpressed). Longest arm spines shorter than half a segment ( Sigsbeia, Ophiozonella falklandica Mortensen, 1936), or between half and one segment long ( Hemieuryale, Ophiozonella longispina (H.L. Clark, 1908), Ophioplus). 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) only lateral or arched (wrapped around the arm) ( Sigsbeia). Dorsal and/or ventral edge(s) of LAPs without constriction. Ventral position of LAP projecting ventro-proximalwards. Ventro-distal tip of LAP not projecting ventralwards. Arm spine articulation with dorsal and ventral lobes; without sigmoidal fold; restricted to (the ventral or central) portion of the distal edge; ventralwards increasing in size. Distance between spine articulations not applicable (two spine articulations). Nerve and muscle openings separated by small ridge if at all. Nerve opening smaller than muscle opening, or approximately as large as muscle opening ( Ophiozonella).

DORSAL DISC. Disc pentagonal to circular; high (above arm level). Integument not obscuring plates. Dorsal disc without granules; with obvious primary plates; with scales; without spines. Dorsal disc scale/plate with tubercles. Radial shield present; without granules/spines; length between one third and half of the disc radius, or length more than half of the disc radius ( Ophioplus); isosceles (mirror-symmetric) triangular to pear-shaped.

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 single. Infradental papillae on oral plate present. Buccal scales on OP absent. Accessory oral papillae on OP absent. Lateral oral papillae on OP present; one lateral papilla along each side of the jaw; block-shaped. Adoral shield spine present. Lyman’s ossicle present. Oral shield covering less than one third of interradius; much wider than long. 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 shorter than half interradius. Genital papillae absent. Dental plate dorsal half widest; entire (single plate). Dental sockets slit-shaped and 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 hourglass-shaped (streptospondylous) or zygospondylous ( Ophiozonella longispina); beyond segment 5 with short keel; without oral bridge.