Protobothrops flavirostris sp. nov.

Table 1, Figs 3, 4, 5 В, C, Suppl. material 1: fig. S 3 A

Holotype.

NUOL R.2024.89, adult female, from the environs of the Khan Kham Cave in Vang Vieng District, Vientiane Province, Laos (elevation 360 m a. s. l.; approximate coordinates: 18.90 ° N, 102.43 ° E; exact coordinates are not released for conservation purposes) collected by R. J. Grassby-Lewis, P. Brakels, N. Maury and S. Sitthivong on 21 October 2024.

Etymology.

The specific name “ flavirostris ” is a Latin adjective in the nominative singular, masculine gender, derived from Latin words “ flāvus ” for “ yellow ” and “ rostrum ” for “ snout ” or “ beak ” and is given in reference to the characteristic yellowish colouration of the snout in the new species. We suggest the following common names for the new species: “ Vang Vieng lance-headed pit viper ” (in English), “ Ngu Phao Ka Ba Khor Kop ” (“ ງ ູ ເພ ົ າກະບາຄ ໍ ກ ົ ບ ”, in Lao) and “ Laosskiy habu ” (“ Лаосский хабу ”, in Russian). Furthermore, the new species is well-known to the Hmong people living in village communities around Vang Vieng and their local name for this species is “ nan jaow ka, ” which is roughly translated as “ a snake that can open its mouth very wide ” or “ big-mouthed snake ”.

Diagnosis.

The new species Protobothrops flavirostris sp. nov. differs from other members of the genus Protobothrops by the following combination of the morphological characters: dorsal scales in 23–21 – 17 rows, all keeled; ventral scales 215; subcaudal scales 79, all paired; supralabials 7–8; infralabials 10; horn-like projection on supraocular absent; head triangular with a typical lance-shaped pattern on dorsal surface; three faint dark vertical stripes on snout; head blackish-brown with rostral, nasals, preoculars, loreals and the two anterior supralabials, as well as the anterior parts of supraoculars yellow-orange; dorsal surfaces of body and tail brown or greyish-brown, dorsum with large dark reddish-brown cross-shaped blotches, edged with black, somewhat fused together forming an interrupted zigzag line; and a row of large brown ventrolateral blotches on each side.

Description of the holotype.

Adult female (Figs 3, 4), specimen in a good state of preservation. Body elongate, thin and slightly compressed (SVL 688 mm, TaL 137 mm, TL 825 mm; TaL / TL ratio 0.17) (Fig. 3 A, B). Head triangular in dorsal view (Fig. 3 E), elongated, clearly distinct from the neck (HL 25.4 mm, HW 16.2 mm, HD 10.2 mm; HW / HL ratio 0.64); covered with small, convex and irregularly-shaped scales (Fig. 3 E). Snout elongate, dorsally flattened and rounded in dorsal view (Fig. 3 E), rather rectangular in lateral view (Fig. 3 C, D), with a distinct and sharp canthus rostralis (SnL 7.9 mm, IN 5.4 mm, NL 3.0 mm). Eyes medium-sized (ED 3.5 mm, EN 5.7 mm; ED / EN ratio 0.61). Rostral triangular, barely visible in dorsal aspect (Fig. 3 E). Pupil vertically elliptical. Loreal pit present, large, triangular in shape, located closer to eye than to nostril (Fig. 3 C, D). Nostril vertical, elliptical, completely enclosed in nasal scale, with a short complete suture dividing the ventral part of nasal just below nostril (Fig. 3 C, D). Nasal scale separated from first supralabial by a complete suture (Fig. 3 C, D). Subocular long, thin, crescent-like, separated from the fourth supralabial by a single scale and separated from the fifth supralabial by 2 / 2 scales (Fig. 3 C, D). Three preoculars on each side of the head; two upper preoculars located dorsally of the loreal pit; first preocular short, rectangular; second preocular elongated, bordering the dorsal margin of loreal pit; the first upper preocular in contact with the posterior loreal; the second upper preoculars in contact with the anterior and posterior loreals, which separate it from the nasal; lower preocular triangular, elongated, forming the ventral margin of the loreal pit; lower preocular in contact with subocular, third and second supralabials (Fig. 3 C, D). A small elongated, rectangular scale between nasal and second supralabial, also in contact with anterior loreal and first supralabial (Fig. 3 C, D); 2 / 2 postoculars; 8 / 7 supralabials, third the largest (Fig. 3 C, D); 10 / 10 infralabials, those of the first pair in contact with each other behind the triangular mental; the first two pairs of infralabials in contact with the single pair of chin shields (Fig. 3 F). Four pairs of gulars aligned between the chin shields and the first preventral (Fig. 3 F). One pair of enlarged internasals, not in contact with rostral and separated from each other by two small scales (Fig. 3 E). One large supraocular, with 7–8 small scales along the transverse line between supraoculars (Fig. 3 E). Scales on snout and in the interorbital region smooth, irregular, subimbricate; temporal and occipital scales feebly keeled (Fig. 3 E, F). Dorsal scales in 23–21 – 17 rows, all of them narrow, pointed and strongly keeled in single and straight keels, including the first row. One preventral and 215 ventrals. Cloacal plate single; 79 subcaudals, all divided (Fig. 3 B).

Colouration.

In life (Fig. 4), the dorsum pale brown to greyish-brown with dense dark brown mottling and ca. 87 / 86 large dark reddish-brown cross-shaped blotches, edged in black, somewhat fused together, forming an interrupted and irregular zigzag line (Fig. 3 A). Tail pale yellow above with dark brown blotches, becoming darker to blackish-brown towards the tail tip, intermittent with small irregular patches of white scales at the tail tip (Fig. 3 A). Dorsal surfaces of the head pale yellow to orange-yellow with oblique dark brown stripes and blotches; the background colouration becoming more brightly yellow towards the snout (Fig. 3 C, D, E). Tongue pinkish-purple. Eyes greyish-brown with dark-brown mottling forming an irregular horizontal dark ocular stripe and a bright golden-yellow edging of the pupil (Fig. 3 C, D). Ventral surfaces pale brown to beige with darker brownish speckling, white blotches and dark brown polygonal spots, which become darker along the lateral sides of the venter. Ventral surfaces becoming cream to off-white on the neck and throat, with the same pattern consisting of dark brownish spots and speckles.

After five months in preservative, the bright colours of the specimen have somewhat faded; the yellowish colouration of the snout, the tail and the eyes have completely disappeared and the general pattern on the dorsum and venter remained unchanged.

Variation.

As only a single specimen was collected by us, the observations on morphological variation of the new species provided below are very scarce and are based on two photo records obtained through the citizen-science platform iNaturalist (www. inaturalist. org). Therefore, we were only able to observe some minor variation of colouration in life of two additional not-collected specimens. The new species was recorded from the Khan Kham Cave (Vang Vieng, Laos) in May 2023 (observation # 159203732) and showed somewhat darker colouration with a grey base colour and no bright yellow marking on the snout (Fig. 5 C); however, the quality of this photo, possibly due to insufficient lighting conditions, is moderate and it is not easy to described the details of the body colouration of this specimen. Another specimen of an unknown sex was recorded from the Nang Oua Khiam Cave (Vang Vieng, Laos) in November 2023 (observation # 190687143), the colouration of this specimen of an unknown sex agreeing very well with the description of the holotype, including the brown background colour and yellowish snout (Fig. 5 B). Another uncollected and unphotographed specimen, observed by I. Stelmah at the Loup Cave in May 2024, also had more greyish rather than brownish base colouration and had a yellowish blotch on its snout (Inna Stelmah, pers. comm.). Overall, there is a certain variation in the background colouration in the new species (greyish or brownish); however, the body pattern is quite similar and the presence of yellowish colouration on the end of the tail and the snout appears to be a diagnostic feature of the new species.

Comparisons.

The main diagnostic characters separating Protobothrops flavirostris sp. nov. from all other 15 currently recognised species of the genus Protobothrops are summarised in Table 1 and further illustrated in Suppl. material 1: figs S 3, S 4.

Sources: 1 = Maki (1931); 2 = Zhao et al. (1998); 3 = Orlov et al. (2009); 4 = Yang et al. (2011); 5 = Huang et al. (2012); 6 = Pan et al. (2013); 7 = Luu et al. (2015); 8 = Sumontha et al. (2020); 9 = David et al. (2023); 10 = this study.

Protobothrops flavirostris sp. nov. is readily distinguished from P. cornutus (distributed in northern and central Vietnam and southernmost China) by having a higher number of ventrals (VEN 215 vs. 187–202); a higher ASR number (23 vs. 19, rarely 21); a lower number of supralabials (SL 7–8 vs. 9–10); the absence of a horn-like projection on supraocular (vs. presence); by having the outermost row of dorsal scales keeled (vs. smooth); and by having a clearly different colour pattern (see Suppl. material 1: fig. S 3 A vs. fig. S 3 B).

The new species is distinguished from P. dabieshanensis (endemic to central China) by having a higher VEN number (215 vs. 187); a higher SC number (79 vs. 54–58); a higher ASR number (23 vs. 21); a higher PSR number (17 vs. 15); a lower IL number (10 vs. 11–12); by having the outermost row of dorsal scales keeled (vs. smooth); and by having a markedly different colour pattern (see Suppl. material 1: fig. S 3 A vs. fig. S 3 C).

Protobothrops flavirostris sp. nov. is further distinguished from P. elegans (endemic to the southern Ryukyu Islands or Yaeyama Islands of Japan) by having a lower TaL / TL ratio (0.17 vs. 0.18–0.23); a lower MSR number (21 vs. 23–25); a lower PSR number (17 vs. 19); two loreals (vs. one); by having the outermost row of dorsal scales keeled (vs. smooth); and by having a different colour pattern (see Suppl. material 1: fig. S 3 A vs. fig. S 3 D).

The new species is further distinguished from P. flavoviridis (endemic to the Okinawa and Amami island groups of the Ryukyu Islands, Japan) by having a lower VEN number (215 vs. 220–237); a lower ASR number (23 vs. 37–41); a lower MSR number (21 vs. 33–39); a lower PSR number (17 vs. 23–25); two loreals (vs. one); by having the outermost row of dorsal scales keeled (vs. smooth); and by having a clearly different colour pattern (see Suppl. material 1: fig. S 3 A vs. fig. S 3 E).

Protobothrops flavirostris sp. nov. is further distinguished from P. himalayanus (distributed in the Himalayan Region, including Nepal, Bhutan, Xizang Province of China and northeast India) by having a higher SC number (79 vs. 65–76); a lower ASR number (23 vs. 25); a lower MSR number (21 vs. 25); a lower PSR number (17 vs. 19); a lower IL number (10 vs. 11–13); by having the outermost row of dorsal scales keeled (vs. smooth); and by having a different colour pattern (see Suppl. material 1: fig. S 3 A vs. fig. S 3 F).

The new species is also easily distinguished from the members of P. jerdonii complex (including: P. j. jerdonii, P. j. bourreti and P. j. xanthomelas) distributed in Nepal, Bhutan, southern and central China, northeast India, northern Myanmar and northern Vietnam by having a higher VEN number (215 vs. 160–192); a lower IL number (10 vs. 11, 12); by having the outermost row of dorsal scales keeled (vs. smooth); and by having a markedly different colour pattern (see Suppl. material 1: fig. S 3 A vs. fig. S 3 G – I).

Protobothrops flavirostris sp. nov. is distinguished from P. kaulbacki (distributed in the Eastern Himalayas in northern Myanmar, south-western China and northeast India) by having a slightly higher VEN number (215 vs. 201–212); a lower ASR number (23 vs. 25); a lower MSR number (21 vs. 25–27); a lower IL number (10 vs. 12–14); by having the outermost row of dorsal scales keeled (vs. smooth); and by having a clearly different colour pattern (see Suppl. material 1: fig. S 3 A vs. fig. S 4 A).

The new species is easily distinguished from P. mangshanensis (endemic to southern China) by having a higher TaL / TL ratio (0.17 vs. 0.13–0.15); a higher VEN number (215 vs. 187–198); a higher SC number (79 vs. 60–67); a lower ASR number (23 vs. 25); a lower MSR number (21 vs. 25); a lower SL number (7–8 vs. 14–15); a lower IL number (10 vs. 13–16); two loreals (vs. one); by having the outermost row of dorsal scales keeled (vs. smooth); and by having a different colour pattern (see Suppl. material 1: fig. S 3 A vs. fig. S 4 C).

Protobothrops flavirostris sp. nov. is further distinguished from P. maolanensis (distributed in southern China and northern Vietnam) by having a higher VEN number (215 vs. 186–199); a lower IL number (10 vs. 11–12); a higher number of dark blotches on dorsum (87 blotches vs. 68–72 cross-bands); and by having a generally different colour pattern (see Suppl. material 1: fig. S 3 A vs. fig. S 4 D).

Protobothrops flavirostris sp. nov. is easily distinguished from P. mucrosquamatus (distributed across northeast India, western and central China, including the Taiwan Island, northern and central Vietnam, central and southern Laos, north-eastern Thailand and also introduced to Okinawa Island of Japan) by having a lower ASR number (23 vs. 25–28); a lower MSR number (21 vs. 23–27); a lower SL number (7–8 vs. 9–11); by having the outermost row of dorsal scales keeled (vs. smooth); and by having a distinctly different colour pattern (see Suppl. material 1: fig. S 3 A vs. fig. S 4 E).

Protobothrops flavirostris sp. nov. is easily distinguished from P. sieversorum (endemic to the Annamite (or Truong Son) Range in central Vietnam and central Laos) by having a lower VEN number (215 vs. 228–235); a lower IL number (10 vs. 13–14); by the absence of a horn-like projection on supraocular (vs. present); and by having a generally different colour pattern (see Suppl. material 1: fig. S 3 A vs. fig. S 4 F).

The new species is further distinguished from P. tokarensis (endemic to the Tokara Islands within the Ryukyu Islands of Japan) by having a higher VEN number (215 vs. 203–208); a lower ASR number (23 vs. 35); a lower MSR number (21 vs. 31); a lower PSR number (17 vs. 19); a lower IL number (10 vs. 12–16); two loreals (vs. one); by having the outermost row of dorsal scales keeled (vs. smooth); and by having a different colour pattern (see Suppl. material 1: fig. S 3 A vs. fig. S 4 G).

Protobothrops flavirostris sp. nov. is easily distinguished from P. trungkhanhensis (distributed in north-eastern Vietnam and southern China) by having lower TaL / TL ratio (0.17 vs. 0.21–0.24); a higher VEN number (215 vs. 188–194); a slightly higher SC number (79 vs. 75–76); a higher ASR number (23 vs. 19); a higher MSR number (21 vs. 19); a lower IL number (10 vs. 11–12); and by having a different colour pattern (see Suppl. material 1: fig. S 3 A vs. fig. S 4 H).

The new species is further distinguished from P. xiangchengensis (endemic to south-western China) by having a higher TaL / TL ratio (0.17 vs. 0.13–0.15); a higher VEN number (215 vs. 175–194); a higher SC number (79 vs. 44–66); a lower ASR number (23 vs. 25); a lower MSR number (21 vs. 23–25); a lower IL number (10 vs. 11–13); by having the outermost row of dorsal scales keeled (vs. smooth); and by having a clearly different colour pattern (see Suppl. material 1: fig. S 3 A vs. fig. S 4 I).

Finally, Protobothrops flavirostris sp. nov. can be readily distinguished from its sister species P. kelomohy (endemic to Dawna Range in north-western Thailand) by having: a slightly lower TaL / TL ratio (0.17 vs. 0.18–0.22); a lower number of ventrals (VEN 215 vs. 231–234; a lower number of mid-body scale rows (MSR 21 vs. 23); a lower number of infralabials (IL 10 vs. 12–13); by having two loreals (vs. one); and by the following colouration differences (see Suppl. material 1: fig. S 3 A vs. fig. S 4 B for comparison). The new species has a higher number of dark blotches on the dorsum (86 or 87 vs. 63–67); dorsally a bright yellowish-orange snout and tail (vs. no yellowish colouration on the snout and tail); transverse dark stripes on the snout brownish with irregular and posteriorly indistinct edges (Fig. 3 C, D) (vs. contrasting blackish transverse stripes on snout and lateral sides of the head, see Suppl. material 1: fig. S 4 B); and by having background colouration greyish-brown to light brown (vs. reddish-brown, see Suppl. material 1: fig. S 4 B).

Distribution and natural history notes.

Currently, Protobothrops flavirostris sp. nov. is known only from three limestone caves within the Vang Vieng karstic massif (Fig. 5 A), namely Khan Kham Cave, Nang Oua Khiam Cave and Loup Caves, all located within the Vang Vieng District, Vientiane Province, Laos. Though at present the species can be considered microendemic to a narrow area in Vang Vieng karsts, its occurrence in the adjacent limestone karst formations in other provinces of north-western Laos, such as Xayabury, Luang Prabang and Xaysombom Provinces, cannot be excluded. Protobothrops flavirostris sp. nov. was recorded at low elevations (200–400 m a. s. l.) in limestone massifs covered by karst forest or within the caves.

Protobothrops flavirostris sp. nov. is nocturnal; the holotype was collected at 21 h 15, although all individuals seen within caves were observed during the daytime hours. All four known observations of the new species are from within caves on limestone karst formations or at the base of limestone karst formations. All four individuals were observed climbing on limestone rocks, stalactites / stalagmites or cave walls. The holotype specimen would constantly anchor itself to anything possible using its tail and was very agile while climbing. Hereby, we identify the new species as a specialised limestone-dwelling rupicolous ecotype, spending most of its life climbing or resting amongst steep limestone rocks and hiding in their crevices.

The diet of the new species is not reliably known, though it may include the local species of bats (Chiroptera), as the species was only recorded in the caves with remnant bat colonies. Bent-toed geckos (primarily Cyrtodactylus pageli Schneider, Nguyen, Schmitz, Kingsada, Auer & Ziegler) were abundant within these same caves and on the adjacent limestone karst formations, so it is possible that it also predates on geckos. Other species of amphibians and reptiles recorded at the same habitat in the type locality during our survey included Microhyla mukhlesuri Hasan, Islam, Kuramoto, Kurabayashi & Sumida, Micryletta cf. menglienica (Yang & Su), Kaloula pulchra Gray, Sylvirana cf. menglaensis (Fei, Ye & Xie), Polypedates megacephalus Hallowell, Gracixalus sp., Rhacophorus kio Ohler & Delorme, Acanthosaura cf. rubrilabris Liu, Rao, Hou, Orlov, Ananjeva & Zhang, Cyrtodactylus pageli, Gehyra mutilata (Wiegmann), Ahaetulla prasina (Boie), Lycodon davidi Vogel, Nguyen, Kingsada & Ziegler, L. davisonii (Blanford), L. neomaculatus Nguyen, Lee, Pauwels, Kennedy-Gold, Poyarkov, David & Vogel, Bungarus fasciatus (Schneider), Trimeresurus macrops Kramer and T. guoi Chen, Shi, Vogel & Ding.

Conservation status.

To date, despite intensive survey efforts by our team and local herpers in the area, only four individuals of the new species have been recorded in relatively close vicinity. This indicates that Protobothrops flavirostris sp. nov. is likely highly secretive and elusive. Since the new species is a highly specialised limestone karst-dweller, the main threats to it are habitat loss and habitat disturbance, while it can also be subject to human prosecution from the locals due to stigma and fear of its dangerous venom. We presume this species to be restricted to limestone karst formations, which are directly threatened around Vang Vieng, mostly due to cement manufacturing, but also due to mining for ores such as iron, gold and other rare ores. Mining of these karst formations has accelerated in recent years. The suitable limestone karst habitat in Vang Vieng is not legally protected by a national park or wildlife sanctuary. If the new species indeed represents a point-endemic restricted to the karst formations surrounding Vang Vieng, this poses a significant threat to its survival. Furthermore, the discovery and formal description of this species may also lead to demand in the animal trade, which can also represent a significant threat.

In Vang Vieng District, bats are heavily sought after by local people for food, with a result that the bat population in this limestone area has been decimated. Unsustainable hunting measures are often used, such as deploying mist nets at cave entrances or exits and starting fires in the caves to flush the bats. Fire on long wooden torches that can reach the cave ceiling are used to burn bat wings so they drop to the ground and are collected for food. Bats are also commonly sold on the local market. In several independent interviews, the locals confirmed that virtually all bat populations around Vang Vieng District have been eradicated due to uncontrolled hunting and collection practices along with exploitation of the caves for tourism, which includes building infrastructure and permanent lighting in caves. This causes a severe disturbance and increases pressure on the cave ecosystems. According to the interview with the local Hmong people, Protobothrops flavirostris sp. nov. was much more common even 10–15 years ago, but became a very rarely observed species during the recent years.

Given the information provided above, we suggest that Protobothrops flavirostris sp. nov. should be considered as Endangered (EN) following the IUCN’s Red List categories (IUCN Standards and Petitions Committee 2019).