Herpetoreas davidi, Lalremsanga & Biakzuala, 2024

Nguyen, Tan Van, Lalremsanga, Hmar Tlawmte, Biakzuala, Lal & Vogel, Gernot, 2024, Taxonomic reassessment of the Herpetoreas xenura (Wall, 1907) (Squamata: Serpentes: Natricidae) from Myanmar with description of a new species, European Journal of Taxonomy 932, pp. 158-203 : 172-177

Herpetoreas davidi sp. nov.

urn:lsid:zoobank.org:act:4A77C927-AC6B-4367-8813-B0D172F99B42

Fig. 5 ; Tables 1–2

Amphiesma xenura (non Herpetoreas xenura Wall, 1907) – Wogan et al. 2008: 87, in part. — Das 2010: 335, in part. — Reza 2010: 64, in part. — Wallach et al. 2014: 35, in part.

Herpetoreas xenura – Ren et al. 2022: 79, in part. — Uetz et al. 2023: page “ Herpetoreas xenura ”, in part.

Herpetoreas sp. – Deepak et al. 2022: 285, in part. — Patel et al. 2023: 431 in supplementary materials.

Diagnosis

Herpetoreas davidi sp. nov. differs from all other members of the genus Herpetoreas by the combination of the following morphological characters: (1) body cylindrical, small size, max. TL 552 mm; (2) tail relatively long in both sexes, TaL/TL 0.301 –0.310; (3) dorsal scale rows 19–19–17; all strongly keeled; (4) ventrals 151–156; cloacal plate single, subcaudals single; subcaudals 97–100; (5) supralabials 9, 4 th –6th entering orbit; (6) head with a faint off-white sagittal line just behind the parietal; (7) dorsum dark olive-brown or dark brown with indistinct series of pale spots; (8) venter off-whitish, each ventral decorated with a pair of indistinct and faint dark-brown spots on their lateral edges.

Etymology

The species epithet is an eponym in honour of Patrick David (MNHN, Paris, France), a French reptile taxonomist, for his contribution to the systematics of snakes of the family Natricidae and to the Asian snake fauna in general. We suggest “Rakhine Keelback” as its English common name.

Type material

Holotype MYANMAR • ♂ adult; Daung Stream, within Rakhine Yoma Elephant Sanctuary , Gwa Township , Rakhine State; 17.5844166667° N, 94.6812777778° E, WGS 84; ca 120 m a.s.l.; 23 Jan. 2002; G.O.U. Wogan and S.W. Kyi leg.; CAS 222969 .

Paratypes MYANMAR • 1 ♀ adult, 1 ♀ subadult, 1 ♂ subadult; Kyat Stream, Rakhine Yoma Elephant Sanctuary , Gwa Township , Rakhine State; 17.7038888889° N, 94.6484166667° E, WGS 84; ca 175 m a.s.l.; 26–27 and 29 Apr. 2021, respectively; J.B. Slowinski, G.O.U. Wogan, H. Win, T. Thin, and K.S. Lwin leg.; CAS 220256 , CAS 220332 , CAS 220378 , respectively • 1 ♂ adult; Daung Stream, Rakhine Yoma Elephant Sanctuary , Gwa Township , Rakhine State; 17.5841833333° N, 94.67815° E, WGS 84; ca 125 m a.s.l.; 1 May 2021; J.B. Slowinski, G.O.U. Wogan, H. Win, T. Thin, and K.S. Lwin leg.; CAS 220550 .

Description of the holotype ( Fig. 5 )

MORPHOLOGY. Body slender, cylindrical, and elongate ( SVL 384 mm, TaL 168 mm, TL 552 mm, ratio TaL/TL 0.304). Head moderately large, moderately distinct from neck (ratio HL/ SVL 0.048, ratio HW/ HL 0.512), moderately distinct from neck ( Fig. 5E–F ); snout broad, obtuse as seen from above; eye large ( ED 2.86 mm, ratio ED/E–Sn 1.036, ratio ED/E–Ns 2.000); pupils round; nostrils crescentic, piercing in the middle of the nasal, oriented laterally ( Fig. 5A–B ).

BODY SCALATION. Dorsal scales in 19–19–17 rows; all scales strongly keeled, notched at apex; 154 ventrals (plus 2 preventrals); cloacal plate single; 99 subcaudals, all single.

HEAD SCALATION. Rostral wider than high, width approximately twice as long as high, visible from above ( Fig. 5D ); nasals pentagonal, slightly elongate, completely divided, anterior part slightly smaller than the posterior one; nostrils located on the middle of nasals ( Fig. 5A–B ); internasals subtriangular, in broad contact with each other, not in contact with loreal, about equal length to width, slightly, but distinctly narrowing anteriorly, the width of the posterior margin approximately twice as long as the anterior margin; 2 prefrontals, hexagonal, slightly broader than long, about 1.3 times as long as internasals; prefrontal sutures slightly longer than length internasal sutures; frontal pentagonal, elongate, length 1.4 times as long as width, about twice as long as prefrontal; supraocular 1/1, rectangular, elongate, narrowed anteriorly, broadly in contact with prefrontal, with supraocular two-thirds as broad as the frontal; parietals in broad contact with each other, parietal suture subequal to length of frontal ( Fig. 5D ). Loreal 1/1, subrectangular, small, about equal in length to depth, in contact with 2 nd –3 rd supralabials, not entering orbit; preoculars 1/1; postoculars 3/3, size decreasing from top to bottom; supralabials 9/9, 2 nd –3 rd in contact with the loreal, 4 th –6 th entering orbit, 8 th largest; temporals 2+3 on both sides; mental subtriangular, wide, 2.5 times as long as high ( Fig. 5A–B ); 9/10 infralabials, first pair in contact with each other behind mental, 1 st –5 th in contact with anterior chin shields; two pars of chin shields; posterior chin shields 1.3 times as long as anterior ones, separated from each other by small scales; mental groove apparent ( Fig. 5C ).

Coloration in preservative

Dorsal surface of head dark brown, with two small and white stripes run from the posterior edge of the 8 th supralabials to the nape. Ventral surface of head uniform whitish. Dorsal surface of body and tail pale dark brown with irregular brown speckling on either side. Ventral surface of body and tail whitish with scales bordered on either side by a blackish-brown stripe. According to CAS staff, no photographs of living specimens of the type series of Herpetoreas davidi sp. nov. were taken.

Variation (for details of information’s see Table 1 and Fig. 5 )

The longest known specimen is 575 mm long ( SVL 397 mm, TaL 178 mm, female; CAS 220550).

BODY SCALATION. 19–19–17 DSR; 151–156 VEN, 97–100 SC, single in all examined specimens, total number of VEN +SC 248–253, without sexual dimorphism. SL: 9 in all occurrences, IL: 9–10.

MAIN CHARACTERS OF PATTERN. Head olive-brown with two small, faint off-white spots on the parietals and a faint off-white sagittal line just behind the parietal. Dorsum dark olive-brown or dark brown with indistinct narrow blackish cross-bars or series of spots; venter off-whitish or cream, each ventral decorated with a pair of dark brown square spots on their lateral edges.

Comparison

We summarize the main characters separating Herpetoreas davidi sp. nov. from the other seven species of the genus Herpetoreas in Table 2 . More specifically, the comparisons with these species are as follows:

Herpetoreas davidi sp. nov. is easily distinguished from H. burbrinki , H. murlen , H. pealii , H. platyceps , H. sieboldii , and H. tpser by having single subcaudals vs divided subcaudals. Particularly, Herpetoreas davidi differs from H. burbrinki , H. murlen , H. platyceps , H. sieboldii , and H. tpser by having a single cloacal plate (vs divided) and fewer ventrals VEN 151–156 (vs 169–172 in H. burbrinki , 179 in H. murlen , 191–234 in H. platyceps , and 174–207 in H. sieboldii ); differs from H. pealii by having more ventrals VEN 151–156 (vs 136–144); and differs from H. tpser by having a smaller size in both sexes (max TL 552 mm in males, 575 mm in females vs 584 mm in males, 679 mm in females).

Finally, Herpetoreas davidi sp. nov. can be distinguished from the superficially similar species H. xenura by having a smaller size in both sexes (max TL 552 mm in males, 575 mm in females vs 870 mm in males, 754 mm in females), higher ratio TaL/TL in both sexes (0.301 –0.304 in males, 0.307 –0.310 in females vs 0.220 –0.283 in males, 0.226 –0.279 in females), and slightly lower number of VEN in both sexes (154–156 in males, 151–155 in females vs 158–165 in males, 155–165 in females).

Distribution and natural history notes

Herpetoreas davidi sp. nov. is so far known only from mountain forests in two locations within Rakhine Yoma Elephant Sanctuary, Gwa Township, Rakhine State, Myanmar ( Fig. 7 ; Appendix 4). Further studies in neighbouring areas, especially in the northern Rakhine Hills, Myanmar, are required to determine the actual distribution and population size and trend of this new species. According to data recorded for specimens deposited in the collections of CAS (http://portal.vertnet.org/search?q= Amphiesma + xenura +CAS+ Myanmar), specimens of Herpetoreas davidi were collected both during the day and at night on the ground near streams. The air temperature varied from 28°C to 31°C, and relative humidity was 94%. This species seems to be distributed at low elevations. The stomach of the holotype CAS 222969 contained a frog of the family Ranidae Batsch, 1796 .

Conservation status

Herpetoreas davidi sp. nov. is currently known only from Rakhine Yoma Elephant Sanctuary, Gwa Township, Rakhine State, Myanmar, a protected area. In absence of other biological data to assess its population status and potential threat, we suggest that the species should be considered a Data Deficient (DD) species, following the IUCN‘s Red List categories ( IUCN Standards and Petitions Committee 2019).

Figures

Fig. 5. Herpetoreas davidi sp. nov. A–F. Holotype, ♂ (CAS 222969) in preservation. A. Lateral view of the head, right side. B. Lateral view of the head, left side. C. Ventral view of the head. D. Dorsal view of the head. E. General dorsal view. F. General ventral view. G–H. Paratype, ♀ (CAS 220256). G. General dorsal view. H. General ventral view. Photos by G. Vogel.

Fig. 7. Map showing the distribution of Herpetoreas davidi sp. nov. in Rakhine Yoma Elephant Sanctuary, Rakhine, Myanmar (red stars). 1. Daung Stream (type locality). 2. Kyat Stream. Herpetoreas xenura (Wall, 1907) sensu stricto in red circles, Hebius khasiensis (Boulenger, 1890) in blue diamonds, and Hebius cf. khasiensis in blue triangle. Our estimated distribution range for Herpetoreas xenura sensu stricto is shaded in red. See Appendix IV for the corresponding locality numbers of the other taxa presented in the map.