taxonID	type	description	language	source
AE7A87925A726E4ACE96FF2F49B7FE47.taxon	description	(Figs. 3 – 4, Tables 2 – 3)	en	Nguyen, Tan Van, Harikrishnan, Surendran, Ray, Sumidh, Mohapatra, Pratyush P., Poyarkov, Nikolay A., David, Patrick (2026): First description of the male of Lycodon irwini Naveen, Zeeshan, Mirza, Choure & Chandramouli, 2025 (Squamata: Colubridae), with an updated account of the herpetofauna of the Great Nicobar Islands, India. Zootaxa 5750 (4): 482-504, DOI: 10.11646/zootaxa.5750.4.2, URL: https://doi.org/10.11646/zootaxa.5750.4.2
AE7A87925A726E4ACE96FF2F49B7FE47.taxon	materials_examined	Holotype. DOSMB 05114 (adult female), deposited in the Department of Ocean Studies and Marine Biology, Pondicherry University, Port Blair, India. Type locality: near Gandhi Nagar, Great Nicobar Island (6.810923 ° N, 93.878795 ° E WGS 84; elevation 140 m asl). Specimens examined. ZSI ANRC- 10643 (adult female, paratype), collected by S. Harikrishnan on 20 June 2008 at 1900 h near the edge of a stream in rainforest within the Great Nicobar Biosphere Reserve, approximately 1 km from Govind Nagar, Campbell Bay Tehsil, Nicobar District, Andaman and Nicobar Islands, India (7.003739 ° N, 93.882476 ° E; elevation 118 m asl). DTU 99 (juvenile male, confirmed by everted hemipenis), recorded photographically by S. Harikrishnan on 15 December 2012 on a roadside about 100 m from the type locality (7.003364 ° N, 93.881626 ° E WGS 84; alt. 125 m asl.); released immediately after examination.	en	Nguyen, Tan Van, Harikrishnan, Surendran, Ray, Sumidh, Mohapatra, Pratyush P., Poyarkov, Nikolay A., David, Patrick (2026): First description of the male of Lycodon irwini Naveen, Zeeshan, Mirza, Choure & Chandramouli, 2025 (Squamata: Colubridae), with an updated account of the herpetofauna of the Great Nicobar Islands, India. Zootaxa 5750 (4): 482-504, DOI: 10.11646/zootaxa.5750.4.2, URL: https://doi.org/10.11646/zootaxa.5750.4.2
AE7A87925A726E4ACE96FF2F49B7FE47.taxon	description	Description of the male specimen DTU 99. Body slender, distinctly laterally compressed (Fig. 3); tail comparatively long, thin, and tapering; head elongate, longer than wide, moderately flattened, and distinct from neck; snout elongate, flattened, projecting beyond lower jaw; nostrils large, dorsolateral, and round; eye large with vertical pupil. Body size. SVL 265 mm; TaL 66 mm; TL 331 mm; TaL / TL ratio 0.20. Body scalation. Dorsal scale rows 17 - 17 - 15, with posterior half of body weakly keeled; scales of vertebral row not enlarged; apical pits absent; ventrals 227; subcaudals 94, all paired; anal plate divided. Head scalation. Rostral heptagonal, wider than high, slightly visible from above; nasal single, elongate, in contact with first two supralabials, rostral, internasal, prefrontal, and loreal; internasals two, curved, slightly wider than long, in contact with rostral anteriorly, nasal, and prefrontal; prefrontals two, large, subrectangular, slightly shorter than frontal, in contact with internasals, nasals, loreal, eye, and frontal; frontal small, pentagonal, tapering posteriorly, shorter than distance from snout tip to frontal; parietals longer than wide, about equal in length to frontal, in mutual contact; supraoculars 1 / 1, distinctly wider than high, in contact with prefrontal; loreals 1 / 1, contacting eye; preoculars absent; suboculars absent; postoculars 2 / 2; temporals 1 + 2; supralabials 8 / 8, first and second contacting nasal, second and third contacting loreal, third and fifth contacting eye, seventh largest; infralabials 9 / 9, first pair in broad contact with each other, first to fifth contacting anterior chin shields; posterior chin shields equal in size to anterior ones, separated medially by a pair of small scales. Colouration in life: Dorsal surface of head glossy dark brown to purplish-black, with off-white supralabials bearing small black spots; dorsal head scales narrowly margined with whitish lines forming a faint pale reticulation (Fig. 3 A – B). A distinct white collar band, about three scales wide at the angle of the jaw and narrowing dorsally to one to one and a half scale rows, present and separated from the parietals by two scale rows. Nuchal area pale grayish white, sharply contrasting with the uniform purplish-black dorsum. Eye large, glossy black. Dorsum of body and tail uniform purplish-black, smooth and slightly iridescent, lacking any crossbands (Fig. 3 C). Ventral surface gray with off-white edges, becoming slightly lighter on the chin and throat. Variation. The available material (three adult females, one juvenile male; Table 2) shows low overall variation in scalation and colour pattern. Dorsal scale rows are consistently 17 - 17 - 15, with feebly keeled posterior dorsals; supralabials 8 (3 rd – 5 th entering orbit), infralabials 9, temporals 1 + 2, and divided cloacal plate in all specimens. Ventrals range from 223 – 238 and subcaudals from 78 – 94, with the male (227, 94, respectively) falling within the range observed in females. Colouration is remarkably uniform in both sexes (Figs. 3 – 4): head dark brown to purplish-black with a distinct pale nuchal collar, dorsum and tail glossy purplish-black without crossbands in adults and juveniles, and venter grey to greyish white with pale edges. Sexual dimorphism is generally absent or extremely limited across most species of Lycodon (e. g. Nguyen et al. 2024 a, b; 2025 b, c; Nguyen & Vogel 2025; Vogel et al. 2024, 2025). Likewise, the material available for L. irwini shows no indication of sex-related differences. The single male specimen conforms to the full range of characters observed in females; however, the small sample size precludes firm conclusions. Notably, within the L. subcinctus complex, L. irwini is exceptional in exhibiting no ontogenetic change in dorsal patterning: both juveniles and adults possess a uniform purplish-black dorsum lacking crossbands on the body and tail. In contrast, congeners such as L. neomaculatus, L. sealei, and L. subcinctus display pronounced ontogenetic variation, with juveniles bearing numerous distinct crossbands that become reduced, faint, or partially lost in adults.	en	Nguyen, Tan Van, Harikrishnan, Surendran, Ray, Sumidh, Mohapatra, Pratyush P., Poyarkov, Nikolay A., David, Patrick (2026): First description of the male of Lycodon irwini Naveen, Zeeshan, Mirza, Choure & Chandramouli, 2025 (Squamata: Colubridae), with an updated account of the herpetofauna of the Great Nicobar Islands, India. Zootaxa 5750 (4): 482-504, DOI: 10.11646/zootaxa.5750.4.2, URL: https://doi.org/10.11646/zootaxa.5750.4.2
AE7A87925A726E4ACE96FF2F49B7FE47.taxon	diagnosis	Revised diagnosis. Lycodon irwini can be distinguished from its congeners within the L. subcinctus complex by the following combination of morphological characters: medium-sized and slender body, maximum total length up to 960 mm; preocular absent, both loreal and prefrontal entering the orbit; dorsal scale rows 17 - 17 - 15; dorsal scales feebly keeled; ventrals 223 – 238; subcaudals 78 – 94, paired; supralabials 8, with the 3 rd – 5 th contacting the orbit, the 6 th largest; two postoculars; temporals 1 + 2; anal plate divided; dorsum uniformly purplish-black in both juveniles and adults without crossbands on the body and tail; venter grey (based on the data of Naveen et al. 2025, this study). A diagnostic feature that clearly separates L. irwini from other members of the complex is the absence of ontogenetic pattern change: juveniles and adults share the same uniform dark dorsum without crossbands, whereas L. subcinctus, L. neomaculatus, and L. sealei exhibit numerous distinct crossbands in juveniles that become reduced, faint, or partially lost in adults.	en	Nguyen, Tan Van, Harikrishnan, Surendran, Ray, Sumidh, Mohapatra, Pratyush P., Poyarkov, Nikolay A., David, Patrick (2026): First description of the male of Lycodon irwini Naveen, Zeeshan, Mirza, Choure & Chandramouli, 2025 (Squamata: Colubridae), with an updated account of the herpetofauna of the Great Nicobar Islands, India. Zootaxa 5750 (4): 482-504, DOI: 10.11646/zootaxa.5750.4.2, URL: https://doi.org/10.11646/zootaxa.5750.4.2
AE7A87925A726E4ACE96FF2F49B7FE47.taxon	discussion	Comparison. Naveen et al. (2025) provided only a brief comparative diagnosis for Lycodon irwini, offering limited evaluation of its differences from other members of the L. subcinctus complex. Here, we expand this comparison by integrating additional morphological characters, ontogenetic pattern considerations, and information from the newly available male specimen. This approach allows a clearer and more comprehensive assessment of how L. irwini differs from closely related congeners. Lycodon irwini can be readily distinguished from all other known congeners, except L. neomaculatus, L. sealei, L. subcinctus, and L. sidiki Wostl, Hamidy, Kurniawan & Smith, by the absence of a preocular scale and the presence of both the loreal and prefrontal scales entering the orbit (Nguyen et al. 2024 a, b, 2025 a). Morphologically, Lycodon irwini most closely resembles L. neomaculatus, L. sealei, and L. subcinctus; therefore, comparisons are made primarily with these three species. The main diagnostic characters separating L. irwini from them are summarized in Table 3 and illustrated in Fig. 5. Lycodon irwini differs from L. neomaculatus (Fig. 5 A – B) having a slightly larger female body size (maximum SVL 960 mm vs. 848 mm); a higher number of ventrals in both sexes (VEN 227 in male, 223 – 238 [mean 229.0] in females vs. 190 – 207 [mean 197.8] in males, 187 – 206 [mean 198.7] in females); a higher number of subcaudals in both sexes (SC 94 in male, 78 – 94 [mean 88.0] in females vs. 69 – 84 [mean 77.1] in males, 69 – 84 [mean 77.1] in females); and a higher combined number of ventrals and subcaudals (VEN + SC 321 in male, 304 – 330 [mean 317.0] in females vs. 263 – 290 [mean 276.0] in males, 263 – 290 [mean 276.0] in females); purplish-black dorsal coloration (vs. black-brown, black-gray, or dark chocolate); and the absence of crossbands on the body and tail in juveniles (vs. present with 16 – 27 [mean 22.4] crossbands). Lycodon irwini differs from L. sealei (see Fig. 5 C – D) by having a larger female body size (maximum SVL 960 mm vs. 697 mm); a higher tail length ratio in both sexes (TaL / TL 0.20 in male, 0.21 – 0.23 [mean 0.21] in females vs. 0.17 – 0.18 [mean 0.18] in males, 0.16 – 0.17 [mean 0.16] in females); a higher number of ventrals in both sexes (VEN 227 in male, 223 – 238 [mean 229.0] in females vs. 202 – 208 [mean 205.0] in males, 204 – 209 [mean 206.5] in males); a higher number of subcaudals in both sexes (SC 94 in male, 78 – 94 [mean 88.0] in females vs. 64 – 68 [mean 66.0] in males, 62 – 64 [mean 63.0] in females); and a higher total number of ventrals plus subcaudals (VEN + SC 321 in male, 304 – 330 [mean 317.0] in females vs. 270 – 272 [mean 271.0] in males, 268 – 271 [mean 269.5] in females); relative size of the largest supralabial scale (sixth supralabial largest vs. seventh supralabial largest); body color purplish-black (vs. black-brown or black-gray); and absence of crossbands on the body and tail in juveniles (vs. present with 9 – 11 [mean 10.0] crossbands). Lycodon irwini differs from L. subcinctus (see Fig. 5 E – F) by having a slightly larger female body size (maximum SVL 960 mm vs. 810 mm); a higher tail length ratio in females (TaL / TL 0.21 – 0.23 [mean 0.21] vs. 0.17 – 0.19 [mean 0.18]); a slightly higher number of ventrals in both sexes (VEN 227 in male, 223 – 238 [mean 229.0] in females vs. 203 – 224 [mean 211.9] in males, 206 – 223 [mean 215.7] in females); a higher number of subcaudals in both sexes (SC 94 in male, 78 – 94 [mean 88.0] in females vs. 76 – 86 [mean 80.3] in males, 68 – 80 [mean 74.5] in females); and a higher total number of ventrals plus subcaudals (VEN + SC 321 in male, 304 – 330 [mean 317.0] in females vs. 279 – 310 [mean 291.6] in males, 279 – 299 [mean 290.2] in females); relative size of the largest supralabial scale (sixth supralabial largest vs. seventh supralabial largest); purplish-black dorsal coloration (vs. blackish); and the absence of crossbands on the body and tail in juveniles (vs. present with 12 – 33 [mean 20.77] crossbands). In addition, Lycodon irwini differs from L. sidiki (endemic to Sumatra Is., Indonesia) by having the prefrontal entering the orbit (vs. not entering); temporals 1 + 2 (vs. 2 + 3); cloacal plate divided (vs. undivided); and adults with a uniform purplish-black dorsum lacking crossbands (vs. dark dorsum with narrow pale crossbars) (see Wostl et al. 2017; Nguyen et al. 2024 a).	en	Nguyen, Tan Van, Harikrishnan, Surendran, Ray, Sumidh, Mohapatra, Pratyush P., Poyarkov, Nikolay A., David, Patrick (2026): First description of the male of Lycodon irwini Naveen, Zeeshan, Mirza, Choure & Chandramouli, 2025 (Squamata: Colubridae), with an updated account of the herpetofauna of the Great Nicobar Islands, India. Zootaxa 5750 (4): 482-504, DOI: 10.11646/zootaxa.5750.4.2, URL: https://doi.org/10.11646/zootaxa.5750.4.2
