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Synoptic Keys to the Genera of Ophiuroidea

Family Ophiothricidae Ljungman, 1866

Family Ophiothricidae Ljungman, 1866

1 (26)

Radial shields low, without a raised crest.

2 (3)

Disc covered above and below by naked skin through which only the distal ends of the radial shields project; no tentacle scales or, at most, scales present only on basal arm-joints. . . . Ophiogymna Ljungman, 1866.

Syn.: Ophiocampsis Duncan, 1887 (see Koehler 1922a, p. 284).

*elegans Ljung., 1866. Indonesia. Littoral.

3 (2)

Disc not covered by naked skin.

page 24
4 (9)

Upper surface of disc bearing granules.

5 (8)

Lower surface of disc covered by skin.

6 (7)

Dorsal surface of arms bearing granules, tubercles or coarse irregular grains, which more or less obscure the plates; dorsal arm-plates reduced in size. . . . Ophiothela Verrill, 1867.

Syn.: Ophioteresis Bell, 1892 (juvenile stage).

*mirabilis Verrill, 1867. Panama. Littoral.

7 (6)

Entire dorsal surface of disc and arms densely coated with uniform granules which completely obscure all plates; tentacles issue from side of arms. . . . Ophiopsammium Lyman, 1874.

*semperi Lyman, 1874. Philippine Is. Littoral.

8 (5)

Lower surface of disc covered by fine scales. . . . Ophiocnemis Mueller & Troschel, 1842.

*Ophiura marmorata Lmk., 1816. Indian Ocean. Littoral.

9 (4)

Upper and lower surfaces of disc covered by plates.

10 (11)

Disc covered by primary plates and radial shields; two arm-spines. . . . Ophiophthirius Doederlein, 1898.

*actinometrae Doed., 1898. Torres Strait. Littoral.

The type (and only known) species was epizoic on a comatulid, and may be a juvenile stage of some other genus.

11 (10)

Disc covered by numerous other plates, besides the primaries; four or more arm-spines.

12 (19)

Radial shields large and conspicuous.

13 (16)

Disc plates bear spines or thorns.

14 (15)

Arm-spines of the proximal arm-joints united by a membranous web into vertical fin-like fans. . . . Ophiopteron Ludwig, 1888.

*elegans Ludwig, 1888. Amboina. Littoral.

Mortensen (1932) has shown that some spp. of Ophiothrix pass through an "Ophiopteron" stage.

15 (14)

Arm-spines of all arm-joints free, not united by webs. . . . Macrophiothrix H. L. Clark, 1938.

Syn.: Placophiothrix H. L. Clark, 1938.

*Ophiura longipeda Lmk., 1816. Indo-Pacific. Littoral.

16 (13)

Disc plates without spines or thorns.

17 (18)

Dorsal arm-plates short and wide; arm-spines smooth and opaque. . . . Ophiomaza Lyman, 1871.

Syn.: Lütkenia Brock, 1888.

*cacaotica Lyman, 1871. Indo-West-Pacific. Littoral.

Species of this genus may occur as epizoic forms on various comatulids.

18 (17)

Dorsal arm-plates not short and wide; arm-spines thorny. . . . Ophiotrichoides Ludwig, 1882.

*lymani Ludwig, 1882. Tropical W. Atlantic. Littoral.

The genus is strongly represented in the Indo-Pacific, and at least one species has an "Ophiopteron" stage; see H. L. Clark (1946, p. 230).

19 (12)

Radial shields small or partly concealed by spinules.

20 (21)

Dorsal arm-plates bearing minute spinelets. . . . Amphiophiothrix H. L. Clark, 1946.

*Ophiothrix demessa Lyman, 1861. Tropical Indo-Pacific. Littoral.

21 (20)

Dorsal arm-plates smooth.

22 (23)

Spines or thorns on disc plates; tentacle-scales present. . . . Ophiothrix Mueller & Troschel, 1840.

page 25

Syn.: Ophionyx M. & T., 1840.

*Asterias pentaphylla Pennant, 1777. Britain. Littoral.

23 (22)

Disc plates with no spines or thorns.

24 (25)

Arm-spines not longer than width of arm; radial shields contiguous along their whole length; androphorous, epizoic on Diadema and Toxopneustes; distal arm-spines hooked. . . . Ophiosphaera Brock, 1888.

*insignis Brock, 1888. Amboina. Littoral.

25 (24)

Arm-spines long and slender, up to four times as long as width of arm; radial shields scarcely contiguous. . . . Lissophiothrix H. L. Clark, 1938.

*delicata H. L. Clark, 1938. Tropical Australia. Littoral.

26 (1)

Radial shields each carry a raised vertical crest. Disc naked above and below, or with only a few small scattered scales imbedded in skin.

27 (28)

Some proximal dorsal arm-plates carry a high median keel; beyond disc ventral arm-plates become rounded and widely separated. . . . Ophiolophus Marktanner-Turneretscher, 1887.

*novarae M-T, 1887. Nicobar Is. Littoral.

28 (27)

Dorsal arm-plates without keels.

29 (30)

Disc and arms minutely granulated. . . . Gymnolophus Brock, 1888.

*Ophiothela holdsworthii E. A. Smith, 1878. Ceylon.

30 (29)

Disc and arms naked. . . . Ophioaethiops Brock, 1888.

Syn.: Ophiohelix Koehler, 1895.

*unicolor Brock, 1888. Amboina. Littoral.