Oligodon bivirgatus Qian, Qi, Shi, Lu, Jenkins, Mo & Li 2021

Oligodon bivirgatus Qian, Qi, Shi, Lu, Jenkins, Mo & Li, 2021 Figs 13, 14, 15, 16, 17, 18, Suppl. material 1: table S 4 Vernacular name. Double Striped Kukri Snake / 双线小头蛇 (Pinyin: Shuāng Xiàn Xiǎo Tóu Shé) Chresonymy. Oligodon ornatus – Kadoorie Farm and Botanic Garden (2001): 15. Type material. Holotype. • SYNU 1907027 (adult female), collected on 13 July 2019 by T. Y. Qian and M. H. Huang. Type locality: Shangxi Nature Reserve, Hainan Province, China (18.834167°N, 110.130833°E; 319 m asl.). Paratype. • SYNU 1808001 (adult female), collected on 17 August 2018 by P. P. Li, T. Y. Qian and M. H. Huang from the same valley as the holotype (18.833611°N, 110.130556°E; 317 m asl.). Specimens examined (N = 3). China. Hainan Province. • QHU R 2024049 (Field NO. LFR 2024108; adult male), from Diaoluoshan, Lingshui Li Autonomous County, (18.6735°N, 109.8776°E; 510 m asl.), collected on 29 May 2024 by C. X. Liao; • SYS r 002952 (iNaturalist 284182249; adult male), a road-killed specimen, from Jianfengling National Forest Park, Ledong Li Autonomous County (18.7386°N, 108.8623°E; 837 m asl.), collected on 23 May 2025 by H. M. Song and S. Qi; • iNaturalist 298113949 (adult male), from Tianchi Village, Jianfengling National Forest Park, Ledong Li Autonomous County (18.73670°N, 108.85386°E; 1042 m asl.), observed on 22 June 2025 by B. Genter, released back into the wild after measurement and photography. Revised diagnosis. A medium sized Oligodon, tail moderate in relative length (TailLR 0.121 –0.164; in males 0.136 –0.164, in females 0.121 –0.131). Dorsal scales in 15–15 – 15 rows, all smooth and no reductions. Ventral scales 150–176 (150–156 in males, 173–176 in females). Cloacal plate divided. Subcaudals 33–37 (33–37 in males, 34–37 in females), paired. Total body scales 184–211 (184–193 in males, 211 in females). Subcaudal ratio 0.161 –0.192, strong dimorphism (0.179 –0.192 in males, 0.161 –0.175 in females). Maxillary teeth 8, posterior three teeth slightly enlarged and blade-like. Internasals separate from prefrontals. Loreal absent, preocular 1, presubocular absent, postoculars 2, and temporals 2 + 2. Temporolabial scale present. Supralabials 6, 3 rd – 4 th in contact with the eye. Infralabials 7 (rarely 6), first four in contact with anterior chin shields. Dorsal surface light brown or reddish brown. Two narrow, dark brown paravertebral stripes running from nuchal chevron to tail and two indistinct lateral stripes along flanks. Head plain with three dark brown markings: an ocular bar, temporal bar, and nuchal chevron. Ventral surface typically white with a lateral series of black rectangular spots and an orange red midventral streak, but also orange red with small, and indistinct cream spots laterally along the anterior third of the body. Hemipenis unilobed, simple sulcus spermaticus, spines uniformly sized, and present across entire organ. Description and variation. Based on Qian et al. (2021) and three newly examined specimens. The main morphological characters of the specimens used in this study are listed in Suppl. material 1: table S 4. Body slender, subcylindrical, broader at midbody. Head oblong, slightly distinct from neck. Snout elongate, narrowing in width in dorsal view, slightly truncate in lateral view. Eyes moderate, pupil round. Nostrils small, subelliptical, pointed laterally. Tail moderate, tapering gradually to a sharp pointed tip. Adult SVL 358–404 mm, TailL 51–70 mm, TotalL 422–465 mm. Juveniles unknown. Largest specimen an adult female (SYNU 1907027) measuring 404 mm SVL and 61 mm TailL. Largest male (SYS r 002952) measured 401 mm SVL and 63 mm TailL. Head measurements as follows (N = 4 unless stated otherwise): HeadL 14.1–14.2 mm (N = 2), HeadW 7.6–9.0 mm, SnoutL 4.3–5.1 mm, EyeD 2.1–2.3 mm, IOD 5.2–5.4 mm, IND 3.7 mm (N = 2), FrontalL 4.6 mm (N = 2), FrontalW 3.8 mm (N = 2). TailLR 0.121 –0.164 (x ̅ = 0.141 ± 0.017; N = 5), in males 0.136 –0.164 (x ̅ = 0.151 ± 0.014; N = 3), in females 0.121 –0.131 (x ̅ = 0.126 ± 0.007; N = 2). HeadW / HeadL 0.54–0.63 (N = 2), SnoutL / HeadL 0.32–0.36 (N = 2), EyeD / SnoutL 0.43–0.50, EyeD / HeadL 0.16 (N = 2), FrontalL / W 1.21–1.29 (N = 2). The type series in Qian et al. (2021) had HeadL values of 12.9–16.8 mm measured “ from snout tip to jaw angles ”, though it is unclear if the “ jaw angles ” refer to the posterior end of the dentary bone (as measured here) or the edge of the mouth. Ratios for these measurements as follows: HeadW / HeadL 0.54–0.60, SnoutL / HeadL 0.30–0.33, EyeD / HeadL 0.13–0.16. Body scalation. Dorsal scales in 15–15 – 15 rows, all smooth, no reductions. Ventral scales 150–176 (x ̅ = 162.0 ± 11.7; N = 5), in males 150–156 (x ̅ = 154.0 ± 3.2; N = 3), in females 173–176 (x ̅ = 175.0 ± 2.1; N = 2), no keeling. Cloacal plate divided. Subcaudal scales 33–37 (x ̅ = 35.0 ± 1.8; N = 5), in males 33–37 (x ̅ = 35.0 ± 2.1; N = 3), in females 34–37 (x ̅ = 36.0 ± 2.1; N = 2), paired. Total body scales 184–211 (x ̅ = 198.4 ± 12.1; N = 5), in males 184–193 (x ̅ = 190.0 ± 5.2; N = 3), in females 211 (x ̅ = 211.0 ± 0.0; N = 2). Subcaudal ratio 0.161 –0.192 (x ̅ = 0.179 ± 0.012; N = 5), in males 0.179 –0.192 (x ̅ = 0.186 ± 0.006; N = 3), in females 0.161 –0.175 (x ̅ = 0.168 ± 0.010; N = 2). Sexual dimorphism recorded for ventrals (Student’s t-test P = 0.00338) and total body scales (Student’s t-test P = 0.01980). Head scalation (Fig. 13). Rostral enlarged, inflated, triangular in dorsal profile, curved onto upper surface of snout, in contact with first supralabial, nasal, and internasals. Posterior suture of rostral obtuse angled, “ gull-wing ” shaped in dorsal profile. Nasal completely divided in type series (SYNU 1907027 and SYNU 1808001) or partially divided below nostril (QHU R 2024049, iNaturalist 298113949). Nostril situated in the anterior edge of the nasal when completely divided; when partially divided, nostril lies in the median part of the entire scale. Internasals subrectangular, paired, entire scale 1.7–1.9 times wider than long (all head scale proportions N = 2 unless noted otherwise), each blocked from contacting anteriorly by suture with rostral. Anterior and posterior internasal sutures concave. Median internasal suture 2.2–2.3 times shorter than entire scale. Prefrontals present, subrectangular, paired, entire scale 1.2 times wider than long. Median prefrontal suture 2.1–2.4 times shorter than entire scale, longer than median internasal suture. Supraoculars longer than wide, narrower than prefrontals, posterior edge wider than anterior edge. Frontal large, pentagonal, shield shaped, longer than wide, 1.3–1.5 times longer than median parietal suture. Anterior frontal suture angled, positioned in front of eye sockets. Posterior vertex of frontal bordering parietal weak obtuse angle (91–98 °). Parietals large, subrectangular, paired, in broad contact, entire scale 1.2 times longer than frontal. Parietal suture bordering supraocular and frontal weak obtuse angle (115–129 °), ray oriented posterolaterally. Parietals surrounded by 9–10 scales (N = 3; excluding postoculars). Loreal absent. Preocular 1 / 1, rectangular, higher than long. Presubocular absent. Postoculars 2 / 2, rectangular, higher than long, uppermost scale slightly larger. Temporals 2 + 2. Lower anterior temporal broad, diamond shaped, present as “ temporolabial ” scale, resulting in narrow contact between fifth and sixth supralabial. Supralabials 6 / 6, first scale smallest, fifth and sixth scale largest. First supralabial in contact with nasal, second in contact with nasal, prefrontal and preocular, third contacts preocular, third and fourth in contact with the orbit, fifth and sixth scale contact anterior and posterior temporal row. Anterior chin shields larger than posterior pair. Infralabials 7 / 7 (6 / 6 in iNaturalist 298113949), first pair in contact at midline, second scale smallest, fourth scale largest. First four scales contact anterior chin shields. Anterior chin shields subrectangular, larger than posterior. Posterior chin shields also subrectangular, in contact at midline for half their length, suture bordering gulars concave. Mental groove poorly defined, present between first infralabials and posterior chin shields. Dentition. Maxillary teeth 8 (N = 3), blade-like, anteriormost two teeth smallest, increasing in size posteriorly. Coloration in life. In life, Oligodon bivirgatus exhibits two distinct color morphs. Dorsal ground color of typical morph pale brown to pale reddish-brown (Fig. 14; Qian et al. 2021). A pair of dark brown paravertebral stripes present extending from nape to tail tip, each on dorsal scale rows 6–7 and 0.5–1.5 scales wide. Middorsal space between stripes 2.5–3.0 dorsal scales wide. Dorsal surface of head light brown. Ocular bar, temporal streak and nuchal chevron all present, each brown, slightly pale medially, bordered by dark pigment. Ocular bar positioned at posterior edge of rostral, extending across internasals, prefrontals, supraoculars, and anterior margin of the frontal, descending through the eye to partially cover the margins of supralabials 3–5. Temporal bar arises near middle of head, extending obliquely downwards from the posterior median of the frontal through each parietal, upper anterior temporal and both posterior temporals before terminating at the lateral end of the nape. Nuchal chevron present as an arrow-shaped marking beginning on the median edge of the parietals before continuing occipitally across the nape. Lateral edges of nuchal chevron continue as paravertebral stripes down the remaining body. Underside of head cream or white, mental scale grayish brown. Scattered irregular dark brown spots on the edges of the first 1–4 infralabials, or medially along gular scales. Ventral surface of body cream or white, small subrectangular black blotches present at intervals of one or two ventral scales on their lateral edges, though they may be continuous in some areas. An orange red midventral streak runs between the dark blo