Lycodon duytan Nguyen, Poyarkov & Vogel, 2025, sp. nov.

Lycodon duytan sp. nov. Table 2, Fig. 5; Suppl. material 1: table S 1, fig. S 14 Type material. Holotype: • DTU [Duy Tan University, Da Nang, Vietnam] 540 (adult male) collected on 19 April 2018 by TVN in Khe Choang Areas within Pu Mat National Park, Chau Khe Commune, Con Cuong District, Nghe An Province, Vietnam (ca 18.964811°N, 104.651873°E; altitude 550 m asl). Paratypes (n = 4): • DTU 541 (adult female), same information with holotype; DTU 542 (adult female) in Vu Quang NP, Huong Quang Commune, Vu Quang District, Ha Tinh Province, Vietnam (ca 18.264117°N, 105.435481°E; altitude 540 m asl), collected in March 2019 by TVN and T. C. Thai; • DTU 543 –544 (adult females), collected from Mac Area within Cuc Phuong NP, Cuc Phuong Commune, Nho Quan District, Ninh Binh Province, Vietnam (ca 20.268796°N, 105.689175°E; altitude 215 m asl), collected in June 2018 by T. N. La and TVN. Referred materials (n = 6). CPNP NHQ.225 (adult female) and CPNP NHQ.240 (adult female), collected from Cuc Phuong NP, Cuc Phuong Commune, Nho Quan District, Ninh Binh Province, Vietnam. CPNP NHQ.2017.18 (adult female), collected from Cuc Phuong NP, Thanh Yen Commune, Thach Thanh District, Thanh Hoa Province, Vietnam (ca 20.288652°N, 105.584416°E; altitude 150 m asl) collected on 26 August 2017 by Q. H. Nguyen. SIFASV 104 and 105 (two adult females, released), collected from Pu Mat NP, Con Cuong District, Nghe An Province, Vietnam, in May 2017 by Q. S. Nguyen. SIFASV 106 (adult female, released), collected from Nam Dong NR, Quan Hoa District, Thanh Hoa Province, Vietnam, in May 2023 by N. V. Ha and TVN. Diagnosis. A larger-sized species, with a maximum snout-vent length of up to 980 mm; loreal usually contacting the eye; dorsal scale rows 17–17 – 15; upper four or five and vertebral dorsal scale rows keeled; 217–230 ventrals; 80–95 subcaudals, paired; cloacal plate undivided; eight supralabials with 3–5 touching the eye; 1 preocular, 2 postoculars; temporals 2 + 2; dorsal crossbands narrow, separating ground colour into ellipse patches, pinkish-orange colour, 54–72 crossbands on body and tail; head black, the plates conspicuously margined with pinkish-orange; venter reddish-orange. Description of the holotype (see Fig. 5): The body is robust and slightly laterally compressed. The tail is relatively long, thin, and tapering. The head is elongate, longer than wide, and moderately flattened, with a distinct separation from the neck. The snout is elongated, flattened, and projects slightly over the lower jaw. The nostrils are relatively large, positioned dorsolaterally, and round in shape. The eyes are relatively large, with vertical pupils. Body size. SVL 890 mm, TaL 223 mm; ratio TaL / TL 0.200. Body scalation. Dorsal scale rows 17–17 – 15, the five upper rows feebly keeled; scales of the vertebral row not enlarged; no apical pit detected; 229 ventrals; 94 subcaudals, all paired; cloacal plate undivided. Head scalation. Rostral heptagonal, wider than high, slightly visible from above; nasal single, elongated; nasal surrounded by the first two supralabials, rostral, internasal, and prefrontal; internasals two, curved, slightly wider than longer, in contact with rostral anteriorly, nasal, and prefrontal; prefrontals two, large, subrectangular, prefrontal length slightly shorter than frontal length; prefrontals in contact with internasals, nasals, preoculars, and frontal; frontal rather small, pentagonal, tapering posteriorly, shorter than the distance from tip of snout to the frontal; parietals longer than wide, in contact approximately the length of the frontal; 1 / 1 supraocular, distinctly wider than high, in contact with prefrontal; 1 / 1 loreal, not contacting with the eye; 1 / 1 preocular, slightly large, higher than wide, in broad contact with prefrontal; subocular absent; 2 / 2 postoculars; 2 + 2 temporals; 8 / 8 supralabials, first and second in contact with nasal, second and third in contact with loreal, third and fourth in contact with eye, sixth largest; infralabials 9 / 9, first pair in broad contact with each other, first to fifth in contact with anterior pair of chin shields; posterior chin shields equal anterior ones, separated from each other by a small pair of scales. Colouration in preservative: The dorsum is blackish-brown, with 49 narrow pale-coloured crossbands on the body and 23 on the tail. Each pale-coloured body crossband is approximately one dorsal scale wide, interconnecting to divide the ground colour into elliptical patches. The ventral surface of the body is uniformly cream, while the ventral surface of the tail is heavily speckled with dark markings. The head is black, featuring a distinct inverted V-shaped marking on the nape. Pale stripes extend downward from the top of the temporal scales to the last supralabial scale. Variation (Table 2, Suppl. material 1: table S 1, fig. S 14). The type series is generally similar to the holotype in terms of body proportions and colouration, with only slight variation observed. All examined specimens of Lycodon duytan sp. nov. from geographically distinct localities in north-central Vietnam (Nghe An, Ha Tinh, Thanh Hoa, and Ninh Binh provinces) exhibit consistent diagnostic features, including the presence of four or five keeled midbody dorsal scale rows, a high number of ventral and subcaudal scales (VEN 217–230; SC 80–95), and narrow, pinkish-orange crossbands on the body and tail. Intraspecific variation was minimal. The number of total crossbands (BB + TB) ranged from 54 to 72. The loreal scale was in slight contact with the eye in seven of ten specimens, likely reflecting minor individual variation or asymmetry. No notable variation was observed in body proportions or overall colour pattern across the examined specimens. The dorsal surface is blackish, with 38–49 narrow pinkish-orange crossbands on the body and 14–24 on the tail; these bands interconnect, dividing the ground colour into elliptical patches. The ventral surface of the body is uniformly pale pink, while the tail’s underside exhibits variable dark speckling. The head is black, with a distinct inverted V-shaped marking on the nape and pale stripes extending from the top of the temporal region to the last supralabial. The overall morphological uniformity across multiple localities and habitats supports the recognition of Lycodon duytan sp. nov. as a distinct and geographically cohesive lineage. Etymology. The species name is derived from the Duy Tan Modernisation Movement (Phong trào Duy Tân) of 1906–1908 in Vietnam, a significant historical reform movement for the modernisation of the country and the society. The specific epithet also acknowledges Duy Tan University, the institution affiliated with the first author, which provided support for this research. We recommend the following common names for this species: Duy Tan Wolf Snake (in English); Duy Tan Grosszahnnatter (in German); R ắn khuy ết Duy Tân (in Vietnamese); Южный краснопоясный волкозуб “ Yuzhnyi krasnopoyasnyi volkozub ” (in Russian). Comparison. Lycodon duytan sp. nov. differs from all known congeners by the unique combination of the following characters: a large body size (maximum SVL up to 980 mm); 4–5 keeled dorsal scale rows at midbody (vs smooth or only weakly keeled in most species); a high number of ventral and subcaudal scales (VEN 217–230; SC 80–95); 54–72 narrow pinkish-orange crossbands on the body and tail, which interconnect to divide the ground colour into elliptical patches; and a uniformly reddish-pink ventral surface. These features clearly distinguish Lycodon duytan sp. nov. from L. rufozonatus, L. walli stat. nov., and other members of the L. rufozonatus – paucifasciatus species complex, including L. anakradaya Nguyen, Duong, Wood & Grismer, L. cardamomensis Daltry & Wüster, L. paucifasciatus Rendahl in Smith, L. poyarkovi Nguyen & Vogel, L. rosozonatus (Hu & Zhao), and L. gibsonae Vogel & David. These species are all medium to large-sized snakes (total length ≥ 600 mm) sharing superficially similar coloration patterns, namely red or pinkish crossbands on a dark background and an inverted V-shaped marking on the nape, but differ from Lycodon duytan sp. nov. in key morphological traits. Given these similarities, detailed comparisons with these eight species are provided below. Lycodon duytan sp. nov. is morphologically very similar to L. rufozonatus but can be distinguished by the following characteristics: a higher number of ventral scales (VEN 217–230, mean 225.1 vs 186–216, mean 199.60), a greater number of subcaudal scales (SC 80–95, mean 88.11 vs 60–88, mean 74.30), and the presence of 4 or 5 keeled scale rows at midbody (vs all dorsal scales smooth). Lycodon duytan sp. nov. differs from L. anakradaya (data from Nguyen et al. 2022), L. cardamomensis (data from Do et al. 2017; Nguyen and Vogel 2025), and L. paucifasciatus (data from Smith 1943; Nguyen and Vogel 2025) by having: pale crossbands on the dorsum and tail that link with each other and separate the ground colour of the body into ellipse-shaped patches (vs separate with each other); a higher number of BB + TB in both sexes (54–72 vs 15–26); and crossbands on the dorsum and tail that are narrow ~ 1.0–1.5 dorsal scales wide along the vertebral scale row (vs wide, ~ 3.0–5.0 dorsal scales). Lycodon duytan sp. nov. differs from L. poyarkovi (data from Nguyen and Vogel 2025) by having: much bigger size in both sexes (max SVL 890 mm in males, 980 mm in females vs 536 mm in males, 675 mm in females); pale crossbands on the dorsum and tail linked with each other and separate the ground colour of the body into ellipse-shaped patches (vs separate with each other); a higher number of BB + TB in both sexes (54–72 vs 31–47); and crossbands on the dorsum and tail narrow, ~ 1.0–1.5 dorsal scales wide along the vertebral scale row (vs slightly wide, ~ 2.0–2.5 dorsal scales). Lycodon duytan sp. nov. differs from L. rosozonatus (data from Nguyen and Vogel 2025) by having: smaller