Taeniura lessoni, 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 : 387-394

Taeniura lessoni sp. nov.

( Figs. 8–12 ; Table 2 )

Taeniura sp.: Last et al., 2016: figs. 2, 5 (molecular data).

Holotype. CSIRO H 7724-01 (tissue accession GN16865), adult male 209 mm DW, Landoro Passage off Uepi Island, Marovo Lagoon , Solomon Islands, ~ 8°25.6’S, 157°55.7’E, 2–3 m depth, 13 May 2015.

Paratypes. 4 specimens: CSIRO H 7724-02 (tissue accession GN16866), female 201 mm DW, collected with holotype; QM I 39329 (tissue accession GN16864), female 220 mm DW, collected with holotype; USNM 350580 , female 180 mm DW, fringing reef, Lamen Island, 9–18 m depth , Vanuatu, 26 Sep 1998 ; USNM 380822 , immature male 185 mm DW, coral surge channel on northwest coast south of Neo Village , Tomotu Island, Santa Cruz Islands , Solomon Islands, 0–10 m depth, 29 Sep 1998.

Diagnosis. Small, blue-spotted stingray of the genus Taeniura lacking of a pair of blue longitudinal stripes along the sides of the tail; a uniformly pale ventral fold; no dorsal fold but upper margin of tail with a firm, blunt ridge; and within the genus possibly a relatively short post-orbital disc (length from rear of orbit to pectoral-fin insertion 63–65% DW), relatively long horizontal snout length (20–21% DW) and prenasal length 14–16% DW, and prenasal length 1.5–1.9 times internasal width.

Description. Disc oval, strongly convex anteriorly; much longer than broad, width 0.87 times length in holotype (0.87–0.88 in paratypes); snout angle 116° (116–122°), anterior disc angle 94° (88–97°); axis of greatest width of disc relatively well forward on disc, anterior to scapular region, its distance from snout tip 1.78 (1.66– 1.87) times in distance from tip of snout to pectoral-fin insertion; abdomen robust, thickness 6.3 (5.7–6.5) times in disc width, raised slightly above cranium and central disc; apex very broadly rounded, pectoral angle 107° (104– 109°); posterior margin strongly convex; free rear tip abruptly angular. Pelvic fins narrowly subtriangular, anterior margin almost straight to undulate, apex narrowly rounded, posterior margin moderately convex, merged with inner margin (free rear tip indiscernible); large, length 29.7% (28.8–30.8%) DW, 1.53 (1.34–1.69) times width across fin bases. Claspers of adult males large, mildly depressed, tapering, apex bluntly pointed; outer length (from axil of pelvic fin) in adult male holotype 21.2% DW.

Tail robust, firm, tapering gradually to caudal sting(s); ventral skin fold prominent, dorsal skin fold absent; base moderately broad and deep, broadly oval in cross-section, weakly convex to almost flat above and below, width 1.53 (1.47–1.67) times depth; depressed, oval in cross-section near origin of ventral skin fold, width 0.75 (0.36–0.51) times height at fold origin; tapering abruptly evenly in dorsoventral view below caudal sting(s); oval, compressed near tip of caudal sting and above mid-length of ventral fold; tail very compressed, narrowly suboval in cross-section towards its tip, width 0.75 (0.36–0.51) times depth at mid-base of ventral fold; dorsal surface of tail immediately posterior to caudal-sting bases with a weak naked groove (partly housing ventral-most sting and extending for about half to its full length); firm, low fleshy ridge on mid-dorsal tail beyond caudal sting, no skin folds present along lateral margin of tail. Ventral skin fold well-developed over its entire length, long, 66.1% (87.8– 95.3)% DW; depth at mid-base 0.94 (0.86–1.38) of tail height at mid-base; originating just forward of first caudal sting origin. Caudal sting positioned posteriorly on tail, horizontal distance from cloaca to sting origin 1.19 (1.14– 1.21) in precloacal length.

Snout fleshy (more so in largest paratype), rather short, broadly rounded; not acute at apex and without obvious apical lobe; tip narrowly rounded when viewed laterally; preoral snout length 1.78 (1.77–1.99) times mouth width, 1.98 (2.14–2.32) times internarial distance, 0.88 (0.90–1.01) times distance between first gill slits; direct preorbital snout length 2.78 (2.64–2.88) times interorbital length; snout to maximum disc width 1.79 (1.74– 1.93) in DW; interorbital space narrow, flat to weakly convex; eyes large, dorsolateral, protruding, well elevated above disc and interorbital space, diameter 0.84 (0.89–0.98) in spiracle length, eye length 1.18 (1.15–1.34) in spiracle length; inter-eye distance 2.75 (2.62–2.94) times eye length. Spiracles large, subrectangular to crescentic, opening dorsolaterally; dorsal margin a firm ridge. Nostril narrowly oval to slit-like, directed slightly obliquely; lateral margin fleshy; nasal fold on lateral margin partly internal, narrow; oronasal groove present; internarial space 1.46 (1.64–1.94) in prenasal length, 1.87 (1.44–1.78) times nostril length. Nasal curtain small, relatively narrow, skirt-like, short, width 2.16 (1.62–2.21) times length; weakly bilobed, posterior margin of each lobe undulate; curtain surface weakly papillate, usually with weak medial groove and covered with minute pores (often obscure); apex recessible within lateral margin of oronasal groove; lateral margin almost straight, smooth-edged, usually partly enveloped by narrow posterior fold of nostril; posterior margin heavily fringed, slightly concave medially, vaguely following contour and usually overlapping lower jaw when mouth closed (when intact).

Mouth small, jaws strongly asymmetric; lateral grooves short, rather well developed, curved slightly, extending from nostril to below corners of lower jaw; mouth not projecting forward when open, not protrusible; skin on chin and margin of lower jaw very fleshy, strongly papillate; teeth uniformly close-set in both jaws, in few oblique rows, not arranged in obvious quincunx; in paratype ( CSIRO H 7724-02) rows in upper jaw ~23, lower jaw ~23. Upper jaw strongly arched, anterior edge strongly double concave; tooth band width similar over its length, only teeth of anteriormost part of upper jaw visible when mouth closed; symphysial part of jaw projecting anteroventrally. Lower jaw strongly convex anteriorly with a rounded anterior margin, lingual edge truncate (tooth band much broader at symphysis than at corner of mouth; partly interlocking into upper jaw when mouth closed; teeth not visible when mouth closed. Upper jaw of female paratype ( CSIRO H 7724-02) with 5th tooth rows from each side of jaw having slightly enlarged teeth with longer cusps than those adjacent (directed lingually); teeth otherwise acuspid or with short cusps; those at symphysis barely larger than those adjacent. Teeth in lower jaw smaller than those of upper jaw, broad based, low, with semi-truncate to weakly cuspid distal margins; anteriormost part of crown with cenulate surface; no rows of enlarged teeth in jaw. Floor of mouth in female paratype ( CSIRO H 7724-02) with two, slender, lobe-like oral papillae, interspace between them subequal to their distance from corner or mouth (holotype not dissected); no smaller papillae near angle of each jaw.

Gill openings elongate S-shaped, margins entire rather than fringed; length of first gill slit 1.33 (1.29–1.62) times length of fifth gill slit, 2.62 (2.17–2.79) times in mouth width; distance between first gill slits 2.24(2.27– 2.54) times internarial space, 0.42 (0.37–0.40) times ventral head length; distance between fifth gill slits 1.38 (1.49–1.54) times internasal distance, 0.26 (0.24–0.26) times ventral head length.

Total pectoral-fin radials 110–112 (110–115); propterygium 48–49 (47–50), mesopterygium 15 (16–18), metapterygium 48 (47–50). Pelvic-fin radials: 1 (1) + 18–19 (19 on right side of male paratype, 23–25 in female paratypes). Vertebral centra total (including synarcual) 175 (181–184 in paratypes); total (excluding synarcual) 175 (180–184); monospondylous (including synarcual) 38 (37–40); monospondylous (excluding synarcual) 38 (37– 39); pre-sting diplospondylous 90 (91–101); post-sting diplospondylous 47 (40–55).

Squamation. Dorsal disc and tail of holotype rough to touch, sparsely covered with small to minute dermal denticles; a single row of short, spear-shaped thornlets along mid-line of disc from mid-scapular region to near pectoral-fin insertion; similar thornlets in 2 rows in nuchal region and 2 similar scapular thornlets on each side of and located very close to median row. Much smaller (often microscopic) prickly denticles scattered mainly over central disc and tail; denticles upright with pungent tips. Ventral surface naked. In largest paratypes, thornlet distribution similar to holotype; prickly denticles also well developed in largest female paratype, but largely absent in smaller specimens.

One caudal sting in holotype (1 or 2 in paratypes), intact, very elongate, slender, narrow based, length subequal to periorbital length; enveloping membrane absent; distance from sting base to pectoral-fin insertion 81.1 (71.9– 81.4%) DW, 3.98 (2.57–3.96) times first sting length; distance from cloaca to sting base 0.72 (0.67–0.72) in disc length.

Taeniura lessoni Taeniura lymma

Holotype Paratypes Non-types

Range Range

......continued on the next page Taeniura lessoni Taeniura lymma Holotype Paratypes Non-types Colour. Live coloration (based on holotype). Dorsal surface yellowish brown with vivid blue spotting; slightly paler brownish pink along margin of disc and pelvic fins; eye golden, orbital membrane similar to disc. Blue spots small to medium-sized (always smaller than corneal length), not distinctly ocellate irregularly spaced, distributed widely over disc but absent from tail; thornlets on medial disc slightly paler than adjacent skin; no mask-like marking on head distinct or dark speckles; claspers paler than disc. Ventral surface centrally on disc uniformly white; lateral and posterior disc margin, and tips of pelvic fins, with distinct, broad yellowish submarginal bands. Tail similar to disc dorsally, lacking a pair of prominent blue lines extending along its dorsolateral margins; caudal sting pale brownish; pre-sting tail white ventrally, ventral fold pale yellowish to whitish.

Fresh paratypes similar to holotype. Blue markings changed to greyish (with slightly darker spot margins) in preservative in CSIRO and NTM types, however, USNM types retained more blue coloration.

Size. Largest specimen a female paratype 220 mm DW (QM I 39329, 568 mm TL). The holotype is a sexually mature male at 209 mm DW; the other male (paratype USNM 380822) was immature at 185 mm DW. No information is available on birth size.

Distribution. Specimens collected from the Solomon Islands and Vanuatu ( Fig. 6 ), but possibly more widely distributed in Melanesia. Underwater images from off Kavieng (New Ireland), and off Kokopo, East New Britain ( Papua New Guinea), were also verified based on colour as being this species. Underwater images viewed on Google Images of Taeniura from Fiji also appear to be this species. Probably mainly inshore, types collected from surge channels in fringing coral reefs, to at least 18 m depth.

Etymology. Epithet in recognition of the work of the 19th C French scientist, René Lesson, who once worked on members of this genus in Melanesia. Vernacular: Oceania Fantail Ray.

Comparisons. Taeniura lessoni is immediately distinguishable from T. lymma in the field by the absence of a pair of blue stripes along the sides of the tail, and the ventral fold is uniformly pale in T. lessoni (fold margin darker than its base in T. lymma with the tail tip usually white). Closer inspection of the tail of T. lymma reveals that its upper post-sting margin in raised slight to form an angular, fleshy ridge that becomes a distinct low fold near the tail tip in juveniles. In the T. lessoni types the margin appears as a firm ridge, not forming a fold and its edge is less acute than in T. lymma . A comparison of the T. lessoni types with 4 similar-sized specimens of T. lymma (QM I 17668, QM I 31356, QM I 8328 and QM I 6666) indicated that these species might differ subtly in some morphometrics details: length from rear of orbit to pectoral-fin insertion 63.4–65.2% vs. 65.6–74.1% DW in T. lymma ; horizontal snout length 20.0–21.2% vs. 17.1–19.4% DW; prenasal length 14.3–15.6% vs. 12.2–14.7% DW, 1.46–1.94 vs. 1.36–1.39 times internasal width; and pelvic-fin length 28.8–30.8% vs. 32.3–34.3% DW. However, no doubt these species are very similar morphologically and more data is needed to determine the extent of interspecific variability. Taeniura lymma may also attain a slightly larger size than T. lessoni (35 cm rather than 22 cm DW, Last et al., in press).

The distributions of these two similar species do not appear to overlap. Both occur off Papua New Guinea, based on underwater images, but they do not appear to be sympatric. Lesson (1831) described Trygon halgani based on material from Waigeo (Indonesia) and Port Praslin (New Ireland). His illustrated syntype ( Fig. 13 ) is clearly referable to T. lymma due to the presence of the longitudinal blue stripes on the tail. The two syntypes attributed to this species are listed as being from Port Praslin. Séret & McEachran (1986) compared the two available New Ireland specimens (MNHN A 7994, Fig. 14 ) to Lesson's drawing, and found some similarities in the pattern of spots between the "larger" specimen and the drawing (mainly on the interorbital space and inner left pectoral fin). However, because of uncertainty as to which of these two specimens Lesson used as the type, they decided to consider both specimens as syntypes and also treated Trygon halgani as a junior synonym of Taeniura lymma .

Lesson also unequivocally mentioned the existence of ‘two soft blue lines extending along the entire length of the tail’ and these markings are evident in his colour painting of the type ( Fig. 13 ) – a key diagnostic feature of T. lymma but absent in T. lessoni . However, while the two syntypes of T. halgani are in good condition, and the blue spots remain distinctive, the blue stripes on the tail are not clearly evident based on images of these specimens. According to B. Séret (pers. comm.), the blue tail stripes mentioned by Lesson were still visible in the preserved specimens as darker bands (most evident on the "larger" specimen) when examined in the 1980s. The confirmed presence of T. lessoni (and possible absence of T. lymma ) from New Ireland confounds this issue. However, given that Lesson’s illustrated ‘type’ clearly depicts T. lymma , T. halgani must be considered a synonym of that species. Additional collections of these rays are needed from New Ireland, and the surrounding island groups of Papua New Guinea, to determine the local range of T. lessoni in this area and whether the two species co-occur. From information gathered to date, T. lymma has been confirmed from Milne Bay ( KRFS unregistered specimens) , Madang ( NTUM 10296 ), Trobriand Islands (e.g. BMNH 1974.5 .25.1, USNM 206313 ) , Port Moresby ( FMNH 120119 ) and Daru (e.g. USNM 222553 ) in Papua New Guinea . Furthermore, Miklouho-Maclay & Macleay (1886) described Discobatis marginipinnis from the Admiralty Islands of PNG . While no type specimens were retained, the illustration and description clearly highlight that the possession of blue lines on the tail diagnostic of T. lymma . In comparison, T. lessoni has been confirmed from Rabaul (East New Britain) and Kavieng (New Ireland) based on underwater images. Thus, T. lymma appears to be common around mainland Papua New Guinea, but T. lessoni may be confined to New Ireland and eastern New Britain.

Figures

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 8. Holotype of Taeniura lessoni sp. nov., adult male 209 mm DW (CSIRO H 7724 - 01), from Marovo Lagoon, Solomon Islands (fresh): (A) Dorsal view; (B) Ventral view.

FIGURE 9. Dorsal view of paratype of Taeniura lessoni sp. nov., female 220 mm DW (CSIRO QM I 39329), from Marovo Lagoon, Solomon Islands (fresh).

FIGURE 10. Oronasal region the paratype of Taeniura lessoni sp. nov., female 180 mm DW (USNM 350580), from Vanuatu (preserved).

FIGURE 11. Denticles of the mid-disc of the holotype of Taeniura lessoni sp. nov., adult male 209 mm DW (CSIRO H 7724 - 01), from Marovo Lagoon, Solomon Islands (preserved).

FIGURE 12. Lateral view of the post-caudal sting tail the holotype of Taeniura lessoni sp. nov., adult male 209 mm DW (CSIRO H 7724 - 01), from Marovo Lagoon, Solomon Islands (preserved); note well-developed ventral skin fold.

FIGURE 13. Original illustration of Trygon halgani from Lesson (1831) clearly showing the paired blue stripes on the tail.

FIGURE 14. Dorsal view of one of the syntypes (MNHN A 7994) of Trygon halgani Lesson (preserved).

Tables

TABLE 2. Morphometric data for the holotype (CSIRO H 7724 - 01) and four paratypes of Taeniura lessoni sp. nov., and four non-type specimens of T. lymm a with ratios expressed as percentages of disc width.

Disc width (mm)	209	180	220	183	246
Total length	243.1	249.2	262.7	232.5	265.6
Disc length	114.8	110.5	114.6	112.9	120.4
Snout to pectoral-fin insertion	99.1	92.6	96.5	97.6	106.1
Orbit to pectoral-fin insertion	64.6	63.4	65.2	65.6	74.1
Snout to maximum disc width	55.7	51.7	57.4	53.0	57.8
Snout to origin of cloaca	97.8	89.4	94.5	93.5	101.7
Cloaca origin to tail tip	145.3	159.8	168.2	158.8	172.1
Cloaca origin to caudal sting	82.4	75.8	83.1	81.5	89.4
Pectoral-fin insertion to caudal sting (horiz)	81.1	71.9	81.4	78.4	88.3
Disc thickness	15.8	15.4	17.4	14.7	19.0
Snout (preorbital) length	25.4	22.1	25.7	21.5	24.0
Snout (preorbital horiz.) length	20.2	20.0	21.2	17.1	19.4
Orbit diameter	10.1	8.8	9.6	9.4	11.3
Eye diameter	7.2	6.6	7.4	7.3	8.4
Spiracle length	8.5	8.0	9.2	8.5	9.4
Orbit and spiracle length	13.9	11.4	13.0	13.6	15.3
Interorbital width	9.1	8.4	9.1	8.3	9.3
Inter-eye width	19.8	17.7	20.0	17.3	19.4
Distance between spiracles	16.9	15.3	16.9	16.4	17.9
Head length	54.5	49.8	53.8	51.8	57.1
Preoral length (to lower jaw)	20.1	18.6	20.7	17.7	19.2
Prenasal length	14.8	14.3	15.6	12.2	14.7
Nostril length	5.4	4.9	5.9	4.5	5.8
Nasal curtain length	5.7	5.2	6.2	5.6	7.4
Nasal curtain width	12.4	9.1	11.7	10.6	14.2
Distance between nostrils	10.1	8.0	9.1	8.9	9.5
Mouth width	11.3	10.0	10.7	9.2	10.8