Lycodon gibsonae, Vogel & David, 2019

Vogel, Gernot & David, Patrick, 2019, A new species of the Lycodon fasciatus complex from the Khorat Plateau, eastern Thailand (Reptiles, Squamata, Colubridae), Zootaxa 4577 (3), pp. 515-528 : 518-522

Lycodon gibsonae spec. nov.

( Figs. 1–4 )

Lycodon fasciatus (nec Ophites fasciatus Anderson ): Inger & Colwell 1977: 235.

Holotype. FMNH 180146 , an adult male (tail dissected), from “Sakaerat Exp. Station, Amphoe Pak Thong Chai”, now the Sakaerat Environmental Research Station , Amphoe Wang Nam Khiao, at the south-western edge of Khorat Plateau, Nakhon Ratchasima Province, Thailand ( Figs. 1 , 3 ); collected by W. Ronald Heyer on 5 th May 1969.

Paratypes (n =2). (1) FMNH 180144 ( Fig. 4 ), an adult male (dissected; hemipenes in situ), from the same locality as the holotype; collected by W. Ronald Heyer on 26 th March 1969.—(2) FMNH 180145 ( Fig. 2 ), an adult male (dissected; hemipenes in situ), from the same locality as the holotype; collected by W. Ronald Heyer on 14 th April 1969 .

Diagnosis. A species of the genus Lycodon , characterized by: (1) loreal entering orbit; (2) 17–17–15 dorsal scale rows; (3) upper 3 or 4 and vertebral dorsal scale rows keeled; (4) about 223–226 VEN in males; (5) about 91– 92 SC in males; (6) relative tail length about 0.198 in males; (7) 17–18 cream, well-defined bands on a dark body; (8) first dorsal band starting at VEN 13–15; (9) width of the first band occupying 4, 5 or 6 vertebral scales; and (10) maximum SVL 906 mm in males.

This species can be recognized by its ventral and subcaudal scale counts (both higher than in L. fasciatus ), by the first band on the body (broader in terms of vertebral scales than in L. fasciatus ), and on the number of bands on the body (lower than in L. fasciatus ). Most other characters match those of L. fasciatus . Detailed comparisons with other species of the genus Lycodon appear below in the Discussion.

Etymology. This species is named after Mrs. Nancy Lynne Gibson, Executive director of the “Bird Conservation Society of Thailand ” and President of the executive committee of the “Love Wildlife Foundation”, for her involvement in the protection of the wildlife in Thailand and, especially, of the primary forest which harbour the type locality of this new species.

We suggest the following common names: Gibson’s Wolf Snake (English); Lycodon de Gibson (French) ; Gibsons Wolfszahnnatter (German); Ngoo Plong-chanuan Gibson (Thai).

Description of the holotype. Body robust, slightly compressed laterally; neck forming a natural angle with the head; head subrectangular, elongate, flattened, well distinct from the neck; snout elongate, strongly flattened, oblique in profile, projecting over the lower jaw, 27.5 % of HL, or 2.2 times as long as diameter of eye; a weak canthus rostralis; upper maxilla strongly arched with an angulous apex, distinctly bent inwards anteriorly (one maxilla dissected); large oval nostril that opens laterally and nearly entirely divides the nasal at its center; eye average, its diameter barely greater than the distance between the edge of the lip and its lower margin, with a vertical pupil; tail comparatively long, thin and tapering.

SVL 906 mm; TaL> 194 mm (mutilate).

Dentition. Based on specimen FMNH 180144: total of 13 maxillary teeth, with the following formula: 4 small anterior teeth + 3 strongly enlarged teeth, thick + a wide gap, longer than the larger anterior teeth + 3 small teeth + a small gap + 3 strongly enlarged posterior teeth, also rather straight.

Body scalation. Dorsal scales in 17–17–15 rows, smooth on 1 st –4 th dorsal rows, moderately keeled on 5 th –9 th rows along the entire body; scales of 1 st dorsal scale row slightly enlarged; scales of the vertebral row not enlarged; no apical pits detected; 225 VEN (+ 2 preventrals),> 73 paired SC; cloacal plate single.

Dorsal scale row formula (recount system):

3+4 Ą 3 (143) 17 ————— 15 3+4 Ą 3 (144)

Head scalation. Complement of upper head scales complete, including two internasals, two prefrontals, two supraoculars, one frontal, and two parietals. Rostral triangular, rather short, much wider than high, well visible from above but barely separating internasals; nasal rectangular, vertically divided into two nearly equal parts by a furrow below and above the nostril piercing in between, altogether about 1.7 times as long as high; internasals small, trapezoidal, about 1.5 times wider than long, widely in contact each with the other and with prefrontals; prefrontals large, subrectangular, 2.2 times longer than internasals, in broad contact with loreal; frontal rather small, hexagonal or ogive-shaped, its apex pointing backwards, 1.2 times longer than wide and about 1.3 times as long as the prefrontals suture; parietals large, elongate, subtriangular, 1.5 times longer than frontal (suture 1.2 times longer than frontal), each edged posteriorly with three large scales, i.e. 2 upper temporals and 1 larger paraparietal; supraocular entire, short and broad, 1.4 times longer than wide, about 0.6 times as wide as frontal; 1 / 1 loreal, pentagonal or subrectangular, very elongate, strongly narrowed posteriorly, about 3.0 times longer than high, entering orbit on a short height, in contact with 2 nd and 3 rd SL, the preocular, the prefrontal, and the posterior part of nasal; 8 / 8 SL, of which the first six are taller than wide, 1 st and 2 nd SL in contact with nasal, 3 rd –5 th SL on the left and 3 rd –4 th SL on the right right side touching the eye, 6 th and 7 th SL largest; 1 / 1 small, subrectangular preocular, located above the posterior part of loreal, reaching the top of the head and broadly in contact with the frontal; 1 large subocular at right, keeping 5 th SL from entering orbit; 2 / 2 postoculars, the upper one slightly larger; 2 anterior temporals on each side, followed by 3 secondary temporals, lower anterior temporal much larger than upper one, posterior temporals smaller; 10 / 10 IL, first pair in contact, 1 st –5 th IL in contact with anterior chin shields, 6 th –8 th infralabials largest; mental triangular, longer than wide; anterior and posterior pair of sublinguals of about same length, but anterior pair wider.

Coloration in preservative. Body and tail dark chestnut brown, with 17 well-defined crossbands on body and eight on tail, cream, strongly speckled with dark brown spots; these crossbands, about 4–5 dorsal scale long at mid- height of sides, widen at their ventrolateral limit, up to about 5–7 dorsal scale long; the first crossband, beginning at the level of VEN 14, is narrow, whereas the second crossband begins at VEN 31; posterior crossbands closer each to the other, separated by 8–10 DSR at mid-height of sides and about 6 DSR just above the venter; crossbands of the tail cream, also speckled with dark brown.

The head is nearly uniformly dark brown, slightly paler on the sides of the snout; supralabials speckled with pale brown, especially behind the level of the eye; no nuchal collar visible. The throat is cream, strongly speckled with dark brown on the chin and infralabials.

The venter is cream, ornate throughout with both strong, narrow dark brown blotches in its middle and the dark brown dorsal color between the cream. The under surface of the tail is as the venter near its base, then mostly dark brown speckled with cream.

Variation. Both paratypes (FMNH 180144 –45) agree in most respects with the description of the holotype. Dorsal bands of specimen FMNH 180145 are only slightly speckled with dark brown. Both paratypes have a faint collar. It appears that these specimens represent animals younger than the holotype, so some of the differences in coloration may indicate an ontogenetical shift. A comparison of the most important morphological characters are summarized in Table 2.

Hemipenis. In everted position, the organ is single, not forked, stout, and reaches the level of the 10 th SC. It is smooth along a short distance proximally, with a fold near its base, then entirely densely covered with short spines distally, with spines longer at the botton of the spinose part; tip smooth; sulcus straight, not prominent.

Distribution. Lycodon gibsonae spec. nov. is at present known only from the Sankambaeng (or Sankamphaeng) Range, a short mountain range of up to 1,350 m a.s.l. in elevation which marks the south-western edge of Khorat Plateau, Province of Nakhon Ratchasima, Thailand. This mountain range, as well as the Dong Phaya Yen Mountains that edge the western limit of the Khorat Plateau, receive heavy rainfall and are still covered with tropical evergreen forest.

Ecological notes. The specimens were collected in the relatively cool evergreen forest covering the southwestern edges of the Khorat Plateau ( Inger & Colwell, 1977). As with other species of the genus, they were found to be terrestrial and nocturnal. Nothing else is known about the biology of this species.

Comparisons. It should be noted that, since no females of Lycodon gibsonae spec. nov. are known, only male characteristics were used in the comparisons. Lycodon gibsonae spec. nov. differs from most other species of the genus Lycodon , except those of the L. fasciatus -group as well as L. subcinctus , L. sidiki , L. dumerili , and L. butleri , by having its loreal contacting the eye. Lycodon gibsonae differs from L. subcinctus and L. sidiki by having a preocular (vs. absent) and from L. dumerili in having 8 infralabials (vs. 9) and by the lower number of subcaudals (91 or 92 vs. 111–120).

Lycodon gibsonae spec. nov. belongs to the group of Lycodon fasciatus . It differs from L. fasciatus by (1) its much larger size (SVL of the largest male of L. gibsonae : 906 mm, SVL of the largest specimen among 26 males of L. fasciatus : 674 mm), (2) the number of ventrals (223–226 vs. 199–213 in 25 males of L. fasciatus ), (3) the number of subcaudals (91 or 92 in 2 specimens of Lycodon gibsonae spec. nov. vs. 74–90 in 20 males of L. fasciatus ), (4) the number of bands on the body (17 or 18 vs. 19–43 in Lycodon fasciatus sensu stricto), and (5) the pattern of the bands on the posterior part of the body: in L. gibsonae spec. nov., bands remain well defined, largely cream and not more strongly speckled with dark brown than anterior bands whereas, in L. fasciatus , bands of the posterior part of the body and tail are much more strongly dark speckled than anterior bands, up to turning nearly entirely brown. There are also a few other minor points, which will be discussed elsewhere in a review of the Lycodon fasciatus complex (Vogel et al. in prep).

Regarding other species of the Lycodon fasciatus group, Lycodon gibsonae spec. nov. differs from L. butleri by the number of bands on the body, less than 19 vs. 30 or more in L. butleri , and by the pattern of the venter. In Lycodon gibsonae spec. nov., bands are more conspicuous posteriorly than on the anterior part of the venter, where the bands are faint, while in L. butleri the bands are more conspicuous anteriorly, while the venter is turning dark posteriorly with faint bands. Lycodon gibsonae spec. nov. differs from L. carvenicolus by the number of ventrals and subcaudals of the males (223–226 against 245 and 91 or 92 against 113 respectively), and in the number of bands on the body (17 or 18 against 36–45). The main difference with L. cardamomensis is the fact that the loreal scale is touching the eye in Lycodon gibsonae spec. nov. whereas it is separate from it in L. cardamomensis . The venter is banded in Lycodon gibsonae spec. nov. whereas it is not in L. cardamomensis . Lycodon gibsonae spec. nov. differs from L. gongshan by its shorter tail (0.198 against 0.231–0.255), by the lower number of bands on the body (17 or 18 against 37–41), and more infralabials (10 against 8 or 9). It differs from L. synaptor by the condition of the loreal scale, entering orbit in Lycodon gibsonae spec. nov. vs. separate from it in L. synaptor . It has more infralabials (10 against 8), a lower number of bands on the body (17 or 18 against 30 or 31), and a different shape of the bands (width of the first band at the base 10 or 11 against 3 ventrals). Finally, Lycodon gibsonae spec. nov. differs from L. liuchengchaoi by the number of ventrals (223–226 vs. 202–204) and subcaudals in males (91or 92 vs. 68), the number of infralabials (10 against 7–9), and the number of bands on the body (17 or 18 against 40–47).

Figures

FIGURE 1. Lycodon gibsonae spec. nov., FMNH 180146, preserved holotype, A: dorsal view; B: ventral view; C: lateral view of head. Photographs by Joshua Mata.

FIGURE 2. Lycodon gibsonae spec. nov., FMNH 180145, preserved paratype, dorsal view. Photograph by Joshua Mata.

FIGURE 3. Lycodon gibsonae spec. nov., FMNH 180146, preserved holotype, compared with an adult L. fasciatus (FMNH 270716, Nan Province, Thailand). A: dorsal view of body; B: dorsal view of head. Photographs by Joshua Mata.

FIGURE 4. Lycodon gibsonae spec. nov., FMNH 180144, preserved paratype, compared with an adult L. fasciatus of the same size (FMNH 270716, Nan Province, Thailand). A: dorsal view of body; B: ventral view of body. Compare the shape of the bands which are well defined posteriorly in L. gibsonae spec. nov. whereas in Lycodon fasciatus posterior bands are much more strongly speckled with dark dots than anterior bands, up to turning nearly entirely brown. Photographs by Joshua Mata.