Bungarus sagittatus, Aksornneam & Rujirawan & Yodthong & Sung & Aowphol, 2024

Aksornneam, Akrachai, Rujirawan, Attapol, Yodthong, Siriporn, Sung, Yik-Hei & Aowphol, Anchalee, 2024, A new species of krait of the genus Bungarus (Squamata, Elapidae) from Ratchaburi Province, western Thailand, Zoosystematics and Evolution 100 (1), pp. 141-154 : 141

Bungarus sagittatus sp. nov.

Figs 3 , 4 , 5

Type material.

Holotype (Fig. 3 ). ZMKU R 01089, adult female collected from Thailand, Ratchaburi Province, Suan Phueng District, Suan Phueng Subdistrict, Khao Krachom (13°33'57"N, 99°11'43"E, 834 m elevation), on 15 May 2022 by Akrachai Aksornneam, Mali Naiduangchan, Kritsada Rungrot, Purinut Numuan, Suphap Sisuk and Goe Wongdee.

Paratypes (Figs 4 , 5A-D ). ZMKU R 01088 (subadult female) bear the same locality data as the holotype. ZMKU R 01090 (juvenile) collected from Thailand, Ratchaburi Province, Suan Phueng District, Suan Phueng Subdistrict, Khao Krachom (13°33'41"N, 99°12'18"E, 619 m elevation), on 15 June 2022, by Akrachai Aksornneam and Naka Taou.

Referred specimen

(Fig. 5E, F ). RIM00012 (subadult male) collected from Thailand, Ratchaburi Province, Suan Phueng District, Suan Phueng Subdistrict, Khao Krachom (13°34'53"N, 99°10'43"E, 987 m elevation), on 16 April 2021, by Parinya Pawangkhanant and Boontorn Wongdee.

Diagnosis.

Bungarus sagittatus sp. nov. is assigned to the genus Bungarus by its recovered phylogenetic position and having enlarged, hexagonal-shaped, midbody vertebrae scales ( Smith 1943; Slowinski 1994). This species can be distinguished from other species of Bungarus by the following combination of characters: 15-15-15 dorsal scale rows; 215-217 ventral scales; 48-56 undivided subcaudal; prefrontal suture 2.4-2.6 times length of internasal suture; anterior chin shields larger than posterior chin shields; head of adult uniform black while juvenile black with small dim white patches on temporal and parietal areas; dorsal surface of body black, with 25-31 white narrow bands, white and black bands at midbody covering 1.5-3.0 and 4.5-6.0 vertebral scales, respectively; dorsal black bands of body not intruding ventrals or intruding ventrals less than 0.5 times of width of outer dorsal scales; ventral surface immaculate white; ventral side of tail white with a row of dark brown triangular patches on middle pointing posteriorly; tail relatively long, tail length/total length = 0.140-0.143.

Description of holotype.

Adult female. Head length 19.9 mm, head width 16.8 mm; head height 10.7 mm, head 1.2 times longer than wide, distance between eyes 9.2 mm. Body length (SVL) 791 mm; tail incomplete, 132 mm; total length 923 mm.

Body scalation. Dorsal scales smooth, in 15-15-15 rows; vertebral scales enlarged, hexagonal, largest at midbody, wider than long. Ventrals 216, preventrals 3, anterior edge of first ventral starting at level of oral rictus. Cloacal plate undivided. Subcaudals 48 undivided, tail incomplete.

Head. Head scales smooth. Λ-shaped rostral visible from above 1.6 times wider than tall. Nasal large, divided into one irregular quadrilateral-shaped prenasal and one crescent-shaped postnasal on both side; prenasal and postnasal bordered by internasal and first supralabial; prenasal contacted with rostral; postnasal surrounded by prefrontal, preocular and second supralabial. External nares large, vertically oval-shaped, about half size of eye diameter. Preoculars 1/1 (left/right) hexagonal-shaped, bordered by orbit, supraocular, prefrontal, postnasal, second and third supralabials. Two internasals, 1.03 times wider than long, surrounded by rostral, prenasal, postnasal and prefrontal. Prefrontals large, 1.06 times wider than long, prefrontals suture length 2.6 times of internasals suture. Frontal shield-shaped, pointing backward to parietals, 1.3 times longer than wide, bordered by prefrontals, supraoculars and parietals; anterior suture of frontal pointed toward prefrontal suture. Supraocular 1/1 small, 1.6 times longer than wide, in contact with preocular, orbit, upper postocular, parietal, frontal and prefrontal. Parietals large and long, 2 times longer than wide, 1.6 times longer than frontal length; left parietal anteriorly and laterally bordered by frontal, supraocular, upper postocular, anterior temporal and upper posterior temporal; right parietal anteriorly and laterally bordered by frontal, supraocular, upper postocular, lower postocular, anterior temporal and upper posterior temporal; posterolateral margins of parietals bordered by 1/1 enlarged elongate scales that anteriorly contact upper posterior temporals; posteriormost extensions of parietals pointed, divided by one of three small dorsal scales bordering posterior end of parietals. Eyes small, oval-shaped, horizontal diameter 2.6 mm, vertical diameter 2.3 mm. Postoculars 2/2, relatively small with one-third size of preoculars; on right side, lower postocular bordered by orbit, fourth and fifth supralabials, anterior temporal, parietal and upper postocular; on left side, lower postocular bordered by orbit, fourth and fifth supralabials, anterior temporal and upper postocular; on right side, upper postocular bordered by orbit, lower postocular, parietal and supraocular; on left side, upper postocular bordered by orbit, lower postocular, anterior temporal, parietal and supraocular. Anterior temporals 1/1, long and subhexagonal-shaped, 1.6 times longer than wide; right anterior temporal bordered by lower postocular, fifth and sixth supralabials, lower posterior temporal, upper posterior temporal and parietal; left anterior temporal bordered by upper postocular, lower postocular, fifth and sixth supralabials, lower posterior temporal, upper posterior temporal and parietal. Posterior temporals 2/2 surrounded by parietals, anterior temporals, sixth and seventh supralabials and dorsal scales. Supralabials 7/7, the third and fourth supralabials touching lower margin of orbit; first supralabials small, subtriangular, 1.2 times wider than height; other supralabials in different pentagonal shapes; second supralabials height pentagonal-shaped, larger than the first, 1.8 times higher than wide; the third supralabial larger than first, second and fourth supralabials, 1.3 times higher than wide; fourth supralabials with 1.5 times higher than wide; fifth and sixth supralabials are two largest, both height equal to width, but fifth supralabials wider at lower part while the sixth supralabials is wider at the upper part; seventh supralabials is the third largest, 1.2 times higher than wide. Mental triangular-shaped, 1.4 times shorter than width of rostral, in contact with first infralabials, mental groove distinct. Infralabials 7/7, first infralabials pentagonal-shaped, long and narrow, 1.6 times longer than wide, in contact behind the mental and anterior chin shields; second infralabials square-shaped, one-third size of the first, 2.1 times longer than wide, in contact with anterior chin shields; the third infralabials enlarged, in contact with anterior chin shields, 1.1 times longer than wide; the fourth is largest infralabial, pentagonal shaped, in contact with anterior and posterior chin shields, 1.2 times longer than wide; fifth infralabials in form of a square, half size of the fourth, 1.2 times longer than wide; the sixth is widest infralabial, 1.9 times wider than long; seventh infralabials is smallest, 1.4 times wider than long. Anterior chin shields larger than posterior chin shields; anterior chin shield suture 2 times the length of the posterior chin shield suture; posterior chin shields bordered by anterior chin shields, fourth infralabials, 2/2 sublabials and three gulars. Three gulars between first ventral and posteriormost extension of posterior chin shield; one gular and three preventrals between first ventral and suture of posterior chin shields.

Coloration in preservative.

Dorsal surface and lateral sides of head, including upper part of supralabial, upper part of rostral uniform black; lower part of head, including portions of lower supralabials and rostral to ventral head uniform creamy white. Dorsal body black with 26 white crossbands (the fifth band incomplete). Some white bands on the body scattered with few dark spots, most bands nearly immaculate creamy white. The white bands cover 0.5 to 2.0 times vertebral scales (average 1.5 ± 0.4, n = 26; 1.5 vertebral scales at midbody), bands widening on flanks before merging with the immaculate creamy white ventral scales. The first white band starts at 16th ventral, 11 vertebral scales between first and second bands and five vertebral scales between 25th and 26th bands. A dark spot is present at the junction between white bands and ventral scales at midbody positions. Black bands on body wide, covering 6.0 vertebral scales at midbody positions, generally not intruding white ventral scales; some bands slightly intruding ventral scales less than 0.5 times width of outer lateral dorsal scales.

Dorsal surface of tail black with eight creamy white bands on dorsal part, covering 1.0-1.5 times of vertebral scales. Ventral surface of tail creamy white with a row of dark brown triangular patches pointing posteriorly at the middle of subcaudals, starting from second subcaudal to the tip of tail.

Variation.

Paratypes and referred specimens closely resemble the holotype in general aspects of morphology and color pattern. First and second white bands on dorsum of ZMKU R 01090 (juvenile) are disconnected. In ZMKU R 01088 (subadult female), the first white band on dorsum is disconnected; the second and third are incompletely connected on lateral side of body. Twentieth white band on dorsum of RIM00012 (subadult male) is incomplete (present only on left side). Juvenile (ZMKU R 01090) head black with small dim white patches on temporal and parietal areas. A row of dark brown triangular patches on ventral surface of tail in juvenile is indistinct. Other variations in measurements, meristics and color pattern among the type series and referred specimen are shown in Table 1 .

Etymology.

The specific epithet sagittatus is derived from sagittata (L.) meaning arrow and in reference to the dark triangular shape on subcaudals which resembles a barbed arrow.

Distribution.

Bungarus sagittatus sp. nov. is currently known from type locality: Khao Krachom, Suan Phueng District, Ratchaburi Province. The area is part of Tenasserim Mountain Range, which lies on Thai-Myanmar borderline.

Ecology.

Most observations of Bungarus sagittatus sp. nov. occurred at night, three specimens (ZMKU R 01088, ZMKU R 01089 and RIM00012) were collected in hill evergreen forest (834 m to 987 m elevation; Fig. 6 ) between 2050 and 2210 h with air temperature 24.1 °C and relative humidity 91.7%. One juvenile (ZMKU R 01090) was collected in a pitfall trap at daytime in mixed deciduous forest (619 m elevation). One subadult (not collected) was found swallowing an adult scincid lizard, Scincella reevesii (Gray, 1839), on forest floor in hill evergreen forest (1,049 m elevation) on 6 November 2022 at 2154 h (Fig. 7 ).

The new species was found sympatrically with other snake species such as Ahaetulla prasina (Boie, 1827), Boiga cyanea ( Duméril, Bibron & Duméril, 1854), Coelognathus flavolineatus (Schlegel, 1837), Gonyosoma oxycephalum (Boie, 1827), Lycodon ophiophagus Vogel, David, Pauwels, Sumontha, Norval, Hendrix, Vu & Ziegler, 2009, Ptyas carinata ( Günther, 1858), Rhabdophis chrysargos (Schlegel, 1837), Psammodynastes pulverulentus (Boie, 1827), Pareas carinatus Wagler, 1830, Argyrophis diardii (Schlegel, 1839), Naja kaouthia Lesson, 1831, Bungarus flaviceps , Ophiophagus hannah (Cantor, 1836) and Trimeresurus cf. popeiorum Smith, 1937.

Comparison.

Bungarus sagittatus sp. nov. is distinguished from all other Bungarus by a combination of morphological and color pattern characteristics (see Suppl. material 3). Bungarus sagittatus sp. nov. differed from B. andamanensis Biswas & Sanyal, 1978 by having 215-217 ventral scales (vs. 192-197); 48-56 subcaudals (vs. 45-47); TaL/TL 0.140-0.143 (vs. 0.156-0.161); 25-31 narrow white body bands (vs. 39-47 yellow or white bands mottled with brown); head uniform black (vs. head brown chocolate); and ventral surface of body immaculate white (vs. anterior and margin of ventral scales tinged with brown).

Bungarus sagittatus sp. nov. differed from B. bungaroides by having 215-217 ventral scales (vs. 220-237); TaL/TL 0.140-0.143 (vs. 0.114-0.130); subcaudals undivided (vs. divided); dorsal body with 25-31 narrow white bands (vs. 46-60 narrow white bands consisting of small white spots); dorsal body with larger black bands covering 4.5-6.0 vertebral scales at midbody (vs. 3.0-4.5 vertebral scales); and ventral surface of body immaculate white (vs. blackish with irregular yellowish white pattern).

Bungarus sagittatus sp. nov. differed from B. caeruleus (Schneider, 1801) by having TaL/TL 0.140-0.143 (vs. 0.111); 25-31 narrow white body bands (vs. 29-65 white bands); and white bands not in pairs (vs. white bands in pairs).

Bungarus sagittatus sp. nov. differed from B. candidus by having prefrontal suture length 2.4-2.6 times of internasal suture (vs. 1.4-2.4 times); TaL/TL 0.140-0.143 (vs. 0.112-0.130); white bands on dorsal body covering 1.5-3.0 vertebral scales at midbody (vs. 3.0-5.0 vertebral scales); black bands on dorsal body covering 4.5-6.0 vertebral scales at midbody (vs. 3.0-5.0 vertebral scales); dorsal body black bands not intruding ventrals or intruding ventrals less than 0.5 times of width of outer dorsal scales (vs. 1.0-2.0 times); adult head uniform black (vs. temporal area and lateral neck stained white); juvenile head black with small dim white patches on temporal and parietal areas (vs. creamy white head); and ventral surface of tail creamy white with a row of dark brown triangular patches on middle (vs. broad dark crossbars).

Bungarus sagittatus sp. nov. differed from B. ceylonicus by having 215-217 ventral scales (vs. 219-235); 48-56 subcaudals (vs. 33-40); 25-31 narrow white body bands (vs. 15-21 narrow white bands); TaL/TL 0.140-0.143 (vs. 0.087); and ventral surface of body immaculate white (vs. broad dark crossbands).

Bungarus sagittatus sp. nov. differed from B. fasciatus by having 48-56 subcaudals (vs. 23-39); TaL/TL 0.140-0.143 (vs. 0.074-0.096); dorsal body and tail black with narrow white bands (vs. broad yellow and black bands); ventral surface of body immaculate white (vs. yellow and black bands); dorsal body black bands not intruding ventrals or intruding ventrals less than 0.5 times of width of outer dorsal scales (vs. black bands encircling ventrals); and ventral surface of tail creamy white with a row of dark brown triangular patches on middle (vs. yellow and black bands).

Bungarus sagittatus sp. nov. differed from B. flaviceps by having 15 dorsal scale rows (vs. 13 rows); dorsal body and tail black with narrow white bands (vs. body black with or without light vertebral and paraventral stripes, tail bright red); and head uniform black (vs. head red).

Bungarus sagittatus sp. nov. differed from B. lividus by having vertebral scales distinctly enlarged (vs. slightly enlarged on the anterior body); 48-56 subcaudals (vs. 35-43); TaL/TL 0.140-0.143 (vs. 0.118); and dorsal body black with narrow white bands (vs. black without bands).

Bungarus sagittatus sp. nov. differed from B. magnimaculatus Wall & Evans, 1901 by having 48-56 subcaudals (vs. 40-48); TaL/TL 0.140-0.143 (vs. 0.115); and 25-31 narrow white body bands (vs. 11-14 broad white bands).

Bungarus sagittatus sp. nov. differed from B. multicinctus by having 25-31 white bands on dorsal body (vs. 31-50); black bands on dorsal body covering 4.5-6.0 vertebral scales at midbody (vs. 3.0-4.0 vertebral scales); dorsal body black bands not intruding ventrals or intruding ventrals less than 0.5 times of width of outer dorsal scales (vs. 1.2-2.0 times); ventral surface of body immaculate white (vs. white with dense brown pigments); and ventral surface of tail creamy white with a row of dark brown triangular patches on middle (vs. dense black bands and patches).

Bungarus sagittatus sp. nov. differed from B. niger by having dorsal body black with mostly complete narrow white bands (vs. body bands absent); and ventral surface of tail creamy white with a row of dark brown triangular patches on middle (vs. immaculate white).

Bungarus sagittatus sp. nov. differed from B. percicus Abtin, Nilson, Mobaraki, Hosseini & Dehgannejhad, 2014 by having 15 dorsal scale rows (vs. 17); 215-217 ventral scales (vs. 236-238); TaL/TL 0.140-0.143 (vs. 0.127-0.134); loreal scale absent (vs. present); and dorsal body black with mostly complete narrow white bands (vs. black with light triangular-shaped crossbars, ending in pairs of rectangular whitish dots or crossbars along the vertebral area).

Bungarus sagittatus sp. nov. differed from B. sindanus by having 15 dorsal scale rows (vs. 17); 215-217 ventral scales (vs. 220-237); and dorsal body black with mostly complete narrow white bands (vs. black with white bands formed by series of white spots).

Bungarus sagittatus sp. nov. differed from B. slowinskii by having 215-217 ventral scales (vs. 225-230); 48-56 subcaudals (vs. 33-41); TaL/TL 0.140-0.143 (vs. 0.120); subcaudals undivided (vs. divided); ventral surface of body immaculate white (vs. black bands encircling with irregular yellowish white pattern); and ventral surface of tail creamy white with a row of dark brown triangular patches on middle (vs. black bands encircling with irregular yellowish white pattern).

Bungarus sagittatus sp. nov. differed from B. suzhenae by having prefrontal suture 2.4-2.6 times of internasal suture (vs. 2.7-3.4 times); 215-217 ventral scales (vs. 220-229); 25-31 narrow white body bands (vs. 26-38); head of juvenile black with small dim white patches on temporal and parietal areas (vs. uniform black head); and ventral surface of tail creamy white with a row of dark brown triangular patches on middle (vs. immaculate white or with small brown dots).

Bungarus sagittatus sp. nov. differed from B. walli Wall, 1907 by having 15 dorsal scale rows (vs. 17); 215-217 ventral scales (vs. 198-207); and dorsal body black with mostly complete narrow white bands (vs. black with white bands formed by series of white spots).

Bungarus sagittatus sp. nov. differed from B. wanghaotingi by having TaL/TL 0.140-0.143 (vs. 0.114-0.132); dorsal body black bands not intruding ventrals or intruding ventrals less than 0.5 times of width of outer dorsal scales (vs. 0.5-1.5 times); head of juvenile black with small dim white patches on temporal and parietal areas (vs. light brown); and ventral surface of tail creamy white with a row of dark brown triangular patches on middle (vs. a row of small light brown dots on middle).

Figures

Figure 3. Holotype of Bungarus sagittatus sp. nov. (ZMKU R 01089) in preservation. A. Lateral view; B. Dorsal view and C. Ventral view; D. Dorsal view; E. Ventral view. Scale bars: 20 mm.

Figure 4. Paratypes in life showing the variation in different age class. A. Subadult female (ZMKU R 01088); B. Juvenile (ZMKU R 01090).

Figure 5. Paratypes and referred specimen in preservation. A. Dorsal and B. Ventral view of subadult female (ZMKU R 01088); C. Dorsal and D. Ventral view of juvenile (ZMKU R 01090); E. Dorsal and F. Ventral view of subadult male (RIM 00012). Scale bars: 20 mm.

Figure 6. Habitat of Bungarus sagittatus sp. nov. A. Macrohabitat at Khao Laem Summit (1,130 m elevation), Khao Krachom, Suan Phueng District, Ratchaburi Province; B. Hill evergreen forest at 1,000 m elevation.

Figure 7. Feeding behavior of Bungarus sagittatus sp. nov. (not collected) on smooth skink (Scincella reevesii) from the type locality, in hill evergreen forest at 1,049 m elevation. Red arrows indicate the tail part of skink.