Oligodon deuvei, David & Vogel & van Rooijen, 2008

David, P., Vogel, G. & van Rooijen, J., 2008, A revision of the Oligodon taeniatus (Günther, 1861) group (Squamata: Colubridae), with the description of three new species from the Indochinese Region, Zootaxa 1965, pp. 1-49 : 28-35

Oligodon deuvei spec. nov.

( Figs. 19–24)

Holotype. – MNHN 1974.1366 (adult male), from “Arboretum de Trang Bôm”, now Arboretum of Bien Hoa , Dong Nai Province, Vietnam. Collected by Sergent Poilane, July 1932.

Paratypes (11 specimens). – BMNH 1938.8 .7.35 (adult male), BMNH 1938.8 .7.36 (juvenile female), BMNH 1969.1810 , BMNH 1696.1817 , BMNH 1969.1831 (3 adult females) , “ Saigon ”, now Ho Chi Minh City, Vietnam; deposited by Malcolm A. Smith ; BMNH 1912.5 . 11.1 (adult female), “ Laos ”, deposited by F. Guitel . – MNHN 1974.1266 – 1267 (2 adult females) , “ Vietnam Sud , Région de Saïgon ”, now the vicinity of Ho Chi Minh City, southern Vietnam; deposited by Sergent Poilane, no date ; MNHN 1974.1367 (adult female) , “Arboretum de Trang Bôm”, now Arboretum of Bien Hoa , Dong Nai Province, southern Vietnam. Collected by Sergent Poilane, July 1932 ; MNHN 1985.0395 (adult female) , “ Laos: Vientiane”, collected (August 1961) and deposited by Jean Deuve. – LSUHC 07883 (adult female), Che Teal Chrum Village , Pursat Province, Cambodia .

Material (12 + 5 specimens). – All specimens examined by us belong to the type series. We also examined unpublished notes of Deuve (1985) and we consider that 5 out of the 8 specimens referred by this author to “ Holarchus taeniatus Günther ” indeed belong to Oligodon deuvei spec. nov.: SRL 43 ( 9 km South of Vientiane) , SRL 65 and SRL 195 (Tha Ngon, 25 km North of Vientiane, Vientiane Prefecture) , SRL 218 (Wattaï, 5 km West of Vientiane, Vientiane Prefecture) (4 males) and SRL 63 (Vientiane; 1 female). These specimens were included here in the variation of characters .

Diagnosis. – A species of the genus Oligodon , characterized by (1) deeply forked hemipenes, not spinose but bearing two large papillae; (2) 17 dorsal scale rows at midbody, 15 before vent; (3) 12–14 maxillary teeth, the last two strongly enlarged; (4) anal plate single; (5) head scalation complete but presubocular absent in all available specimens but one; (6) 7 (rarely 8) supralabials; (7) 8 or 9 infralabials; (8) a conspicuous, broad vertebral stripe orange, bright rusty red or pale yellow, edged with two darker faint paravertebral stripes or with more or less numerous dark dots in the paravertebral region; (9) no dorsolateral stripe or a series of dark dots; (10) 4 or 5 major markings on upper head surface: one anterior transverse blotch across the snout, sometimes a small sagittal blotch on upper head surface, often reduced to spots, two oblique streaks, directed posteriorly downwards, and one broad nuchal, arrow-shaped; and (11) branches of the oblique central streaks not reaching the ventral scales in all examined specimens.

This species differs from other species of the O. taeniatus -group by the combination of (1) 17 dorsal scale rows, (2) usually 7 supralabials, (3) a broad, often bright vertebral stripe not or barely edged with dark stripes, (4) no dorsolateral stripes, (5) body often strongly fasciated, and (6) usually no blotches on the tail.

Oligodon deuvei spec. nov. is quite close to O. barroni in scalation. It differs from the latter one by the combination of some morphological characters (see below), a higher mean number of maxillary teeth, the lack of large dorsal blotches and the presence of a broad vertebral stripe (vertebral stripe absent in O. barroni ). Specimens with a “conspicuous yellow vertebral stripe and no dorsal spots on tail” mentioned by Smith (1943: 210) under Oligodon taeniatus sensu Günther (1864) , namely with 17 DSR ( Oligodon mouhoti ), are referable to this species.

In our sample, 13 specimens show the orange or rusty brown vertebral stripe, four others, all large females from southern Vietnam and Laos, have a more subdued yellowish-brown stripe with darker dots. Only one specimen, the holotype, shows two blotches on the upper tail surface similar to those of Oligodon mouhoti . However, we could not find any other character to separate these two morphs and we consider the colour of the stripe to be variable. Specimens with the subdued yellowish-brown vertebral stripe are quite similar in pattern to Oligodon formosanus (Günther, 1872) , but these two species are easily separated by the number of MSR (19 in O. fomosanus vs. 17), the number of ventrals and subcaudals (more than 160 and 45 respectively in O. formosanus ) and different hemipenes.

Etymology. – For his major contributions to the herpetology of Laos, this species is named in honour of Mr. Jean Deuve (1918-2008). Mr. Deuve spent about 20 years in Laos where he carried out several political and military duties and conducted researches on its wildlife, especially the snakes ( Deuve, 1970).

Description of the holotype ( Figs. 19–22). – Body elongated but not especially thin; head ovoid, typical of the O. taeniatus group, short, thick, barely distinct from the thick neck; snout projecting over the lower jaw, long, rounded, amounting to 28.8 % of HL, or 1.7 times as long as diameter of eye; eye rather small, with a round pupil; tail short, thick, tapering.

SVL: 241 mm; TaL: 48 mm; TL: 289 mm; HL: 11.7 mm; ratio TaL/TL: 0.166.

Dentition. 14 maxillary teeth, the last two being strongly enlarged and blade-like.

Body scalation. DSR: 17–17–15; scales small, ovoid, all smooth. VEN: 146 (plus 2 preventrals), slightly angulated; SC: 36, all paired; anal plate entire.

Head scalation. Rostral thick, curved onto the upper snout surface, well visible from above, separating internasals by about one half of their length; nasals slightly “butterfly-shaped”, about 1.4 times as long as high, vertically divided, with the posterior part distinctly smaller than anterior one; nostril crescentic, piercing middle of nasal just in front of the division; internasals subrectangular, in broad contact, shorter than prefrontals; prefrontals subrectangular, much wider than long; frontal hexagonal, ogive-like, broad, 1.1 times as long as wide; a supraocular on each side, distinctly longer than wide, about as wide as prefrontals; two very large, subtriangular parietals, much longer than the frontal, in broad contact; 1/1 small, elongate loreal scale, in contact with the nasal; 7/7 supralabials, 1 st SL small, 2 nd and barely 3 rd in contact with the loreal, 3 rd and 4 th entering orbit, 5 th and 6 th largest; 1/1 preocular, high and narrow; no presubocular; 2/2 small postoculars; 1+2/1+2 temporals, anterior ones elongated; 8/8 infralabials, first pair in contact, IL 1–4 in contact with anterior chin shields, 5 th IL the largest.

Colouration and pattern in alcohol. The upper surface is dark reddish brown, with dorsal scales strongly edged with dark brown; a broad (vertebral row + about 1/3 of each adjacent row), pale yellow vertebral stripe extends from the neck to the tip of the tail; on each side of the vertebral stripe, numerous dark brown irregular spots every 4 to 6 scales, more rounded anteriorly; irregular blackish-brown spots scattered on the sides, not forming a stripe. Dorsally, the tail is similar to the upper body surface, with a broad and conspicuous vertebral stripe; a few scattered dark brown dots; two small, dark brown transversal vertebral blotches, one just after the level of the vent, the other one about 5 SC before the tip of the tail respectively.

The head is brownish-grey, darker than body, with small scattered dark dots; supralabials pale yellowishbrown, SL 1–4 largely dotted with brown; an irregular dark brown marking on the snout, in front of eyes, not reaching the internasals, extending downwards and backwards across the eye then downwards, to produce a short, dark, conspicuous oblique streak on SL 4; another oblique dark brown spot on SL 6; several irregular dark brown spots on the frontal and parietals; one large and broad subrectangular nuchal blotch; one large, oblique dark brown lateral streak on the side of the neck, not reaching the ventral scales; infralabials, chin and throat pale yellow ochre strongly dotted with dark brown.

The venter is pale yellow, with a row of large irregular blackish-brown blotches near the tips of the ventrals, becoming progressively larger and sometimes in contact medially in the posterior half of the body. Tail below with strong blotches, disappearing abruptly at the posterior first part of the tail.

Description and variation. – Based on 12 specimens plus 5 specimens described by Deuve (1985) which are positively identifiable. Characters are as described for the holotype, with the following variation or differences:

Morphology. Snout long, amounting to 27.3–32.1 % (x = 29.3 %, s = 1.4) of HL, or 1.7–1.9 (x = 1.8, s = 0.1) times as long as diameter of eye; tail rather short and thick.

Maximal total length known is 530 mm ( SVL 460 mm, TaL 70 mm) for a female ( SRL 63 ; not seen). The longest specimen examined by us is 353 mm long ( SVL 302 mm, TaL 51 mm; female; MNHN 1985.0395 ). The largest examined male is 333 mm long ( SVL 275 mm, TaL 58 mm; BMNH 1938.8.7.35). Ratio TaL/TL: 0.132 –0.172, with a strong sexual dimorphism (see below) .

Dentition. 12–15 maxillary teeth (x = 13.6, s = 1.1), the last two strongly enlarged and blade-like.

Body scalation. DSR: 17–17–15 rows in all specimens; scales small, all smooth. VEN: 142–163 (plus 1–2 preventrals), slightly angulate; SC: 31–47, all paired (with a weak sexual dimorphism); anal plate entire.

Head scalation. Rostral barely separating the internasals; nasals about 1.6–1.8 times as long as high, vertically divided; internasals in broad contact and much shorter than prefrontals; frontal hexagonal, 1.25–1.35 times as long as wide (x = 1.30, s = 0.03); a supraocular on each side, distinctly longer than wide, about as wide as prefrontals; 1/1 small, subrectangular loreal scale, about 1.3–1.7 times as long as high; 7/7 (in 16/ 17 specimens) or 8/8 (1/17) supralabials, 1 st SL small, usually only the 2 nd SL (in 18/34 occurrences) or 2 nd + 3 rd (in 16/34) in contact with loreal, 3 rd + 4 th entering orbit in all specimens, 5 th and 6 th largest; 1/1 preocular, high and narrow; presubocular absent in 33/34 occurrences, present but small in only 1 specimen; 2/2 small postoculars in all examined specimens; 1 (in 33/34 occurrences) or 2 (1/34) elongated anterior temporal, 2 posterior temporals; 8/8 (in 11/ 17 specimens) or 9/9 infralabials (6/17), first pair in contact, IL 1–4 in contact with anterior chin shields, 5 th IL the largest.

Colouration and pattern in alcohol (data in life according to Deuve, 1985). The upper surface is reddishbrown, reddish-grey or dark yellowish-grey (greyish-brown, reddish-brown or reddish-tan in life), with dorsal scales usually narrowly but distinctly edged with dark brown producing faint, irregular crossbars, quite strong in some specimens; scattered dark brown dots on the body; usually a broad, conspicuous pale yellow, orange, rusty red or yellowish-brown vertebral stripe (orange, rusty red or red ochre in life), sometimes dull yellowish-grey, subdued and spotted with greyish-brown in larger specimens ( Figs. 23–24), extends from the neck up to the tip of the tail; vertebral stripe edged on each of its sides either with scattered dark brown, more or less rounded spots, or, sometimes, with a faint wider dark brown or dark tan paravertebral stripe (ochre or dark reddish-brown in life) with scattered black spots on its edge, no dorsolateral stripes on the body, sometimes a series of aligned dark brown dots (dark reddish-brown in life). Tail is similar to upper body surface, with a broad vertebral stripe, sometimes edged on each side with a diffuse dark stripe which reaches the tip of the tail, often only with dark brown spots; usually no large blotches on upper surface of the tail, but present in the holotype.

The head is brownish-grey or brown, darker than the body; supralabials ivory (cream in life), edged with brown (dark brownish-red in life) or variegated with dark brown (greyish-brown in life); a total of 4 to 5 major markings on upper head surface, as follows: a more or less narrow transversal dark brown marking on the snout, just in front of eyes, extends downwards obliquely backwards across the eye down to SL 4; a short, narrow, water drop shaped, longitudinal streak on the frontal, sometimes absent or reduced to disjunct dots in some specimens; on each side, a large, oblique dark brown or blackish-brown (dark brownish-red edged with ochre in life) sagittal marking on frontal, not in contact each with the other, anterior part of parietals and posterior temporals, reaches the neck side behind the corner of the mouth but does not reach the ventral scales in all specimens; a broad, subrectangular, arrow- or heart-shaped, dark brown nuchal blotch, pointing forward. Infralabials, chin and throat cream spotted with brown or sometimes uniformly ochre-yellow with a few dark brown spots.

The venter is creamish-yellow or light grey (cream then bright pink then red posteriorly red in life), nearly uniform with a few rectangular scattered spots, or usually with a numerous, large blackish-brown subrectangular spots near both tips of ventrals; lower tail surface as venter, uniform or with subrectangular blotches in its anterior half, uniform behind.

Hemipenis (in situ; based on MNHN 1974.1366). – The hemipenis is similar to that of Oligodon taeniatus in morphology, forked opposite the 5 th or 6 th SC and reaching SC 12. On its proximal part, it is covered with calyces and with a few folds; the distal parts are smooth and entirely devoid of spines. On each branch a long, smooth papilla is present as in O. taeniatus .

Sexual dimorphism. – Clear in the three following characters: (1) difference in the ratio TaL/TL: males: 0.158 –0.172 (x = 0.165, s = 0.007); females: 0.132 –0.149 (x = 0.142, s = 0.004); (2) difference in the number of ventrals: males: 140–147 (x = 144.7, s = 3.3); females: 147–155 (x = 152.1, s = 4.3); (3) difference in the number of subcaudals: males: 36–47 (x = 41.5, s = 5.0); females: 31–38 (x = 34.6, s = 2.3). Lastly, all specimens with a broad but yellowish-brown, subdued vertebral stripes are large females, although some also have a colourful stripe.

Distribution. - Vietnam. Known only from the south of the country: provinces or district of Dong Nai (Bien Hoa; our data and specimen USNM 166984) and Ho Chi Minh District (Ho Chi Minh). – Laos. Known only from Vientiane Prefecture (Vientiane and its vicinity, Tha Ngon, and Wattaï). – Cambodia. Known only from Pursat Province (Che Teal Chrum Village). This species has been confused with O. mouhoti and its distribution is surely still largely unrecorded. We expect it to occur also in northeastern Thailand.

Biology. – This small species is terrestrial and secretive. Deuve (1970) encountered his specimens of “ Oligodon taeniatus ”, which turned out to be mostly Oligodon deuvei , during all seasons. Juvenile specimens appeared during the rainy season (July to October). According to Deuve (1985), specimens were collected at day time on the ground, under various vegetal scrapes, or in gardens. Its biology is presumed mostly similar to O. mouhoti .