Myliobatis hamlyni Ogilby, 1911

White, William T., Kawauchi, Junro, Corrigan, Shannon, Rochel, Elisabeth & Naylor, Gavin J. P., 2015, Redescription of the eagle rays Myliobatis hamlyni Ogilby, 1911 and M. tobijei Bleeker, 1854 (Myliobatiformes: Myliobatidae) from the East Indo-West Pacific, Zootaxa 3948 (3), pp. 521-548 : 523-531

Myliobatis hamlyni Ogilby, 1911

( Figs. 1–8 , 17 a; Table 1 )

Myliobatis hamlyni Ogilby, 1911: 40 (Queensland, Australia): Ogilby, 1916: 89 (Queensland, Australia); McCulloch, 1929: 29 (Queensland, Australia); Whitley, 1939: 258, fig. 18 (Queensland, Australia); Whitley, 1940: 223, fig. 256 (Queensland, Australia); Last & Stevens, 1994: 454, pl. 80, figs (northern Australia); Compagno & Last, 1999: 1513, 1519, fig. ( Australia); Johnson, 1999: 718 (Moreton Bay, Queensland); Kyne et al., 2005: 325 (Queensland, Australia); Schwartz, 2008: 39 ( Australia); Last & Stevens, 2009: 472, pl. 86, fig. 52.5 (northern Australia); Johnson, 2010: 307 (Queensland, Australia).

? Aetobatis tobijei : Snyder, 1912: 489 (Naha, Okinawa, Japan).

Myliobatis tobijei: Chen, 1948: 11 , fig. 9 ( Taiwan); Chen & Chung, 1971: 44 ( Taiwan);? Okamura & Kitajima, 1984: 73, fig. 40 (Okinawa Trough); Chen & Yu, 1986: 162 ( Taiwan); Nakaya & Shirai, 1992: 41 (Okinawa Trough); Chen & Joung, 1993: 90, pl. 13 (fig. 5) ( Taiwan); Shao et al., 1993: 126 ( Taiwan);? Yano, 1999: 356 (Ryukyu Islands);? Randall & Lim, 2000: 111 (South China Sea); Chen, 2004: 25 ( Taiwan); White et al., 2006: 300, fig. ( Indonesia); White & Dharmadi, 2007: 1815 ( Indonesia); Shao et al., 2008: 237 ( Taiwan); Ward et al., 2008: p. 3 of Accessory Publication 1 ( Indonesia); Shen & Wu, 2011: 104, fig. ( Taiwan); Naylor et al., 2012: 82, fig. 62 ( Taiwan, Philippines); Ebert et al., 2013: 367 ( Taiwan); Straube et al., 2013: 276 ( Taiwan).

Holorhinus hamlyni: Fowler, 1941: 460 (Queensland, Australia).

Myliobatis tobiyei: Kamohara, 1958: 8 ( Formosa [= Taiwan]).

Myliobatis cf. tobijei: Compagno et al., 2005: 79 ( Philippines) .

? Myliobatis sp.: Obara et al., 2009: 19, 20 (Tokyo Submarine Canyon)—uncertain.

Aetobatus tobijei: Kuroda, 1951: 317 ( Formosa [= Taiwan]).

Holotype. QM I. 1567, juvenile male 270 mm DW (~ 474 mm TL), Moreton Island, Queensland, Australia, 27°02’ S, 153 ° 28 ’ E.

Other specimens. Australia (5 specimens): AMS I 23718-003, (1000 mm TL), off Coffs Harbour, New South Wales, Australia, 30°23’ S, 153°24’ E, 229 m depth, 25 Jul. 1981; CSIRO CA 2878, female 456 mm DW (907 mm TL), north of Forestier Island, Western Australia, 18°31’ S, 118°09’ E, 200–201 m depth, 2 Apr. 1982; CSIRO H 2578-01, adult male 704 mm DW (1351 mm TL), southwest of Shark Bay, Western Australia, 26°45’ S, 112°36.6’ E, 346–367 m depth, 31 Jan. 1991; CSIRO H 3860-01, female 596 mm DW (1006 mm TL), east of Swansea, New South Wales, 33°07’ S, 151°56’ E, 117–121 m depth, 9 Nov. 1994; QM I 33318, female 429 mm DW (943 mm TL), Swains Reef, Queensland, Australia, 20°40’ S, 151°20’ E, 210–220 m depth, 7 Aug. 1999. Indonesia (3 specimens): CSIRO H 5866-02 (Genbank accession EU398924 ), female 838 mm DW (1663 mm TL), Kedonganan fish market, Jimbaran Bay, Bali, 24 Mar. 2002; CSIRO H 5889-36, adult male 697 mm DW, Kedonganan fish market, Jimbaran Bay, Bali, Jul. 2002; MZB 15442, adult male 651 mm DW, Tanjung Luar fish market, Lombok, 11 Oct. 2004. Philippines (3 specimens): BRU 165, female 540 mm DW, BRU 166, subadult male 479 mm DW (1064 mm TL), Cadiz Pala-Pala, caught off Samal Island, 6 Apr. 2000; JPAG 329, female 663 mm DW, Pasil Fish Port II, Cebu City, Philippines, 13 Apr. 2000. Taiwan (6 specimens): AMNH 258303 (tissue accession GN9949), female 395 mm DW, CSIRO H 6296-06, female embryo 192 mm DW, Da-xi fish market, northeastern Taiwan, 25 May 2005; NMMBP 6308, Da-xi fish market, northeastern Taiwan, 30 Apr. 2002; NMMBP 15686, female 417 mm DW (849 mm TL), Da-xi fish market, northeastern Taiwan; NMMBP 16227 (tissue accession GN9950), subadult male 478 mm DW (952 mm TL), Da-xi fish market, northeastern Taiwan, 13 Mar. 2012; NMMBP 18796, female 401 mm DW (802 mm TL), Taiwan; Japan (1 specimen): OCA-P 20030411-6, off Kunigami, Okinawa, 20 m depth, Apr. 2003.

Diagnosis. A medium-sized Myliobatis (attaining at least 1142 mm DW) with the following combination of characters: dorsal surfaces uniformly purplish brown to greenish brown, without dark spots or blotches; tail with a distinct, low ventral skin fold; stinging spine(s) relatively long (longest spine 13.1–15.9% DW); interorbital space moderately concave in adult males; anterior margins of pectoral fin straight to slightly convex; cranial fontanelle (visible in dorsal view without dissection) relatively wide with slightly convex lateral margins; claspers of adult males 5.5–5.7% DW; predorsal length 63.6–68.6% DW; teeth in 7 rows in each jaw, with a broad median row flanked by three smaller rows on each side; pectoral-fin radials 85–92 (excluding rostral propterygial radials anterior of eyes); total vertebral centra (including synarcual) 114–119; males mature at about 650 mm DW.

Description. Disc diamond-shaped, broad, moderately long, width about 1.64 in holotype (1.61–1.76 in other specimens) times disc length; anterior projection 4.62 (3.50–4.17) in disc length; axis of greatest width of disc just posterior to scapular region, over anterior abdominal cavity, its horizontal distance from snout tip 1.38 (1.31–1.50) times in distance from tip of snout to pectoral-fin insertion; moderately deep, greatest thickness above scapular region and posterior head, thickness 7.89 (8.55–10.15) in disc width; without denticles or thorns; a short, bony ridge on midline above scapular region. Pectoral fins very large, wing-like, triangular, weakly falcate; anterior margin nearly straight to weakly convex, moderately convex distally; apex narrowly rounded, pectoral angle 61 (57–62)°; posterior margin shallowly concave; free rear tip angular; inner margin moderately convex; length of anterior margin 49.6 (46.9–49.8)% DW, 1.13 (1.11–1.20) times its base length, inner margin 6.36 (5.82–7.78) in its base; origin below posterior margin of eye; apex located at slightly posterior to pectoral mid-base; insertion posterior to pelvic-fin origin by about half eye diameter, well anterior to dorsal-fin origin; free rear tip overlapping about half or nearly entire pelvic-fin anterior margin.

Head pronounced, relatively low, short and broad; projecting well anterior to pectoral-fin origins; subquadrangular in cross-section at pectoral-fin origin; cranial region of head very truncate in dorsoventral view; snout abruptly convex anterior of eyes, becoming deeply concave at origin of rostral lobe; weakly to moderately convex ventrally; ventral head length 28.1 (26.3–31.4)% DW, 1.40 (1.34–1.64) times width at pectoral-fin origins, 4.86 (3.62–6.16) times preorbital length (horizontal), 2.78 (2.64–3.39) times interorbital width; preoral snout length 1.25 (0.98–1.53) times mouth width, 1.48 (1.36–1.92) times internarial width, 0.73 (0.61–0.98) times distance between first gill slits; head width at pectoral-fin origin 20.1 (18.5–20.1)% DW, 1.98 (1.73–2.24) times its height. Rostral lobe fleshy, broad, short (slightly longer in adult males); broadly rounded to broadly parabolic in dorsoventral view with a bluntly pointed apex; narrowly rounded in lateral view; dorsal surface with a roughly Tshaped patch of pores medially; its length 5.0 (3.9–7.6)% DW, 5.04 (3.87–7.58) in head length, its width 1.19 (1.20–1.39) in head width at pectoral-fin origin.

Interorbital space broad, weakly concave, with a broad medial depression over the cranial fontanelle, without ridges, denticles or thorns; interorbital width 10.1 (8.7–10.4)% DW, 1.59 (1.41–1.98) times orbit length, 0.53 (0.53–0.61) times head width at mid-eye; margins of cranial fontanelle narrowest posteriorly, gradually widening anteriorly, then rapidly becoming its widest near the front of head. Eyes relatively large, oval, lateral on head (eyes not visible in dorsal view), angling very slightly inwards anteriorly, diameter 1.88 (1.59–3.02) in spiracle length, 4.97 (5.05–7.71) in head width at pectoral-fin origin; orbits pronounced and visible above upper margin of head; a small, distinct bony protuberance present above anterior quarter of each orbit in adult males. Spiracles moderately large, elliptical to slit-like, situated almost entirely laterally on head (not or only slightly visible in dorsal view), just posterior to orbit and above pectoral-fin origin, length 7.6 (6.2–7.6)% DW, 3.40 (4.09–7.56) times width; upper margins with a fleshy fold which is mostly nearly straight but angled inwards near posterior margin of spiracle.

Nostrils narrowly oval with a narrow, fleshy oronasal groove; anterior nasal fold thin, membranous, internal; posterior nasal fold larger, fleshy, extending about half of nostril width from its lateral margin; internarial space 0.79 (0.74–1.19) in prenasal length, 1.58 (1.39–2.03) times nostril length. Nasal curtain large, broad, elongate, width 1.63 (1.71–1.98) times length; lateral margin weakly concave with a small lateral protuberance at widest point; posterior margin weakly concave to straight, without a medial notch, bordered by a long, curtain-like fringe which follows contour of lower jaw; apices rounded; a patch of minute pores present near central posterior margin; apex and posterolateral margin recessible within oronasal groove; a small, low fleshy protuberance present on mid ventrolateral margin.

Holotype Other specimens (n=12)

Min. Max. Mean ......continued on the next page Holotype Other specimens (n=12)

Min. Max. Mean Mouth moderately large, broad, transverse, located ventrally, width 8.8 (9.1–10.0)% DW, 0.80 (0.66–1.02) times preoral length, 2.28 (1.92–2.14) in head width at pectoral-fin origin; margin of lower jaw slightly concave laterally and moderately convex medially, not indented at symphysis; not strongly protrusible, one series of anterior teeth of lower jaw visible when mouth closed in some specimens; skin on chin and at margin of lower jaw fleshy, strongly furrowed, papillate. Teeth in 7 rows in each jaw, coalesced to form plates; middle series of teeth in both jaws broad and hexagonal, flanked by three rows of much smaller, similarly-sized, diamond-shaped teeth on each side arranged in a pavement-like fashion; median tooth row about 5 times width of outer tooth rows; upper tooth plate length almost equal to its width, in about 9 series (based on CSIRO H 5889-36, Fig. 7a ); lower jaw tooth plate length about 1.6 times its width, its width almost two thirds mouth width, in 13 series (based on adult male CSIRO H 5889-36, Fig. 7 b).

Gill openings small, elongated S-shaped, forming a weakly fringed lobe laterally; length of first gill slit 1.53 (1.12–1.59) times length of fifth gill slit, 4.50 (3.83–5.79) in mouth width; distance between first gill slits 2.03 (1.95–2.33) times internarial space, 0.54 (0.47–0.61) times ventral head length; distance between fifth gill slits 1.12 (0.95–1.13) times internarial distance, 0.30 (0.23–0.31) times ventral head length.

Pelvic fins relatively large, moderately broad (broadest in adult females), subquadrangular, anterior margin nearly straight to very slightly convex, apex subangular, posterior margin mostly straight with scalloped edge, free rear tip very broadly rounded to subangular, inner margin slightly convex; extending well beyond pectoral-fin free tips; pelvic-fin length 15.3 (14.3–16.0)% DW, 1.06 (0.94–1.12) times width across fin bases, inner margin 6.7 (6.1– 7.7)% DW. Claspers of adult males (n=2) moderately long, moderately broad, not tapering distally except near tip, apex bluntly pointed, outer length (5.5–5.7)% DW.

Dorsal fin small, raked back, its origin just to well posterior to pelvic-fin free rear tips; anterior margin moderately convex; apex broadly rounded, just anterior to insertion of fin; posterior margin moderately convex; free rear tip subangular, inner margin short, straight; predorsal length 1.54 (1.46–1.57) in disc width, fin length 6.6 (5.8–7.3)% DW, height 0.55 (0.44–0.56) times its length, inner margin 4.70 (3.96–8.26) in fin length.

Tail very long, slender, whip-like, its length (from cloaca origin) 1.24 (1.19–1.70) times disc width; tapering gradually to about mid-length of stinging spine, and gradually becoming more whip-like beyond sting; base compressed, oval in cross section at pelvic-fin insertion, tail width at pelvic insertion 1.44 (1.15–1.85) times height; almost quadrangular to hexangular in cross section near origin of stinging spine, width (1.02–1.37) times height at first spine origin; no dorsal skin fold (rarely a very weak fold evident); a weak, very low ventral skin fold usually present; a lateral skin fold present on either side from about level of mid-pelvic inner margin to below base of first stinging spine; a weak groove on dorsal surface of tail immediately posterior to base of stinging-spine(s), partially housing spines. Stinging spines 1–2, very elongate, slender, moderately broad-based, strongly tapered, mostly serrated laterally except near its base; distance from sting base to pectoral-fin insertion (18.1–23.1)% DW; longest stinging spine (13.1–15.9)% DW, (2.26) times dorsal-fin length.

Vertebral centra total (including synarcual) 114–119 (n=9); total (excluding synarcual) 108–114 (n=9); monospondylous (including synarcual) 30–38 (n=13); monospondylous (excluding synarcual) 24–32 (n=13); predorsal diplospondylous 37–48 (n=10); post-dorsal diplospondylous 36–45 (n=9). Total pectoral-fin radials (excluding propterygial radials anterior of eyes) 85–92 (n=12); rostral propterygium (anterior of eyes) ~8–11 (n=7); propterygium (posterior of eyes) 20–23 (n=12), mesopterygium 18–22 (n=13), metapterygium 42–49 (n=12). Pelvic-fin radials: 1 (2 fused elements) + 17–~19 (n= 5 males); 1 (2–3 fused elements) + 21–~24 (n= 8 females).

Colour. When fresh: Dorsal surface uniformly purplish brown to greenish brown; no spots or blotches; dark (dorsal) and pale (ventral) surfaces well demarcated (waterline) along edge of pectoral fins and rostral lobe; slightly paler laterally below eye. Tail dark dorsally; anterior third paler ventrally with a mottled, diffuse waterline on lower lateral margin; uniformly dark posteriorly. Ventral surface mostly whitish; pectoral fin apices and most of posterior margins darkish brown, with junction between brown areas and whitish ventral colour strongly mottled; distal third of pelvic fins brownish; rostral lobe and nasal curtain white.

Size. Specimens examined in this study ranged in size from 270–838 mm DW (up to 1663 mm TL). Two males of 478 and 479 mm DW were adolescent, while two of 697 and 704 mm DW were adult. Compagno et al. (2005) also reported two additional adolescent males of 557 and 571 mm DW. An additional six adult males recorded at the Tanjung Luar and Kedonganan fish landing sites in Indonesia ranged from 651–800 mm DW and 9 females ranged from 600–1142 mm DW.

Distribution. Patchy distribution in the East Indo –West Pacific ( Fig. 8 ). In Australia, known from several locations off eastern Australia (Swain Reefs and the type locality Cape Moreton in Queensland; and off Swansea and Coffs Harbour in New South Wales) and off Western Australia (off Forestier Island and Shark Bay) in depths of 120– 350 m. In Indonesia, recorded in the landings at the Tanjung Luar fishing port in eastern Lombok and the Kedonganan fish market in southern Bali. Depth of capture unknown but landed with Mustelus and Squalus spp., presumably on the outer continental shelf and upper slope; not landed with shallower water species such as Rhinobatos , Gymnura and dasyatids. In the Philippines, reported from the Pasil fish market in Cebu City and Palapala fishing port in Cadiz City ( Compagno et al., 2005). Recorded in the South China Sea by Randall & Lim (2000), but specimens needed to confirm their identity. In Taiwan, recorded from the Da-xi fish market in Yilan; no depth information available. In Japan, one specimen was taken from off Okinawa. Records from Ryukyu Islands and Okinawa Trough ( Okamura & Kitajima, 1984; Yano, 1999) possibly refer to this species but this requires verification. Specimens recorded off the Tokyo Submarine Canyon by Obara et al. (2009), as Myliobatis sp., between 150 and 500 m depth may also refer to this species, but this needs to be confirmed. Deepwater records of M. tobijei from Japan may refer to this species.

Figures

FIGURE 1. Dorsal view of the holotype of Myliobatis hamlyni (QM I 1567, juvenile male 270 mm DW, preserved).]

FIGURE 2. Dorsal view of Myliobatis hamlyni: A) CSIRO H 3860 - 01, female 596 mm DW from eastern Australia (fresh); B) MZB 15442, adult male 651 mm DW from Lombok, Indonesia (fresh).

FIGURE 3. Ventral view of Myliobatis hamlyni MZB 15442 (adult male 651 mm DW).

FIGURE 4. Ventral view of the head of Myliobatis hamlyni MZB 15442 (adult male 651 mm DW, fresh).

FIGURE 5. Lateral view of head of Myliobatis hamlyni CSIRO H 5866 - 02 (female 838 mm DW, fresh).

FIGURE 6. Lateral view of orbit and spiracle in an adult male Myliobatis hamlyni (CSIRO H 2578 - 01 (704 mm DW, fresh) illustrating the orbital thorn.

FIGURE 7. A) Upper and B) lower tooth plates of Myliobatis hamlyni CSIRO H 5889 - 36 (adult male 697 mm DW).

FIGURE 8. Distribution of Myliobatis hamlyni (black star—holotype; black circle—other records); and M. tobijei (crossed square—holotype; black square—other records) in the East Indian and West Pacific.

FIGURE 17. Outline of cranial fontanelle (in dorsal view) of: A) Myliobatis hamlyni and B) Myliobatis tobijei.

Tables

TABLE 1. Proportional dimensions as percentages of disc width for the holotype of Myliobatis hamlyni (QM I 1567) with ranges and means for 12 other specimens.

Disc width (mm)	270	401	838	541
Total length	175.6	168.8	222.1	200.3
Pre-dorsal length	64.9	63.6	68.6	66.4
Disc, length	60.9	56.8	62.0	59.3
Snout to pectoral-fin insertion	54.6	51.2	55.4	53.1
Disc thickness	12.7	9.9	11.7	10.8
Snout to pectoral-fin origin	13.2	14.2	17.7	15.3
Posterior orbit to pectoral-fin insertion	42.3	40.0	42.7	41.6
Snout to maximum width (horiz.)	39.7	35.3	40.8	37.7
Pectoral-fin anterior margin	49.6	46.9	49.8	48.4
Pectoral-fin posterior margin	49.0	44.9	48.4	46.7
Pectoral-fin base length	43.9	40.9	43.5	42.0
Pectoral-fin inner margin	6.9	5.5	7.3	6.3
Head length (ventral)	28.1	26.3	31.4	28.0
Preorbital length	10.4	8.5	10.8	9.5
Preorbital length (horiz.)	5.8	4.4	8.7	5.9
Head width at pectoral-fin origins	20.1	18.5	20.1	19.2
Head height at pectoral-fin origins	10.1	8.8	10.8	9.9
Head width at mid-eye	18.8	16.2	17.8	16.9
Head height at mid-eye	9.0	8.0	9.9	9.2
Interorbital width	10.1	8.7	10.4	9.6
Interspiracular width	15.3	13.0	14.4	13.6
Spiracle length (longest)	7.6	6.2	7.6	7.1
Spiracle width (narrowest)	2.2	0.9	1.8	1.4
Orbit diameter	6.3	4.8	6.5	5.8
Eye diameter	4.0	2.5	3.9	3.3
Orbit and spiracle length	13.6	11.8	13.2	12.4
Preoral length	11.0	9.8	14.6	11.2
Prenasal length	7.4	6.9	9.7	7.6
Prenasal length (horiz.)	5.9	5.5	9.0	6.6
Rostral lobe width	16.9	14.5	16.0	15.0
Rostral lobe length	5.0	3.9	7.6	5.1
Mouth width	8.8	9.1	10.0	9.6
Width of upper tooth plate	–	4.7	6.0	5.4
Width of lower tooth plate	–	4.7	5.7	5.0
Internarial width (external)	7.5	6.8	7.6	7.1
Nasal curtain length	5.4	4.7	5.5	5.2
Nasal curtain width	8.8	8.6	9.8	9.3
Nostril length (internal)	4.7	3.6	4.9	4.2
Width of first gill slit	2.0	1.6	2.5	2.1
Width of third gill slit	2.2	2.2	2.9	2.4