Dasyatis longicauda, Last, Peter R. & White, William T., 2013

Last, Peter R. & White, William T., 2013, Two new stingrays (Chondrichthyes: Dasyatidae) from the eastern Indonesian Archipelago, Zootaxa 3722 (1), pp. 1-21 : 3-11

Dasyatis longicauda sp. nov.

Figs 1–7 , 13 ; Tables 1 and 2

Dasyatis sp. 1: White et al., 2006: 232, figs. (images are of the nominated holotype); White & Dharmadi, 2007: 1814.

Holotype. MZB 21462 (Genbank accession KF604914 ), juvenile male 162 mm DW, beach at Merauke, West Papua, Indonesia (08°31’ S; 140°22’ E), less than 0.5 m depth, 9 Oct. 2002.

Paratypes. (15 specimens) CSIRO H 5976-23 (Genbank accession KF604918 ), female 133 mm DW, CSIRO H 5976-24 (Genbank accession KF604913 ), juvenile male 118 mm DW, same location as holotype, 7 Oct. 2002; CSIRO H 5980-08 (Genbank accession KF604911 ), juvenile male 132 mm DW, CSIRO H 5980-09 (Genbank accession KF604915 ), juvenile male 121 mm DW, CSIRO H 5980-10, juvenile male 91 mm DW, CSIRO H 5980- 11, female 122 mm DW, CSIRO H 5980-12, juvenile male 117 mm DW, CSIRO H 5980-13, female 114 mm DW, CSIRO H 5980-14, juvenile male 96 mm DW, CSIRO H 5980-15, juvenile male 112 mm DW, CSIRO H 5980-16, female 130 mm DW, CSIRO H 5980-17, juvenile male 134 mm DW, CSIRO H 5980-18, juvenile male 124 mm DW, collected with holotype; MZB 15071, female 108 mm DW, MZB 15072, juvenile male 143 mm DW, same location as holotype, 10 Oct. 2002.

Diagnosis. A small species of Dasyatis with the following combination of characters: disc subcircular, width 1.0–1.1 times length; snout weakly triangular, angle 113–117°, length 1.7–2.1 times interorbital width; preoral length 2.1–2.3 times mouth width; internasal distance 1.7–2.0 in prenasal length; median body and pre-sting tail with a broken series of lanceolate to spear-shaped thorns extending posteriorly from nuchal region (162 mm DW); tail very elongate (2.3–2.9 times DW), filamentous to whip-like beyond sting, and sub-quadrangular in crosssection at mid-ventral skin fold, width 0.9–1.3 times its depth, postcloacal tail length 2.8–3.5 times precloacal length; ventral skin fold elongate, low, its length 1.8–2.4 in DW, height 0.3–0.4 in tail depth at its midlength; dorsal skin fold short or absent, when present low, barely taller than a ridge, much shorter than ventral fold; distance from cloaca to sting 1.5–1.7 in precloacal length; pectoral-fin radials 103–108; total vertebral centra (excluding 1st synarcuals) 114–120.

Description. Disc subcircular, not obviously angular anteriorly and apex barely produced; its width 1.03 times length in holotype (1.02–1.07 in measured paratypes); axis of greatest width over scapular region, its distance from snout tip 2.12 (1.87–2.08) of distance from tip of snout to pectoral-fin insertion; body moderately depressed, thickness 8.9 (7.5–8.7) times in disc width, barely raised above cranium (marginally more so above scapular region); anterior margin of disc straight to weakly convex; apex broadly rounded, pectoral angle 99° (95–100°); posterior margin convex; free rear tip broadly rounded to weakly angular. Pelvic fins strongly triangular, anterior and posterior margins almost straight, apices narrow and bluntly pointed, free rear tip broadly rounded; relatively small, length 22.5% (18.7–22.0%) DW; 1.09 (0.85–1.10) times width across fin bases. Tail very elongate, slender, postcloacal tail 3.47 (1.79–2.90) times precloacal length; with a long, low ventral skin fold, 54.6 (41.5–50.6) % DW, and usually a much shorter, ridge-like dorsal skin fold; base moderately depressed, suboval in cross-section, weakly convex above and below, width 1.44 (1.52–1.80) times its depth; dorsal profile tapering gradually and evenly to sting base; narrowly oval in cross-section near origin of ventral skin fold, width 1.20 (1.35–1.64) times height at fold origin; dorsal profile tapering more rapidly below sting insertion; very slender, filamentous and whip-like beyond sting; subquadrangular in cross-section above mid ventral fold, its width 1.15 (0.90–1.31) times depth; at end of ventral fold suboval, weakly depressed, width 1.05 (1.01–1.38) times height; filamentous, more strongly depressed towards tail tip; dorsal surface of tail posterior to sting base with a narrow, tapering, naked groove (presumably housing sting when present); no skin folds or ridges along lateral margin of tail. Dorsal skin fold usually reduced to a low, elongate ridge (sometimes absent), length about 12 (6–19) times its height, 4.21 (4.15–5.09) in snout length, 8.71 (7.18–9.35) in length of ventral fold; its height 1.33 (0.68–1.92) in height of mid ventral fold; sometimes located in a shallow dorsal furrow, not forming a ridge posteriorly. Ventral skin fold elongate, low, length 1.83 (1.98–2.41) in disc width, 5.24 (5.43–5.55) in post cloacal tail; origin 1.0% (1.0–1.3%) before sting origin; depth at quarter length 0.18 (0.16–0.24), at mid length 0.42 (0.27–0.42), at three quarter 0.31 (0.27–0.49) in adjacent tail height; originating beneath sting origin; insertion usually distinct but fold sometimes terminating in a weakly defined ridge; distance from cloaca to sting origin 1.52 (1.52–1.67) in precloacal length; length of tail beyond ventral fold 0.31 (0.30–0.31) in fold length, 1.62 (1.67–1.69) in tail length. Sensory pores not demarcated on ventral surface, lateral line distinct.

Snout moderately elongate, strongly depressed, weakly triangular; apex with a short, well-defined, triangular lobe; angle 114.5° (113–117°); preoral snout length 2.14 (2.20–2.32) times mouth width, 2.30 (2.11–2.39) times internarial distance, 1.18 (1.08–1.21) times distance between first gill slits; direct preorbital snout length 2.14 (1.75–2.07) times interorbital length; snout to maximum disc width 2.42 (2.20–2.37) in DW; interorbital space broad, slightly convex medially; eye small, almost lateral, protruded slightly, its ventral margin partly covered by thin skin fold; orbit usually elevated slightly above interorbit, its diameter 1.39 (1.25–1.45) in spiracle length; eye diameter 2.13 (1.99–2.41) in spiracle length; inter-eye distance 4.56 (4.56–5.35) times eye diameter. Spiracle subrectangular to suboval, enlarged, dorsolateral. Nostrils narrow, slit-like, parallel to slightly oblique; anterior margin not elevated; anterior nasal fold internal, broad, membranous; oronasal groove well defined; internasal distance 1.86 (1.73–1.96) in prenasal length, 2.55 (2.34–2.59) times nostril length. Nasal curtain skirt-like, relatively narrow, elongate, width 1.74 (1.65–1.80) times length; not strongly bilobed; its surface flat, smooth, without a longitudinal medial groove and not covered with prominent sensory pores; apex recessible within lateral margin of oronasal groove; lateral margin almost straight, smooth edged; posterior margin very finely fringed, weakly concave, not following contour of lower jaw, falling slightly short of symphysis of lower jaw when mouth closed.

Jaws asymmetrical; lateral groove deep, curved slightly, extending from half way to nostril anteriorly to well below lower jaw angle posteriorly, its length much shorter than nasal curtain length. Upper jaw strongly arched, most teeth concealed, symphysial part of jaw projecting ventrally (usually visible). Lower jaw very strongly convex, deeply concave at symphysis in all types, only outer symphysial teeth visible when mouth closed; not projecting forward when mouth open, mouth not protrusible; skin posterior to lower jaw (chin) not fleshy, weakly corrugate and not papillate. Floor of mouth in paratype (CSIRO H 5976-23) with 3 prominent, closely spaced, medial oral papillae of similar size, and 2 rudimentary papillae near each corner. Teeth in upper jaw small, broadly lozenge-shaped, and similar in shape and size across jaw; without obvious cusps at this stage of development. Teeth in lower jaw smaller (about 2/3 width of those in upper jaw), acuspid. Teeth uniformly close-set in both jaws, arranged quincuncially; tooth rows count unclear, about 33 rows in upper jaw, about 38 rows in lower jaw.

Gill slits distinctly S-shaped, edges not fringed laterally; length of first gill slit 1.37 (1.16–1.65) times length of fifth gill slit, 3.80 (3.39–3.89) times in mouth width; distance between first gill slits 1.95 (1.88–2.02) times internasal distance, 0.44 (0.42–0.45) times ventral head length; distance between fifth gill slits 1.15 (1.07–1.22) times internasal distance, 0.26 (0.25–0.27) times ventral head length.

Squamation. Disc and tail largely naked in all types, lacking granular denticles. In holotype (MZB 21462, 162 mm DW), a prominent row of 14 variably-sized, lanceolate to spear-shaped thorns, extend from nuchal region to mid pre-sting tail; last 3 thorns much larger than those preceding (each subequal to eye diameter in length), crowns elevated and directed posterodorsally, surfaces concave, tips pungent; anterior lanceolate thorns on disc small to moderate in size, largest about equal to half eye diameter. Smaller types with less well developed squamation; 3 paratypes (CSIRO H 5980-09, CSIRO H 5980-15 and CSIRO H 5980-16, 112– 130 mm DW) each with low, lanceolate, suprascapular thorn (about equal to half eye diameter), remainder of disc and tail naked; remaining paratypes (91–134 mm DW) totally naked. All type specimens with stinging spines missing at preservation. Distance from sting base to pectoral-fin insertion 50.2% (43.2–51.1%) DW; distance from cloaca to sting base 0.56 (0.52–0.57) in disc length.

Dasyatis longicauda sp. nov. Dasyatis fluviorum

Holotype Paratypes (n=7) n=3

Min. Max. Min. Max. Disc width (mm) 162 96 134

......continued on the next page Dasyatis longicauda sp. nov. Dasyatis fluviorum

Holotype Paratypes (n=7) n=3

Min. Max. Min. Max. Meristics. Total pectoral-fin radials 103 (103–108, n=8); propterygials 43–44 (43–52), mesopterygials 14–15 (12–17) and metapterygials 45 (41–46). Total pelvic-fin radials 22–23 (20–25). Total vertebral segments (excluding first synarcual centra) 120 (114–120; n=12); monospondylous centra (excluding first synarcuals) 35 (31–36; n=12); diplospondylous centra 85 (81–88; n=12).

Coloration. When fresh: Dorsal surface greyish brown, slightly paler around margin of disc; tail darker, similar to mid disc; eyes blackish; thorns white, prominent. Ventral surface uniformly white. In preservative: Dorsal disc greyish to yellowish, distinctly paler around margin; dorsal margin of spiracle, and anterior and ventral margins of orbit, white; ventral surface of disc uniformly pale, no obvious dark outer margin; middle of tail brownish black forward of sting, whitish laterally and ventrally; tail beyond sting blackish dorsally, whitish ventrally, becoming uniformly dark beyond insertion of ventral skin fold; dorsal skin fold black; ventral skin fold white anteriorly beneath sting base, becoming blackish posteriorly (fold sharply demarcated from white ventral area of tail beneath missing sting scar).

Size. Possibly a small stingray; known only from the juvenile type specimens which ranged in size from 91 to 162 mm DW.

Distribution. Known only from the type specimens collected near Merauke in West Papua ( Fig. 13 ) where it is bycatch of an artisanal beach seine fishery for penaeid prawns. Found in very shallow water (<1 m depth) close to the shoreline; offshore distribution unknown. Possibly more widely spread along the southern coasts of West Papua and probably also in Papua New Guinea. However, it was not collected from coastal northern Australia or deeper parts of the Arafura Sea, despite comprehensive surveys of the ichthyofauna in these areas being conducted.

Etymology. The species is named longicauda in allusion to its very long tail. Proposed vernacular name: Merauke Stingray.

Barcode results. The holotype and 2 paratypes of D. longicauda with CO1 sequences available in the BOLD database (www.boldsystems.org) grouped closest to D. fluviorum from northern Australia ( Fig. 7). The new species had an average sequence divergence of 1.5% (minimum interspecific divergence of 1.4%) from D. fluviorum . The three type specimen sequences differed from each other by only 0.2–0.3%. These two species group with members of the D. akajei complex, i.e. D. akajei (Müller & Henle, 1841) from Japan (4.1–4.2% divergence; n=2), D. bennetti (Müller & Henle, 1841) from China and Indonesia (4.3–4.7% divergence; n=14) and a single specimen of D. parvonigra from Bali, Indonesia (9.3% divergence). Two additional specimens of D. longicauda (CSIRO H 5980-08 and -09) had sequences differing from each other by 8.9% and from the three type specimens by ~12.5 and ~8% ( Fig. 7). Given that no morphological or meristic differences were detected between these specimens and three above type specimens, the sequences of these two specimens were considered anomalous and probably erroneous.

exposed sting origin dorsal skin fold ventral skin fold Dasyatis longicauda KF604915 West Papua, Indonesia

Dasyatis longicauda KF604911 West Papua, Indonesia

Dasyatis fluviorum DQ108182 West Papua, Indonesia

Dasyatis fluviorum DQ108183 West Papua, Indonesia

Dasyatis fluviorum HM902583 West Papua, Indonesia

Dasyatis longicauda KF604913 West Papua, Indonesia Dasyatis longicauda KF604918 West Papua, Indonesia Dasyatis longicauda KF604914 West Papua, Indonesia

Dasyatis akajei EU339356 Japan Dasyatis akajei JF952715 Japan

Dasyatis bennetti FJ237978 China

Dasyatis bennetti KF604916 Jakarta, Indonesia Dasyatis bennetti KF604910 Jakarta, Indonesia Dasyatis bennetti FJ237982 China

Dasyatis parvonigra EU398732 Bali, Indonesia

Dasyatis brevicaudata EU398724 Western Australia 2% Comparisons. Dasyatis longicauda belongs to a group of small to medium-sized stingrays, the akajei group, which includes D. bennetti and D. fluviorum in the Indo –Australian region. These species differ from each other in their CO1 barcodes, as well as in meristics, squamation and morphometrics. Dasyatis longicauda appears to have been confused with D. fluviorum in the past – the two are very similar in appearance. Its distribution was initially mapped along the southern Papua New Guinea coast by Last & Stevens (1994), based on a image provided by Patricia Kailola, but was later regarded as a likely misidentification by Last & Stevens (2009) based on new data. Dasyatis longicauda has a slightly lower vertebral count (total centra excluding those of the first synarcual 114– 120 vs. 118–125 in D. fluviorum , unpublished data), lower pectoral-radial count (103–108 vs. 108–116), a longer tail (2.3–2.9 times vs. about twice DW when undamaged), and has larger and less numerous thorns along the middisc and tail ( D. fluviorum lacks very long spear-shaped, pre-sting thorns on the tail at all stages of development, although it can have short, pointed thorns in adults that are shorter than the orbit diameter, rather than almost twice the orbit diameter as in D. longicauda ).

Apart from differences in the genetic barcode ( Fig. 7), young of D. longicauda differ from young D. bennetti in having a more angular disc, relatively larger thorns on the disc at a similar size, and lacking a pair of lateral denticles patches on the scapular region. To date, the authors have been unsuccessful in obtaining adult material of D. longicauda to compare with adults of its congeners. Members of the genus Dasyatis in the Indo –Pacific are presently under review by the first author.

D. longicauda sp. nov. D. fluviorum

Holotype Paratypes (n=7) n=3

Min. Max. Min. Max.

Figures

FIGURE 1. Dasyatis longicauda sp. nov., juvenile male holotype, MZB 21462 (162 mm DW, Merauke, West Papua, Indonesia, 9 Oct. 2002): A. dorsal surface, fresh colour; B. ventral surface, preserved.

FIGURE 2. Dorsal surface of an early juvenile male paratype of Dasyatis longicauda sp. nov., CSIRO H 5980 - 14 (96 mm DW, preserved, Merauke, West Papua, Indonesia, 9 Oct. 2002).

FIGURE 3. Oronasal region of the juvenile male holotype of Dasyatis longicauda sp. nov. MZB 21462 (162 mm DW, preserved, Merauke, West Papua, Indonesia, 9 Oct. 2002).

FIGURE 4. Squamation on the central disc of the juvenile male holotype of Dasyatis longicauda sp. nov., MZB 21462 (162 mm DW, preserved, Merauke, West Papua, Indonesia, 9 Oct. 2002).

FIGURE 5. Enlarged, thorn-like denticles on the anterior dorsal tail of the juvenile male holotype of Dasyatis longicauda sp. nov., MZB 21462 (162 mm DW, preserved, Merauke, West Papua, Indonesia, 9 Oct. 2002): A. dorsal view; B. lateral view.

FIGURE 13. Map of the Indo – Australian region showing the collection localities for the types of Dasyatis longicauda (black circle) and Himantura javaensis (black star).

Tables

TABLE 1. Morphometric data for the holotype of Dasyatis longicauda sp. nov. (MZB 21462), with ranges and means provided for measured paratypes, and for 3 juvenile D. fluviorum. Measurements expressed as a percentage of disc width.

Total length	368.5	316.9	342.7	289.1	334.9
Disc length	97.4	93.5	98.2	90.8	94.7
Snout to pectoral-fin insertion	87.5	84.7	88.6	80.4	84.1
Disc thickness	11.2	11.5	13.4	10.8	12.9
Snout (preorbital) length	26.4	25.4	27.4	22.9	25.8
Snout (preorbital) horizontal length	24.8	23.7	25.0	21.6	24.4
Pelvic-fin (embedded) length	22.5	18.7	22.0	21.8	23.7
Width across pelvic-fin base	20.7	19.5	22.4	18.6	20.8
Greatest width across pelvic fins	42.6	37.5	41.2	35.2	38.8
Cloaca origin to tail tip	286.1	233.3	260.9	209.7	255.5
Tail width at axil of pelvic fins	9.7	10.1	10.9	8.3	8.8
Tail height at axil of pelvic fins	6.7	6.1	6.9	5.0	6.5
Pectoral-fin insertion to sting origin	50.2	43.2	51.1	38.3	45.3
Cloaca origin to sting	54.2	48.7	56.2	44.6	48.4
Tail width at base of sting	4.4	4.7	6.0	3.1	3.7
Tail height at base of sting	3.2	3.0	4.2	2.7	3.5
Sting 1 length	-	-	-	18.5	25.1
Snout preoral (to lower jaw) length	26.3	24.5	26.6	21.8	25.3
Mouth width	12.3	10.8	11.8	10.2	11.7
Distance between nostrils	11.4	10.8	11.9	9.7	11.0
Interorbital width	12.3	12.8	14.6	12.3	13.7