Squamophis amamiensis ( Okanishi & Fujita, 2009 )

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 : 3

Squamophis amamiensis ( Okanishi & Fujita, 2009)

( Fig. 1E–H )

Asteroschema amamiense Okanishi & Fujita, 2009: 152 , figs. 115–129, figs. 4–6, 7B–D, 8; Okanishi et al., 2011b: 6. Squamophis amamiensis .— Okanishi et al., 2011b: 6, 13.

Material Examined. USNM 1072572 , Pioneer Cruise 17, south of Lombok , eastern Indian Ocean, 10°50’S, 117°50’E, 1000 m, 17 March 1964, 1 specimen, disc diameter 8 mm ( Fig. 1E–H ).

Description. Aboral and oral surfaces of disc and arms uniformly covered with slightly tumid, smooth, polygonal to rounded plate-shaped external ossicles ( Fig. 1G ). Oral frame and jaws similarly covered ( Fig. 1H ). Aboral surface external ossicles range from 300–500 µm in diameter; average diameter 370 µm ( Fig. 1G ). Oral surface external ossicles 111–333 µm in diameter; average diameter 228 µm ( Fig. 1H ). On both surfaces, external ossicles tend to be slightly larger towards disc margin. External ossicles (sensu Okanishi et al. 2011b) uncommon, of one type, granule-shaped, 80 µm in average length. Oral interradial disc with deep depressions leading to genital slits ( Fig. 1H ).

Five arms ca. 100 mm long, higher than wide at the base ( Fig. 1E–F ). First and second tentacle pores outside of oral slit without associated arm spine ( Fig. 1H ); thereafter one short blunt arm spine less than an arm segment in length, to each tentacle pore in the basal portion of the arms. Subsequently, the spines become progressively longer until they reach a length that is an average of 1.5 times the length of an arm segment. The spines do not reach a length of twice that of an arm segment.

Remarks. This species is characterized by a very simple smooth body cover of plate-shaped external ossicles, a few granule-shaped external ossicles, and a single arm spine to each arm segment beyond the first two. As a unique specimen is currently available in this study, we are reluctant to undertake the destructive analyses required to determine if the radial shields are multi-layered or single-layered, or to more thoroughly survey the nature and distribution of external ossicles. Therefore, as some important information of taxonomic value at the generic level is lacking, it is not possible to definitely assign the species to one of the five genera of Asteroschematidae as defined by Okanishi et al. (2011b). However, external features of this specimen match those of Squamophis amamiensis . For the present, therefore, we refer the species to S. amamiensis , and we expect that in the future a richer material will help to firmly establish its taxonomic position.

The type specimens of S. amamiensis were collected off Amami Ohshima Islands , southwestern Japan, 158 m depth and its occurrence in the Indo-Pacific region is thus a very large extension of its range.

Regrettably, the specimen has a four-digit catalogue number indelibly inscribed on its aboral disc surface. This was done at an institution at which the IIOE collection was temporarily stored. Various non-invasive attempts were made to remove the number, without success. Similar numbers were also inscribed on the type specimens of Astrocladus goodingi and A. socotrana . These numbers should be ignored.

Distribution. JAPAN: off Amami Ohshima Islands, southwestern Japan ( Okanishi & Fujita, 2009, type locality); INDONESIA: southeastern Indonesia (this study). Depth ranges 168–1000 m.

Figures

FIGURE 1. Asteroschema arenosum (USNM 1072539) (A–D) and Squamophis amamiensis (USNM 1072572) (E–H). A, aboral view; B, oral view; C, aboral disc; lateral view of distal arm; E, aboral view; F, oral view; G, aboral disc; H, oral disc. Abbreviation: AS, arm spine.