Oligodon culaochamensis, Nguyen, Sang Ngoc, Nguyen, Luan Thanh, Nguyen, Vu Dang Hoang, Phan, Hoa Thi, Jiang, Ke & Murphy, Robert W., 2017

Nguyen, Sang Ngoc, Nguyen, Luan Thanh, Nguyen, Vu Dang Hoang, Phan, Hoa Thi, Jiang, Ke & Murphy, Robert W., 2017, A new species of the genus Oligodon Fitzinger, 1826 (Squamata: Colubridae) from Cu Lao Cham Islands, central Vietnam, Zootaxa 4286 (3), pp. 333-346 : 335-343

Oligodon culaochamensis sp. nov.

( Figs. 2–5 )

Holotype. ITBCZ 5646 , adult male, collected from Hon Lao , Cu Lao Cham Islands, Quang Nam Province, Vietnam; coordinates 15°56’38”N, 108°30’44”E; elevation 41 m a.s.l. by L.T. Nguyen, V.D.H. Nguyen, and S.N. Nguyen on 27 July 2016.

Paratypes. Five specimens, also collected from Hon Lao, Cu Lao Cham Islands. ITBCZ 5618 , adult females, collected on 21 July 2016, coordinates 15°56’27”N, 108°31’13”E; elevation 106 m a.s.l. ; ITBCZ 5631, adult male, collected on 24 June 2016, coordinates 15°56’40”N, 108°30’44”E; elevation 68 m a.s.l. by L.T. Nguyen, V.D.H. Nguyen, and S.N. Nguyen; ITBCZ 5655–6, two adult females, and ITBCZ 5658, a juvenile, collected in 2012 by L.T. Nguyen and H.T. Phan. ( Figs. 4 & 5 )

Diagnosis. Oligodon culaochamensis sp. nov. is distinguished from its congeners by a combination of the following morphological characters: (1) medium size in adults (TL ± 582 mm); (2) 17 or 19 dorsal scale rows at neck and midbody and 15 or 17 rows before vent; (3) LaL/TL ratio 0.218–0.219 in males, 0.166–0.169 in females; (4) ventrals 167–169 in males and 179–182 in females; (5) subcaudals 63–66 in males and 51–52 in females; (6) presubocular present; (7) 8 supralabials, fourth and fifth entering orbit; (9) 9–10 maxillary teeth, posterior three enlarged; (10) nasal divided; (11) temporal streak absent; (12) long and deeply forked hemipenes, extending to 20th subcaudal, without spines and papillae but with a prominent diagonal ridge, oblique flounces and distal calyces; (13) cloacal plate undivided; (14) 10–11+3–4 dorsal blotches; and (15) vertebral stripe on tail and anterior part of body.

Description of holotype. Adult male; head small and elongate (HW/HL = 0.579), faintly distinct from neck; body rather slender; SVL 424 mm; tail quite long (TaL/TL = 0.219), 119 mm in length; eye small with round pupil, eye diameter equal to distance between eye and nostril; snout quite pointed with a large oval nostril piercing the upper part of nasal.

Head scalation. Rostral thick and curved on to upper snout surface, visible from above, pointed posteriorly, touching nasals, internasals and first supralabial on both sides; the portion of rostral visible from above shorter than its distance from frontal; supralabials 8/8, the 4th and 5th bordering eye; 1/1 loreal; 1/1 presubocular; 1/1 preocular; 2/2 postoculars; nasal divided vertically; 2+2/2+2 temporals, anterior ones elongated; prefrontal wider than long and larger than internasal; frontal large and hexagonal, longer than wide; parietals larger than frontals, bordered laterally by the upper temporals and anteriorly by frontal, supraoculars and postoculars; 9/9 infralabials, first pair medially in contact with each other, first four in contact with anterior chin shield, the 5th largest and touching posterior chin shield; two pairs of gular scales between posterior chin shield and first ventral.

Body scalation. Dorsal scales smooth, in 17–17–15 rows; scale row reductions from 17 to 16 at ventral 135 and from 16 to 15 at ventral 141; vertebral scales similar to other dorsal scales in size and shape; ventrals 167; cloacal plate entire; subcaudals 63, all paired; terminal caudal scale forming a pointed cap.

Dentition. Maxillary teeth 9, curved posteriorly, smaller and shorter anteriorly; posterior three being enlarged ( Fig. 2 ); palatine and pterygoid teeth developed and slightly curved posteriorly.

Hemipenis. Hemipenis long with two twisted lobes, deeply forked at the level of 6th SC and tip of each organ reaching the SC 20 ( Fig. 3 ), without spines and papillae; each lobe with numerous smooth, small and oblique folds, which a deep diagonal groove interrupts; folds form smooth hexagonal calyces at the distal part of the organ ( Fig. 3 ); prominent diagonal ridge starting from in front of the forked point and extending to near the tip; diagonal ridge easily visible when pressing the tail base to evert the hemipenis ( Fig. 3 , top); surface of the ridge with calyces changes directly from the oblique folds; hemipenes becoming twisted in everted condition when water injected inside.

Coloration. In life, overall dorsal coloration brown to pinkish brown with 10 darker blotches on body and 3 on tail. Body blotches about 3–4 dorsal scales wide. Numerous scattered dorsal black spots confined to edges of the scales. Edge of each scale and intervening skin pink. Bright vertebral strip on anterior part of body and tail. A dark brown band from eye to eye through preoculars, supraoculars, frontal, prefrontals and internasals, continues over the 4th and 5th supralabials ending at lower part of the 6th supralabial. Head with another dark brown arrow-shaped marking, apex pointing forward and reaching the posterior part of frontal, backwards obliquely crossing neck and nearly reaching the 6th and 7th ventrals. Temporal streak absent. Snout, lateral and lower parts of head white. Ventral color cream to pink or reddish with black rectangular blotches. Ventral surface of tail white with black spots. Iris black and round; remaining part of the eye somewhat bicolor diagonally; anterior part with uniform color streak, posterior part mainly bright yellow. In alcohol, color becoming paler, but the pattern remains; iris white; venter cream to white with black blotches and dots, pink or reddish color disappears.

Variation. Table 1 summarizes variation in size and scalation of the holotype and five paratypes. In life, paratype ITBCZ 5618 has a pink edge on each dorsal scale and the intervening skin, as occurs in the holotype. In comparison, the edge of each dorsal scale and the intervening skin of paratype ITBCZ 5631 is white and its dorsal coloration is grey. Color in life of the other paratypes was not recorded. ITBCZ 5618 has a vertebral stripe not only on tail and anterior part of body but also on posterior part of body ( Fig. 5 A). The juvenile paratype (ITBCZ 5658, Fig. 5 D) is similar to the adults in coloration and patterned. The ventral surface of the tails of two paratypes (ITBCZ 5618 and ITBCZ 5656) are white without grey spots.

The most variable character is the number of dorsal scale rows. The paratype (ITBCZ 5655) has 17–19–17 dorsal scale rows, increasing from 17 to 18 at VS 16 and to 19 at VS 33, reducing from 19 to 18 at VS 102 and to 17 at VS 106. The paratype (ITBCZ 5656) has 19–19–17 dorsal scale rows, the first and second reductions occur at VS 105 and 110, respectively. The paratype (ITBCZ 5631) has 18–17–15 dorsal scale rows, reducing from 18 to 17 at VS 18, increasing from 17 to 18 at VS 40, from 18 to 19 at VS 42, reducing from 19 to 18 at VS 78, from 18 to 17 at VS 82, from 17 to 16 at VS 153 and from 16 to 15 at 158, and increasing from 15 to 16 near the vent at VS 162. The paratype (ITBCZ 5618) has 17–19–17 dorsal scale rows, increasing from 17 to 18 at VS 22 and to 19 at VS 24, reducing from 19 to 18 at VS 103 and to 17 at VS 105.

Hemipenis of the second male (paratype ITBCZ 5631, Fig. 4 ) is similar to that of the holotype. It also extends to SC 20 and twisted, but deeply forked at the level of 7th SC.

Natural history. All specimens were collected at night and on the ground in dry primary forests or plantations, usually near the bank of small streams. The stomach of the holotype contained two soft shell eggs (size 15 mm x 7 mm). These eggs probably belong to a snake or lizard.

Sexual dimorphism. Males have longer tails than females (male TaL/TL = 0.218–0.219 vs. 0.166–0.169), a larger size (maximal SVL = 544 mm vs. 383 mm), more subcaudals (SC 63–66 vs. 51–52) but fewer ventrals (VS 167–169 vs. 179–182).

Distribution. The new species is currently known only from Cu Lao Cham Islands, Quang Nam Province, Vietnam.

Etymology. The specific epithet culaochamensis is derived from Cu Lao Cham Islands, where the new species was discovered.

Comparisons. Based on hemipenal morphology (deeply forked, no papillae, no spines), O. culaochamensis sp. nov. is a member of the O. cyclurus group as defined and mentioned in previous publication ( Smith 1943, David et al. 2008a, 2008b; Green et al. 2010; Neang et al. 2012; Nguyen et al. 2016). Therefore, the new species differs from all congeners within the Oligodon taeniatus group ( David et al. 2008b; Neang et al. 2012; Nguyen et al. 2016), which includes O. barroni (Smith) , O. deuvei David, Vogel & Rooijen , O. moricei David, Vogel & Rooijen , O. mouhoti (Boulenger) , O. pseudotaeniatus David, Vogel & Rooijen , and O. taeniatus (Günther) , because they have obvious papillae on hemipenes, except for O. moricei in which males remain unknown; from all congeners within the O. cinereus group ( David et al. 2008a, 2012; Green et al. 2010; Neang et al. 2012; Vassilieva 2015; Nguyen et al. 2016), which includes O. albocinctus (Cantor) , O. cinereus (Günther) , O. inornatus (Boulenger) , O. joynsoni (Smith) , O. maculatus (Taylor) , O. melanozonatus Wall , O. nagao David, Nguyen, Nguyen, Jiang, Chen, Teynie & Ziegler , O. splendidus (Günther) and O. woodmasoni (Sclater) , because they do not have forked hemipenis, except for O. melanozonatus , in which the hemipenis remains unknown; from all congeners within the O. dorsalis group ( Smith 1943, Vassilieva 2015; Nguyen et al. 2016), which includes O. catenatus (Blyth) , O. dorsalis (Gray & Hardwicke) , O. eberhardti Pellegrin , O. erythrogaster Boulenger , O. hamptoni Boulenger , O. lacroixi Angel & Bourret , and O. mcdougalli Wall , because they have unforked or slightly forked hemipenis, except for O. lacroixi , in which the hemipenis is unknown; from all congeners within the O. torquatus group ( Green et al. 2010, Smith 1943, Vassilieva 2015; Nguyen et al. 2016), which includes O. cruentatus (Günther) , O. planiceps (Boulenger) , O. theobaldi (Günther) , and O. torquatus (Boulenger) , because they have unforked hemipenis with papillae. The new species can be distinguished from O. moricei , which is known from a female only, by having dorsal blotches (vs. absent), longer tail (TaL/TL = 0.166–0.169 vs 0.113), more subcaudals (51–52 vs 41), fewer maxillary teeth (9–10 vs. 12) and a presubocular (vs absent); from O. melanozonatus by having dorsal blotches (vs. cross-bars), a loreal (vs. absent), a single cloacal plate (vs. divided), more supralabials (8 vs. 6), and more subcaudals (51–66 vs. 42–45); and from O. lacroixi by having an entire cloacal plate (vs. divided), more scale rows at midbody (17–19 vs. 15), more supralabials (8 vs. 5) and a loreal (vs. absent).

Oligodon culaochamensis sp. nov. differs from other congeners in the Indochinese region ( Vietnam, Laos, Cambodia, Thailand, Myanmar, Peninsular Malaysia, and southern China [Yunnan]), except for those of the O. cyclurus group, as follows: from O. annamensis Leviton by having more dorsal scale rows (17–19 at neck and midbody and 15 before vent vs. 13–13–13), more supralabials (8 vs. 6), more maxillary teeth (9–10 vs. 8) and by dorsal color pattern (blotches vs. cross-bars); from O. arenarius by having deeply forked hemipenis (vs. unforked), a larger size (582 mm vs. 389 mm), more maxillary teeth (9–10 vs. 6–8) and more ventrals (167–183 vs. 131–144); from O. booliati Leong & Grismer by having more supralabials (8 vs. 6 or 7), more ventrals (167–182 vs. 143–153) and dorsal color pattern (blotches vs. cross-bars); from O. jintakunei Pauwels, Wallach, David & Chanhome by having more dorsal scale rows at midbody (17–19 vs. 15), fewer ventrals (167–182 vs. 189), entire cloacal plate (vs. divided) and dorsal pattern (blotches vs. cross-bars) ( Pauwels et al. 2002; Vassilieva 2015); from O. octolineatus (Schneider) by having a smaller size (582 mm vs. 780 mm), more supralabials (8 vs. 6), the 4th and 5th supralabials entering the eye (vs. SL 3rd and 4th) and dorsal color pattern (blotches vs. broad stripes); from O. purpurascens (Schlegel) by having a smaller size (TL 582 mm vs. 790 mm), portion of rostral visible from above much shorter (vs. as long as) than its distance from the frontal, dorsal color pattern (blotches vs. transverse bands or cross-bars) and the absence of temporal streak (vs. presence); and from O. vertebralis Günther by having more supralabials (8 vs. 7), SL 4th and 5th entering the eye (vs. SL 3rd and 4th), more dorsal scale rows at midbody (17–19 vs. 15), and an entire cloacal plate (vs. divided).

Oligodon culaochamensis sp. nov. differs from all other congeners within the O. cyclurus group by the combination of the following characters: maximum size, TaL/TL ratio, ventrals, subcaudals, maxillary teeth, length and shape of hemipenis, dorsal pattern and temporal streak (see Table 2).

The new species is different from O. condaoensis by having a longer tail in males (TaL/TL = 0.218–0.219 vs. 0.129–0.132) and females (0.166–0.169 vs 0.126), more subcaudals in males (63–66 vs. 37) and females (51–52 vs. 33–34), more anterior temporal (2 vs. 1), a presubocular (vs. absent), fewer maxillary teeth (9–10 vs. 11–13), different hemipenis ( LHSC = 20 vs. 13–14, presence of oblique folds and diagonal ridge vs. absent) and different dorsal color pattern (blotches vs. uniform or faint tripe); from O. cattienensis by having a longer tail in males (TaL/ TL = 0.218–0.219 vs. 0.110–0.130) and females (0.166–0.169 vs 0.110), more ventrals in females (179–182 vs. 168), more subcaudals in males (63–66 vs. 32–36) and females (51–52 vs. 32), fewer maxillary teeth (9–10 vs. 11– 12), fewer number of dorsal blotches (10–11+3–4 vs. 24–33+5), different head pattern (absence [vs. presence] of temporal streak) and different hemipenis shape (deeply forked vs. forked near the tip); from O. cyclurus (Cantor) by having a smaller size (582 mm vs. 710 mm), longer tail in males (TaL/TL = 0.218–0.219 vs. 0.127–0.156) and females (0.166–0.169 vs 0.107–0.138), more ventrals in females (179–182 vs. 168–172), more subcaudals in males (63–66 vs. 37–43) and females (51–52 vs. 30–44), a longer hemipenis ( LHSC = 20 vs. 15–18), different dorsal pattern (presence [vs. absence] of vertebral stripe on tail and anterior part of body) and different head pattern 2008a, Neang et al. 2012, Nguyen et al. 2016, Pope 1935, Smith 1943, Vassilieva et al. 2013, Wall 1923 and examined specimens. See Material and Methods for abbreviations; *, values given species, not for males or females.

(absence [vs. presence] of temporal streak); from O. fasciolatus (Günther) by having a smaller size (582 mm vs. 807 mm), fewer dorsal scale rows at neck (17–19 vs. 21–23) and midbody (17–19 vs. 21), more subcaudals in males (63–66 vs. 43–61) and females (51–52 vs. 34–48), different dorsal pattern (presence [vs. absence] of vertebral stripe on tail and anterior part of body) and different head pattern (absence [vs. presence] of temporal streak); from O. formosanus (Günther) by having a smaller size (582 mm vs. 942 mm), longer tail in males (TaL/ TL = 0.218–0.219 vs. 0.165–0.195), more subcaudals in males (63–66 vs. 49–55) and females (51–52 vs. 43–48), different hemipenis length ( LHSC = 20 vs. 15–18) and shape (short papillae absent [vs. present]), different dorsal pattern (blotches vs. reticulate) and different head pattern (absence [vs. presence] of temporal streak); from O. juglandifer (Wall) by having a smaller size (582 mm vs. 853 mm), more supralabials (8 vs. 7) and the SL 4th and 5th entering the eye (vs. SL 3rd and 4th), different dorsal pattern (blotches vs. bands, presence [vs. absence] of dorsal stripe) and different head pattern (absence [vs. presence] of temporal streak); from O. kampucheaensis Neang, Grismer & Dattry by having a longer tail in males (TaL/TL = 0.218–0.219 vs. 0.151), more dorsal scale rows at neck and midbody (17–19 vs. 15), more ventrals (167–169 vs. 165) and subcaudals (63–66 vs. 39) in males, a longer hemipenis ( LHSC = 20 vs. 11), different dorsal pattern (blotches vs. cross-bars, presence [vs. absence] of dorsal stripe) and different head pattern (absence [vs. presence] of temporal streak); from O. kheriensis Acharji & Ray by having a longer tail (TaL/TL = 0.166–0.219 vs. 0.121–0.161), fewer ventrals (167–182 vs. 196), more subcaudals (51–66 vs. 38–43), and different dorsal pattern (blotches vs. uniform and presence [vs. absence] of dorsal stripe); from O. macrurus (Angel) by having a shorter tail (TaL/TL = 0.218–0.219 vs. 0.240), more ventrals (167–182 vs. 143–152), fewer subcaudals (51–66 vs. 76–83), a shorter hemipenis ( LHSC = 20 vs. 29), dorsal pattern (blotches vs. uniform and presence [vs. absence] of dorsal stripe) and head pattern (absence [vs. presence] of temporal streak); from O. ocellatus (Morice) by having a smaller size (582 mm vs. 825 mm), a remarkably longer tail in both males (TaL/TL = 0.218–0.219 vs. 0.112–0.141) and females (TaL/TL = 0.166–0.169 vs. 0.094– 0.114), more ventrals in males (167–169 vs. 156–165), more subcaudals in both males (63–66 vs. 32–44) and females (51–52 vs. 26–33), a longer hemipenis ( LHSC = 20 vs. 15–17), dorsal pattern (presence [vs. absence] of dorsal stripe), and head pattern (absence [vs. presence] of temporal streak); and from O. saintgironsi by having a smaller size (582 mm vs. 676 mm), fewer ventrals in females (179–182 vs. 184), more subcaudals in males (63–66 vs. 55–59), a shorter hemipenis ( LHSC = 20 vs. 27–28), hemipenis shape (oblique folds or flounces vs. large calyces throughout; presence [vs. absence] of diagonal ridge) and head pattern (absence [vs. presence] of temporal streak).

Oligodon culaochamensis sp. nov. is similar to O. chinensis (Günther) in having hemipenis with oblique folds and a prominent diagonal ridge ( Pope 1935; Smith 1943). However, the new species can be distinguished from O. chinensis by having a smaller size (582 mm vs. 729 mm), longer tail in males (TaL/TL = 0.218–0.219 vs. 0.187– 0.195), fewer ventrals in both males (167–169 vs. 175–184) and females (179–182 vs. 182–206), presubocular (vs. usually no presubocular), two anterior temporals (vs. usually one), remarkably longer hemipenis (LHSC = 20 vs. 12–14), dorsal pattern (blotches vs. cross-bars) and head pattern (absence [vs. presence] of interrupted temporal streak).

Figures

FIGURE 2. HOlOtype Of Oligodon culaochamensis sp. nov., ITBCZ 5646. A, dOrsal view; B, ventral view; C, maxillary teeth; D – F, dOrsal and lateral views Of head.

FIGURE 3. Hemipenis Of hOlOtype Of Oligodon culaochamensis sp. nov., ITBCZ 5646. TOp, everted hemipenis (befOre injecting water) shOws Oblique fOlds and prOminent diagOnal ridges; middle, fully everted hemipenis after injecting water; bOttOm, hemipenis extends tO subcaudal 20.

FIGURE 4. Paratype Of Oligodon culaochamensis sp. nov., ITBCZ 5631, male. TOp, dOrsal and ventral views; middle, fully everted hemipenis after injecting water shOws Oblique fOlds, prOminent diagOnal ridges, and free terminal end with calyces; bOttOm, hemipenis extends tO subcaudal 20.

FIGURE 5. Paratypes Of Oligodon culaochamensis sp. nov., A, ITBCZ 5618, female; B, ITBCZ 5655, female; C, ITBCZ 5656, female; D, ITBCZ 5658, juvenile.