Halicmetus ruber Alcock, 1891

Vernacular name: Red Shortnose Seabat

Figures 2D, 6, 7; Tables 1–2

Halicmetus ruber Alcock, 1891:27, pl. 8, figs. 1, 1a–b. (type locality: Andaman Sea, 344–402 m). Alcock, 1898:pl. 19, fig. 5 (figure). Bradbury, 1967:415 (in part). Bradbury, 2003:5 (in part). Ho et al., 2008:767.

Material examined. 8 specimens, 14.4–65.9 mm SL. NMV A29679-007 (2, 18.4–19.1 mm SL), North West Shelf, Western Australia, 16°44.3’S, 119°15.0’E, 693–698 m, 17 Jun. 2007 . NMV A29720-004 (1, 51.7), North West Shelf, 14°33’S, 121°15.4’E, 1021–1023 m, Western Australia, 4 Jul. 2007 . NMV A29719-011 (2, 17.2–18.0), North West Shelf, Western Australia, 14°36.9’S, 121°19.7’E, 698–705 m, 3 Jul. 2007 . NMV A29684-005 (2, 14.4– 14.8), 17°01’S, 119°35.5’E, North West Shelf, Western Australia, 440–451 m, 18 Jun. 2007 . WAM P.31798.003 (1, 65.9), N of West Cape, Western Australia, 21°30.4’S, 113°56’E, 650 m, 11 Mar. 2001 .

Diagnosis. A species of Halicmetus distinguished by the following combination of characters: body disk relatively narrow, 63–75% SL; orbit large, 8.8–10.5% SL; interorbital very narrow, 5.1–6.4% SL; illicial trough opening moderately high; mid-dorsal disk with small scattered bucklers, robust and multicuspid spinules and scattered tiny tubercles, the later imperceptible without magnification; belly covered with relatively widely spaced, robust, simple and bifurcate spinules, larger tubercles and bucklers absent; dorsal-fin rays absent in adult; pectoralfin rays 12–13; fresh colour unknown, uniformly creamy white when preserved; peritoneal membrane with dense coverage of melanophores (visible from ventral surface); distal parts of pectoral, pelvic and anal fins blackish.

Remarks. Australian material and the diagnosis given above is consistent with the description of this species provided by Ho et al. (2008).

Alcock (1891) mentioned that his specimens of Halicmetus ruber (2 syntypes) have 11 pectoral-fin rays, whereas the majority of specimens examined in the genus had 12–14 (except H. reticulatus which sometimes had 11). We may assume that Alcock had overlooked 1 or 2 small rays which are usually hard to detect, especially in cases where the pectoral fin is shrunken through partial desiccation. Although Alcock (1891) mentioned that the species is “uniformly light pink”, all specimens we examined have various black pigmentation on body and fins (Ho et al., 2008; present study).

Brauer (1902) recorded 0–3 dorsal-fin rays and 10–11 pectoral-fin rays in specimens collected off the western coast of Sumatra, Indonesia, and off eastern coast of Africa. However, his specimens are most likely misidentifications of H. marmoratus . The number of pectoral-fin rays is a still slightly lower than that of H. marmoratus so a detailed re-examination on Brauer’s specimens is needed.

It is notable that all six juveniles (14.4–19.1 mm SL) have 3–4 very short dorsal-fin rays, whereas all adults (> 30 mm SL, n=14, Ho, per. data) have no dorsal-fin rays. It is very possible that all or some Halicmetus species have dorsal-fin rays initially and these are gradually reduced or lost with growth. We have not examined juveniles of H. niger, H. cf. ruber or H. drypus which all lack dorsal-fin rays in adults so this hypothesis needs further investigation.