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Synoptic Keys to the Genera of Ophiuroidea

Suborder Euryalae Mueller & Troschel, 1840

Suborder Euryalae Mueller & Troschel, 1840

Family Gorgonocephalidae Ljungman, 1867, emend. Mortensen, 1933

1 (39)

Arms forked.

2 (3)

Seven arms, bifurcating once about halfway out: girdle hooklets minute, without secondary teeth: reproducing by transverse fission. . . . Schizostella A. H. Clark, 1952.

*bifurcata A. H. C., 1952. Caribbean. Littoral.

3 (2)

Five arms.

4 (7)

More than 30 arm-joints before the first fork.

5 (6)

Disc and arms with transverse ridges. . . . Astrocnida Lyman, 1872.

*Trichaster isidis Duchassaing, 1850. Caribbean. 100 fms.

6 (5)

Disc and arms without transverse ridges. . . . Astroclon Lyman, 1879.

*propugnatoris Lyman, 1879. Indonesia. 100 fms.

7 (4)

Less than 20 arm-joints before the first fork.

8 (38)

Primary plates inconspicuous: radial shields elongate, bar-like.

9 (17)

Five madreporites of similar size.

9a (10)

Hooklets with a secondary tooth. . . . Astroglymma Doederlein, 1927.

Syn.: Astrodactylus Doederlein, 1911 (preoccupied).

*Astrophyton sculptum Doed., 1896. Indonesia.

10 (9a)

Hooklets with no secondary teeth.

11 (14)

Armspines occurring below the disc before the first or second fork.

12 (13)

Radial shields without transverse ridges: arm-spines occurring before the first fork. . . . Astrogordius Doederlein, 1911.

*Astrophyton cacaoticum Lyman, 1874. Caribbean. Littoral.

13 (12)

Radial shields with transverse ridges. . . . Astrocyclus Doederlein, 1911.

*Astrophyton caecilia Ltk., 1856. Caribbean. 100 fms.

14 (11)

Armspines lacking before the fourth fork.

15 (16)

Disc and arms with transverse rows of spines. . . . Astrocaneum Doederlein, 1911.

(Synonym Astrocynodus A. H. Clark, 1918.)

*Astrophyton spinosum Lym., 1875. Panama, Pearl Is. Littoral.

16 (15)

Disc and arms without spines. . . . Astrodictyum Doederlein, 1927.

*Astrophyton panamense Verr., 1867. Panama, Pearl Is. Littoral.

17 (9)

One madreporite (exceptionally 2 or 3 of different sizes).

18 (27)

Arm-spines present before the first fork.

19 (20)

Madreporite placed at the proximal border of the soft interbrachium.

page 8
20 (19)

Madreporite separated by accessory plates on the soft interbrachium: mouth in a crater-like depression. . . . Astracme Doederlein, 1927.

*Astrophyton mucronatum Lyman, 1869. Caribbean. 100 fms.

21 (24)

Disc and arms covered with large tubercles or spines.

22 (23)

Radial shields conspicuously separated. . . . Astroconus Doederlein, 1911.

*Astrophyton australe Verrill, 1876. Tasmania. Littoral.

23 (22)

Radial shields scarcely separated. . . . Conocladus H. L. Clark, 1909.

*oxyconus H. L. C., 1909. E. Australia. 50 fms.

24 (21)

Disc and arms bearing only small spinules or granules, or else naked.

25 (26)

Disc with a zone of calcareous plates at the margin. . . Gorgonocephalus Leach, 1815

This genus, originally intended to embrace all ophiuroids with branching arms, has successively been restricted by Lyman, 1882, and Doederlein, 1911.

*Asterias caputmedusae L., 1758. N. Europe. Littoral.

26 (25)

Disc-margin without calcareous plates. . . . Astrodendrum Doederlein, 1911.

*Gorgonocephalus sagaminus Doed., 1902. Japan. 100 fms.

27 (18)

Arm-spines absent before the first fork.

28 (33)

Arm-spines beginning at the edge of the disc, after the first or second fork.

29 (30)

Madreporite at the inner border of the soft interbrachium; warts or tubercles usually present on disc. . . . Astrocladus Verrill, 1899.

*Asterias euryale Retzius, 1783. S. Africa. Littoral.

30 (29)

Madreporite separated from the soft interbrachium by accessory plates.

31 (32)

Disc and arms smooth. . . . Astrospartus Doederlein, 1911.

*Euryale mediterraneus Risso, 1826. Mediterranean. Littoral.

32 (31)

Disc and arms with warts. . . . Astroplegma Doederlein, 1928.

*expansum Doed., 1928. Indonesia. 100 fms.

33 (28)

Arm-spines beginning at some distance from the disc, not before the fourth fork.

34 (35)

The arms near the disc nearly as high as broad, with a narrow ventral side.

35 (34)

Free arms near the disc conspicuously broader than high, with flat, broad ventral surfaces. . . . Astrochalcis Koehler, 1905.

*tuberculosus Koehler, 1905. Indonesia. Littoral.

36 (37)

Radial shields with a longitudinal series of tubercles or spines: hooklets without any secondary teeth. . . . Astrophyton Mueller & Troschel, 1842.

As originally proposed Astrophyton was an absolute synonym of Gorgonocephalus: the current usage is derived from Lyman, 1882.

*Euryale muricatum Lmk., 1816. Caribbean. 200 fms.

37 (36)

Radial shields without tubercles or spines: hooklets with a secondary tooth. Astroboa Doederlein, 1911.

Syn.: Astrorhaphis Doederlein, 1911.

*Astrophyton clavatum Lyman, 1861. Indian O. Littoral.

38 (8)

Primary plates conspicuous, covering much of disc surface: radial shields ovate. . . . Ophiocrene Bell, 1894.

Bell, 1894, himself points out that the type specimen of O. oenigma Bell may be a juvenile form. Should it prove to be the young stage of a genus described since 1894, Ophiocrene will take priority. H. L. Clark, 1915, has suggested it may be a young Astrochalcis.

*oenigma Bell, 1894. Indian Ocean. Littoral.

page 9
39 (1)

Arms simple.

40 (58)

Disc covered by granulation, sometimes including small spinules or shallow scales, but without coarse projecting spikes or tubercles.

41 (42)

Arms annulated by alternating belts of granules and hooklets, and with the belts continued on to the disc, so that concentric ridges and furrows mark the dorsal surface: seen from above the animal looks "as if composed only of 5 arms, whose bases were thickened and wedged together" (Lyman, 1882). Hooklets with 1 secondary tooth. . . . Astroporpa Oersted & Lütken, 1856.

*annulata Lütken, 1856. Caribbean. 100 fms.

42 (41)

No concentric furrows and ridges on disc.

43 (46)

Granulation of disc more or less covered, and partly obscured, by a soft skin.

44 (45)

About two arm-joints included within the disc: genital clefts shorter than 1 arm-joint: ventral arm-plates fragmented: 4 arm-spines. . . . Astrochlamys Koehler, 1911.

(The type species, A. bruneus Koehler, is viviparous, and the females carry a dwarf-male clinging to the dorsal side of the disc: a second species, A. sol Mortensen, has 10 arms.)

*bruneus K., 1911. W. Antarctica. 100 fms.

45 (44)

About six arm-joints included within the disc: genital clefts as long as 3 arm-segments: 4–5 arm-spines: girdle hooklets with 2 or 3 secondary teeth. . . . Astrochele Verrill, 1878.

*lymani Verr., 1878. N. Atlantic. 300–1,000 fms.

46 (43)

Granulation not invested in skin.

47 (48)

A peripheral zone of stumpy granules demarcates the ventral margin of the disc, which is otherwise covered by a fine granulation: a zone of spinules surrounds the mouth: 3 or 4 conspicuous arm-spines, each about as long as an arm-joint. . . . Astrostephanus Doederlein, 1930.

*Astrotoma vecors Koeh., 1904. Indonesia. 100 fms.

48 (47)

No peripheral zone of specialized granules.

49 (50)

A continuous mosaic of small platelets covers the ventral side of the arms and disc: the genital clefts small and restricted to the peripheral region, outside the mosaic: 6 arm-spines. . . . Astrozona Doederlein, 1930.

*Astrogomphus munitus Koehler, 1904. Indonesia. 600 fms.

50 (49)

Not so.

51 (52)

Girdle-hooklets without secondary teeth: about 5 arm-spines. . . . Astrotoma Lyman, 1875.

*agassizii Lyman, 1875. Antarctic. 100 fms.

52 (51)

Girdle-hooklets with secondary teeth.

53 (54)

Girdle-hooklets with 1 secondary tooth: 5 to 10 armspines. . . . Astrothorax Doederlein, 1911.

*misakiensis Doed., 1911. Japan. Litt.

54 (53)

Girdle-hooklets with 2 to 6 secondary teeth.

54a (55)

Five arm-spines: disc uniformly covered by granules, and excavated inter-radially, so that radial lobes occur at the arm-bases: genital clefts short: hooklets with 2 secondary teeth. . . . Astrohelix Doederlein, 1930.

*Astrotoma bellator Koehler, 1904. Indonesia. 150 fms.

55 (54a)

Two or three arm-spines.

page 10
56 (57)

Two or three secondary teeth: disc covered by larger rounded and smaller angular granules. . . . Astrothrombus H. L. Clark, 1909.

*rugosus H. L. C., 1909. E. Australia. 50 fms.

57 (56)

Three to six secondary teeth: thorny granules occur among the disc granules. . . . Astrothamnus Matsumoto, 1915.

*echinacea Matsumoto, 1912. Japan. Littoral.

58 (40)

Disc carrying coarse spikes or prominent tubercles.

59 (64)

Disc carrying coarse prominent tubercles, but no spikes.

60 (63)

Three or four arm-spines.

61 (62)

Scattered large tubercles on dorsal side of disc, and clusters of platelets on the ventral arm-bases around the mouth: arms annulated by bands of coarser granules, in 4 transverse rows, which alternate with bands of much more numerous and finer granules, in many transverse rows: girdle-hooklets with 1 or 2 secondary teeth. . . . Astrocrius Doederlein, 1927.

*Astrotoma sobrinus Matsumoto, 1912. Japan.

62 (61)

Disc covered above and below by coarse granules and tubercles: arms annulated by double rows of granules, alternating with rows of hooklets which have one feeble secondary tooth. . . . Astrohamma Doederlein, 1930.

*Astrothamnus tuberculatus Koehler, 1923. Antarctica. 70 fms.

63 (60)

One flat, scale-like arm-spine, some large tubercles on the dorsal side of disc resembling a cluster of pearls: hooklets of arm with 3 or 4 secondary teeth. . . . Ophiozeta Koehler, 1931.

*turgida Koehler, 1931. Indonesia. 200 fms.

64 (59)

Disc with irregularly disposed conical spikes on dorsal surface, a mosaic of minute granules occupying the spaces between: oral papillae spiniform, similar to teeth: lateral plates meeting ventrally, and continued upward as double rows of nodules and hooks. . . . Astrogomphus Lyman, 1869.

*vallatus Lym., 1869. N. Atlantic. 300 fms.

Family Euryalidae Gray, 1840
(Syn. Trichasteridae sensu Mortensen, 1933)

1 (6)

Arms simple.

2 (5)

Arms with a prominent dorso-lateral ridge of spines or granules on either side: arm-spines short, of equal size.

3 (4)

Dorso-lateral ridges carrying numerous, very prominent tubercles: additional interradial plates lying distal to the adoral shields. . . . Asterostegus Mortensen, 1933.

*tuberculatus Mrtsn., 1933. S. Africa. 200 fms.

4 (3)

Dorso-lateral ridges with scattered tubercles or spines: no additional interradial plates distal to the adoral shields, interredius naked ventrally. . . . Astroceras Lyman, 1879.

For a review of this genus see Mortensen, 1933a.

*pergamena Lyman, 1879. Japan. 100 fms.

5 (2)

Arms rounded above, without dorsolateral ridges: inner arm-spine usually longer than the outer. . . . Asteromorpha Lütken, 1869.

Synonym Ophiogelas Koehler.

*Asteroschema rousseaui Michelin, 1862. Indian O. 100 fms.

6 (1)

Arms forking several times: arm-spines short, both of equal size.

7 (10)

More than 18 arm-joints occurring before the first fork.

page 11
10 (7)

Less than 10 arm-joints before the first fork: arms forking repeatedly over most of their length: gonads entering the arms. . . . Euryale Oken, 1815.

Euryale is usually attributed to Lamarck, 1816: however, Oken's usage appears to have priority. The current employment of Euryale stems from Lyman, 1882; previously it was an absolute synonym of Gorgonocephalus: for discussion, see Verrill, 1899.

*asperum Lmk., 1816. Indonesia. Littoral.

8 (9)

Arms with dorso-lateral ridges, often set with spines or granules: lateral plates widely separated on ventral surface of arm: arms branching only in their distal halves: gonads entering arms. . . . Trichaster Agassiz, 1836.

*Euryale palmiferum Lmk., 1816. Indian O. 100 fms.

9 (8)

Arms symmetrically rounded above, without dorso-lateral ridges: lateral plates meeting on ventral midline of arm: gonads confined to disc. . . . Sthenocephalus Koehler, 1898.

*indicus Koehler, 1898. Indonesia. 30 fms.

Family Asteronychidae Verrill, 1899
(Emend. Mortensen, 1933)

1 (2)

More than 3 arm-spines which (except for the 3 inner ones) are modified as simple hooklets. Disc and arms covered above by naked skin. . . . Asteronyx Mueller & Troschel, 1842.

*loveni M. & T., 1842. North circum-polar. 100 fms.

2 (1)

Three (rarely 2) arm-spines, never hooked; disc covered above and below by thin, imbricating scales, especially well-developed at the margin. . . . Astrodia Verrill, 1899.

*tenuispina Verrill, 1899. N. Atlantic. 2,000 fms.

Family Asteroschematidae Verrill, 1899
(Restr. Mortensen, 1933)

1 (2)

Radial shields small, naked, glassy, without spines: disc and arms plated or granulated, arm-spines very small and irregular: proximal part of arm usually dilated, contracting abruptly at the disc. . . . Astrocharis Koehler, 1904.

*virgo Koehler, 1904. Indonesia. 300 fms.

2 (1)

Radial shields covered by skin or granules: proximal part of arm not dilated.

3 (8)

Ventral arm-plate separating lateral plates.

4 (5)

Arms short, 2–5 times disc-diameter (possibly juvenile stages of other genera). . . . Ophiuropsis Studer, 1884.

*lymani Studer, 1884. S. W. Africa. 60 fms.

5 (4)

Arms long, many times disc-diameter.

6 (7)

Large buccal shield. . . . Astrobrachion Doederlein, 1927 (as restricted by Mrtsn. 1933a).

*Ophiocreas constrictus Farquhar, 1900. New Zealand. Littoral in fiords and archibenthic.

7 (6)

No buccal shield. . . . Astroscolex Mortensen, 1933a.

*Ophiocreas adhaerens Studer, 1884. Australia. 50 fms.

8 (3)

Lateral arm-plates fused together on the ventral midline, not separated by ventral plate.

page 12
9 (10)

Disc covered by granulated skin. . . . Asteroschema Oersted & Lütken, 1856.

Syn.: Laspalia Ljungman.

*Asterias oligactes Pallas, 1788. Caribbean. 100 fms.

10 (9)

Disc covered by naked skin. . . . Ophiocreas Lyman, 1879.

*lumbricus Lyman, 1879. Caribbean. 100 fms.