Ahaetulla rufusoculara Lam & Thu & Nguyen & Murphy & Nguyen 2021, sp. nov.

Ahaetulla rufusoculara sp. nov. Holotype. ITBCZ 7504, adult male, collected from My Phuoc Forest, My Tu District, Soc Trang Province, Vietnam; coordinates 9.56670 oN, 105.74772 oE; elevation 2 m a.s.l. by S.N. Nguyen and N.Q. Lam, on 31 December 2019 (Figs. 2 & 3). Paratypes. Five specimens: ITBCZ 7502, ITBCZ 7503, ITBCZ 7505 (subadult females) and ITBCZ 7506 (subadult male), also collected from My Phuoc Forest by the same collectors, on the same date and site as the holotype; ITBCZ 6799 (adult male) collected on 25 July 2018 by N.Q. Lam at the same site as the holotype (Figs. 4 & 5). Diagnosis. Ahaetulla rufusoculara sp. nov. is distinguished from all of its congeners by a combination of the following morphological characters: bright red eyes; medium size in adult (largest TL 1085 mm in male); snout without dermal appendage, more than two times as long as the eye diameter in adult (SnL/ED 2.33–2.37); internasal separated from supralabial by loreal; body scale rows 15-15-13; tail long (TaL/TL ratio 0.34–0.35 in males and 0.31–0.32 in females); ventrals 186–190 in males and 182–185 in females; subcaudals 143–153 in males and 128 or 129 in females; 8 (rarely 9) supralabials, fourth and fifth or fourth to sixth entering orbit; 12–14 maxillary teeth; hemipenis short, reaching 6 th or 7 th SC; cloacal plate divided; dorsum bright green; and yellow or white stripe along lower flank. Description of holotype. Adult male; head elongate and triangular (HL/HW = 2.68), distinct from neck; body elongate and compressed; SVL 682 mm; tail long (TaL/TL = 0.35), 370 mm in length; eye small, pupil horizontal, eye diameter much shorter than snout length (SnL/ED: 2.33); snout pointed without dermal appendage. Head scalation. Dorsal head scales smooth, abutting along midline rather than overlapping (Fig. 2); rostral directed forward and upward, well visible from above, touching nasals, internasals and 1 st supralabial on both sides; supralabials 8/8, 4 th, and 5 th bordering eye; 3/3 loreals; 1/1 presubocular; 1/1 enlarged preocular; 2/2 postoculars; nostril in posterior part of an elongated nasal; 2+2/2+2 temporals, with a very small scale on left side bordered by anterior temporals and postoculars; internasals longer than wide (3.0 mm in length and 1.9 mm in width), separated posteriorly from supralabials by two loreals on both sides; prefrontal bending down sharply at canthus, strongly convex, longer than wide (4.3 mm long and 2.7 mm wide), larger than internasal; frontal longest (7.6 mm long and 4.4 mm wide), widened anteriorly and much narrowed posteriorly; parietals shorter but slightly wider than frontal (6.9 mm long, 4.5 mm wide), bordered laterally by upper temporals and postocular and anteriorly by frontal and supraoculars; 9/9 infralabials, first pair medially in contact with each other, first four in contact with anterior chin shield, 5th largest and touching posterior chin shield; posterior chin shields longer than anterior ones; four pairs of gular scales between posterior chin shield and 1st ventral. Body scalation. Dorsal scales smooth, in 15-15-13 rows, lateral scales disposed obliquely, vertebral scale row slightly enlarged; scale row reduction from 15 to 13 at ventrals 149 and 150 by fusing the second and third rows of body scales on both sides; scales of sacral region strongly keeled and keel usually broken into tubercles (Fig. 3C); ventrals 190; cloacal plate entire; subcaudals 153, all paired; terminal caudal scale forming a pointed cap. Dentition. Maxillary teeth 12, forming two groups separated by a diastema: anterior group with 6 teeth, gradually enlarged posteriorly, other group with 6 teeth, first four small, last two grooved and suddenly enlarged. Hemipenis. Hemipenis short and unforked, reaching 6 th SC, with three main distinct areas: distal end papillate calyces; central part spinose with some enormous spines; and proximal area of longitudinal folds with minor scattered spines. Sulcus spermaticus sunken, not forked (Fig. 3D–F). Coloration. In life, dorsal and lateral parts of body and tail purely green; upper part of head purely green, upper lips, rostral and posterior part of canthus yellow; lower part of head yellow posteriorly and white anteriorly, except for part of 1st left and 2nd right infralabials, which are yellow; iris red; about one-third of venter yellow, gradually changing to green on remaining two-thirds of venter; ventral side of tail green; pair of longitudinal yellow parallel lines on outer margin of ventrals, extending to anterior part of tail; interstitial skin black and white, forming oblique bars, black one being fewer in number and more or less forming oblique bands when skin expanded (Figs. 2 & 3). In preservation, color faded but pattern remained: iris white; two parallel lines changing to white; all yellow parts becoming white; green faded to grey or dark brown. Variation. In adult specimens, ratio SnL/ED greater than that of subadult specimens (2.33–2.37 vs. 1.92–2.18). Paratype ITBCZ 7502 with small scale divided from upper part of 2 nd and 3 rd supralabials; suture between them forms a Y-shaped slit. Paratype ITBCZ 7503 with 9 supralabials, 4 th –6 th entering eye on both sides. Left side 5 th and 6 th supralabials not separated completely from each other, their suture not reaching edge of upper lip. Paratype ITBCZ 7505 with 2 loreals on right side and no presubocular on left side; 10 th and 14 th ventrals divided partially by transverse suture half width of given ventral. Paratype ITBCZ 7506 with incompletely divided precloacal plate. Paratypes ITBCZ 7502, ITBCZ 7505, ITBCZ 7506, and ITBCZ 6799 with 2 preventrals, posterior one contacting 1st ventral divided. Table 4 summarizes variation in size and scalation of type series. Field notes. All specimens were collected at night, from 7:00 PM to 1:00 AM, in open areas along channel banks in wetland forest dominated by cajuput samet tree (Melaleuca cajuputi Powell) (Fig. 6). The snakes were sleeping on bushes at 1–2 m above ground. Congener Ahaetulla cf. nasuta was found sympatrically. Sexual dimorphism. Males (n = 3) have longer relative tails than those of females (n = 3) (TaL/TL 0.34–0.35 in males; 0.31–0.32 in females) and more subcaudals (SC 134–153 in males, 128 or 129 in females) (Table 4). Keeled scales on sacral region present on males only. In life, males have venter yellow anteriorly and green posteriorly while venter of females is white with light green blotches posteriorly. Distribution. The new species is currently known only from My Phuoc Forest, My Tu District, Soc Trang Province, Vietnam (Fig. 6). Etymology. The specific epithet rufusoculara refers to the red color of the eyes and is derived from the Latin adjective rufus (meaning “red”) and oculus (means “eye”). We recommend “Red-eyed vine snake” and “Rắn roi mắt đȯ” as the common English and Vietnamese names of the new species, respectively. Comparisons. Ahaetulla rufusoculara sp. nov. differs morphologically from all congeners as follows: from A. anomala Annandale, A. borealis Mallik, Srikanthan, Pal, D’Souza, Shanker & Ganesh, A. farnsworthi Mallik, Srikanthan, Pal, D’Souza, Shanker & Ganesh, A. isabellina (Wall), A. laudankia Deepak, Narayanan, Sarkar, Dutta & Mohapatra, A. malabarica Mallik, Srikanthan, Pal, D’Souza, Shanker & Ganesh, A. nasuta, A. oxyrhyncha (Bell), A. pulverulenta (Dumeril, Bibron & Dumeril), and A. sahyadrensis Mallik, Srikanthan, Pal, D’Souza, Shanker & Ganesh by the absence (vs. presence) of dermal appendage on snout (Deepak et al. 2019; Mallik et al. 2020); from A. dispar (Gunther) by having more ventrals (182–190 vs. 136–156) and more subcaudals (128–153 vs. 84–119) (Smith 1943); from A. fasciolata (Fischer) by having fewer ventrals (182–190 vs. 221–231), fewer subcaudals (128–153 vs. 185–194), and precloacal divided (vs. entire) (Boulenger 1896); from A. fronticincta (Gunther) by having nasals distinctly separated from each other (vs. nasals usually in contact with one another above the rostral), 3 rd and 4 th supralabials not horizontally divided (vs. horizontally divided), and 2 or 3 supralabials (vs. 1) entering eye (Boulenger 1896; Smith 1943); from A. mycterizans by having fewer ventrals in males (186–190 vs. 192–194), fewer subcaudals (143–153 vs. 167 or 168 in males, 128 or 129 vs. 132–156 in females), precloacal divided (vs. entire), and slightly longer hemipenes (extending to SC 6 or 7 vs. 5) (Linnaeus 1758; Smith 1943; Miralles & David 2010); from A. perroteti (Dumeril, Bibron & Dumeril) by having more ventrals (182–190 vs. 136–146), more subcaudals (143–153 vs. 65–75 in males and 128 or 129 vs. 71–168 in females), and presence (vs. absence) of 2 or 3 loreals (Smith 1943); from A. prasina by having fewer ventrals (182–190 vs. 194–235) and fewer subcaudals (143–153 vs. 165–187 in males and 128 or 129 vs. 151–172 in females) (Smith 1943); and from A. travancorica Mallik, Srikanthan, Pal, D’Souza, Shanker & Ganesh by having more ventrals (186–190 vs. 153 in males) and more subcaudals (143–153 vs. 130 in males) (Mallik et al. 2020).Published as part of Lam, Ngon Quang, Thu, Tran Thi Anh, Nguyen, Luan Thanh, Murphy, Robert W. & Nguyen, Sang Ngoc, 2021, A new species of Ahaetulla Link, 1807 (Squamata: Colubridae) from the Mekong Delta, Vietnam, pp. 290-304 in Zootaxa 4966 (3) on pages 296-301, DOI: 10.11646/zootaxa.4966.3.2, http://zenodo.org/record/473663