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| Oligodon speleoserpens Pawangkhanant, Poyarkov, Ward-Smith, Grassby-Lewis, Sumontha, Kliukin, Idiiatullina, Trofimets, Suwannapoom & Lee, 2024 Photos by Parinya Pawangkhanant, and Harry Ward–Smith. |
Abstract
We describe a new species of kukri snake (Oligodon Fitzinger, 1826) from the limestone karst formations of Satun and Trang Provinces in southern Thailand. Phylogenetic analyses based on three mitochondrial DNA fragments (12S–16S ribosomal rRNA and cytochrome b) recover the new species within the Oligodon cinereus species complex, where it forms a deeply divergent yet poorly supported clade sister to Oligodon saiyok Sumontha et al., 2017 and another unnamed lineage currently referred to Oligodon cinereus (Günther, 1864) from southwest Myanmar. Morphologically, the new species is distinguished from all other members of the genus by the following combination of characters: ventral scales 189–193 with distinct lateral keeling; subcaudal scales 47–54, paired; anterior dorsal scale rows 17–19, with the reduction from 19 to 17 rows occurring above the 28th–30th ventral scale when present; maxillary teeth 8, blade-like and laterally compressed; dorsum olive–gray, plain; ventral surface white anteriorly, dark gray posteriorly; underside of tail dark gray, smeared with white. We briefly discuss the natural history and conservation status of this new species and provide observations of other kukri snakes inhabiting limestone karst habitats. Our study also incorporates genetic samples of four recently described Oligodon endemic to Thailand, all of which are recovered in the O. cinereus species complex. In agreement with previous studies, we demonstrate that species-level diversity within the O. cinereus species complex is underestimated, and additional sampling is necessary to revise this taxonomically challenging clade.
Keywords: Biodiversity, molecular phylogenetics, Serpentes, Southeast Asia, systematics, taxonomy, Thai–Malay Peninsula
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| Photographs of the holotype of Oligodon speleoserpens sp. nov. (ZMMU Re-17696, adult male) (a) dorsal and (b) ventral views in life. Photographs taken by Parinya Pawangkhanant. |
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| Photographs of the holotype of Oligodon speleoserpens sp. nov. (ZMMU Re-17696, adult male) (a) right lateral, (b) dorsal and (c) ventral views of the head in life; (d) partially everted hemipenes. Photographs by Parinya Pawangkhanant (a–c), and Mali Naiduangchan (d). |
Oligodon speleoserpens sp. nov.
Diagnosis: O. speleoserpens sp. nov. is referred to the genus Oligodon based on the presence of enlarged blade-shaped maxillary teeth without a diastema, an elongate and subcylindrical body, and the presence of a large inflated rostral scale that blocks the internasal scales from contacting anteriorly (Wall 1923; Smith 1943; David et al. 2023). It is distinguished from all other Oligodon by the following combination of morphological characters: 1) head oblong-shaped with a truncated snout and slightly inflated rostral scale; 2) 8 maxillary teeth, with the posterior three teeth enlarged and blade-like; 3) dorsal scales in 19–17–15 rows (17–17–15 rows in one specimen); 4) reduction from 19 dorsal scale rows to 17 dorsal scale rows occurring at the 28th–30th ventral scale; 5) reduction from 17 dorsal scale rows to 15 dorsal scale rows occurring at the 100th–113th ventral scale; 6) cloacal plate entire; 7) 189–193 ventral scales (189–190 in male; 193 in female), distinctly keeled; 8) 47–54 paired subcaudal scales (47–54 in male; 48 in female); 9) 238–244 total body scales; 10) relative tail length 0.136–0.139 and subcaudal ratio 0.198–0.221; 11) 8 supralabials on either side of the head, with the fourth and fifth scales in contact with the orbit; 12) 9 infralabials on either side of the head with the first four scales in contact with the first pair of chin shields; 13) one loreal and one presubocular present; 14) 1+2 temporal scales; 15) dorsal color pattern uniform gray or grayish–brown without any markings or reticulations; 16) anterior half of ventral surface white with gray–brown irregularly shaped spots, posterior half immaculate dark gray, underside of tail splashed with white markings; 17) hemipenis bilobed with broad, awn-shaped lobes, simple sulcus spermaticus and smooth calyces.
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| Photographs (a) of the holotype of Oligodon speleoserpens sp. nov. (ZMMU Re-17696, adult male) in life; (b) habitat at the type locality, Tham Le Stegodon cave, Satun Province, Thailand; (c) paratype of Oligodon speleoserpens sp. nov. (ZMMU Re-17697, adult female) in life from Tham Khao Ting cave, Trang Province, Thailand; and (d) uncollected adult male specimen of Oligodon speleoserpens sp. nov. from the same locality as the paratype. Photos by Parinya Pawangkhanant (a, b), Nikolay A. Poyarkov (c), and Harry Ward–Smith (d). |
Etymology: The species epithet “speleoserpens” is a compound name combining the Latinzed Greek noun “spēlēum”, meaning “cave” and the Latin noun “serpens [= serpentis]”, the present active participle of “serpō” meaning “to crawl or creep”, often used in reference to snakes. This roughly translates to “cave crawler” or “cave serpent”, an allusion to both the type locality and the discovery of the paratype. We recommend the English common name “Cave Kukri Snake” and the Thai common name “งูปี่แก้วควนหิน” (Ngu Pi Kaew Kuan Hin) for this species.
Parinya Pawangkhanant, Nikolay A. Poyarkov, Harry Ward-Smith, Rupert Grassby-Lewis, Montri Sumontha, Nikita S. Kliukin, Sabira S. Idiiatullina, Alexei V. Trofimets, Chatmongkon Suwannapoom and Justin L. Lee. 2024. A New Species of Karst-associated Kukri Snake (Reptilia: Squamata: Colubridae: Oligodon Fitzinger, 1826) from southern Thailand. Vertebrate Zoology. 74: 359-379. DOI: 10.3897/vz.74.e112132