Rhinobatos punctifer Compagno & Randall 1987

Spotted Guitarfish

(Figs 6, 7, 10–12; Tables 1, 3)

Rhinobatos punctifer Compagno & Randall, 1987, Proc. California Acad. Sci, 44(14): 335–342, fig. 1. Holotype: BPBM 20843, 705 mm. adolescent male, Red Sea, Gulf of Aqaba, Israel.

Rhinobatos RHY: Henderson et al., 2007, 160, fig.2.

Rhinobatos sp. Henderson et al., 2016, 431, fig. 8 (top); Almojil et al., 2015, 100, fig.

Material examined. 18 specimens. AMS I 46415-001 (desiccated), adult male ~ 641 mm TL, off Muscat, Gulf of Oman (collected Muttrah Souq fish market, Muscat), Oman, A. Henderson, probably caught in less than 100 m, collected in 2003; CSIRO H 6231-03 (abdomen and some vertebrae removed) , female 662 mm TL, same data as AMS I 46415-001; CSIRO H 6231-04 (abdomen and some vertebrae removed), adult male 654 mm TL, same data as AMS I 46415-001; CSIRO H 6231-05 (abdomen and some vertebrae removed), female 668 mm TL, same data as AMS I 46415-001; CSIRO H 6231-06 (desiccated), adult male ~ 625 mm TL, same data as AMS I 46415-001; CSIRO H 6231-07 (desiccated), female ~ 614 mm TL, same data as AMS I 46415-001; CSIRO H 6231-08 (desiccated), female ~ 670 mm TL, same data as AMS I 46415-001; CSIRO H 7413-03, adult male 646 mm TL, Deira fish market, Dubai, United Arab Emirates, W. White, 10 Oct 2012 ; CSIRO H 7553-01, female 792 mm TL, off Al-Wusta coast, Arabian Sea, Oman, collected in 2004; CSIRO H 7551-02 , adult male 725 mm TL, off Muscat, Gulf of Oman (collected Muttrah Souq fish market, Muscat), Oman, A. Henderson, probably caught in less than 100 m, collected in 2003; CSIRO H 7551-03 , female ~ 775 mm TL, same data as CSIRO H 7551-02; MNHN 2014 - 0 156 (abdomen and some vertebrae removed), female 570 mm TL, same data as AMS I 46415-001; MNHN 2014 - 0 157 (desiccated), adult male ~ 643 mm TL, same data as AMS I 46415-001; SQU unregistered ( Suliam 10), adult male 666 mm TL, SQU unregistered (Suliam 9), female 765 mm TL, Gulf of Oman, As Seeb fish market, Muscat, Oman, collected P. Last, 11 July 2012 ; CSIRO H 7621-03, adult male 745 mm TL, Karachi Fish Market, Pakistan, collected P. Psomadakis, 24 Apr 2014 ; CSIRO H 7623-01, female 690 mm TL, CSIRO H 7623-02, immature male 655 mm TL, Karachi Fish Market, Pakistan, collected P. Psomadakis, 23 Apr 2014 .

Diagnosis. A medium-sized species of the genus Rhinobatos (attaining at least 889 mm TL) distinguished by the following combination of characters: disc wedge-shaped, width 29–34% TL, length 1.2–1.3 times width; snout relatively short, length 2.2–2.6 times interspiracular distance, 3.6–3.9 times interorbital width in large males (2.9– 3.4 in females); orbit diameter 1.2–1.7 times spiracle length; nostrils weakly oblique, their length 1.3–1.9 times internarial distance; mouth narrow, width 5.4–5.6% TL in large males (5.8–6.2% in females); posterior nasal flaps broad; two spiracular folds, outermost fold slightly taller than inner fold; ridges of rostral cartilage almost parallel, converging slightly anteriorly but not constricted medially; anterior cartilage subtriangular to sickle shaped, usually blunt posteriorly; distance between fifth gill slits 2.8–3.1 times in ventral head length in large males (2.5–2.6 in females); prebranchial sensory pore patch obvious, extending to outer margin of first gill slit; postscapular sensory canal usually obvious, notched, with exposed lateral pores; inconspicuous thorn patches on supraorbit and scapular region, and single row along dorsal midline rudimentary; denticles confined to anterior portion of dorsal fins, posterior two-thirds naked; dorsal fins relatively tall, height of first 7.6–9.5% TL; pelvic-fin inner margin shorter than its base length; interdorsal distance 2.1–2.7 times first dorsal-fin base; dorsal caudal margin 2.1–2.2 times preventral margin; upper jaw with ~76 tooth rows; snout angle 60–75°; 69–75 pectoral radials; 175–184 postsynarcual centra; ~59 nasal lamellae; dorsal coloration highly variable, plain brownish to greenish brown, faintly or strongly marked with small white spots, ocellated, or with a combination of reticulations and ocelli; posterior half of dorsal and caudal fins usually dusky or blackish; snout with pale or dusky tip, but lacking long teardrop-shaped marking.

of key ratios for males and a female of the plain morph, and a female ocellate morph.

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Distribution. Red Sea (Gulf of Aqaba, Israel), Persian Gulf, and the northern Arabian Sea to Pakistan (possibly further east into India). Benthic inshore on continental shelf to 70 m depth (Séret et al., 2016).

Remarks. Compagno and Randall (1987) described the preserved dorsal coloration of the holotype of Rhinobatos punctifer from the Red Sea as being medium brown with small light spots (largest about 5 mm wide) mostly arranged in sparse transverse rows. While this white-spotted morph seems to be the most common form in the Persian Gulf, R. punctifer is highly variable in coloration and body shape, both across and within its range, and the various forms were initially suspected of being different species (e.g. Henderson et al., 2016). Individuals collected from Oman by A. Henderson varied from being sparsely white spotted (some spots paired while others are random, Figs 6A, B), or vividly marked with prominent dark-edged ocelli (Fig. 6D) that are often variably connected by fine reticulations and lines. Material collected more recently from the Karachi fish market (Pakistan, provided for examination by P. Psomadakis) was represented by a plain coloured morph (Fig. 6C), but a single individual (CSIRO H 7623-01) had an ocellated/reticulated pattern resembling those from Oman (Fig. 6E). Molecular analysis of 166 specimens of R. punctifer, including representatives of these four morphs from Pakistan and Oman, demonstrate two weakly divergent subgroups (Naylor, unpublished data). While analysis of a reduced data set including 8 of these specimens of R. punctifer suggests that one of these subgroups might consist of plain and white-spotted morphs and the other subgroup the ocellated morph (Fig. 15), an examination of images associated with the larger subset showed that ocellated forms were distributed in both subgroups. It is conceivable that the imperfect association between color pattern and the genetically defined groupings examined herein could be the consequence of hybridization between lineages, but the data at hand do not allow this to be evaluated. Morphological data derived from the limited material available did not support differences between these morphs. Accordingly, we provisionally support the retention of a single intraspecifically variable species, but suggest that a more comprehensive regionally investigation of these forms is needed.

Morphometric data based on a small sample from Oman of 3 adult males (all white-spotted morph) and 3 large females (2 white-spotted morph, one ocellate morph) indicated that this Rhinobatos species is strongly sexually dimorphic for some characters. Despite the small sample sizes, ranges for several characters did not overlap, e.g.: maximum disc width 29.1–32.1% TL in males (33.3–34.1% TL in females); snout length 13.1–13.6% TL in males (12.1–12.9% TL in females); interorbital width 3.5–3.7% TL in males (3.8–4.2% TL in females); preoral length 15.9–16.3% TL in males (15.0–15.3% TL in females); mouth width 5.4–5.6% TL in males (5.8–6.2% TL in females); distance between fifth gill openings 8.3–9.4% TL in males (9.7–10.2% TL in females); pelvic-fin length 14.8–16.1% TL in males (16.9–17.3% TL in females). These and other data obtained herein suggest that adult males of R. punctifer typically have a narrower disc, longer snout and preoral length, narrower interorbital space and mouth, more narrowly separated gill openings, and smaller pelvic fins than females. A subset of the morphological data for the plain coloured morph and an ocellated/reticulated individual (CSIRO H 7623-01) from Pakistan were morphometrically similar to the material from Oman (Table 3), and also displayed similar levels of sexual dimorphism. Interestingly, some of the sexual characters discussed above are amongst the most useful morphometric characters for distinguishing other species within the genus. Nonetheless, more comparative data is needed for both sexes of poorly known Rhinobatos species to establish the extent of variability and improve their diagnoses.

A record of R. schlegelii (possibly R. punctifer) from the western sector of the northern Indian Ocean (Fowler, 1956) based on Zugmayer (1913), was considered by Compagno and Randall (1987) to be erroneous. More recent studies (Séret et al., 1916; Séret and Last, unpublished data) support this conclusion, with R. schlegelii being confined to the western North Pacific.