Himantura australis, Last, Peter R., White, William T. & Naylor, Gavin, 2016

Last, Peter R., White, William T. & Naylor, Gavin, 2016, Three new stingrays (Myliobatiformes: Dasyatidae) from the Indo – West Pacific, Zootaxa 4147 (4), pp. 377-402 : 378-386

Himantura australis sp. nov.

( Figs. 1–7 ; Table 1 )

Himantura toshi (not Whitley): Whitley, 1940: 212 (in part), brief description (misidentification).

Himantura uarnak (not Gmelin): Paxton et al., 1989: 42 (listed); Last & Stevens, 1994: 406 -07, description, illustration; Last & Stevens, 2009: 449 -50, description, illustration (misidentifications).

Himantura uarnak 2: Naylor et al., 2012: 70, 255 (molecular data).

Himantura sp. 4: Last et al., 2016: figs. 3, 5 (molecular data).

Holotype. CSIRO H 7798-04 (tissue accession GN15798), juvenile male 415 mm DW, west of Oriomo River , Daru, Western Province, Papua New Guinea, 9°04.43’S, 143°08.53’E, 25 Oct 2014.

Paratypes. 13 specimens: CSIRO H 1134-1, late embryo male 292 mm DW, north of Port Hedland , Western Australia, 19°35.6’S, 118°42.8’E, 32–34 m depth, 21 Sep 1987 ; CSIRO H 1463-3, juvenile male 283 mm DW, north of Cape Lambert , Western Australia, 20°06.1’S, 117°21.4’ E, 41 m depth, 20 Sep 1988 ; CSIRO H 1920-01 (tail only), mother of CSIRO H 1463-3, North-West Shelf , Western Australia, 20 Sep 1988 ; CSIRO H 4016-01, neonatal female 309 mm DW, north of Cape Preston , Western Australia, 20°21.1’S, 116°07.3’E, 41–42 m depth, 25 Aug 1995 ; CSIRO H 4422-01, juvenile male 314 mm DW, near Proserpine , Repulse Bay, Queensland, Australia, 20°38’S, 148°41.75’E, 11 Nov 1993 ; CSIRO H 4542-06, juvenile male 310 mm DW, Kamora River estuary, West Papua, Indonesia, 4°49.36’S, 136°38.17’E, 5–10 m depth, 30 May 1996 ; CSIRO H 7839-01 (tissue accession GN15784), juvenile male 333 mm DW, Daru fish market, Western Province, Papua New Guinea, 9°03.91’S, 143°12.59’E, 21 Oct 2014 ; CSIRO H 7840-01 (tissue accession GN15789), juvenile male 241 mm DW, fishing camp near Daru , 9°02.26’S, 143°11.49’ E, 24 Oct 2014 ; NTM S 11144 -001, juvenile male 285 mm DW, King Creek , Shoal Bay, Darwin Harbour, Northern Territory, Australia, 12°21.48’S, 131°1.02’E, 15 Jan 1983 ; NTM S 11507 -006, juvenile male 343 mm DW, Ludmilla Creek , Darwin Harbour, Northern Territory, Australia, 12°24.78’S, 130°50.22’E, 19 Dec 1984 ; KFRS unregistered (field accession 220349; tissue accession GN15785), juvenile female 350 mm DW, Katatai , Western Province, Papua New Guinea, 9°01.25’S, 143°20.51’E, 23 Oct 2014 ; KFRS unregistered (field accession 220420; tissue accession GN15790), juvenile female 286 mm DW, fishing camp near Daru , Western Province, Papua New Guinea, 9°02.26’S, 143°11.49’ E, 24 Oct 2014 ; KFRS unregistered (field accession 230247; tissue accession GN16607), late-term embryo 300 mm DW (from female 1400 mm DW), Gulf of Papua, Papua New Guinea, 7°55’S, 145°00’ E, 1 Dec 2014 .

Other material. 15 specimens: CSIRO H 1134-2, juvenile female 297 mm DW, north of Port Hedland, Western Australia, 19°35.6’S, 118°42.8’E, 32–34 m depth, 21 Sep 1987 ; CSIRO H 1479-03, juvenile female 259 mm DW, CSIRO H 1479-04, juvenile male 255 mm DW, CSIRO H 1479-05, juvenile male 262 mm DW, CSIRO H 1479-06, juvenile female 273 mm DW, north of Dampier Archipelago , Western Australia, 20°09.5’S, 116°47.7’E, 43 m depth, 24 Sep 1988 ; CSIRO H 2371-02, juvenile female 290 mm DW, CSIRO H 2371-03, juvenile female 278 mm DW, CSIRO H 2371-04, juvenile male 283 mm DW, CSIRO H 2371-05, juvenile male 293 mm DW, north of Cape Lambert , Western Australia, 20°06.1’S, 117°21.4’E, 41 m depth, 20 Sep 1988 ; CSIRO H 4786-01 (tissue accession GN5082), juvenile male 310 mm DW, CSIRO H 4786-02 (tissue accession GN1596), juvenile male 322 mm DW, near mouth of Buffalo Creek , Lee Point, Northern Territory, Australia, 12°20.25’S, 130°54.48’E, 7 Aug 1997 ; CSIRO H 7629-02; CSIRO H 7807-02; PNG-232047; PNG- 230349.

Diagnosis. A species of Himantura distinguished by a combination of the following features: disc weakly rhomboidal; preorbital snout moderately short (length 19–22% DW), rather broad, angle 117–127°, with a distinct apical lobe; lateral apices narrowly rounded; orbits moderately large, often strongly protruding (particularly in young); 1–2, mostly heart-shaped suprascapular denticles (not preceded before and after by a row of smaller primary denticles); secondary denticle band developed before birth; dorsal surface of juveniles (smaller than 370 mm DW) dark spotted or with spots and weak reticulations, subadults and adults (exceeding 390 mm DW) more strongly reticulated; dorsal tail of juveniles with 3 rows of spots before caudal sting, faint dark saddles beyond sting (tail lacking alternating black and white bands); tail uniformly dark ventrally; pectoral-fin radials 1 46–152; vertebral centra (excluding synarcual) 123; including synarcual 124.

Description. Disc rhomboidal, width 1.05 in holotype (1.01–1.06 in paratypes, all early juveniles and neonates <350 mm DW) times length; anterior angle 110° (103–118°), pectoral angle 96° (92–94°); most robust on cranial region of head, raised slightly on mid-scapular region, maximum thickness 7.55 (6.37–9.09)% disc width (DW). Snout with a distinct apical lobe, angle 117° (117–127°); anterior margin of disc almost straight (not noticeably double convex), lateral apices narrowly rounded; posterior margin broadly convex, free rear tip narrowly rounded. Pelvic fins rather small, length 18.9 (18.3–19.5)% DW; width across base 13.9 (12.2–15.4)% DW; not protruding far beyond disc. Claspers of adult male unavailable for examination. Tail very long and slender, tapering gently from base toward caudal sting then becoming whip-like; total length 3.8–4.2 times DW when undamaged (3.0 in holotype but tip missing), tail length 3.5–4.0 times precloacal length when intact; base narrow, slightly depressed and oval, width 1.58 (1.26–1.56) times height. No obvious skin folds on dorsal or ventral surfaces of tail, but midventral surface of tail in neonates with a long and narrow, longitudinal fleshy ridge (presumably a rudimentary fold) extending posteriorly from about level of caudal sting for a distance equivalent to tail length before sting; no evidence of ventral ridge in large individuals.

Snout rather short, angular, strongly depressed; preoral snout length 2.04 (2.42–2.55) times mouth width, 2.26 (2.34–2.73) times internarial distance, 20.6 (21.2–21.8)% DW; direct preorbital snout length 1.46 (1.34–1.66) times interorbital length; snout to maximum disc width 40.3 (38.9–43.3)% DW, interorbital space almost flat; eye moderately large, length 2.08 (1.80–2.64) in spiracle length; orbits protruding well beyond disc in young, exceedingly so in neonates and less so in large individuals; diameter 1.21 (1.08–1.58) in spiracle length, interorbital distance 2.54 (2.04–2.56) times orbit. Spiracles large, subrectangular, situated laterally or dorsolaterally.

Nostrils moderately large, narrowly elongate, oblique, posterior half recurved in posterolateral direction; lateral margin with weak double concavity, length 1.94 (1.85–2.28) in internasal distance; internasal distance 1.75 (1.78–2.03) of prenasal length. Nasal curtain subrectangular, skirt-shaped, relatively broad, width 1.85 (1.77–2.11) times length; lateral margin almost straight, smooth edged; posterolateral apex depressible into shallow groove; posterior margin weakly fringed, weakly concave.

Mouth moderately arched; prominent knob at symphysis of upper jaw, retractable mesially into deep notch at symphysis of lower jaw; oronasal groove shallow, extending posteriorly from posterolateral edge of mouth to chin; skin on ventral surface of lower jaw moderately papillose, not confined to narrow strip around lips; no circumoral grooves. Jaws of types not dissected to reveal details of mouth, but images of oral region of discarded material indicate a mouth floor with mainly 4 well-developed papillae (medial pair occasionally separated by a smaller papilla); medial pair simple, broad, flattened, rounded distally, subequal in size (slightly larger than outer pair), located near to each other; single outer papilla located near each corner of mouth, well separated from inner pair. Teeth in a juvenile paratype ( CSIRO H 4542-06) small, subequal in size in upper and lower jaws; narrowly rhombic with 1–2 low, transverse ridges on crown, ridges separated by prominent groove; ~59 vertical rows in upper jaw.

Gill openings S-shaped, strongly arched posteriorly, margins smooth; length of first gill slit 1.64 (1.11–1.50) times length of fifth, 2.78 (2.59–3.37) in mouth width; distance between first gill slits 2.39 (2.18–2.54) times internasal distance, 0.48 (0.44–0.48) of ventral head length; distance between fifth gill slits 1.46 (1.45–1.66) times internasal distance, 0.29 (0.29) in ventral head length.

Squamation. Ontogenetic stages 2 and 4 present in available material; stages 0, 1, 3, 5 and 6 not applicable (data on large individuals inadequate). Denticle development relatively rapid; late-term embryos display welldeveloped suprascapular denticles and a loose band of primary denticles along median disc.

Stage 2: Suprascapular and narrow secondary denticle band present in late embryos. Secondary denticles extending from interorbital region, along median disc, almost to pectoral-fin insertions at birth (240–350 mm DW); 1–2 (usually 2), well-developed, heart-shaped (occasionally pearl-shaped) suprascapular denticles; first suprascapular denticle largest, with convex crown (length 7.2–9.5 mm in morphometric types); second with flatter crown than first; secondary denticles heart-shaped, similar in size to each other and none enlarged beside suprascapular denticles. Denticles absent on tail of neonates.

Stage 4: Secondary denticle band developing more widely over central disc and on head. In juvenile male holotype ( CSIRO H 7798-04, 415 mm DW), band moderately dense, covering entire interorbit, width at scapular region ~24% DW; small flattened denticles scattered over median dorsal surface of pre-sting tail; remaining disc smooth. In CMO3-65 (560 mm DW) denticles minute (not tightly spaced), extending well forward of the eyes. In adult ( CSIRO H 1920-01) denticles present over nearly all of tail (absent near ventral base); flattened denticles interspersed with slightly larger and more widely spaced, upright, stellate-based tubercular denticles.

Meristics. Total pectoral-fin radials (non-types) 146–152 (n=3); propterygium 60–64, mesopterygium 17–21, metapterygium 68–70. Pelvic-fin radials difficult to count, possibly 25–27 (n=4). Vertebral centra (excluding synarcual) 123 (n=1), (including synarcual) 124 (n=1); monospondylous (including 2nd synarcual) 50–52 (n=2), pre-sting diplospondylous 66–73 (n=4); and post-sting diplospondylous 0 (n=4).

Colour. When fresh (holotype): Dorsal disc entirely covered with dark brown, coarsely reticulate colour pattern; reticulate markings differing in length, formed from clusters of sequentially coalesced spots; width of reticulations about half of pupil diameter; reticulations separated from each other by narrower and paler yellow wavy lines (mostly much narrower than dark reticulations); dark spots not fused around outer disc and pelvic-fin margins; tail before caudal sting with 3 irregular rows of dark spots (medially and dorsolaterally), beyond sting more uniformly greyish (blotched but not with alternating light and dark bands), darkest distally. Ventral surface of disc largely white; narrow outer margin of disc and pelvic fins dusky with some small darker markings (margins of paratypes often densely covered with black spots); tail white forward of caudal sting, dark to black posterior to sting, similar to dorsal surface and not banded.

Other material: Displays two primary developmental colour morphs (based on all available images, both retained and non-retained material): a dark spotted or spotted/weakly reticulated juvenile form (largest observed 370 mm DW) and subadult and adult forms which are more strongly reticulate (smallest observed 390 mm DW). The smallest individuals (e.g. CSIRO H 7840-01, 241 mm DW, Fig. 5 a; CSIRO H 1463-03, 283 mm DW, Fig. 5 b) have a honeycomb pattern consisting of irregularly shaped brownish black spots (of more or less similar size and similar to pupil diameter) on central disc separated by narrow yellowish lines; some spots coalesced to form short wavy lines; spots on head and around disc margin typically smaller; dorsal tail before caudal sting with 3 irregular rows of similar dark blotches, not obviously banded beyond sting. Some individuals (e.g. CMO 3-57, 290 mm DW) of this morph had the bulk of their markings coalesced to form a distinct reticulate pattern; dark markings only slightly broader than pale lines separating them. Tail of smallest individuals prominently marked; on pre-sting tail upper surface with single median row of dark spots, dorsalateral surfaces with row of similar spots, ventral surface white; lateral spots persist slight beyond caudal sting; anterior tail beyond sting not strongly banded, but with vague light and dark dorsal saddles, sides of tail pale and ventral surface uniformly dark; posterior most part of tail beyond sting entirely black. Smallest fully reticulate form (CMO 3-13, 390 mm DW) with very dark, coarse reticulate markings covering entire disc; pale lines separating them much less than half their width; tail markings before caudal sting similar, tail dark greyish or black beyond sting; pattern persisting until about 55 cm DW (CMO 3-10, 550 mm DW). Latter stages becoming more finely reticulate (CMO 3-65, 560 mm DW, Fig. 5 d; PNG not retained 100043, 830 mm DW, Fig. 5 e; PNG not retained 130028, 1120 mm DW; PNG not retained 130022, 1400 mm DW, Fig. 5 f) or reticulated and partly ocellated ( PNG not retained 100096, 1140 mm DW).

Holotype Paratypes

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

Range Size. One paratype ( CSIRO H 1463-3), a late-term embryo recovered from an adult female ( CSIRO H 1920- 01), was 283 mm DW. Two neonates with strong evidence of umbilical scars were 292 and 309 mm DW. A smaller immature male has a healed scar at 241 mm DW. Smallest confirmed adult male 1120 mm DW; largest specimen a 1400 mm DW pregnant female containing 2 embryos 300 mm DW (White, unpublished).

Distribution. Once considered to be conspecific with Himantura uarnak ( Gmelin, 1789) and widespread in the Indo–West Pacific. Now appears to be confined to the Australasian Plate; known from off Papua New Guinea and northern Australia, from Shark Bay (off Western Australia) to Brisbane (off Queensland); type material displayed in Fig. 6 . Depth distribution not well documented, but primarily in shallow-water from near the shore to at least 45 m depth.

Etymology. Noun in apposition referring to the tropical Southern Hemisphere distribution of this Himantura . Vernacular name: Australian Whipray.

Comparisons. Himantura australis and H. leoparda Manjaji-Matsumoto & Last, 2008 are the only members of the genus Himantura (sensu Last et al., 2016) occurring in Australasian seas. The species are similar but differ in coloration: Himantura australis has a more reticulated pattern on the dorsal disc in adults (adult H. australis have an ocellated pattern, typical of H. leoparda , but the ocelli are smaller and remain dominated by reticulations), the suprascapular denticles are few (1–2, rather than being preceded and followed by a row of slightly smaller primary denticles), and the snout is broader (rather than being produced slightly and more angular) in young and mostly in adults. Juveniles differ in the following morphometric details: preoral length 2.04–2.55 times mouth width (vs. 2.79–3.30 in H. leoparda ), and 20.6–21.8% DW (vs. 23.3–27.6%); distance between first gill slits 2.18–2.54 times internasal distance (vs. 1.98–2.18); distance between fifth gill slits 1.45–1.66 times internasal distance (vs. 1.38– 1.40), ~ 0.29 in ventral head length (vs. 0.25–0.28).

Himantura australis is not sympatric with its other congeners and its relationship to these species is part of a revision of the group in progress. It exhibits strong molecular divergence from the other reticulate Himantura species, H. uarnak and H. undulata ( Bleeker, 1852) (see Last et al., 2016, Fig. 3 ). Morphologically it differs from H. undulata in having smaller reticulations, a less elongate snout, and lacks a pair of pearl-shaped suprascapular denticles characteristic of H. undulata . Its reticulate pattern in adults is typically more pronounced than in H. uarnak , but elucidating characters to separate them across all size groups is a work in progress.

Figures

FIGURE 1. Holotype of Himantura australis sp. nov., juvenile male 420 mm DW (CSIRO H 7798 - 04), from Papua New Guinea: (A) Dorsal view (fresh); (B) Ventral view (preserved).

FIGURE 2. Oronasal region of the holotype of Himantura australis sp. nov., juvenile male 420 mm DW (CSIRO H 7798 - 04), from Papua New Guinea (preserved).

FIGURE 3. Denticles of the mid-disc of the holotype of Himantura australis sp. nov., juvenile male 420 mm DW (CSIRO H 7798 - 04), from Papua New Guinea (preserved).

FIGURE 4. Post-caudal sting tail of the holotype of Himantura australis sp. nov., juvenile male 420 mm DW (CSIRO H 7798 - 04), from Papua New Guinea (preserved). A. Dorsal view; B. Lateral view; C. Ventral view.

FIGURE 5. Comparison of dorsal colour pattern changes with growth in Himantura australis sp. nov. (fresh): A. 241 mm DW; B. 283 mm DW; C. 350 mm DW; D. 560 mm DW; E. 830 mm DW; and F. 1400 mm DW.

FIGURE 6. Map showing locations of the type material of Himantura australis sp. nov. (red), Taeniura lessoni sp. nov. (yellow), and Telatrygon biasa sp. nov. (blue). Stars denote primary types (holotypes) and solid circles denote secondary types (paratypes). (Map data © 2016 NASA, TerraMetrics, Google Earth).

FIGURE 7. Late embryos of Himantura leoparda (left, CSIRO H 635 - 02, 200 mm DW) and H. australis (right, CSIRO H 1134 - 01, 292 mm DW).

Tables

TABLE 1. Morphometric data for the holotype (CSIRO H 7798 - 04) and five paratypes of Himantura australis sp. nov., with ratios expressed as percentages of disc width.

Disc width (mm)	415	241	350
Total length	damaged	306.1	419.1
Disc length	95.2	94.0	98.5
Snout to pectoral-fin insertion	84.3	83.6	87.4
Orbit to pectoral-fin insertion	59.9	58.7	61.6
Snout to maximum disc width	40.3	38.9	43.3
Snout to origin of cloaca	79.0	77.2	83.3
Cloaca origin to tail tip	damaged	228.3	335.8
Cloaca origin to caudal sting	39.0	42.0	47.9
Pectoral-fin insertion to caudal sting (horiz)	35.1	34.7	45.6
Disc thickness	13.3	11.0	15.7
Snout (preorbital) length	20.0	19.0	22.4
Snout (preorbital horiz.) length	16.7	16.4	18.9
Orbit diameter	5.4	5.6	6.6
Eye diameter	3.1	3.3	4.0
Spiracle length	6.5	7.1	9.3
Orbit and spiracle length	10.1	9.8	11.3
Interorbital width	13.7	12.0	14.6
Inter-eye width	22.2	21.6	25.2
Distance between spiracles	20.3	19.5	21.6
Head length	45.3	43.5	47.2
Preoral length (to lower jaw)	20.6	21.2	21.8
Prenasal length	16.0	16.0	17.4