Trimeresurus lanna, Idiiatullina & Nguyen & Pawangkhanant & Suwannapoom & Chanhome & Mirza & David & Vogel & Poyarkov, 2024

Idiiatullina, Sabira S., Nguyen, Tan Van, Pawangkhanant, Parinya, Suwannapoom, Chatmongkon, Chanhome, Lawan, Mirza, Zeeshan A., David, Patrick, Vogel, Gernot & Poyarkov, Nikolay A., 2024, An integrative taxonomic revision of the Trimeresurus popeiorum group of pitvipers (Reptilia: Serpentes: Viperidae) with descriptions of two new species from the Indo-Burma Biodiversity Hotspot, Vertebrate Zoology 74, pp. 303-342 : 303

Trimeresurus lanna sp. nov.

Figs 8 , 9; Tables S3, S4

Trimeresurus Chresonymy.

Trimeresurus gramineus (non Coluber gramineus Shaw, 1802) - Pope and Pope (1933: 9, in part).

Trimeresurus popeiorum (non Trimeresurus popeiorum Smith, 1937) - Smith (1943: 518-519, in part); Taylor and Elbel (1958: 1171, in part), Taylor (1965: 1073-1075, in part); Malhotra and Thorpe (2000: 201, in part); Nabhitabhata (2000: 142, in part); David et al. (2001: 221, in part), Gumprecht (2001: 20-30, in part), Leviton et al. (2003: 446-447, in part); Malhotra and Thorpe (2004: 97, in part); Vogel et al. (2004: 19, in part); Sanders et al. (2004: 183-184, in part); Gumprecht et al. (2004: 36 in part, 257-258); Sanders et al. (2006: 361, in part); Castoe and Parkinson (2006: 105, in part); Leviton et al. (2008: 80-81, in part); Das (2010: 307, in part); Malhotra et al. (2010: 175, in part); Teynié and David (2010: 268-270); Chanhome et al. (2011: 325-326, in part); Chuaynkern and Chuaynkern (2012: 148, in part); Wallach et al. (2014: 575-576, in part); Guo et al. (2015: 267-268, 274, in part); Chan-ard et al. (2015: 345-346, in part); Wostl et al. (2016: 637, in part); Chen et al. (2019: 20, in part); Nguyen et al. (2020: 239, 241, in part); Wang et al. (2020: 205); Janzen (2021: 14, 20-21, in part); Liu et al. (2022: 86-87); Maury et al. (2022: 90); Ngo et al. (2023: 592, 594-595; in part), Vogel et al. (2022: 348, 363), Wang et al. (2022: 6); David et al. (2023: 59, 68-69, 92, 98, 105 [all T. lanna ] and 813-820, in part); Poyarkov et al. (2023: 142, in part); Uetz et al. (2024, page " Trimeresurus popeiorum ", in part).

Popeia popeorum [sic] - Guo et al. (2009: 153, in part), Liu et al. (2015: 266), Li et al. (2020); Wu et al. (2023: Table S1).

Trimeresurus popeiorum popeiorum (non Trimeresurus popeiorum Smith, 1937) - Regenass and Kramer (1981: 186-187, in part).

Popeia sp. 1 - Mirza et al. (2023: 94).

Trimeresurus cf. popeiorum 1 - Idiiatullina et al. (2023: 701), Idiiatullina et al. (2024: 17).

Holotype.

AUP-00180, an adult male from Siriphum Waterfall, Doi Inthanon National Park (18.5467°N, 98.5124°E; elevation 1450 m), Chiang Mai Province, Thailand; collected by P. Pawangkhanant, C. Suwannapoom, and N. A. Poyarkov on 30 August 2017.

Paratypes

(n = 8).

Thailand.

Chiang Mai Province: AUP-00178 (adult male), AUP-01574 (adult female) data same with holotype; FMNH 178656 (adult male), collected by O.G. Young, and NHMUK 1937.2.1.25 (adult male), collected by M.A. Smith in 1937, no specific locality. Lampang Province: IRSNB 2736 (formerly IRSNB 16545; adult male) and IRSNB 2737 (formerly IRSNB 16546; subadult female) from Chae Son NP. Laos. Phongsaly Province: FMNH 14430 (adult male) from Ban Muangyo, collected by R.E. Wheeler on 9 May 1929; MNHN-RA-2004.0262 (adult male), between Nathen and Long Nai, collected on 26 July 2004.

Referred specimens

(n = 21). Thailand. Chiang Mai Province: MNHN-RA-1987.3836 (adult male), PSGV S0062 (subadult male), and AUP-00181, PSGV S0063 (two subadult females) from Doi Inthanon NP.; USNM 84757 (subadult female) from Khun Chae NP.; NHMW 27947 (adult male), FMNH 178655, FMNH 178658 (two subadult males), and NHMUK 1937.2.1.24, NHMUK 1937.2.1.26 (two subadult females), no specific localities. - Laos. Luangphrabang or Xaignabouli provinces: NHMUK 1862.7.28.4 (adult male) and NHMUK 1862.7.28.1 (adult female), "Lao Mountains, Cochinchina", now Luangphrabang Range, western Laos, probably between Paklay (Xaignabouli Province) and Luangphrabang (Luangphrabang Province). - Myanmar. Mon Sate: CAS 222195, CAS 240640 (two adult males), and CAS 216609 (subadult male) all from Kyaik Hti Yo WS. Bago Reigon: CAS 205847 (adult female) from Bago Yoma City. Kayah State: NHMB 2596-97, NHMW 23923:1-2, and ZMB 11637 (five adult males) from Monts Karen Mt.

Etymology.

The new species name " lanna " represents a noun in apposition and is given in reference to the Lan Na Kingdom, or "Kingdom of a Million Rice Fields". The Kingdom of Lan Na, also known as Lannathai, was centered in present-day northern Thailand from the 13th-18th centuries. The territories and cultural influence of the Lan Na Kingdom spread from easternmost Myanmar to northern Laos and southernmost present-day Yunnan of China, a geographic area that matches well the range of the new species. Though eventually the Lan Na Kingdom was united with the Siamese State in the early 19th century, its culture had a profound influence on different parts of northern Indochina. We suggest the following common names for the new species: "Ngu Khiew Hang Mai Thong Khiew Nua" (เขียวหางไหม้ท้องเขียวเหนือ) (in Thai), “Lán nà zhú yè qīng” (蘭納竹叶青) (in Chinese), "Lanna green pitviper" (in English), “Trimérésure vert du Lanna" (in French), "Lanna Bambusotter" (in German), and "Chiangmaiskaya bambukovaya kufiya" (in Russian).

Diagnosis.

Trimeresurus lanna differs from other members of the subgenus Trimesurus Popeia by the combination of the following morphological characters: (1) dorsal surfaces deep green, without crossbands; (2) in males, a vivid, wide, bicolored ventrolateral stripe, bright and deep red below, white above; in females, ventrolateral stripe thin, pale yellow anteriorly, whitish posteriorly; (3) in males, a conspicuous, bicolored postocular streak, white and thin ventrally, broad and bright red dorsally, covering two or three temporal scales; in females, streak absent or only white; (4) eyes red to deep red in both males and females; (5) 21 (93.3%) or rarely 20 (6.7%) dorsal scales rows at midbody, strongly keeled except those of the first dorsal scale row, always smooth; (6) 145-167 ventral plates (145-167 in males; 157-166 in females); 56-75 paired subcaudal scales with weak sexual dimorphism (59-75 in males, 56-64 in females); (7) first supralabial entirely separated from the nasal scale by a distinct suture; (8) supraoculars relatively narrow, narrower than internasals, separated by 10-13 cephalic scales; (9) internasals never in contact, separated by one or two scales; (10) hemipenes long and forked, reaching at least 25thSC, without spines; (11) 9-14 cephalic scales between the supraoculars in males, 11-13 in females; (12) relative tail length 0.18-0.21 in males, 0.16-0.17 in females.

Description of the holotype

(Fig. 8A-D ). An adult male, specimen in a very good state of preservation.

Morphology.

Body cylindrical, long, and laterally compressed; SVL 640 mm, TaL 175 mm, TL 815 mm, TaL/TL 0.215. Head triangular in dorsal view, elongate, clearly distinct from the neck (HL 36.8 mm, HL/SVL 0.06); snout elongate, flattened, and rounded when seen from above, rather rectangular when seen from lateral side, with a very distinct and sharp canthus rostralis; loreal pit present, triangular in shape. Eye average (ED 4.5 mm, SnL 11.3 mm, ED/SnL 0.40); pupil vertically elliptic.

Body scalation.

Dorsal scales in 23-21-15 rows; dorsal scales all moderately keeled, except the first row the scales of which are smooth; 157 ventrals (plus single preventral); cloacal plate single; 71 subcaudals, all divided.

Head scalation.

Rostral slightly visible from above, triangular, broader than high; one enlarged internasal on each side, internasals separated by one small scale behind the top of rostral (Fig. 8A ); nostril completely included in the entire nasal scale, pentagonal, undivided, elongate, as long as high; nasal scale completely separated from the first supralabial (Fig. 8C ); one internasal on each side, pentagonal, curved, wide, transversely elongate, separated by one small scale; two small scales between the nasal and the second supralabial; scales on the upper snout surface and in the interorbital region smooth, irregular, barely imbricate; 3/3 canthal scales, slightly larger than adjacent snout scales, bordering the canthus rostralis between the internasal and corresponding supraocular; temporal and occipital scales obtusely keeled; one relatively large triangular loreal between the upper preocular and the nasal; two elongate upper preoculars above loreal pit, lower one bordering the upper margin of loreal pit, upper one visible from above, both elongate and in contact with loreal; lower preocular forming lower margin of loreal pit; one supraocular on each side, long, much longer than wide, 0.7/0.8 times as wide as the internasals; cephalic scales relatively small, irregular or slightly rounded, juxtaposed, flat and smooth; 11 irregular cephalic scales between the supraoculars; one long, thin, crescent-like subocular scale; occipital scales rhombohedral, distinctly but obtusely keeled; 2/2 small postoculars; 10/10 supralabials, first supralabial short, entirely separated from the nasal by a distinct suture; second supralabial tall, forming the anterior border of loreal pit; third supralabial the largest and in contact with the subocular on each side; fourth and fifth supralabials much lower than the third one, separated from the subocular by one scale on each side (Fig. 8C ); 12/12 infralabials, those of the first pair in contact with each other behind the mental, the first three pairs in contact with the single pair of chin shields. Five pairs of gulars aligned between the chin shields and the first preventral (Fig. 8B ).

Coloration in preservative

(Fig. 8A-D ). The body is uniform deep bluish-green (bright grass-green in life), without darker areas or crossbands; a conspicuous, bicolored ventrolateral stripe extends from the beginning of the neck to the vent, pinkish-brown (bright deep red in life) ventrally, this color covering nearly the whole scales of the first dorsal scale row except their upper posterior corner that is cream, and dorsally cream (white in life) on the lower half of scales of the second row. The tail is bluish-green like the dorsum; the ventrolateral stripe extends up to the first third of the tail; near its end, the dorsal surface of the tail is irregularly mottled with pinkish-orange (rusty-red in life).

The dorsal surface of the head and the temporal region are bluish-green like the body; the side of the head below the eye (i.e., the sides of the snout, nasal scale, anterior supralabials and lower temporals) is distinctly paler than the dorsal surface of the head, namely pale bluish-green (pale green in life); a broad, bicolored postocular streak, its ventral part narrow and cream (white in life) covering the lower row of temporals, its upper part, broader (two rows of temporals), pinkish-brown (bright deep red in life), extends from the postoculars obliquely towards the angle of the mouth but the postocular streak does not connect with the ventrolateral stripe. The chin and throat are pale sea-green (pale green in life), uniform but with few faint darker areas on infralabials sometimes. The eye is grey but it was deep fire-red in life. The venter is uniform pale sea-green (pale green in life); tips of ventrals of the same green color, not red. The ventral surface of the tail is as the venter anteriorly, becoming pinking-orange in its posterior quarter (reddish-brown in life).

Description of hemipenes

(based on adult male CAS 240640, Fig. 8H ). The organ is long and thin, deeply forked, extending to the 18th subcaudal scale in situ, forked at the level of fifth to sixth subcaudal scales; the base of the organ, up to the point of bifurcation, is entirely smooth with longitudinal folds, except for the sulcus spermaticus; from the point of bifurcation up to the tip of the organ, each fork is finely calyculate. The sulcus is prominent; it divides near the base of the organ and ends near the tip of the fork.

Variation.

See also Table S3.

Morphology.

The longest known specimen is 845 mm long (SVL 709 mm, TaL 136 mm; female, NHMUK 1862.7.28.1). The longest known male is 815 mm long (SVL 640 mm, TaL 175 mm; holotype). The body is robust, relatively slender in males, thicker in large females, laterally compressed; head triangular, elongate, wide posteriorly, flattened in males, moderately thick in females, clearly distinct from the neck; snout elongate, distinctly flattened, rounded seen from above, angular and obliquely truncated in profile view, with a distinct canthus rostralis; nostril piercing in the middle of nasal scale; eye average, amounting for 0.9-1.2 times in males and 0.7-1.0 times in females the distance between the lower margin of eye and upper lip border; tail average to long, progressively tapering and distinctly prehensile; ratio TaL/TL 0.149-0.211, with a sexual dimorphism (males: 0.182-0.211; females: 0.149-0.173).

Body scalation.

Dorsal scales in 23-21-15 (50%), 21-21-15 (36.7%), or rarely 25-21-15 (10%) and 22-21-15 (3.3%) rows, moderately or strongly keeled; scales of the first dorsal scale row smooth and not enlarged; 145-167 ventral plates (plus one or two preventrals), rounded; 56-75 subcaudal scales with a weak sexual dimorphism (59-75 in males, 56-64 in females), all paired; total number of VEN+SC: 213-241, without sexual dimorphism; cloacal plate entire.

Head scalation.

The head scalation is as described for the holotype, with the following variation: internasals separated by one (84%) or rarely two (16%) small scales; three or four canthal scales bordering the canthus rostralis between the internasal and corresponding supraocular; one supraocular on each side, entire and rather narrow, about 0.7-0.9 times as wide as the internasals, indented on their inner margins by the upper head scales; cephalic scales juxtaposed, flat and smooth; 10-13 cephalic scales on a line between supraoculars; occipital scales rhombohedral, distinctly obtusely keeled in males, weakly keeled or even smooth in females; temporals generally moderately but distinctly keeled (80%), rarely smooth (20%) in males, always smooth in females; on each side, one thin, elongate subocular scale, crescent-shaped; two or three small postoculars; 9-11 supralabials; third supralabial the longest and highest, rather tall, in contact with the subocular or separated from this latter scale by one scale; fourth supralabial separated from the subocular by one scale in all examined specimens; fifth supralabial smaller than the fourth one, separated from the subocular by one or two scales of similar size; 10-14 (generally 12-13) infralabials, those of the first pair in contact with each other.

Coloration and pattern

(Figs 8 , 9 ). In life or in freshly preserved animals, the body is uniform bright green, grass-green, emerald-green or deep green (in preservative, the general background color remains green or turns to bluish-green); no dark transversal crossbands or white vertebral dots; in males, the broad, bicolored ventrolateral stripe is as described above, namely bright red, deep red or rusty brown on its lower part, white or whitish-yellow above, always present and conspicuous; in females, the ventrolateral stripe is absent or thin and faint, white or cream. The tail is of the same green color than the dorsum, irregularly mottled with reddish-brown or rusty brown posteriorly.

The dorsal surface of the head and the temporal region are uniform green or bluish-green like the body; the sides of the head below the eye, i.e., the lower sides of the snout, nasal scale, and anterior supralabials and lower temporals are distinctly paler than the dorsal surface of the head, pale green or pale bluish-green; in males, the vivid, broad, bicolored postocular streak, white ventrally, bright red, rusty-red or brownish-red dorsally, is always present; in females, the postocular streak is usually absent (85.7%) or present as a white and thin line (14.3%). The chin and throat are pale green or pale sea-green, uniform or with infralabials marbled with green. The eye is bright red, fire-red or deep red in specimens of both sexes. The venter is uniform pale green or pale sea-green; tips of ventrals green. The ventral surface of the tail is as the venter anteriorly, becoming rusty-red on its posterior half to third.

Comparisons.

We here compare T. lanna with the four other species of the subgenus Trimesurus Popeia ( T. nebularis , T. phuketensis , T. popeiorum , and the T. sabahi complex). The main diagnostic characters separating the new species from these four species are summarized in Table S4.

Trimeresurus lanna is morphologically very similar to T. popeiorum but it is distinguished from this latter species by having: (1) lower max TL in males (815 mm vs. 925 mm), but higher max TL in females (884 mm vs. 854 mm); (2) slightly lower number of ventral plates in males (145-167, x̄ = 159.9 vs. 162-171, x̄ = 165.7; p = 0.0004); (3) slightly lower total number of VEN+SC in males (213-241, x̄ = 227.81 vs. 229-240, x̄ = 234.71; p = 0.0004); (4) bicolor postocular streak in males broad, covering 2-3 temporal scales vs. narrow, covering 1-2 temporal scales; (5) temporals strongly keeled in males (vs. feebly keeled).

Trimeresurus lanna is distinguished from T. nebularis by having: (1) eye color deep red in both sexes vs. usually green; (2) bicolor postocular streak present in males vs. absent; presence of a white ventrolateral stripe in females vs. absent; (3) lower max TL in both sexes (815 mm in males, 854 mm in females vs. 1002 mm in males, 948 mm in females); (4) higher total number of VEN+SC in both sexes (213-241, x̄ = 228.1 vs. 210-218, x̄ = 214.0 in males; p = 0.007; 213-229, x̄ = 221.2 vs. 197-210, x̄ = 205.6 in females; p = 0.021).

Trimeresurus lanna differs from T. phuketensis by having: (1) higher max TL in both sexes (815 mm in males, 854 mm in females vs. 640 in males,748 mm in females); (2) lower total number of VEN+SC in both sexes (213-241, x̄ = 227.8 vs. 242-249, x̄ = 246.4 in males; p = 0.0032; 213-229, x̄ = 221.2 vs. 226-237, x̄ = 230.6 in females; p = 0.015); (3) eye color deep red in both sexes vs. copper; (4) body without dorsal crossbands vs. present and conspicuous.

Trimeresurus lanna can be further differentiated from the five subspecies of T. sabahi as follows:

- from T. s. barati by having: (1) 21 dorsal scales rows at midbody (vs. 17-19); (2) eye color deep red in both sexes vs. deep orange; (3) bicolor postocular streak present in males vs. absent; (4) slightly higher max TL in both sexes (815 mm in males, 854 mm in females vs. 740 mm in males, 720 mm in females);

- from T. s. buniana by having: (1) dorsum uniform bright green vs. dark bluish-green or verdigris with conspicuous reddish-brown or violet, irregular crossbands; (2) eye color deep red in both sexes vs. copper; (3) bicolor postocular streak (red plus white) present in males vs. postocular streak reddish-brown; (4) slightly lower ratio TaL/SVL in both sexes (0.18-0.21, x̄ = 0.20 vs. 0.22-0.23, x̄ = 0.22 in males; p = 0.007; 0.14-0.17, x̄ = 0.16 vs. 0.21 in females); (5) lower total number of VEN+SC in both sexes (213-241, x̄ = 228.5 vs. 246-250, x̄ = 248.0 in males; p = 0.0004; 213-229, x̄ = 221.4 vs. 231 in females);

- from T. s. fucatus by having: (1) slightly lower ratio TaL/TL in both sexes (0.18-0.21, x̄ = 0.20, vs. 0.19-0.24, x̄ = 0.22 in males; p = 0.000002; 0.14-0.17, x̄ = 0.16 vs. 0.16-0.19, x̄ = 0.17 in females; p = 0.05; (2) eye color deep red in both sexes vs. copper; (3) dorsal crossbands absent in males vs. present; (4) white vertebral spots absent vs. present; (5) bicolor postocular streak wide (red plus white) present in male vs. sometimes absent, or white, or white with its upper part dark red and thin;

- from T. s. toba by having: (1) eye color deep red in both sexes vs. deep orange; (2) ventrolateral stripe bicolor, wide in males vs. white and thin; (3) slightly higher max TL in both sexes (815 mm in males, 854 mm in females vs. 730 mm in males, 798 mm in females);

- from T. s. sabahi by having: (1) bicolor postocular streak present in males vs. absent; (2) slightly lower TaL/TL ratio in both sexes (0.18-0.21, x̄ = 0.20 vs. 0.19-0.24, x̄ = 0.21 in males; p = 0.05; 0.14-0.17, x̄ = 0.16 vs. 0.17-0.18, x̄ = 0.18 in females; p = 0.04); (3) slightly higher total number of VEN+SC in females (213-229, x̄ = 221.2 vs. 212-217, x̄ = 214.7; p = 0.034).

Furthermore, in western Laos and northern Thailand T. lanna may be recorded in sympatry with the superficially similar T. (Viridovipera) gumprechti David et al., 2002. The two species can be easily distinguished from each other by hemipenial morphology: in the new species hemipenes are long, slender and deeply forked, reaching in situ at least the 25th subcaudal, lacking spines (vs. hemipenes short, thick, barely forked and strongly spinous, extending at most up to the 13th-15th subcaudals in T. gumprechti ). Furthermore the eye of T. lanna is always deep red or fire-red in life in both sexes (vs. eye in life red in males, copper or yellow in females in T. gumprechti ); and the head is flat with a distinctly obliquely truncated snout (vs. snout barely obliquely truncated, rather rectangular or rounded in T. gumprechti ).

Distribution.

Trimeresurus lanna is currently known from a large expanse in northern Indochina around the infamous "Golden Triangle", including southeastern Myanmar. Based on our data, we establish the distribution of this species as follows: Myanmar (southeastern part of the country: Mon and Kayah States, and the Bago Region). China (Yunnan Province: Puer, Jinghong, and Mengla Counties). Laos (Houaphan, Luangnamtha, Luangphrabang, Oudomxay, Phongsali, Xaignabouli, and Vientiane Provinces). Thailand (northern and western parts of the country: Chiang Mai, Chiang Rai, Kamphaeng Phet, Kanchanaburi, Lampang, Mae Hong Son, Nan, Tak, and Uthai Thani Provinces; the southern limit of the range is in Sri Sa Wat District, Kanchanaburi). The occurrence of the new species in Shan and Kayin States of Myanmar, in the province of Bokeo in Laos, and in Phayao and Phrae Provinces in Thailand, is strongly anticipated.

Natural history notes.

Trimeresurus lanna typically inhabits humid tropical submontane primary evergreen and secondary forests, subtropical montane evergreen, semi-evergreen and mixed forests, as well as mixed secondary submontane forest, generally at elevations between 600 and 2000 m but it can be found at much lower elevations in suitable cool and humid habitats. It feels also at home in moist monsoon and other deciduous forests, bamboo thickets, and plantations. In Chiang Mai Province, Thailand, it is normally found in evergreen submontane and montane forest at elevations between 500 and 1700 m. It occurs in regions where winter temperatures can be as low as 3-7°C. The preferred microhabitats of this pitviper are markedly cool, humid, and shaded places. It is generally associated with dense shrubs, thickets, bushes, scrubs, the foliage of low trees, and tall grasses. This species is generally found in the low, humid vegetation of riparian areas, especially in the vicinity of freshwater habitats. Wogan and Chan-ard (2012, 2022; reported as T. popeiorum ) stated that individuals can often be found hanging over streams and in bushes. It is also often seen along the edges of forest clearings and sides of forest tracks.

Trimeresurus lanna is arboreal, crepuscular, and nocturnal. It is usually found coiled up above small streams or sometimes as high as 4 or 5 m above the ground. In Tak Province, Thailand, GV observed an individual on the ground in a submontane forest. In Oudomxay Province, Laos, Nguyen et al. (2020; reported as T. popeiorum ) found individuals perched at night (1900-2300 h) from 0.5-4 m above the ground along a road in a forested valley. Still in Laos, Maury et al. (2022) recorded many specimens during the day and at night between elevations of 450-1300 m, the species being more abundant near streams and other freshwater habitats. Snakes were perched high in trees, between about 2 m and 10 m during dry days, where they were probably resting. At night, especially during rainy weather, specimens were found much closer to the ground, at heights between 10 cm and 2 m. This pitviper feeds mainly on frogs and lizards, especially geckos, also small mammals, and birds. It is ovoviviparous. On Doi Suthep Mt., Chiang Mai Province, Thailand, one of the authors (P. Pawangkhanant) observed a mating pair in October; mating started after a big rainfall around 1750 h, the adult male stayed near the female for almost two weeks. Newborns have been observed along a small stream on Doi Inthanon NP, Chiang Mai Province, Thailand (elevation ca. 1230 m) in late April to May.

Conservation status.

Further research is required to clarify the extent of the distribution, population size and trends before the conservation status of this new species can be assessed. Trimeresurus lanna is distributed over a large area including many protected areas. Across its range the new species generally seems to be quite common. The density of some populations may be high as Maury et al. (2022) found up to 25 individuals in a single evening. These authors stated that it was common to find over 15 individuals at the same place in secondary forest. Thus, we tentatively suggest T. lanna be considered a species of Least Concern (LC) following the IUCN’s Red List categories (IUCN Standards and Petitions Committee 2019).

Figures

Figure 8. Trimeresurus lanna sp. nov. in preservative. Specimen AUP- 00180 (holotype, adult male): A Dorsal view of the head; B Ventral view of the head; C Lateral view of the head, right side; D General dorsal view. Specimen CAS 240640 (adult male): E Lateral view of the head, right side; F Lateral view of the head, left side; G Dorsal view of the head; H Hemipenis in asulcal aspect. Photos by: P. Pawangkhanant (A-D), and G. Vogel (E-H).

Figure 9. Trimeresurus lanna sp. nov. in life. Thailand: A Doi Inthanon NP, Chiangmai (mating adult couple); B, C Doi Phu Kha NP, Nan, Thailand; D Doi Suthep-Pui NP., Chiangmai (subadult female); E Doi Luang Mt., Chiang Rai (adult male); F Umphang, Tak (adult male). Laos: G, H Phongsaly (adult male and female, respectively). China: I Mengla, Xishuangbanna, Yunnan, China (adult male). Photos by: P. Pawangkhanant (A, D), T. Smith (B, E, F), R. Jaihan (C), T. Calame (G), P. Brakels (H), and J. Ming (I).