Oligodon huahin, Pauwels, Olivier S. G., Larsen, Henning, Suthanthangjai, Winai, David, Patrick & Sumontha, Montri, 2017

Pauwels, Olivier S. G., Larsen, Henning, Suthanthangjai, Winai, David, Patrick & Sumontha, Montri, 2017, A new kukri snake (Colubridae: Oligodon) from Hua Hin District, and the first record of O. deuvei from Thailand, Zootaxa 4291 (3), pp. 531-548 : 532-535

Description of Oligodon huahin sp. nov.

( Figs 1–9 )

Holotype. QSMI 1501 (field number MS 602); adult male from the road 3218 to Pala-U waterfall (12.528768 N, 99.527812 E), about 2 km east of the entrance gate to Kaeng Krachan National Park , Hua Hin District, Prachuap Khiri Khan Province, peninsular Thailand; collected by H. Larsen on 20 December 2016.

Paratypes. QSMI 1502 and PSUZC 720 , adult males, same locality and collector as holotype, collected on 12 and 20 December 2016, respectively.

Diagnosis. Oligodon huahin sp. nov. can be distinguished from all other congeneric species by its maximal known SVL of 553.7 mm, 7 or 8 supralabials, 17-17-15 or 17-15-15 dorsal scale rows, 166–173 ventrals, single anal, 35–41 subcaudals, deeply forked hemipenes without spines, 6 maxillary teeth, faint to very faint striped dorsal pattern without blotches on head, nape, dorsum or belly, and ivory ventral surface.

Description of holotype. Adult male. Body robust but elongate. Head short, barely distinct from the poorly marked neck. Pupil round. SVL 454.8 mm. TaL 70.8 mm. Tail robust, tapering, accounting for 13.5 % of the TL (525.6 mm). HL 13.5 mm; HW 8.7 mm; HD 7.0 mm. SnL 5.0 mm. Snout long (37 % of HL, 2.4 times as long as ED). ED 2.1 mm.

Body scalation. DSR 17-15-15, all smooth. DSR reduction from 17 to 16 occurs on the right side above the 73rd VEN by fusion of DSR 3 and 4; from 16 to 15 on the left side above the 82nd VEN by fusion of DSR 4 and 5. One PV + 173 VEN, laterally angulated. Anal plate single. SC 41, all divided.

Head scalation. Rostral thick, curved onto upper snout surface, well visible from above, separating internasals by about one half of their length. Rostral width 3.3 mm, rostral height 2.9 mm. Nasals vertically divided, with the posterior part smaller. Nostril large, piercing top of middle of nasal. Internasals in broad contact, shorter than prefrontals. Prefrontals subrectangular, distinctly wider than long. Length of suture between internasals subequal to length of suture between prefrontals. Frontal pentagonal, 1.3 times as long as wide; 1/1 supraoculars, distinctly longer than wide; SL 8/8, 2nd and 3rd in contact with LOR, 4th and 5th in contact with orbit, 6th largest. LOR 1/1, distinctly longer than high. PreOc 1/1, tall and narrow; no PreSubOc. PosOc 2/2, the upper one larger. Tem 1+2 on each side. Mental width 2.3 mm, mental length 1.5 mm. IL 8/8, 1st pair in contact behind mental, IL 1 to 4 in contact with anterior chin shields. First pair of chin shields much longer than 2nd pair.

Dentition. Six MT, the first four progressively increasing in size posteriorly, curved backwards, sharp, the two posterior ones much enlarged, kukri-like.

Hemipenes. The hemipenes are deeply forked and lack spines ( Fig. 5 ).

Coloration in life. Dorsum surface light grayish brown, with a poorly defined brownish broad mediodorsal stripe on vertebral and adjacent rows. Some vertebral or paravertebral scales, irregularly distributed, have partly black posterior margins. No dorsolateral stripes. Upper head surface grayish brown, with faint, irregular lighter and darker markings. No interorbital dark band, no dark chevron on nape or neck, no large dark markings on head. Ventral surfaces of head, belly and tail uniformly ivory, gradually transitioning dorsally to grayish brown on the lowest dorsal scale row on body and tail, and on supralabials on head. Iris greenish golden, speckled with black. The tongue, including its forked tip, is uniformly bright red.

Variation. Table 1 presents the main meristic and morphometric characters for the type series and for four other specimens released after they were photographed and examined: ‘‘specimen 4’’ caught on 18 Dec. 2016 (12.528397 N, 99.528897 E), ‘‘specimen 5’’ caught on 21 Dec. 2016 (12.528533 N, 99.527408 E), ‘‘spec. 6’’ on 22 Dec. 2016 (12.528727 N, 99.529424 E), and ‘‘spec. 7’’ on 1st Jan. 2017 (12.528759 N, 99.527993 E). The largest known specimen has a TL of 553.7 mm. The relative tail length (TaL/TL) for the type series and other examined specimens (see Table 1) varies between 12.3 and 13.9 %. In QSMI 1502, the DSR reduction from 17 to 16 occurs on the right side above the 93rd VEN by fusion of rows 4 and 5; from 16 to 15 on the left side above the 96th VEN by fusion of rows 4 and 5. In PSUZC 720, the DSR reduction from 17 to 16 occurs on the left side above the 73rd VEN; from 16 to 15 on the right side above the 75th VEN; from 15 to 14 on the left side above the 160th VEN; all three reductions involve a fusion of the 4th and 5th DSR. The extension in situ of the hemipenis till the 14th SC has been verified in PSUZC 720 and QSMI 1502. The MT of PSUZC 720 and QSMI 1502 have been examined and are exactly similar in number and relative sizes to those of the holotype. Some of the examined specimens show a dorsal coloration identical to that of the holotype, or with faint dark brown paravertebral and lateral (DSR 3 and 4) stripes on dorsum and tail and a rusty brown vertebral stripe (see Figs. 6–7 ). PSUZC 720 and specimens 5 and 6 show dusky spots on the posterior part of the belly, but no dark subrectangular or other well defined blotches.

* On the left side the 6th SL is prevented from contacting the lip by a slight contact between the 5th and the 7th SL along the lip. ** The PreSubOc prevents the 3rd SL to contact the orbit. *** On the right side there is a contact by a point between the PreOc and the LOR, so it cannot be accounted as a PreSubOc.

Distribution and natural history. Oligodon huahin sp. nov. is currently known only from its type locality in Hua Hin District ( Figs. 10–11 ). The species has never been found in Kaeng Krachan National Park and neighboring areas in spite of nearly two decades of field research ( Pauwels et al. 2000, 2003, 2009, 2016; Pauwels & Kheowyoo 2004, Pauwels & Chan-ard 2006; Sumontha et al. 2012), but it most probably occurs within the park, at least along the road leading to Pala-U waterfall. It is also expected to occur in similar habitats in the southern parts of Phetchaburi Province, especially in southern Cha-Am, Kaeng Krachan and Tha Yang districts.

All specimens were found crossing the road in a bamboo forest between 6.15 and 7.15 PM, which indicates an activity peak at dusk. All were males, suggesting that late December corresponds to a time when males are actively looking for females. A short yearly activity peak could explain why the species had not been found so far. None of the individuals tried to bite when handled, and they only rarely stroke from a distance when disturbed, for example when photographed. Their defensive behavior included raising the tail rolled into a spiral and showing its underside ( Fig. 7 ), as is commonly observed in other members of the genus, but without everting the hemipenes (Wüster & Cox 1992). When handled they pushed their snout hard towards the skin of the hand but without biting. Most of the individuals are infested by multiple ticks (Acari, see Figs. 4 , 8 ). In addition to the seven specimens listed in Table 1, which were all caught alive, an 8th individual was found dead-on-road on 2 January 2017.

Other reptiles we found in syntopy at the type locality include Calotes versicolor (Daudin) (Agamidae) , Cyrtodactylus phetchaburiensis Pauwels, Sumontha & Bauer, 2016 , Dixonius siamensis (Boulenger) , Hemidactylus platyurus (Schneider) (Gekkonidae) , Eutropis macularia (Blyth) (Scincidae) , Ahaetulla prasina (Boie) , Boiga siamensis Nootpand and B. cyanea (Bibron in Duméril, Bibron & Duméril) , Chrysopelea ornata (Shaw) , Coelognathus radiatus (Boie) , Dryocalamus davisoni (Blanford) , Lycodon capucinus Boie in Boie , Oligodon fasciolatus (locally very common) ( Colubridae ), Naja kaouthia Lesson , Ophiophagus hannah (Cantor) (Elapidae) , Hypsiscopus plumbea (Boie) (Homalopsidae) , Psammodynastes pulverulentus (Boie) (Lamprophiidae) , Xenochrophis piscator (Schneider) (Natricidae) , Pareas carinatus Wagler and P. margaritophorus (Jan in Bocourt) (Pareatidae) , Python reticulatus (Schneider) (Pythonidae) and Trimeresurus albolabris (Gray) (Viperidae) . Syntopic amphibians we observed include Ichthyophis kohtaoensis Taylor (Ichthyophiidae) , Duttaphrynus melanostictus (Schneider) (Bufonidae) , Fejervarya limnocharis (Gravenhorst) , Limnonectes blythii (Boulenger) and L. jarujini Matsui, Panha, Khonsue & Kuraishi (Dicroglossidae) , Glyphoglossus guttulatus (Blyth) and G. molossus Günther , Microhyla fissipes Boulenger and M. heymonsi Vogt , Micryletta inornata (Boulenger) (Microhylidae) , Hylarana erythraea (Schlegel) (Ranidae) and Polypedates megacephalus Hallowell (Rhacophoridae) .

Etymology. The specific epithet is an invariable noun in honor of the administrative district where the typelocality lies and of its charming main city Hua Hin. We suggest the following common names: Ngu Ngod Hua Hin (Thai) , Hua Hin Kukri Snake (English) , Oligodon de Hua Hin (French) , Hua Hin Kukrinatter (German) .

Figures

FIGURE 1. Live holotype of Oligodon huahin sp. nov. in dorsal view. Photograph by H. Larsen.

FIGURE 2. Preserved holotype of Oligodon huahin sp. nov. in lateroventral view. Photograph by M. Sumontha.

FIGURE 3. Dorsal, left and ventral views of the head of the live holotype of Oligodon huahin sp. nov. Photographs by H. Larsen.

FIGURE 4. Dorsal, left and ventral views of the head of the live paratype of Oligodon huahin sp. nov. (PSUZC 720), showing a presubocular scale on each side. Photographs by H. Larsen.

FIGURE 5. Hemipenes of the preserved holotype of Oligodon huahin sp. nov. Photograph by M. Sumontha.

FIGURE 6. Live Oligodon huahin sp. nov. (QSMI 1502) in situ at the type locality. Photograph by H. Larsen.

FIGURE 7. Live Oligodon huahin sp. nov. (‘‘ specimen 4 ’’) in defensive posture, showing the underside of its tail. Photograph by M. Sumontha.

FIGURE 8. Dorsal, right and ventral views of the head of Oligodon huahin sp. nov. (‘‘ specimen 5 ’’), showing a multiple tick infestation. Photographs by H. Larsen.

FIGURE 9. Ventral view of the tail of Oligodon huahin sp. nov. (‘‘ specimen 7 ’’), showing the subcaudal count, the single anal and the typical immaculate ivory surface. Photograph by H. Larsen.

FIGURE 10. Geographical location of the type-locality of Oligodon huahin sp. nov. in Prachuap Khiri Khan Province, peninsular Thailand (red star), and of the first Thai record of O. deuvei in Loei Province, northeastern Thailand (blue dot). Map by W. Sodoab.

FIGURE 11. Biotope of Oligodon huahin sp. nov. at the type locality. Photograph by H. Larsen.