Trimeresurus labialis Fitzinger

Vogel, Gernot, David, Patrick & Chandramouli, S. R., 2014, On the systematics of Trimeresurus labialis Fitzinger in Steindachner, 1867, a pitviper from the Nicobar Islands (India), with revalidation of Trimeresurus mutabilis Stoliczka, 1870 (Squamata, Viperidae, Crotalinae), Zootaxa 3786 (5), pp. 557-573 : 561-564

Trimeresurus labialis Fitzinger in Steindachner, 1867

( Fig. 2 )

“ Bothrophis labialis ” Steindachner, 1861: 411.— Type locality. “ Nicobaren ”.— Onomatophore. None cited. — Status. A nomen nudum; no description.

Trimeresurus labialis Fitzinger in Steindachner, 1867: 86; Pl. III: Figs. 1–2 .— Type locality. Restricted here to Car Nicobar Island, Nicobar Archipelago, India (see above).— Onomatophores. Three syntypes (see above): NMW 18813:1–18813:3, all adult females; collected in February 1858 by members of the Frigate Novara Expedition.

Material (n = 10). Nicobar Archipelago. Car Nicobar Island. BMNH 1936.7.7.43, BNHS 3329, FMNH 134919, NMW 18813:1–3 (syntypes; locality here ascertained), ZSI 23161–23162, ZSI 255550, ZSI AN/R/4.

Comments. Steindachner (1861) cited the nominal taxon “ Bothrophis labialis ” in the list of species obtained during the Novara Expedition without providing any description. Steindachner (1867) credited the description of Trimeresurus labialis to “Fitzinger in litteris ”. As a consequence, according to the Code (Art. 51.1.1), the authorship must be credited as such.

This species was recognized as valid by Theobald (1876: 221), later Boulenger (1890: 428) considered it a synonym of Trigonocephalus cantori Blyth, 1846 (as Trimeresurus cantoris ). It was eventually resurrected by Werner (1926: 253). Smith (1943) and all recent authors recognized it as a valid species, with the exception of Mahendra (1984) who regarded it as a subspecies of Trimeresurus purpureomaculatus (Gray, 1832) . Trimeresurus labialis is monotypic. Following Malhotra et al. (2004), who placed this species in the genus Cryptelytrops Cope, 1860 , and David et al. (2011), it belongs to the subgenus Trimeresurus Lacépède, 1804 .

Before the present paper, Trimeresurus labialis , as now defined, had been depicted only in Steindachner (1867: Pl. 3: Fig. 1–2 ) and in Vijayakumar & David (2006: Fig.18).

Diagnosis. A small pitviper of the genus Trimeresurus with (1) First supralabial entirely or partly fused to nasal; (2) 21 or 23 scale rows at midbody; (3) internasals usually in contact; (4) 168–172 VEN, 51–66 SC; (5) 10–12 cephalic scales between supraoculars; (6) total length up to 511 mm; (7) a strong dimorphism in relative tail length (see below); and (8) a dorsal background colour in the shades of pale grey, greyish-green or pale olivegreen, never bright green ( Table 1).

Taxon Max TL TaL/TL VEN

3 Ƥ Ƥ Ƥ

Trimeresurus labialis 476 511 0.188–0.193 0.129–0.151 168–172 168–171 (n = 2 3, 8Ƥ*) (x = 0.140) (x = 169.3)

(s = 0.007) (s = 1.4) Trimeresurus mutabilis 425 490 0.174–0.182 0.124–0.154 158–164 154–164 (n = 5 3**, 22Ƥ) (x = 0.178) (x = 0.140) (x = 160.6) (x = 159.2)

(s = 0.004) (s = 0.008) (s = 2.4) (s = 2.6) Taxon SC MSR Cep In sep

Ƥ 3 Ƥ

Trimeresurus labialis 62–66 51-56 21 21–23 10–11 0 (1) (n = 2 3, 8Ƥ*) (x = 53.1) (x = 22.5) (x = 10.6) (s = 1.8) (s = 0.9) (s = 0.5)

Trimeresurus mutabilis 60–62 46–54 21 21 (23)*** 9–12 1 (n = 5 3**, 22Ƥ) (x = 61.3) (x = 49.7) (x = 21.1) (x = 10.7) (s = 1.0) (s = 2.5) (s = 0.4) (s = 1.0)

Abbreviations.—See in Material and Methods

* —One female of Trimeresurus labialis with damaged SC was not included in TaL/TL and SC values. ** —One male of Trimeresurus mutabilis with part of the tail missing was not included in TaL/TL and SC values. *** —23 only in one out of 22 specimens

Species description and variation. Morphology. The body of this species is quite slender, thicker in females; the triangular head is rather long, flat, wide at its base and clearly distinct from the neck; the snout is also rather long and narrow, at least twice as long as eye diameter, flattened, rounded seen from above, obliquely truncated seen from the side, with a distinct canthus rostralis; the eye is small or average with a diameter smaller than the distance lower eye margin-lip margin; the tail is cylindrical, average, tapering progressively and strongly prehensile.

The maximal recorded total length is 511 mm (SVL 442 mm; TaL 69 mm; NMW 18813:2, female; syntype). The longest known male is 476 mm long (SVL 384 mm, TaL 92 mm; ZSI 23161). Ratio TaL / TL: 0.129–0.198 with a strong sexual dimorphism.

Body scalation. DSR 25–21:21–23:15–17(19) scales, rhomboid, smooth or weakly keeled; VEN 168–172, SC 51–66, all paired; anal entire. The two examined males have 21 DSR but 6 out of 8 females have 23 DSR at midbody.

Head scalation. Rostral broader than high, triangular, visible from above; nasal subrectangular, undivided, with nostril in its middle; one pair of moderately enlarged, subrectangular internasals, about twice as wide as and longer than adjacent upper snout scales, usually in contact each with the other or separated each from the other by 1 small scale (in 3 / 10 specimens); 4 or 5 canthal scales bordering the canthus rostralis between internasal and corresponding supraocular, enlarged compared with adjacent snout scales; one small triangular loreal between upper preocular and nasal; two upper preoculars above loreal pit, lower one bordering the upper margin of loreal pit, both elongated and in contact with loreal; lower preocular forming lower margin of loreal pit; on each side 1 supraocular, elongate and narrow, about 3.0–3.5 times as long as wide, not much wider than the adjacent upper head scales, 0.8–0.9 times as wide as internasals, not indented by upper head scales; scales on dorsal surface of head small, smooth, irregular in shape, larger on snout than in the frontal area; 10–11 cephalic scales in a line between supraoculars; scales on the occiput flat and smooth; temporals smooth; on each side 2–3 postoculars and 1 elongated, crescent-like subocular; 9–12 SL, comparatively large (the specific epithet labialis is a Latin adjective based on the noun labium (plural labia), the lips, by reference to the large size of the supralabial scales), 1st SL and nasal completely fused or partly separated by an incomplete and shallow furrow, 2nd SL tall, in contact with nasal and forming the anterior border of loreal pit, 3rd SL largest, elongate, about 1.15–1.25 times longer than high, in contact with subocular or sometimes separated by 1 small scale, 4th SL lower than third one, separated from subocular by 1 or rarely 2 small scales, 5th and other posterior SL separated from subocular by 2 scales; 11–14 IL, first pair in contact with each other, 1st–3rd pairs in contact with anterior chin shields; 8–9 rows of smooth gular scales; chin shields regularly arranged.

Coloration and pattern. The colouration of this species is variable. The body is in various shades of pale brown, grey, greyish-brown, greyish-green or pale olive-green, slightly paler on the lower parts of the side; dark brown dorsal blotches or crossbands, more or less faint, 2 to 3 scales wide on each side; these dorsal blotches may be divided on the vertebral line and their halves slightly set off each from the other; a lateral series of irregular, dark grey or dark brown spots on the 4th, 5th or 6th dorsal scale rows, numerous, more or less aligned as a very discontinuous stripe, especially of 4th DSR, or widely scattered on any of these scale rows; a series of dark brown spots on scales of the 1st and lower part of those of the 2nd scale rows, usually widely separated; in some specimens a cream, narrow ventrolateral stripes extends on tip of ventrals and the lower part of the first dorsal scale row, dissected by brown spots of the ventrolateral series. The tail is as the body, with faint darker crossbars; posterior quarter of tail darker grey, pinkish-gray or greyish-green, with dark crossbars; tip uniformly dark.

Head more or less dark brown, greyish-brown or dark olive above and on temporal regions, slightly darker than the body; supralabials barely paler than upper head surface; in most specimens a thin, white, more or less diffuse temporal streak extends on the 2nd row of temporals above the last posterior supralabials from the eye to the corner of the mouth. Infralabials, chin and throat are pale grey or greyish-green, heavily speckled with dark grey or dark brown spots, especially on infralabials and chin. In life, the iris is brown, marbled with dark brown; black pupil.

The venter is grey, brown or yellowish-grey, rather uniform or usually heavily marbled or speckled with dark brown or dark grey; tips of ventrals dark brown or greenish-grey. The ventral part of the tail is in the colour of the venter, pinkish-gray near its tip; subcaudals usually with dark margins.

Sexual dimorphism. There is a sexual dimorphism in (1) relative tail length: 0.188–0.193 (n=2) in males vs. 0.129–0.151 (n=8) in females; and (2) the number of subcaudals: 62–66 in males and 51–56 in females.

There is also a weak dimorphism in the number of dorsal scale rows at midbody: 21 in the two available males and 2 out of 8 females, 23 in 6/ 8 females.

Distribution ( Fig. 1 ).On the basis of the present paper, this species is endemic to Car Nicobar island, Nicobar Archipelago, India.

Vogel (2006) included two pictures of this species stated to originate from “Andaman Islands, India ”. In fact, this locality was erroneous. The specimen shown on pictures Nr RS02585-4 and RS02587-4 indeed stemmed from Car Nicobar Island (S. P.Vijayakumar, pers. comm., August 2013).

Etymology. The specific epithet labialis is a Latin adjective based on the noun labium (plural labia), the lips, by reference to the large size of the supralabial scales.

Figures

FIGURE 1. Map of the Andaman and Nicobar archipelago, (insert: Nicobar Islands showing: Car Nicobar Island (red), type locality of Trimeresurus labialis; Camorta Island, type locality, and distribution of Trimeresurus mutabilis (blue).

FIGURE 2. Trimeresurus labialis Fitzinger in Steindachner, 1867. Car Nicobar Island. Photograph by S. P. Vijayakumar / Bandana Aul.