Gorgonocephalidae Ljungman 1867

Family Gorgonocephalidae Ljungman, 1867

Type genus

Gorgonocephalus Leach, 1815.

Other genera

Asteroporpa Örstedt & Lütken, 1856; Astracme Döderlein, 1927; Astroboa Döderlein, 1911; Astrocaneum Döderlein, 1911; Astrochalcis Koehler, 1905; Astrochele Verrill, 1878; Astrochlamys Koehler, 1912; Astrocladus Verrill, 1899; Astroclon Lyman, 1879; Astrocnida Lyman, 1872; Astrocrius Döderlein, 1927; Astrocyclus Döderlein, 1911; Astrodendrum Döderlein, 1911; Astrodictyum Döderlein, 1927; Astroglymma Döderlein, 1927; Astrogomphus Lyman, 1869; Astrogordius Döderlein, 1911; Astrohamma Döderlein, 1930; Astrohelix Döderlein, 1930; Astroniwa McKnight, 2000; Astrophyton Fleming, 1828; Astroplegma Döderlein, 1927; Astrosierra Baker, 1980; Astrospartus Döderlein, 1911; Astrothamnus Matsumoto, 1915; Astrothorax Döderlein, 1911; Astrothrombus H.L. Clark, 1909; Astrotoma Lyman, 1875; Astrozona Döderlein, 1930; Conocladus H.L. Clark, 1909; Ophiocrene Bell, 1894; Ophiozeta Koehler, 1930; Schizostella A.H. Clark, 1952.

Description

ARM. Arm shape unbranched, or shape branched; length more than 4× disc diameter; covering with granules.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 present (Gorgonocephalus caputmedusae (Linnaeus, 1758)) or absent in some genera. Spines all similar in shape. Arm spine cross section oval. The ratio of thickness of distal ⅓ of arm spine to maximum thickness (in a given crosssectional plane) 0.9–1. Arm spines flat; at proximal segments only on ventral side of arms; predominantly erect, standing perpendicular to arm axis. Longest arm spines between half and one segment long. Tentacle scales present; pores visible along the arm; slightly longer than wide; shorter than the spine nearby; cross section round. Position of lateral arm plate (LAP) only lateral. 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 without dorsal and ventral lobes; restricted to (the ventral or central) portion of the distal edge; all similar. Distance between spine articulations ventralwards increasing. Nerve and muscle openings separated by large, prominent ridge or regular stereom. Nerve opening smaller than muscle opening.

DORSAL DISC. Disc 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; with/without granules; length more than half of the disc radius; bar-like.

VENTRAL DISC. Gonads restricted to the disc. Ventral interradii with granules. Scales on ventral interradii absent. Ventral teeth several (tooth papillae). Infradental papillae on oral plate absent. Buccal scales on OP absent. Accessory oral papillae on OP present. Lateral oral papillae on OP absent.Adoral shield spine absent. Lyman’s ossicle absent. Oral shield covering less than one third of interradius; much wider than long. Madreporite one; 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 shorter than half interradius. Genital papillae absent. Dental plate of equal width all over; fragmented. 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 covering the entire dental plate evenly.

VERTEBRAE. Vertebrae hourglass-shaped (streptospondylous); beyond segment 5 with short keel; without oral bridge.