Trimeresurus popeiorum Smith, 1937

Nguyen, Tan Van, Brakels, Peter, Maury, Nathanael, Sudavanh, Somchit, Pawangkhanant, Parinya, Idiiatullina, Sabira, Lorphengsy, Sengvilay, Inkhavilay, Khamla, Suwannapoom, Chatmongkon & Poyarkov, Nikolay A., 2020, New herpetofaunal observations from Laos based on photo records, Amphibian & Reptile Conservation (e 248) 14 (2), pp. 218-249 : 241

Trimeresurus popeiorum Smith, 1937

Pope’s Pitviper ( Figs. 10E–F, 11B)

Multiple individuals of T. popeiorum were observed by P. Brakels and N. Maury from 21–25 August 2019 in Xay District , Oudomxai Province (20°39.598’N, 102°04.241’E; elevation 850 m asl) .

Morphological characters of the individuals from Oudomxai Province agreed well with the descriptions of Vogel et al. (2004), Guo et al. (2015), and Mulcahy et al. (2017). The photographed individuals ( Fig. 10E–F) agree with the diagnosis of T. popeiorum in the following characters: base of tail not especially enlarged in males (see Fig. 11B); body slender, laterally compressed; head triangular, clearly distinct from the neck; eye medium; pupil vertical; internasals separated from each other by a scale; loreal pit present; two small scales between the nasal and the shield bordering the anterior region of the loreal pit; 3 preoculars; 1 crescent-shaped subocular; 2 postoculars; temporals small; 10–11 supralabials, the 1 st separated from the nasal, 3 rd large, in contact with subocular, 4 th and 5 th separated from subocular by a small scale; dorsal scale rows strongly keeled but smooth on the outermost row; ventrals 166 in a single male, 159– 162 in females; cloacal undivided; subcaudals 78 in a single male, 55–58 in females, all divided. Coloration of dorsal surfaces deep green with bicolored (with dorsally white, ventrally red) ventrolateral stripe present in male, in females thin ventrolateral stripe, anteriorly yellowish, posterior whitish; lateral surfaces of head with a white postocular streak ventrally edged with red in male, absent in female; tail greenish with the posterior half dorsally rusty red; ventrally green; eyes red to deep red both in male and females.

Ecological notes. The individuals from Oudomxai Province were found at 1900–2300 h perching just at 0.5–4 m above the ground along a road in a forested valley. The surrounding habitat was mixed secondary submontane forest .

Distribution. In Laos, this species has been previously recorded only from Phongsali, Louangphabang, Xaignabouli, and Vientiane provinces ( Vogel et al. 2004; Sanders et al. 2006). This is the first record from Oudomxai Province. Elsewhere, this species has been reported from India, Nepal, China, Myanmar, and Thailand ( Uetz et al. 2020).

Remarks. Trimeresurus popeiorum is can be confused with T. gumprechti , but differs from it by the shape of its hemipenes (long, without spines vs. short, strongly spinose), a generally longer tail, a generally higher number of subcaudals in males: 59–78 (avg. 68.1) vs. 55–71 (avg. 64.7); and eye color (deep red in both sexes in adult specimens vs. deep red in males, yellow in females) ( David et al. 2002; Vogel et al. 2004; Guo et al. 2015).