Oligodon pseudotaeniatus, 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: 18-23

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Oligodon pseudotaeniatus

spec. nov.

Oligodon pseudotaeniatus   spec. nov.

( Figs. 10–14)

Holotype. – BMNH 1938.8.7.37 (adult male), from “ Khorat ”, Khorat Plateau, Nakhon Ratchasima Province, Thailand. Collected and deposited by Malcolm A. Smith, October 1916.  

Paratypes (3 specimens). – BMNH 1938.8.7.38 (adult male), “ Khorat, near Bangkok ”   ; BMNH 1969.1838 (adult male), “ Bangkok ”   ; BMNH 1969.1828 (adult female), “ Siam ”; all collected and deposited by Malcolm A. Smith. All examined material belongs to the type series   .

Diagnosis. – A species of the genus Oligodon   , characterized by (1) deeply forked hemipenes, not spinose but fitted with two large papillae; (2) 17 dorsal scale rows at midbody, 15 before vent; (3) 15 maxillary teeth, the last two strongly enlarged; (4) anal plate single; (5) head scalation complete, including a presubocular in all available specimens; (6) 8 supralabials; (7) 8 or 9 infralabials; (8) a reduced pattern, with two darker longitudinal paravertebral stripes edging a faint, paler vertebral stripe, and on each side a poorly distinct dorsolateral stripe; and (9) only 3 major blotches on upper head surface: one anterior transverse marking, one frontal, and one large, straight nuchal butterfly-shaped marking across the neck, of which the lateral branches directed downwards do not reach the ventral scales.

Oligodon pseudotaeniatus   spec. nov. differs from all other members of the taeniatus   -group by the combination of the vertebral pattern of Oligodon taeniatus   but with a more subdued dorsal colour pattern, the absence of dorsolateral stripes and blotches on the tail, and only 17 dorsal scale rows at midbody.

The four type specimens do not fit either with O. taeniatus   (unless specimens with 17 DSR and a reduced pattern occur in this species) or with O. mouhoti   (unless specimens without tail blotches and a much longer tail exist in this species). Referring these four specimens to any known species would alter their diagnoses established on the basis of several tens of specimens. We hence consider these specimens with 17 DSR to belong to a distinct taxon. Smith (1943: 210), under his “ Oligodon taeniatus   ”, stated that one or both blotches of the tail may be absent, obviously referring to specimens of Oligodon pseudotaeniatus   .

Etymology. – The specific nomen is a Latin adjective formed on the basis of the adjective taeniatus   , meaning striped, by allusion to the overall similarity of this new species to Oligodon taeniatus   .

Description of the holotype ( Figs. 10–13). – Body elongated but not especially thin; head ovoid, short, thick, barely distinct from the poorly defined neck; snout projecting over the lower jaw, long, rounded, amounting to 30.8 % of HL, or 1.9 times as long as diameter of eye; eye rather small, with a round pupil; tail thick and tapering. SVL: 236 mm; TaL: 61 mm; TL: 297 mm; HL: 11.70 mm; ratio TaL/TL: 0.205.

Dentition. 15 maxillary teeth, the last two being strongly enlarged and blade-like.

Body scalation. DSR: 17–17–15 rows, all smooth; scales small, ovoid. VEN: 143 (plus 2 preventrals), slightly angulated; SC: 46, 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 1.5 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, distinctly wider than long; frontal hexagonal, ogive-like, 1.3 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 very small, elongate loreal scales, in contact with the nasal; 8/8 supralabials, 1 st SL small, 2 nd and 3 rd in contact with the loreal, 4 th and 5 th entering orbit, 6 th and 7 th largest; 1/1 preocular, high and narrow; 1/1 small 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.

Colour and pattern in alcohol. The upper surface is brownish-grey, with scales narrowly edged with dark brown; a narrow, greyish-brown vertebral stripe, edged on each of its sides with a wider darker brown (dark tan) paravertebral stripe, with only scattered black spots on its edge, extends back from the neck before fading progressively; the paravertebral stripes reach the tail; a faint but wide, greyish brown dorsolateral stripe with some scattered black dots extends up to the vent on DSR 3–4. The tail is above as the upper body surface, with a very faint vertebral stripe formed by the merging of the paravertebral stripes of the body, not edged with black; no other markings.

The head is brownish-grey, slightly darker than body, with small scattered dark dots; supralabials paler, yellowish-brown, SL 1–4 brown on their lower half; a faint, irregular, barely darker transverse 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 (top) and 5–6; another dark brown spot on SL 7; a short, elongated, longitudinal streak, constricted in its middle, on the frontal; one large darker marking straight across the neck, with the shape of a butterfly with four long “wings”, the two upper ones less distinct, reaching the middle of the parietals, the lateral ones directed straight downwards (not oblique) on the side of the neck, without reaching the ventral scales; infralabials, chin and throat uniformly pale yellow ochre.

The venter is pale yellow, with two (rarely one) irregular blackish-brown blotches near the tips of the ventrals, small, rounded and even often absent in the first quarter of the body, then progressively larger, subrectangular and more conspicuous in the posterior half. Tail below with strong blotches on its anterior half, disappearing abruptly from the middle of the tail.

Description and variation (on the basis of 4 specimens). – The most important characters of the available specimens, all belonging to the type series, appear in Table 5. All other morphological characters agree well with those described for the holotype and are not repeated here. A specimen identified by Taylor (1965: p. 776: Fig. 40) as Oligodon barroni   most likely belongs to O. pseudotaeniatus   . The few characters given for this specimen agree well with our data.

Morphology. Snout amounting to 28.5–30.8 % (x = 29.5 %, s = 0.8) of HL, or 1.6–1.9 (x = 1.7, s = 0.1) times as long as diameter of eye. The maximal total length known is 320 mm ( SVL 254 mm, TaL 66 mm) for a male ( BMNH 1969.1838). The sole examined female is 258 mm long ( SVL 222 mm, TaL 36 mm). Ratio TaL/TL: 0.140 –0.206, with a strong sexual dimorphism (see Table 5) GoogleMaps   .

Dentition. 15 maxillary teeth in all specimens, the last two being strongly enlarged and blade-like.

Body scalation. All scales are smooth. DSR: 17–17–15, without exception; scales small, ovoid. VEN: 137–156 (plus 1–2 preventrals), slightly angulate; SC: 34–46, all paired (with a strong sexual dimorphism); anal plate entire.

Head scalation. Generally as for holotype; nasals about 1.6–1.8 times as long as high; internasals much shorter than prefrontals; prefrontals subrectangular, distinctly wider than long; frontal 1.25–1.35 times as long as wide (x = 1.30, s = 0.04); 1/1 small, elongate, subrectangular loreal scale, about 1.4–1.5 times as long as high; 8/8 supralabials, 2 nd and 3 rd in contact with loreal, 4 th and 5 th entering orbit, 6 th and 7 th largest; 1/1 preocular, high and narrow; 1/1 small presubocular; 2/2 small postoculars in all examined specimens; 1/1 elongated anterior temporal in all specimens, 2/2 posterior temporals; 8/8 (in 2 specimens) or 9/9 infralabials, first pair in contact, IL 1–4 in contact with anterior chin shields.

The colouration and pattern are more or less as described in the holotype (see Fig. 14). In BMNH 1946.8.7.38 the pattern is similar to that of Oligodon taeniatus   , with distinct but subdued paravertebral stripes. Hemipenis (in situ). – It is similar to the Oligodon taeniatus   organ. Distribution. – Thailand. Currently endemic to this country and known from the provinces of Nakhon Ratchasima (Khorat), Bangkok (examined material), and Saraburi (Muak Lek; Taylor [1965: 776, as O. barroni   ]). Biology. – No data but presumed to be similar to Oligodon taeniatus   .