Oligodon promsombuti Pauwels & Thongyai & Chantong & Sumontha 2021, sp. nov.
Creators: name: Pauwels, Olivier S. G.
name: Thongyai, Kanokorn
name: Chantong, Pajapon
name: Sumontha, Montri
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Reptilia
Squamata
Colubridae
Oligodon
Oligodon promsombuti

description: Description of Oligodon promsombuti sp. nov.
(Figs 6–8)
Holotype. QSMI 1508 (field number MS 710); adult male found at the foot of Khao Phanom Wang (= Phanomwung; ca. 9°05’35.3”N, 99°36’30.9”E), a limestone hill in Kanchanadit District, Surat Thani Province, peninsular Thailand; collected by Saksit Promsombut and Kanokorn Thongyai on 28 January 2017.
Diagnosis. Oligodon promsombuti sp. nov. can be distinguished from all other congeneric species by a combination of its maximal known SVL of 552.7 mm; 12 maxillary teeth, the posterior three enlarged; two internasals; two prefrontals; eight supralabials; loreal present; two postoculars; 17-17-15 dorsal scale rows; 177 ventrals and 40 divided subcaudals; a single anal; deeply forked hemipenes lacking spines; dorsal color blackish brown with nearly indistinct paravertebral stripes; no dorsal or supracaudal blotches or crossbars; background color of belly ivory, heavily speckled with subrectangular blackish blotches.
Description of holotype. Adult male. Body robust but elongate. SVL 552.7 mm; TaL 86.9 mm. Tail robust, tapering, accounting for 13.6 % of the TL (639.6 mm). Pupil round. Head short (HL 18.3 mm, i.e. 3.3 % of SVL; HW 11.2 mm; HD 8.4 mm), barely distinct from the poorly marked neck. SnL 6.3 mm. Snout long (34 % of HL, 2.5 times as long as ED). ED 2.5 mm; ELip 2.6 mm; distance eye-nostril 3.3 mm. Straight distance between nostrils 4.6 mm. Distance between eyes 7.4 mm.
Body scalation. DSR 17-17-15, all smooth. DSR reduction from 17 to 15 occurs above the 105 th VEN (left) and 106 th VEN (right) by fusion of DSR 3 and 4. 2 PV + 177 VEN, laterally angulated. Anal plate single. SC 40, all divided.
Head scalation. Rostral thick, curved onto upper snout surface, well visible from above, separating internasals by about one half of their length (Fig. 7B). RosW 4.1 mm, RosH 3.9 mm. Nasals vertically divided, with the posterior part smaller. Nostril large, piercing top of middle of nasal (Fig. 7A). Two internasals, in broad contact, shorter than prefrontals. Two prefrontals, subrectangular, distinctly wider than long, partly separated posteriorly by a triangular anterior projection of the frontal. Length of suture between internasals (1.2 mm) about twice the length of suture between prefrontals. Frontal octagonal, 1.3 times as long as wide; 1/1 supraoculars, distinctly longer (4.7/ 4.1 mm) than wide (2.5/ 2.7 mm); SL 8/8, 2 nd and 3 rd in contact with LOR, 4 th and 5 th in contact with orbit, posterior three distinctly larger than the five anterior ones. LOR 1/1, distinctly longer than high. PreOc 2/2, the upper one much taller on each side; no PreSubOc (the lower PreOc is in contact with the loreal, so it cannot be regarded as a PreSubOc); no SubOc. PosOc 2/2, the upper one larger. Tem 1+1+2 on each side. Parietals length 5.6/ 5.7 mm; parietals larger than the frontal, in contact on 2/3 of their length behind the frontal. Parietals bordered posteriorly by undifferentiated dorsal scales. Mental width 2.7 mm, mental length 1.3 mm. IL 8/8, 1 st pair in contact behind mental, IL 1 to 4 in contact with anterior chin shields. First pair of chin shields much longer (4.1/ 4.4 mm) than 2 nd pair (2.4/ 2.2 mm). Second pair of chin shields in contact on each side with the 4 th and 5 th IL.
Maxilla dentition. Twelve MT, the three posterior ones enlarged, kukri-shaped; no obvious diastema. Hemipenes. Both hemipenes of the holotype were everted (Fig. 7D). They are bilobed and deeply forked at the level of the 5 th SC. Sulcal surface mostly smooth. Distal ends of hemipenial lobes with small calyces. Spines absent. Hemipenes tip reaching SC 13; hemipenes possibly not fully everted.
Coloration in life. Dorsal surface of the head blackish brown, with poorly contrasted, difficult-to-see darker marks: an interorbital transversal bar and a chevron pointing forward whose apex is on the middle of the frontal, extending backwards on each side of the neck. The lateral sides of the head are blackish brown, slightly lighter on the lower parts of the supralabials. The dorsum is blackish brown. Two paravertebral stripes, near-invisible as they are just very slightly darker than the background color, each less than two dorsals wide, begin on the nape and run along the dorsum. Uniformly dark pink tongue. The ventral color of the head, belly and tail is ivory, but a large proportion of the ventrals and subcaudals have their left or right side, or sometimes both, of the same color as the dorsum, giving a checkered appearance. Only the anteriormost part of the throat and the underside of the tail tip are uniformly ivory without dark marks. In preservative, the general color lightens, the cephalic marks become very difficult to see, and the dorsal vertebral stripes nearly disappear; the contrasted ventral pattern remains.
Variation. A second adult individual was encountered in Na Yong District (ca. 7°31’51.5”N, 99°47’35.7”E), central-eastern Trang Province (Fig. 8), but was not preserved. Photographs of the left side of the head of this individual alive showed the same scalation features as in the holotype, except that the lower PreOc is not in contact with the LOR, so it should be rather regarded as a PreSubOc; the frontal lacks a triangular anterior projection, and is thus pentagonal (the shape of the anterior part of the frontal of the holotype is probably an abnormality). Live coloration is similar to the holotype.
Distribution and natural history. Oligodon promsombuti sp. nov. is currently known only from its type-locality in the Kanchanadit District of Surat Thani Province (Fig. 9) and in the Na Yong District of the adjacent Trang Province. In spite of intensive surveys in the whole Thai peninsula since more than two decades, we never found other individuals of the new species. We believe that it is associated to limestone hills (Fig. 10) and restricted to the Nakhon Si Thammarat Mountain Range. Other squamates found in the immediate surroundings on the hill at the type-locality include Cnemaspis chanardi Grismer, Sumontha, Cota, Grismer, Wood, Pauwels & Kunya, Cyrtodactylus lekaguli Grismer, Wood, Quah, Anuar, Muin, Sumontha, Ahmad, Bauer, Wangkulangkul, Grismer & Pauwels (an individual from this locality was illustrated by Grismer et al. 2012: 19, 21) and C. zebraicus (Taylor), Gehyra mutilata (Wiegmann), Gekko gecko (Linnaeus) (Gekkonidae), Elaphe taeniura ridleyi (Butler) (Colubridae) and Trimeresurus venustus Vogel (Viperidae). The two known individuals of Oligodon promsombuti sp. nov. were kept in captivity in Thailand and refused any food. They were not aggressive and could be easily handled (Fig. 8). We have never seen Oligodon promsombuti sp. nov. in the pet trade, and its dull color will probably preserve it from animal dealers. The two known localities are situated at proximity to three protected areas, Namtok Sikhit, Tai Rom Yen and Khao Pu-Khao Ya national parks, where it should be searched.
Etymology. The specific epithet is a mark of friendship to Saksit Promsombut, one of the collectors of the holotype. We suggest the following common names: Ngu Pee Kaew Surat Thani (Thai), Surat Thani Kukri Snake (English), Oligodon de Surat Thani (French), and Surat Thani Kukrinatter (German).
Comparisons of Oligodon promsombuti sp. nov. with other species. By its possession of a single anal plate, Oligodon promsombuti sp. nov. is readily distinguished from the following species which show a divided anal plate: O. catenatus, O. cruentatus, O. dorsalis, O. eberhardti, O. jintakunei, O. mcdougalli, O. planiceps and O. theobaldi. Its 17 MSR easily separate it from Oligodon annamensis (13), O. catenatus (13), O. cyclurus (19), O. dorsalis (15), O. eberhardti (13), O. fasciolatus (21), O. inornatus (15), O. jintakunei (15), O. kampucheaensis (15), O. mcdougalli (13), O. ocellatus (19), O. planiceps (13), O. purpurascens (19 or 21), O. rostralis (15), O. taeniatus (19) and O. vertebralis (15). The absence of a prominent striped pattern separates it from Oligodon arenarius, O. catenatus, O. condaoensis, O. cruentatus, O. deuvei, O. dorsalis, O. huahin, O. mcdougalli, O. moricei, O. mouhoti, O. octolineatus, O. pseudotaeniatus, O. taeniatus and O. vertebralis. Lacking a blotched, banded and/or reticulated pattern makes Oligodon promsombuti sp. nov. is distinguishable from O. annamensis (banded), O. barroni (blotched), O. booliati (banded), O. cattienensis (blotched), O. cruentatus (reticulated), O. cyclurus (reticulated/blotched), O. fasciolatus (reticulated/blotched), O. jintakunei (banded), O. joynsoni (reticulated/banded), O. kampucheaensis (banded), O. moricei (striped and reticulated), O. mouhoti (two blotches above tail), O. ocellatus (reticulated/blotched), O. planiceps (reticulated), O. purpurascens (blotched/reticulated), O. rostralis (blotched/reticulated), O. saintgironsi (blotched/reticulated), O. saiyok (banded/blotched), O. signatus (blotched/banded) and O. vertebralis (blotched). The VEN number of Oligodon promsombuti sp. nov. (177) is distinctly higher than in O. arenarius (131 – 144), O. barroni (136 – 160), O. booliati (143 – 153), O. deuvei (140 – 155), O. kampucheaensis (164), O. macrurus (139 – 162), O. mouhoti (145 – 163), O. planiceps (132 – 145), O. pseudotaeniatus (137 – 156), O. rostralis (167), O. signatus (141 – 157), O. taeniatus (142 – 165) and O. vertebralis (136 – 154), and distinctly lower than in O. jintakunei (189), O. joynsoni (186 – 198) and O. mcdougalli (199). Its bifurcate hemipenes put Oligodon promsombuti sp. nov. apart from the following among the above listed species for which hemipenes are known to be unforked: O. arenarius, O. catenatus, O. cinereus, O. cruentatus, O. inornatus, O. joynsoni, O. mcdougalli, O. octolineatus, O. planiceps, O. purpurascens, O. signatus, O. theobaldi and O. vertebralis (hemipenes unknown in O. booliati, O. eberhardti, O. jintakunei, O. moricei and O. saiyok). With its 12 MT, Oligodon promsombuti sp. nov. is distinguished from O. annamensis (8), O. arenarius (6 – 8), O. catenatus (7), O. cattienensis (8 – 10), O. cruentatus (14 – 16), O. cyclurus (9 – 10), O. dorsalis (6 – 7), O. eberhardti (7), O. fasciolatus (9 – 10), O. huahin (6), O. jintakunei (6), O. kampucheaensis (11), O. macrurus (13), O. mcdougalli (6), O. mouhoti (14 – 16), O. ocellatus (9 – 11), O. octolineatus (9 – 10), O. planiceps (10), O. pseudotaeniatus (15), O. purpurascens (9 – 10), O. rostralis (6), O. saiyok (13), O. signatus (7 – 8), O. taeniatus (14 – 17), O. theobaldi (15 – 16) and O. vertebralis (8 – 9) (number of MT unknown in O. booliati).
Oligodon promsombuti sp. nov. can be distinguished from O. phangan sp. nov. described above by its larger size (SVL 553 mm vs. 358 mm), its higher VEN number (177 vs. 163 – 166), its two PreOc, or one PreOc with one PreSubOc (vs. one PreO and no PreSubOc), its darker dorsal coloration, and its ivory belly with numerous subrectangular blackish blotches (vs. pinkish-orange belly without such blotches).
description: Published as part of Pauwels, Olivier S. G., Thongyai, Kanokorn, Chantong, Pajapon & Sumontha, Montri, 2021, Two new Kukri Snake species (Colubridae: Oligodon) from the Nakhon Si Thammarat Mountain Range, and addition of O. ocellatus to the fauna of Thailand, pp. 537-557 in Zootaxa 4908 (4) on pages 545-549, DOI: 10.11646/zootaxa.4908.4.7, http://zenodo.org/record/4447253