Astroboa nigrofurcata Döderlein, 1927

Baker, Alan N., Okanishi, Masanori & Pawson, David L., 2018, Euryalid brittle stars from the International Indian Ocean Expedition 1963 - 64 (Echinodermata: Ophiuroidea: Euryalida), Zootaxa 4392 (1), pp. 1-27 : 9

Astroboa nigrofurcata Döderlein, 1927

( Figs. 6A–E , 7D )

Astroboa nigrofurcata Döderlein, 1927: 45 , pl. 4 figs. 1–4; Baker, 1980: 60, figs. 23, 28, 30.

Material Examined. USNM 1072537 , Anton Bruun Cruise 1 Station 18A, southern Andaman Sea, 7°34’N, 98° 00’E, 77 m, 21 March 1963, 2 specimens ( Fig. 6A–E ) ; USNM 1234012 , Anton Bruun Cruise 9 Station 465, off NE Somalia, 11° 37’N, 51° 27’E, 67–72 m, 18 December 1964, 2 specimens .

Remarks. The specimens range between 17 and 40 mm ( Fig. 6A–B ) disc diameter. The smallest specimen has a disc cover of dense low granules, 8 in 1 mm on the radial shields ( Fig. 6C ). One unusual feature of this specimen, possibly related to its small size, is the presence of 2–4 transverse rows of taller granules bridging the pairs of radial shields. In the largest specimen, the arms bifurcate at least 25 times, and are covered with smooth polygonal plates, with prominent girdle bands continuing over the arm—a characteristic of this species ( Figs. 6D–E , 7D ). The colour pattern of this species is distinctive—disc pale green, with contrasting irregular brown or pink freckles; arms with a continuous series of dark freckles, one per segment.

This record, in the southern Andaman Sea, is an extension of the known range from the Western Australian coast, Indonesia and the Philippines ( Baker 1980).

Figures

FIGURE 6. Astroboa nigrofurcata (USNM 1072537) (A–C, smaller specimen, D–E, larger specimen) and Astrocladus ludwigi (USNM 1072478) (F–I). A, aboral view; B, oral view; C–D, aboral peripheral disc; E, aboral basal portion of the arm; F, aboral view; G, oral view; H, aboral disc, a square part is enlarged in I; I, aboral peripheral disc, a circle indicates girdle hooklets.

FIGURE 7. Astrocladus goodingi, holotype (USNM 1072479) (A–C) and Astroboa nigrofurcata (USNM 1072537) (D). A, aboral view; B, oral view; C, aboral disc and basal portion of the arms; D, lateral view of basal portion of the arm.