Platyrhina psomadakisi, White, William T. & Last, Peter R., 2016

White, William T. & Last, Peter R., 2016, Platyrhina psomadakisi sp. nov., a new species of fanray (Batoidea: Platyrhinidae) from the Andaman Sea, the first record of this family in the Indian Ocean, Zootaxa 4121 (5), pp. 533-544 : 534-543

Platyrhina psomadakisi sp. nov.

Andaman Fanray

( Figs. 1–8 ; Table 1)

Holotype. CSIRO H 7861-01, adult male 378 mm TL, west of Lord Loughborough Island, Andaman Sea, Myanmar, 10°20’58” N, 97°46’8” E, 69 m depth, 29 May 2015.

Paratypes. (3 specimens). CSIRO H 7859-01, female 341 mm TL, northern Andaman Sea, Myanmar, 14°55’56” N, 94°28’50” E, 58 m depth, 11 May 2015; CSIRO H 7860-01, juvenile male 197 mm TL, west of Sir Charles Metcalfe Island, Andaman Sea, Myanmar, 12°22’31” N, 97°01’39” E, 158 m depth, 23 May 2015; Department of Fisheries, Yangon (specimen 604), female 245 mm TL, west of Sir Charles Metcalfe Island, Andaman Sea, Myanmar, station 137, 12°22’31” N, 97°01’39” E, 158 m depth, 23 May 2015.

Diagnosis. A medium-sized fanray with the following combination of characters: a single row of hooked thorns on dorsal midline body and tail (extending from nape to first dorsal fin); thorns on orbital, nape and scapular regions not encircled by pale pigment; dorsal surface of adults with patches of prickly denticles (rough to touch); dorsal fins well separated, interdorsal distance 8.5–9.1% TL; greyish brown dorsally with a series of darker brown saddles on tail.

Description. Disc broadly rounded to shovel-shaped; anterior margin slightly to moderately convex, apex and posterior margin broadly rounded; slightly longer than wide, much shorter than tail, disc length 0.90 (0.85–0.89) times width. Pelvic fins moderate sized, length 15.5 (15.8–17.3)% TL, 1.40 (1.39–1.45) times base length, 1.66 (1.60–1.96) times width; anterior margin slightly convex to slightly concave, apex broadly rounded, posterior margin nearly straight to moderately convex. Clasper very long, extending well posterior to first dorsal-fin origin in holotype; outer length 12.2% TL in holotype, 2.1 times pelvic-fin inner margin. Tail elongate, slender anteriorly, tapering gradually; in cross-section nearly flat below, slightly rounded above; tail length from anterior cloaca 1.58 (1.41–1.49) times precloacal length, 1.35 (1.23–1.32) times disc length, 7.57 (7.78–7.95) times its width at pelvicfin insertions. Dermal lateral fold on tail, originating about midway between free rear tip of pelvic fin and first dorsal-fin origin, reaching just behind ventral caudal-fin origin; fold well developed, maximum width below second dorsal-fin base.

Head broadly rounded anteriorly with a slightly produced apical lobe, its ventral length 25.6 (25.2–26.6)% TL; snout short, broadly wedge-shaped; preoral length 1.47 (1.28–1.38) times mouth width, 2.95 (2.57–3.09) times internasal distance, 0.68 (0.66–0.75) times dorsal caudal-fin margin, 2.28 (1.92–2.05) times distance from nostril to margin of disc; preorbital snout length (direct) 1.46 (1.27–1.41) times interspiracular length, 2.68 (2.51–2.76) times orbit diameter, 2.25 (1.82–2.24) times interorbital width. Interorbital space slightly concave, relatively broad; orbit small, slightly dorsolateral, not elevated or protruding; diameter 1.60 (1.14–1.36) times spiracle length, 0.84 (0.72– 0.82) times interorbital distance. Spiracles narrowly bean-shaped, relatively large; no skin folds on posterior margin.

Nostrils relatively narrow, slightly oblique and well separated, nasal flaps well developed; no oronasal grooves; anterior aperture subcircular; nostril length 2.21 (1.94–2.44) times anterior aperture width, 1.21 (1.08– 1.17) times anterior nasal-flap base, 0.82 (0.62–0.76) times distance from nostril to edge of disc, 1.06 (0.83–1.10) times internasal distance. Anterior nasal flap large with long, moderately broad process anteriorly, posterior margin strongly fringed; flap base extending over full length of nostril, length 2.43 (2.08–2.76) times its width at process, 1.82 (1.79–2.12) times anterior aperture width; inserted slightly into internasal space; distance between insertions of flaps 4.67 (3.88–4.18) in greatest distance across nostrils anteriorly, 1.65 (1.45–1.50) in minimum internasal distance; process of flap narrowly rounded distally, overlapping posterolateral nasal flap and largely determining hind margin of anterior aperture. Posterolateral nasal flap lobe-like, broadest anteriorly; originating beside and well away from lateral extremity of anterior nasal aperture, extending posteromedially as a free lobe to beyond middle of posterior aperture. Posterior nasal flap present as a narrow, heavily fringed fold; extending along posterior boarder of nostril from near base of free lobe of posterolateral nasal flap and almost connected to insertion of anterior nasal-flap at its insertion.

Mouth width 1.89 (2.00–2.43) times nostril length, 4.43 (4.10–4.38) in precloacal length; positioned over hind margin of orbit; skin grooves present; upper and lower jaw arched; lower lip pronounced; deep, short lateral grooves around corners of mouth. Teeth very small, rhomboidal, quincuncial; crowns pointed in adult male holotype, blunt in female and juvenile paratypes; ca. 71 rows in upper jaw in holotype; upper and lower jaw teeth similar in shape and size.

Gill openings weakly S-shaped, fifth less so; length of third gill slit 2.20 (1.95–2.15) in nostril length, 5.51 (5.36–6.47) in distance between fifth gill slits; distance between first gill slits 1.44 (1.36–1.47) times distance between fifth gill slits; distance between fifth gill slits 2.65 (2.63–3.03) times internasal distance, 1.32 (1.29–1.36) times mouth width, 0.45 (0.48–0.50) of ventral head length.

Dorsal fins similar in size and shape, well separated, moderately large, subtriangular, relatively upright; anterior margins slightly convex, apices moderately rounded; posterior margins nearly straight to slightly convex; free rear tips relatively short, not produced; first dorsal fin slightly taller than second in all but one paratype, length of first 1.07 (1.11–1.52) times its height, base length 2.69 (1.27–2.00) times inner margin length; second dorsal-fin length 1.45 (1.28–1.46) times its height, base length 1.88 (1.66–2.29) times inner margin length. First dorsal fin well behind pelvic-fin rear tip, pelvic-fin insertion to first dorsal-fin origin 1.69 (1.44–0.59) times interdorsal distance; interdorsal space long, 1.89 (1.70–1.90) times second dorsal-fin height, 2.05 (2.10–2.38) times base of first dorsal fin, 1.31 (1.33–1.52) times tail width at origin of first dorsal fin, 1.89 (1.60–2.11) times interspace between second dorsal-fin insertion and upper origin of caudal fin. Caudal fin medium-sized, deep; dorsal caudal margin 1.41 (1.33–1.57) times preventral margin length.

Skin of largest specimens with patches of prickly dermal denticles of varying sizes, greatly enlarged on anterior snout, central disc and in two, well-spaced paired rows along either side of tail. Skin of juvenile paratypes velvety. Thorns well developed, sharp, hooked, not on prominent ridges; a regular median row extending from nape to first dorsal fin, 4–6 main orbital thorns, two symmetrical shoulder patches on each side of disc (outermost patch with 2 thorns, innermost patch one thorn); thornlets on anterior rostral ridges.

Nasal lamellae 31–33 in holotype (29–30 in larger female paratype). Pectoral skeleton with 34 (32–33) propterygial, 8–9 (9–11) mesopterygial, 23 (23) metapterygial and 65–66 (64–66) total radials. Total pelvic radials 1 (1) + 19 (~18) excluding clasper in males. Vertebral column with 138 (137–139) total centra; 95 (93–104) total precaudal centra; 25 (23–24) monospondylous precaudal centra; 30 (29–31) diplospondylous predorsal centra; 70 (69–81) diplospondylous precaudal centra; 43 (35–44) diplospondylous caudal centra.

Holotype Paratypes

Min. Max. Total length (mm) 378.0 197.0 341.0 Disc width—maximum 50.5 53.1 54.3 Disc length 45.2 45.3 48.5 Head length—dorsal 17.4 16.8 17.9 Head length—ventral 25.6 25.2 26.6 Snout length—presocket 10.9 10.4 10.7 Orbit diameter 4.1 3.8 4.2 Spiracle length 2.5 3.1 3.3 Orbit and spiracle length 5.4 5.9 6.3 Interorbital width 4.9 4.7 5.9 Interspiracular width 7.5 7.4 8.4 Preoral length 12.9 11.9 13.3 Mouth width 8.7 9.3 9.8 Prenarial distance 9.8 8.8 9.3 Nostril length 4.6 3.8 4.9 Anterior aperture—width 2.1 1.9 2.1 Anterior nasal flap—base length 3.8 3.6 4.4 Anterior nasal flap—width 1.6 1.3 2.1 Distance across anterior nasal apertures 12.3 12.0 12.6 Internarial distance—minimum width 4.4 4.2 4.8 Distance between anterior nasal flaps 2.6 2.9 3.2 Distance from nostril to disc margin 5.6 6.2 6.5 Third gill opening—width 2.1 1.9 2.4 Distance between first gill openings 16.6 17.5 18.6 Distance between fifth gill openings 11.5 12.4 12.8 Pelvic fin—length 15.5 15.8 17.3 Pelvic fin—anterior margin length 9.1 9.8 10.3 Pelvic fin—width 9.3 8.8 9.9 Pelvic fin—base length 11.1 11.4 11.9 Pelvic fin—inner margin length 5.7 6.1 7.0 First dorsal fin—length 6.2 5.9 7.1 First dorsal fin—anterior margin length 8.4 7.8 8.2 First dorsal fin—height 5.8 4.6 5.7 First dorsal fin—base length 4.4 3.8 4.3 First dorsal fin—inner margin length 1.6 2.1 3.0

......continued on the next page Holotype Paratypes

Min. Max. Colour. (Based on paratype CSIRO H 7859-01). Dorsal surfaces medium brown with a series of mostly indistinct cross bars on disc and five broad dark brown saddles on tail; dorsal fins similar colour to disc, slightly darker at anterior of base adjacent to dark saddles on tail dorsal-fin bases. No pale areas around the large thorns on head, body or tail. Ventral surface whitish, slightly darker near posterior margins of disc.

Size. Known from the four type specimens; an adult male (378 mm TL), a juvenile male (197 mm TL) and two females (341 and 245 mm TL).

Geographical distribution. The types, and only known specimens, were collected off Myanmar in the Andaman Sea at depths of 58–158 m ( Fig. 9 ).

Etymology. Named after Dr Peter N. Psomadakis whose efforts to obtain valuable specimens of sharks and rays, as well as many teleosts, from a number of poorly sampled locations in the northern Indian Ocean have greatly improved our understanding of the biogeography of this complex region.

Comparison with congeners. Platyrhina psomadakisi sp. nov. can be readily distinguished from P. sinensis in having a single row of hooked thorns on the dorsal midline of tail (vs. 2 rows in P. s i ne n s i s). It also differs from P. sinensis in: having a much shorter snout (preoral length 11.9–13.3 vs. 15–17% TL; preorbital length 10.4–10.9 vs. 15–16% TL) and distance from pelvic-fin insertion to first dorsal-fin origin 12.2–15.3 vs. 17–25% TL.

Platyrhina psomadakisi sp. nov. differs from P. hyugaensis , P. s i ne n s i s and P. tangi in the following characters: dorsal fins much more widely separated (interdorsal space 8.5–9.1 vs. 4–6% TL), more pectoral radials (64–66 vs. 56–61), and a series of darker brown bands on body and tail (vs. no banding evident). The types of the new species also have more vertebrae than the three Pacific species based on data presented in Iwatsuki et al. (2011), i.e. total centra 137–139 vs. 125–134. However, two P. tangi specimens (CSIRO H 7395-13 and -14) from Taiwan, which were also radiographed in this study were both found to have 140 total centra. This discrepancy needs to be further investigated to determine whether this extends the range of total centra for P. tangi (reported to be 133–134 in Iwatsuki et al., 2011) or whether there are differences in count methodology or radiograph quality.

Platyrhina psomadakisi sp. nov. is also easily distinguished from P. tangi in lacking pale pigment around the hooked thorns on the orbital, nape and scapular regions (vs. distinctly encircled in pale pigment in P. tangi ).

Figures

FIGURE 1. Holotype of Platyrhina psomadakisi sp. nov. (CSIRO H 7861 - 01, adult male 378 mm TL, preserved): (A) dorsal view; (B) ventral view.

FIGURE 2. Paratype of Platyrhina psomadakisi sp. nov. (CSIRO H 7859 - 01, female 341 mm TL, fresh): (A) dorsal view; (B) ventral view.

FIGURE 3. Dorsal view of juvenile paratype of Platyrhina psomadakisi sp. nov. (CSIRO H 7860 - 01, juvenile male 197 mm TL, preserved).

FIGURE 4. Oronasal region of Platyrhina psomadakisi sp. nov.: (A) holotype (CSIRO H 7861 - 01, adult male 378 mm TL, preserved); (B) paratype (CSIRO H 7859 - 01, female 341 mm TL, preserved).

FIGURE 5. Dorsal view of tail region of Platyrhina psomadakisi sp. nov.: (A) holotype (CSIRO H 7861 - 01, adult male 378 mm TL, preserved); (B) paratype (CSIRO H 7859 - 01, female 341 mm TL, preserved).

FIGURE 6. Lateral view of thorns on midline of head and disc of Platyrhina psomadakisi sp. nov.: (A) holotype (CSIRO H 7861 - 01, adult male 378 mm TL, preserved); (B) paratype (CSIRO H 7859 - 01, female 341 mm TL, preserved).

FIGURE 7. Dorsal view of orbital and scapular region of Platyrhina psomadakisi sp. nov.: (A) holotype (CSIRO H 7861 - 01, adult male 378 mm TL, preserved); (B) paratype (CSIRO H 7859 - 01, female 341 mm TL, preserved).

FIGURE 8. Dorsolateral view of the left orbit and spiracle of Platyrhina psomadakisi sp. nov.: (A) holotype (CSIRO H 7861 - 0 1, adult male 378 mm TL, preserved); (B) paratype (CSIRO H 7859 - 01, female 341 mm TL, preserved).

FIGURE 9. Map showing capture locations for the holotype (red star) and paratypes (red circles) of Platyrhina psomadakisi sp. nov. (Map data © 2016 Terrametrics, Google Earth).