Himantura randalli

description

Description. Disc rhomboidal, width 1.02 times length in adult male holotype (1.02 – 1.08 in the four largest paratypes,> 245 mm disc width, DW); robust, raised at mid-scapular region (more pronounced in largest specimens), maximum thickness 14 % (12 – 17 %) of DW; preorbital snout moderately long, with small medial lobe at the snout tip, angle 97 ° (96 – 98 °) (no obvious ontogenetic or sexual variability); anterior margins of disc almost straight (sometimes weakly concave), apices rounded rather than angular, posterior margins broadly and evenly convex, free rear tip narrowly rounded. Pelvic fins subtriangular, short, length 19.4 % (18.5 – 21.2 %) DW; lateral margin almost straight, apex narrowly rounded; free rear tip broadly rounded, combined with inner and posterior margins to form strongly convex edge; width across base 15.4 % (13.3 – 16.8 %) DW. Claspers of adult male moderately elongate, stout basally, tapering strongly, depressed slightly; lining of pseudopera smooth; hypopyle short, about 1 / 3 rd of length of clasper outer margin; without prominent anterior notch; distance from cloaca origin to sting 0.38 (0.37 – 0.43) of disc length. Tail slender, whip-like; tapering gr

Himantura randalli sp. nov., a new whipray (Myliobatoidea: Dasyatidae) from the Persian Gulf

diagnosis

Diagnosis. A medium-sized species of Himantura (to at least 62 cm DW) distinguished by the following combination of features: disc weakly rhomboidal; preorbital snout moderately elongate with weak apical lobe, snout angle 113 – 119 °; pectoral-fin apices rounded, angle 96 – 98 °; orbits small, protrusible; mouth relatively broad, width 0.9 – 1.2 in internasal width; distance between first gill slits 2.5 – 2.6 times internasal distance; distance between fifth gill slits times 1.5 – 1.7 times internasal distance, 27 – 29 % of ventral head length; pelvic-fin base broad, 13 – 17 % DW; tail behind sting of juveniles subcircular with deep longitudinal ventral groove and prominent mid-lateral ridge, weakly depressed in adults; 1 – 2 (usually 1) small, broadly heart-shaped to seed shaped suprascapular denticles, primary denticle band and thorns absent; secondary denticle band irregularly suboval, relatively narrow (its maximum width across scapulocoracoid barely exceeding its width at spiracles), with well-defined lateral margins, narrowly tapering near tail base; band fully developed and covering entire dorsal surface of tail by 33 cm DW; dorsal surface mainly uniformly coloured (occasion

Himantura randalli sp. nov., a new whipray (Myliobatoidea: Dasyatidae) from the Persian Gulf

discussion

Remarks. The existence of Himantura randalli was first known to one of the authors (PL) in the 1990 s from loaned specimens collected in Kuwait by J. E. Randall. It has frequently been confused locally with H. gerrardi and H. uarnacoides. The commonly used FAO identification guide for the Persian Gulf (Carpenter et al., 1997) includes only H. gerrardi and H. bleekeri (a junior synonym of H. uarnacoides which has not been recorded from the western Indian Ocean). H. uarnacoides is also plain coloured which may have led to confusion between this species and H. randalli. Manjaji (2004) listed two southern African taxa in the synonymy of H. randalli (as H. sp. B) – Dasyatis jenkinsii (not Annandale): Wallace, 1967, 47, fig. 23 (description, illustration of a 437 mm disc width immature male) and Himantura gerrardi (not Gray): Compagno 1986, 139, fig. 30.9 (brief description, illustration of a 190 mm disc width female). However, inspection of new material from South Africa and the results of molecular barcoding, indicate that these forms are not conspecific with H. randalli (PL unpublished data) or H. gerrardi morphs (Naylor et al., in press). Further investigation is needed to determine

Himantura randalli sp. nov., a new whipray (Myliobatoidea: Dasyatidae) from the Persian Gulf

distribution

Distribution. Known from the Persian Gulf (off Kuwait, Bahrain, Qatar and Iran) from where it is possibly endemic. The Persian Gulf, which is mostly shallower than 40 m and rarely exceeds 60 m depth, has soft substrates dominated by sand and mud. Considered to occur in the Gulf of Oman off Oman and off southern Africa (e. g. Randall, 1995; Manjaji, 2004) but these rays appear to be other species (see discussion below).

Himantura randalli sp. nov., a new whipray (Myliobatoidea: Dasyatidae) from the Persian Gulf