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Synoptic Keys to the Genera of Ophiuroidea

Family Amphiuridae Ljungman, 1867

Family Amphiuridae Ljungman, 1867

1 (18)

Oral papillae, not forming a continuous row along the side of the jaw, but instead there is a gap between the infradental papillae and the outer papillae: the mouth angle is therefore permanently gaping: outermost papillae arise from adoral shield: an additional papilla occurs dorsal to the infradental papilla (Amphiura group).

2 (7)

Disc bearing spines, or spiny processes.

3 (4)

No true (articulating) spines on disc, but scales of ventral side and margin of dorsal side end each in a small spiniform tubercle. . . . ACROCNIDA Gislén, 1926.

(Compare Paracrocnida Mortensen)

*Asterias brachiata Montagu, 1804. N. Europe. Littoral.

4 (3)

True (articulating) spines occur on some of the disc-scales.

4a (4b)

One infradental papilla. . . . Amphiocnida Verrill, 1899.

*Ophiocnida putnami Lyman, 1871. N. Pacific, littoral.

4b (4a)

Two infradental papillae.

5 (6)

Two infradental papillae and 3 outer papillae on the adoral shield: radial shields contiguous: large primary plates: spines are carried by the lesser disc scales: tentacle-papillae 2–3 at base of arm, 1 elsewhere: 5–6 armspines. . . . Anamphiura H. L. Clark, 1939.

*valida H. L. C., 1939. Indian Ocean. 150 fms.

6 (5)

Two infradental and 2 outer oral papillae, the latter spiniform: radial shields contiguous distally but widely separated proximally: numerous discspines: usually no tentacle-scales: 5–10 arm-spines. . . . Ophiocentrus Ljungman, 1867.

*aculeatus Ljung., 1867. Indonesia. "Deepwater".

7 (2)

Disc free from spines.

8 (9)

A supplementary plate present between the oral plate and adoral shield, on either side. . . . Paramphiura Koehler, 1895.

*Ophiocoma punctata Forbes, 1841. N. Europe. Littoral.

9 (8)

No supplementary plate between oral plate and adoral shield.

10 (11)

Disc covered by smooth naked skin: radial shields narrow and bar-like. Ophionema Lütken, 1869.

*intricata Lütken, 1869. Caribbean. Littoral.

11 (10)

Disc covered by scales, at least on dorsal side.

page 21
12 (13)

Two tentacle-scales, the outer one spiniform and bearing barbs: two outer oral papillae, the outermost rounded and flat, the inner one acutely pointed. Amphioncus H. L. Clark, 1939.

*platydiscus H. L. Clark, 1939. Aden. 100 fms.

13 (12)

No spiniform tentacle-scales.

14 (15)

Arm-spines hooked on distal joints of arm. Disc covered by primary plates. Epizoic on echinoid Laganum. . . . Nannophiura Mortensen, 1933.

*lagani Mortensen, 1933. Indonesia. Littoral.

15 (14)

Arm-spines not hooked on distal joints of arm.

16 (17)

Disc-scales fine, flattened, imbricating, not chunky: oral shields not meeting the first lateral arm-plate. . . . Amphiura Forbes, 1842.

Syn: Ophiopelte Verrill, 1899; Ophiopeltis Dub. & Koren, 1845; Hemilepis Ljungman.

*chiajii Forbes, 1842. North Sea. Littoral.

17 (16)

Disc-scales coarse, chunky, arranged in an irregular mosaic: outermost oral papilla spiniform, the other two papillae rounded: ten to twelve armspines arranged in an erect, lateral comb. . . . Ctenamphiura Verrill, 1899.

*Amphiura maxima Lyman, 1879. Torres Strait. 30 fms.

18 (1)

Three or more oral papillae, forming a continuous row along the side of the jaw, and so closing over the mouth angle.

18a (18b)

Second oral tentacle-pore opening outside the oral slits. . . . Ophiomonas Djakonov, 1952.

*bathybia Djakonov, 1952. N.W. Pacific, 2,000 fms.

18b (18a)

Second oral tentacle-pore opening within the oral slit.

19 (28)

Four or five oral papillae, the outermost carried on the adoral shield; an additional papilla occurs just dorsal to the infradental one (Amphioplus group).

20 (23)

Disc free from spines.

21 (23)

Outermost oral papilla larger than others, and operculiform: radial shields contiguous. . . . Amphichilus Matsumoto, 1917.

*trichoides Matsumoto, 1917. N. Pacific.

22 (21)

Outermost oral papillae small, not operculiform: radial shields divergent. Amphioplus Verrill, 1899.

*Amphiura tumida Lym., 1899. Caribbean. 300 fms.

23 (20)

Disc bearing spines, or some spiniform processes.

24 (25)

No true (articulating) spines on disc, but scales of the ventral side and margin of the dorsal side end each in a small spiniform tubercle. . . . Paracrocnida Mortensen, 1940.

Compare Acrocnida Gislén.

*persica Mrtsn., 1940. Persian Gulf. Littoral.

25 (24)

True (articulating) spines occur on some of the disc-scales.

26 (27)

Two spiniform tentacle-scales, the adradial one being long and slender: 6–10 arm-spines: conical, spaced, oral papillae, the outermost long and spiniform: radial shields contiguous. . . . Amphilimna Verrill, 1899.

*Ophiocnida olivacea Lyman, 1869. N. Atlantic. 120 fms.

27 (26)

Tentacle-scales short, flat, leaf-like: 3–5 arm-spines: close-set oral papillae, the outermost short and flat. Radial shields not contiguous, or merely touching at their distal ends. . . . Amphiacantha Matsumoto, 1917.

*Amphioplus acanthinus H. L. C., 1911. Japan. 100 fms.

page 22
28 (19)

Three or four oral papillae, the outermost carried on the oral plate: no papillae on the adoral shield, and no additional papilla just dorsal to the infradental one.

29 (36)

Three oral papillae, the outermost much larger than the others and meeting its fellow of the other side, so as to seal the distal half of the mouth angle (Amphipholis group).

30 (31)

Some disc-scales bearing spines. . . . Ophiostigma Lütken, 1856.

(To this genus I refer provisionally Amphistigma H. L. Clark, 1938; it was founded on a single specimen of a juvenile stage.)

*tenue Luetken, 1856. Caribbean. Littoral.

31 (30)

Disc-scales without spines.

32 (33)

One tentacle-scale: arm-spines of distal arm-joints transformed into hooklets: male dwarfed, and carried on the ventral side of the female, which is epizoic on the echinoid Echinodiscus. . . . Amphilycus Mortensen, 1933.

*androphorus Mortensen, 1933. E. Africa. Littoral.

33 (32)

Two tentacle-scales.

34 (35)

Two erect, valve-like tentacle-scales which close together like a clam-shell when the tentacle is retracted. . . . Amphiomya H. L. Clark, 1939.

*notabilis H. L. C., 1939. Indian Ocean.

35 (34)

Two flat, leaf-like tentacle-scales. . . . Amphipholis Ljungman, 1866.

*Ophiolepis gracillima Stimpson, 1852. Caribbean. Littoral.

36 (29)

Three or four subequal oral papillae (Amphiodia group).

37 (38)

Disc with numerous scattered spines. . . . Ophiocnida Lyman, 1865.

Syn.: Ophiocnidella Ljungman, 1872.

*Ophiolepis hispida Le Conte, 1851. Panama. Littoral.

38 (37)

Disc without spines (though some peripheral scales may have a spine-like process).

39 (40)

Naked skin covering disc above and below, save for the elongate radial shields. . . . Ophionephthys Lütken, 1869.

*limicola Lütk., 1869. West Indies. Littoral.

40 (39)

Disc partly or wholly scaled.

41 (42)

Disc with dorsal scales, but densely granulated on ventral side: genital scales broad with several parallel furrows: 2 tentacle-scales. . . . Amphichondrius Nielsen, 1933

*granulosus Nielsen, 1933. California. Littoral.

42 (41)

Disc scaled above and below, without granulation.

43 (44)

Radial shields contiguous: marginal scales of disc erect, or spiniform, arranged to form a more or less sharply defined "fence" around the rim. Ophiophragmus Lyman, 1865.

Mortensen (1940) speaks of "spines along the border of the disc", but spines are not mentioned in Lyman's original diagnosis. Nielsen (1932) has also defined Amphispina (as a sub-genus of Amphiodia) having only spiniform marginal scales, not articulated spinules—but Lyman (1865) had already assigned this character to his Ophiophragmus. I therefore regard Amphispina Nielsen, 1933, as a synonym.

*Amphiura wurdemanii Lyman, 1860. N. Atlantic.

44 (43)

Radial shields divergent: disc without specially distinguished marginal scales. . . . Amphiodia Verrill, 1899.

*Amphiura pulchella Lyman, 1869. Caribbean. 40 fms.