Synoptic Keys to the Genera of Ophiuroidea
Family Ophiomyxidae Ljungman, 1866
Family Ophiomyxidae Ljungman, 1866
1 (36) |
Oral shields small; adoral plates long and slender, lying between the oral shield and the first lateral arm-plate. Vertebrae long and slender, their articular peg well developed (i.e., zygospondylous). Subfamily Ophiomyxinae |
2 (19) |
Second oral tentacle-pores opening partly or entirely outside mouth-angles. |
3 (16) |
Teeth present, in a single vertical row. |
4 (7) |
Radial shields present. |
5 (6) |
Radial shields large, each with a conspicuous spine at the proximal end. . . . Ophiostyracium H. L. Clark, 1911. *trachyacanthum H. L. C., 1911. North Pacific. 400 fms. |
6 (5) |
Radial shields small, and only their distal ends visible at arm-base. . . . Astrogeron Verrill, 1899. H. L. Clark regards this as a synonym of Ophiogeron. *Ophiogeron supinus Lym., 1883. West Indies. 200–400 fms. |
7 (4) |
No radial shields. |
8 (9) |
No ventral arm-plates, except on the first arm-segment. . . . Ophiocanops Koehler, 1922a. Ophiocanops is keyed here as a practical convenience, as the characters of the gonads and stomach may escape notice. See Family Ophiocanopidae, p. 15. |
9 (8) |
Ventral arm-plates present. |
10 (11) |
Disc delicately scaled above. Oral papillae, teeth spiniform. Spines on outer segments are replaced by minute umbrella-shaped spinules. . . . Ophiohelus Lyman, 1880. *umbella Lyman, 1880. West Indies. 100 fms. |
11 (10) |
Disc without scales. |
12 (15) |
Oral angles devoid of oral papillae. |
13 (14) |
Disc covered by naked skin. . . . Ophiogeron Lyman, 1878. *edentulus Lyman, 1878. Fiji. 1,350 fms. |
14 (13) |
Disc covered by finely granulated skin. . . . Ophiosciasma Lyman, 1878. *attenuatum Lyman, 1878. E. Brazil. 350 fms. |
15 (12) |
Oral angles bearing spiniform oral papillae, which resemble the teeth and tooth papillae. . . . Ophioscolex (s.s.) Mueller & Troschel, 1842. The genus was restricted by Mortensen (1933); synonym Ophiocynodus H. L. Clark, 1911. *glacialis M. & T., 1842. Arctic. 100 fms. page 14 |
16 (3) |
Teeth vestigial; resembling spinules. |
17 (18) |
Uppermost arm-spines of successive segments united to one another by a horizontal membrane running longitudinally along the arm. No dorsal arm-plates. . . . Ophiosyzygus H. L. Clark, 1911. *disacanthus H. L. C., 1911. Japan. 100 fms. |
18 (17) |
No membrane uniting arm-spines: thin hyaline dorsal arm-plates. . . . Ophioleptoplax H. L. Clark, 1911. *megapora H. L. C., 1911. North Pacific. 70 fms. |
19 (2) |
Second oral tentacle opening entirely within the mouth-angles. |
20 (29) |
Teeth and oral papillae acutely pointed. |
21 (22) |
Conspicuous radial shields, disc scaled above and below; dorsal arm-plates present: 1 tentacle scale: distal part of arm, the upper 2 arm-spines are modified into double hooklets. . . . Ophiolycus Mortensen, 1933c. *inermis Mrtsn., 1933c. S. Africa. 200 fms. |
22 (21) |
Radial shields not distinguishable from other plates, or lacking altogether. No dorsal arm-plates. |
23 (24) |
A conspicuous coating of large granules covers the dorsal surface of the disc and arms. . . . Ophiovesta Koehler, 1931. *granulata Koehler, 1931. Indonesia. Littoral. |
24 (23) |
Platelets or granules form a conspicuous marginal border round the disc, which is otherwise covered by skin. |
25 (28) |
Genital cleft shorter than an arm-segment. |
26 (27) |
No tentacle scale: arm-spines hyaline with several hooklets. . . . Ophiostiba Matsumoto, 1915. *hidekii Matsumoto, 1915. Japan. 300 fms. |
27 (26) |
Single tentacle-scale: arm-spines not hooked. . . . Ophiomora Koehler, 1907. *elegans Koehler, 1907. East Africa. |
28 (25) |
Genital cleft as long as 4 arm-segments: 6 or 7 short, blunt arm-spines. . . . Neoplax Bell, 1884. *ophiodes Bell, 1884. Indian O. Littoral. |
29 (20) |
Teeth and oral papillae broadly expanded with denticulate free margins. |
30 (33) |
Disc plates present around the margin, disc otherwise covered by skin. |
31 (32) |
Dorsal arm-plates entire: radial shields rudimentary: arm-spines modified as compound hooks. . . . Ophiohyalus Matsumoto, 1915. *gotoi Matsumoto, 1915. Japan. |
32 (31) |
Dorsal arm-plates fragmented; radial shields conspicuous: arm-spines not hooked, save at tip of arm. . . . Ophiomyxa Mueller & Troschel, 1840. *Ophiura pentagona Lmk., 1816. Mediterranean. |
33 (30) |
No marginal disc-plates. |
34 (35) |
No radial shields: arm-spines webbed. . . . Ophiohymen H. L. Clark, 1911. *gymnodiscus H. L. C., 1911. North Pacific. 100 fms. |
35 (34) |
Radial shields present: arm-spines free. . . . Ophiodera Verrill, 1899. *serpentaria Lyman, 1883. N. Atlantic. 350 fms. H. L. Clark (1915) refers the type to Ophiomyxa. Mortensen (1927) synonymizes Ophiodera with Ophiomyxa. |
36 (1) |
Oral shields and adoral plates fused together and very thick: adoral plates lying proximal to the oral shields. Vertebrae short, thick, their articular peg page 15rudimentary or absent (i.e., streptospondylous). . . . Subfamily Ophiobyrsinae |
37 (38) |
Only 1 genital cleft in each interradius: oral shield present in only 1 interradius. . . . Ophioschiza H. L. Clark, 1911. *monacantha H. L. C., 1911. Bering Sea. 300 fms. |
38 (37) |
Genital clefts paired: 5 oral shields. |
39 (44) |
Radial shields conspicuous, elongate, bearing spinules. |
40 (41) |
No dorsal arm-plates: arm-spines very long and serrated. . . . Ophiophrixus H. L. Clark, 1911. *acanthinus H. L. C., 1911. Japan. 100 fms. |
41 (40) |
Fragmented dorsal arm-platelets occur: arm-spines not long, nor serrated. |
42 (43) |
Oral papillae forming a regular lateral row along the sides of the oral angle: ca. 5 spiniform teeth at jaw-apex, as well as dental papillae. . . . Ophiobyrsella Verrill, 1899. *serpens Lyman, 1883. Caribbean. 70 fms. H. L. Clark (1915) refers the type to Ophiobyrsa. |
43 (42) |
Only 1 oral papilla, and no teeth: a few spiniform dental papillae at the jaw-apex. . . . Ophiobyrsa Lyman, 1878. *rudis Lyman, 1878. Australia. Littoral. |
44 (39) |
Radial shields inconspicuous or absent. |
45 (46) |
Only lateral arm-plates on arm: 1 oval tentacle-scale. . . . Astrogymnotes H. L. Clark, 1914. Referred by H. L. Clark and Doederlein to Trichasteridae: but Mortensen states vertebrae are zygospondylous: the solitary genotype is hexamerous, and this character may prove to be generic. *catasticta H. L. C., 1914. W. Australia. 100 fms. |
46 (45) |
Ventral arm-plates as well as lateral arm-plates. |
47 (48) |
Disc bearing spinules: oral and dental papillae spiniform. . . . Ophiobrachion Lyman, 1883. *uncinatus Lyman, 1883. Cuba. 250 fms. |
48 (47) |
Disc free from spinules: oral and dental papillae, and teeth, all alike, stout, stumpy, blunt and thorny at the tip. . . . Ophiosmilax Matsumoto, 1915. *mirabilis Matsumoto, 1915. Japan. 300 fms. |