Oligodon cicadophagus, Pauwels & Donbundit & Sumontha & Meesook, 2025

Oligodon cicadophagus sp. nov.

( Figs. 1–5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 , 7 View FIGURE 7 ; Tables 1–2 View TABLE 1 View TABLE 2 )

Holotype. CUMZ-R-2625(field no.MS 922), adult male caught on 28October 2021 in a limestone cave (8°05’11.8”N, 98°52’39.7”E) at Sai Thai , Muang Krabi District, Krabi Province, southern Thailand, by Punya Tulyasuk. GoogleMaps

Paratype. CUMZ-R-2626 (field no. MS 921), adult male caught on 2 December 2021 at Nong Thalay (8°05’02.5”N 98°51’35.4”E), Muang Krabi District, Krabi Province, southern Thailand, by Punya Tulyasuk GoogleMaps .

Diagnosis. Oligodon cicadophagus sp. nov. can be distinguished from all other congeneric species by the combination of its maximal known SVL of 537 mm; 11 maxillary teeth; eight supralabials; one preocular and one presubocular; 17-17-15 dorsal scale rows; 159–168 ventrals and 50 subcaudals in males; a single anal; hemipenes bilobed with large broad lobes, no distinct flounced calyces and unforked sulcus spermaticus; dorsal surface of head, body and tail uniformly olive-gray, without nuchal chevron, dorsal stripes, crossbands, blotches or reticulations; and a venter cream anteriorly turning to dark gray posteriorly.

Description of the holotype. Adult male ( Figs. 1–3 View FIGURE 1 View FIGURE 2 View FIGURE 3 ). Body robust but elongate. SVL 523.7 mm; TaL 95.4 mm; TL 619.1 mm. Head short, barely distinct from the poorly marked neck. Pupil round. Tail robust, tapering, accounting for 15.4 % of the TL (619.1 mm). HL 16.9 mm; HW 10.6 mm; HD 7.4 mm. SnOrb 5.9 mm. Snout long (35 % of HL, 2.3 times as long as OrbD). OrbD 2.6 mm; OrbLip 2.5 mm; distance eye-nostril 3.5 mm. Straight distance between nostrils 4.4 mm. Distance between eyes 6.7 mm.

Body scalation. DSR 17-17-15, all smooth. DSR reduction from 17 to 15 occurs above the 104 th (left) and 106 th (right) VEN by fusion of DSR 4 and 5 (left) or 3 and 4 (right). 2 PV + 159 VEN, laterally angulated. Anal plate single. SC 50, 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. 2 View FIGURE 2 ). RosW 4.4 mm, RosH 3.7 mm. Nasals vertically divided. Nostril large, piercing middle of nasal. Two internasals, in broad contact, shorter than prefrontals. Two prefrontals, subrectangular, distinctly wider than long. Length of suture between prefrontals 2.4 times the length of suture between internasals. Frontal pentagonal, 1.2 times as long as wide; 1/1 supraoculars, distinctly longer than wide; SL 8/8, 2 nd and 3 rd in contact with LOR, 4 th and 5 th in contact with orbit, posterior four distinctly larger than the four anterior ones. LOR 1/1, distinctly longer than high. PreOc 1/1; PreSubOc 1/1; no SubOc; PosOc 2/2, the upper one slightly larger; no PosSubOc. Temporals 2+2 on each side; the anterior upper temporal small and not in contact with the posterior upper temporal. Parietals larger than the frontal, in contact on more than 2/3 of their length behind the frontal. Parietals bordered posteriorly by undifferentiated dorsal scales. Mental width 2.7 mm, mental length 1.8 mm. IL 8/9, 1 st pair in broad contact behind mental, IL 1 to 3 in contact with anterior chin shields on the left side, IL 1 to 4 on the right side. First pair of chin shields distinctly longer than 2 nd pair. Second pair of chin shields in contact with the 3 rd and 4 th IL on the left side, and with the 4 th and 5 th IL on the right side.

Maxilla dentition. Eleven MT (six teeth present + five empty sockets), increasing in size posteriorly, without diastema. Three posteriormost MT distinctly enlarged, kukri-like.

Hemipenes. Long ( Fig. 3 View FIGURE 3 ); bilobed with large broad awn-shaped lobes; no distinct flounced calyces; unforked sulcus spermaticus.

Coloration in life. Dorsal surface of the head uniformly dark olive-gray, without marks. No nuchal chevron. Lateral sides of the head olive-gray, lower half of supralabials cream. Chin and throat cream. Tongue purple brown. Dorsum and dorsal surface of the tail uniformly olive-gray, without marks or reticulations. Flanks olive-gray, turning to dark gray on the lower dorsal row. Venter cream anteriorly, progressively turning to dark gray posteriorly. Underside of tail dark gray with white blotches anteriorly, completely white posteriorly. In preservative, the dorsal color darkens, and the ventral colors become more contrasted.

Variation. Main morphometric and meristic characters of the two types are provided in Table 1 View TABLE 1 . In the paratype ( Figs. 4–5 View FIGURE 4 View FIGURE 5 ) the DSR reduction from 17 to 15 rows occurs above the 99 th (left) and 97 th (right) VEN by fusion of DSR 3 and 4. The lower anterior temporal of the paratype is very small and does not contact the posterior temporal row ( Fig. 5 View FIGURE 5 ). Similarly to the holotype, the paratype shows six MT present and five empty sockets, without diastema. Females still unknown.

Distribution and natural history. Within the cave at the type locality ( Fig. 6 View FIGURE 6 ), the holotype was caught in strict syntopy with the cave-dwelling colubrid Elaphe taeniura ridleyi (Butler) , and a few meters from the colubrid Ahaetulla prasina (Boie) and the pitviper Trimeresurus venustus Vogel. An adult individual caught at night by snake rescuers at Khao Phung Chang (8°26’32.7”N, 98°30’57.5”E) in Phang-Nga Province regurgitated a cicada nymph (Cicadoidea) (T. Butmee, pers. comm.). Unfortunately, this latter individual escaped and could not be preserved, but was photographed ( Fig. 7 View FIGURE 7 ). This snake does not seem aggressive; none of the three known individuals attempted to bite when handled. The species is so far known only from the above-mentioned three localities within Krabi and Phang-Nga provinces ( Fig. 8 View FIGURE 8 ). The Phang-Nga locality is situated about 55 km NW of the Krabi localities.

Etymology. The specific epithet is a Latinized adjective meaning “cicada eater” and refers to the unusual prey item recovered from an individual in Phang-Nga Province, Thailand. We suggest the following common names: งูปี่แก้วกระบี่ (Ngu Pi Kaew Krabi, Thai), Cicada-eating Kukri Snake (English), and Oligodon cicadophage (French) .

Comparisons with other species

Among the Oligodon species found in the southern Indochinese and Thai-Malay regions, only the following seven ones consistently show no distinct nuchal chevron, no distinct dorsal transversal pattern (bands, marked reticulations), and no dorsal or supracaudal blotches: O. booliati , O. condaoensis , O. huahin , O. inornatus , O. phangan , O. promsombuti and O. speleoserpens . It should be noted that a hatchling identified as Oligodon inornatus showed some black dorsal reticulations ( David et al. 2023).

Oligodon cicadophagus sp. nov. can be distinguished from O. booliati of Pulau Tioman (= Tioman Island) by its distinctly higher maximum known SVL (537 mm versus 389 mm), a distinctly lower TaL/TL ratio in males (0.15–0.17 versus 0.25), higher VEN number (159–168 versus 143–153), lower SC number (50 versus 54–60), higher SL number (eight versus six or seven), higher IL number (eight or nine versus seven), presence (versus absence) of a presubocular, an olive-gray (versus red) dorsum, and a cream to gray (versus dark orange) venter; from O. condaoensis from the Con Dao Islands by its higher TaL/TL ratio in males (0.15–0.17 versus 0.13), distinctly higher SC number (50 versus 33–37), presence (versus absence) of a presubocular, and olive-gray (versus dark gray) dorsum; from the western Thai O. huahin by its slightly higher TaL/TL ratio in males (0.15–0.17 versus 0.12–0.14), distinctly higher SC number (50 versus 35–41), olive-gray (versus light gray, tan or orange) dorsum, and cream to gray (versus plain white) venter.

It is distinct from the Indochinese O. inornatus by its 17 (versus 15) MSR, lower VEN number (159–168 versus 169–173), higher SC number (50 versus 31–43), presence (versus absence) of a presubocular, an olive-gray (versus dark greyish brown or reddish-brown) dorsum, and a cream to gray venter (versus c ream with rectangular dark blotches on sides; see Figs. 9 View FIGURE 9 and 10 View FIGURE 10 ). It is to be noted that the photograph of an individual from “ Thailand ” provided by David et al. (2023: 369) to illustrate Oligodon inornatus was taken at the Siam Serpentarium in Bangkok (I. Das, pers. comm.), and that its precise geographic origin is hence indeed unknown, and its taxonomic identity unverifiable.

Oligodon cicadophagus sp. nov. is readily separated from O. phangan of Phangan Island (and possibly with a wider distribution, see Pawangkhanant et al. 2024) by its distinctly higher maximum known SVL (537 mm versus 369 mm), higher SC number (50 versus 33–42), presence (versus absence) of a presubocular, 11 (versus 12) MT, olive-gray (versus light orange-brown) dorsum, and cream to gray (versus pinkish orange) venter; from the southern Thai O. promsombuti by its slightly higher TaL/TL ratio in males (0.15–0.17 versus 0.14), lower VEN number (159–168 versus 177), higher SC number (50 versus 40), single preocular (versus two), presence (versus absence) of a presubocular, 11 (versus 12) MT, olive-gray (versus blackish brown) dorsum, and venter cream anteriorly, dark gray posteriorly (versus ivory, heavily speckled with subrectangular blotches); and from the southern Thai O. speleoserpens by its higher TaL/TL ratio in males (0.15–0.17 versus 0.14), distinctly smaller maximum known SVL (537 mm versus 681 mm), 17 (versus generally 19) ASR, generally eight (versus nine) IL, distinctly lower VEN number (159–168 versus 189–193), and 11 (versus 8) MT.

Besides these species which consistently show a uniform pattern, Oligodon cinereus , pending a confirmation of its current list of subjective synonyms (see David et al. 2023) displays a variety of dorsal patterns, among them an immaculate morph, the typical “ cinereus morph”, originally described from Cambodia. This immaculate morph differs from Oligodon cicadophagus sp. nov. by its lower SC number (27–43 versus 50) and its pinkish gray or dark gray (versus olive-gray) dorsum.

As shown by recent molecular analyses, Oligodon cinereus , O. condaoensis (if distinct from the former species), O. huahin , O. inornatus , O. phangan , O. promsombuti and O. speleoserpens all belong to the Oligodon cinereus group which is widely distributed from eastern India to Sundaland ( David et al. 2023; Pawangkhanant et al. 2024; Lee et al. 2024). The hemipenes of Oligodon cicadophagus sp. nov. resemble those of other members of the O. cinereus group ( Table 2 View TABLE 2 ; Yushchenko et al. 2023a; Pawangkhanant et al. 2024).