Pareas victorianus, Vogel & Nguyen & Zaw & Poyarkov, 2021

Vogel, Gernot, Nguyen, Tan Van, Zaw, Than & Poyarkov, Nikolay A., 2021, A new species of the Pareas monticola complex (Squamata: Serpentes: Pareidae) from Chin Mountains with additions to the Pareas fauna of Myanmar, Journal of Natural History 54 (39 - 40), pp. 2577-2612 : 2591-2597

Pareas victorianus sp. nov. Vogel, Nguyen and Poyarkov

( Figures 3 and 4 (b); Tables 1 and 6)

ZooBank registration: http://www.zoobank.org/urn:lsid:zoobank.org:act:3EAC4E75-

CD83-42BF-B1DC-F744B420AA43

Chresonymy

Pareas monticola – (in part) Wogan et al. 2008: 87.

Holotype. CAS 235254 , adult male collected on 21 May 2006, by A.K. Shein and L. Shein, from montane tropical forest between Kanpetlet town and Nat Ma Taung Mt., in Nat Ma Taung NP, Chin Hills, Mindat District , Chin State, western Myanmar (21.207556°N, 94.020056°E; at an elevation of 2280 m asl).

Diagnosis. Pareas victorianus sp. nov. differs from all other members of the genus Pareas by the combination of the following morphological characters: a slender yellow-brown medium-sized snake (total length 487 mm); frontal scale subhexagonal with the lateral sides converging posteriorly; anterior pair of chin shields longer than broad; loreal contacting the eye; prefrontal contacting the eye; preocular and presubocular absent; temporals 2 + 3; slightly enlarged median vertebral row; 7 supralabials; 6 or 7 infralabial scales; 7 scale rows slightly keeled at midbody; 164 ventrals without lateral keels; 58 subcaudals, all divided; about 64 slightly billowing vertical dark bars on the trunk; 2 slight thin black postorbital stripes starting from lower and upper edges of postorbital scales; lower postorbital stripe reaching the anterior part of seventh supralabial, not continuing to the lower jaw and chin; the left and right upper postorbital stripes merge forming a black nuchal collar.

Description of the holotype. Body slender and laterally flattened; head comparatively large, elongated, clearly distinct from thin neck (head more than 2 times wider than neck width near the head basis); snout blunt; eye rather large, pupil vertical and slightly elliptical ( Figures 3 (c,d) and 4(b)).

Body size. SVL 385 mm; TaL 102 mm; TL 487 mm; TaL/TL: 0.209.

Body scalation. Dorsal scales in 15–15–15 rows, slightly keeled in 7 scale rows at midbody, lacking apical pits; vertebral scales slightly enlarged (1 medial row); outermost dorsal scale rows not enlarged; ventrals 164 (+ 1 preventral), lacking lateral keels; subcaudals 58, all divided; cloacal plate single.

Head scalation. Rostral not visible from above ( Figure 3 (e)); single nasal, not divided; 2 internasals, much wider than long, narrowing and slightly curving back laterally (in dorsal view), anteriorly in contact with rostral, laterally in contact with nasal and loreal, posteriorly in contact with prefrontal, not contacting preocular; 2 large irregular pentagonal prefrontals, much larger than internasals and with a slightly diagonal suture between them, contacting the eye ( Figure 4 (b)); single frontal hexagonal in shape with the lateral sides converging posteriorly, longer than wide, smaller than parietals ( Figure 3 (e)); presubocular absent; on the left side subocular and postocular fused into a crescent-shaped scale; on the right side single subocular not fused with postocular; 1 large loreal, broadly in contact with eyes, replacing the preocular, contacting prefrontal, internasal, nasal, 2 nd supralabial and subocular; 7/7 supralabials, 3 rd –5 th SL touching the subocular, none reaching the eye, 6 th by far the largest, elongate; 1/1 supraocular; 2/2 anterior temporals, lower ca. 2 times larger than the upper; 2/3 posterior temporals ( Figures 3 (c,d) and 4(b)); 7/6 infralabials, anteriormost in contact with opposite one along midline, bordering mental, anterior 5 pairs of infralabials bordering anterior chin shields; 4 pairs of chin shields interlaced, 2 nd pair very small, no mental groove under chin and throat; anterior chin shields relatively large, much longer than broad, followed by 2 pairs of chin shields that are much broader than long ( Figure 3 (f)).

Colouration. In preservative, body light brown with about 64 dark unclear bands getting weaker posteriorly and hardly visible in the posterior half of the body. Whole body and tail with fine dark speckling. Head dorsally dark with some marbling, ventrally uniformly cream. Head laterally with 2 postocular stripes: lower one as dark line from the middle of the eye onto the anterior part of the last supralabial; upper one as a dark line from the upper part of the eye, up to behind the jaw angle. Upper labials with some fine irregular speckling. Body ventrally cream with fine mottling on the lateral parts of the ventrals ( Figure 3 (a,b)). Colouration in life unknown.

Comparisons. Comparative morphological information on species diagnostics in the genus Pareas is summarised in Table 6. Pareas victorianus sp. nov. differs from P. andersonii by loreal in contact with eye (vs not in contact); by preoculars absent (vs present); by the shape of temporal scales (short vs elongated); by a single row of enlarged vertebral scales (vs vertebral scales not enlarged); by a slightly higher number of ventrals (164 vs 141–162); by a higher number of subcaudals (58 vs 35– 47); and by body colouration (light brown vs dark grey). The new species differs from P. atayal by loreal in contact with eye (vs not in contact); by preoculars absent (vs present); by a lower number of vertebral scales enlarged (1 vs 3); by a lower number of ventrals (164 vs 174–188); by a lower number of subcaudals (58 vs 71–79); and by indistinct transverse bands on the body (vs distinct). Pareas victorianus sp. nov. can be distinguished from P. boulengeri by a lower number of infralabials (6 or 7 vs 8 [rare 9 or 7]); by a single row of enlarged vertebral scales (vs not enlarged); by a lower number of ventrals (164 vs 176–187); and by a lower number of subcaudals (58 vs 62– 77). The new species differs from P. carinatus and from P. menglaensis by frontal scale shape (subhexagonal with the lateral sides converging posteriorly vs hexagonal with the lateral sides parallel); by anterior pair of chin shields longer than broad (vs broader than long); by loreal in contact with eye (vs not in contact); by prefrontal contacting eye (vs not in contact); by preoculars absent (vs present); by 2 anterior temporals (vs 3); and by a lower number of enlarged vertebral scales (1 vs 3). Pareas victorianus sp. nov. can be distinguished from P. chinensis by loreal contacting eye (vs not in contact); by preoculars absent (vs present); by a lower number of enlarged vertebral scales (1 vs 3); by a lower number of ventrals (164 vs 169–180); and by a lower number of subcaudals (58 vs 69–76). The new species differs from P. formosensis by loreal contacting eye (vs not contacting); by preoculars absent (vs present); by 7 dorsal scale rows at midbody keeled (vs all smooth); by a lower number of enlarged vertebral scales (1 vs 3); by a lower number of ventrals (164 vs 170–180); and by a lower number of subcaudals (58 vs 69–82). Pareas victorianus sp. nov. can be distinguished from P. hamptoni by loreal contacting eye (vs not contacting); by the absence of preoculars (vs presence); by a lower number of ventrals (164 vs 195); and by a lower number of subcaudals (58 vs 96). The new species can be distinguished from P. iwasakii by loreal contacting eye (vs not contacting); by the absence of preoculars (vs presence); by a lower number of infralabials (6 or 7 vs 9–11); by a lower number of ventrals (164 vs 189–194); and by a lower number of subcaudals (58 vs 76–84). Pareas victorianus sp. nov. differs from P. komaii by loreal contacting eye (vs not contacting); by the absence of preoculars (vs presence); by a lower number of keeled dorsal scales at midbody (7 vs 9–13); by a lower number of enlarged vertebral scales (1 vs 3); and by a slightly lower number of subcaudals (58 vs 60–76). The new species can be distinguished from P. macularius by loreal contacting eye (vs not contacting); by the absence of preoculars (vs presence); by enlarged vertebral scales (vs not enlarged); by a higher number of subcaudals (58 vs 39–53); and by different colouration of body (light brown vs dark grey). Pareas victorianus sp. nov. differs from P. margaritophorus by loreal contacting eye (vs not contacting); by the absence of preoculars (vs presence); by shorter temporal scales (vs temporals elongated); by 7 keeled dorsal scale rows at midbody (vs all smooth); by enlarged vertebral scales (vs not enlarged); by a slightly higher number of ventrals (164 vs 133–160); by a slightly higher number of subcaudals (58 vs 35–54); and by different body colouration (light-brown vs dark grey). The new species can be distinguished from P. mengziensis by light-brown colouration of dorsum with indistinct darker crossbars (vs solid black marking on back of head extending to dorsum); by preoculars absent (vs present); by loreal contacting eye (vs not contacting); by a single row of enlarged vertebral scales (vs 3 rows); and by a slightly lower number of ventrals (164 vs 167–173). The new species can be distinguished from P. modestus by loreal contacting eye (vs not contacting); by preoculars absent (vs present); by shorter temporal scales (vs elongated); by a slightly higher number of keeled dorsal scales at midbody (7 vs 3–5); by a single row of enlarged vertebral scales (vs not enlarged); by a slightly higher number of ventrals (164 vs 151–159); by a higher number of subcaudals (58 vs 35–46); and by different colouration of body (light-brown vs dark grey to black). The new species differs from P. nigriceps by loreal contacting eye (vs not contacting); by the absence of preoculars (vs presence); by 2 anterior temporals (vs 1); by a lower number of ventrals (164 vs 175–184); by a lower number of subcaudals (58 vs 73–77); by 2 black postorbital stripes (vs no postocular stripes); and by indistinct transverse bands on the body (vs distinct). Pareas victorianus sp. nov. differs from P. nuchalis by the shape of the frontal scale (subhexagonal with the lateral sides converging posteriorly vs hexagonal with the lateral sides parallel); by the anterior pair of chin shields longer than broad (vs broader than long); by loreal contacting eye (vs not contacting); by the absence of preoculars (vs presence); by 7 keeled dorsal scale rows at midbody (vs all smooth); by 2 anterior temporals (vs 3); by a lower number of ventrals (164 vs 201–220); and by a lower number of subcaudals (58 vs 102–120). The new species can be distinguished from P. stanleyi by a slightly lower number of keeled dorsal scales at midbody (7 vs 13); by a single row of enlarged vertebral scales (vs not enlarged); by a slightly higher number of ventrals (164 vs 151–160); and by supralabials not touching the eye (vs usually touching). Pareas victorianus sp. nov. differs from P. vindumi by the absence of presubocular (vs presence); by a higher number of supralabials (7 vs 6); by 7 keeled dorsal scale rows at midbody (vs all smooth); by a single row of enlarged vertebral scales (vs not enlarged); by a lower number of ventrals (164 vs 178); and by dark collar and cross bands present on body (vs absent). Finally, Pareas victorianus sp. nov. can be distinguished from its sister species P. monticola by the absence of presubocular (vs presence); by 7 keeled dorsal scale rows at midbody (vs all smooth); by a much lower number of ventrals (164 vs 178–199); by a lower number of subcaudals (58 vs 69–90); and by eye separated from supralabials by a subocular scale (vs 4 th or 4 th –5 th supralabials touching eye) ( Figures 4 (a,b), 5(c,d) and 6).

Etymology. The specific epithet ‘ victorianus ’ is a Latin adjective in nominative singular (masculine gender), and is given in reference to the type locality of this species, which was collected near the Nat Ma Taung Mt. (historically known as Mt. Victoria), the highest peak of the Chin Hills Ridge (elevation 3070 m asl). We suggest the following common names: ‘Mt. Victoria slug snake’ (English); ‘ Natmataung khayusar mwe ’ (Burmese).

Notes on distribution and ecology. Pareas victorianus sp. nov. is presently known only from mountain forests of Chin State, western Myanmar ( Figure 1 , locality 20) . The Chin Hills Ridge continues southwards to Magway and Rakhine divisions of Myanmar, and northwards to Mizoram State of India . The actual extent of distribution of the new species

is unknown; however, records from the aforementioned parts of Chin Hills in the territory of western Myanmar and the north-east portion of India are anticipated. Ecological data on Pareas victorianus sp. nov. are scarce. Wogan et al. (2008) reported the sympatry of the new species with Pareas andersonii (as P. macularius ). The type specimen was found at 07:27 h on the ground; the air temperature at the time of collection was 23.5°C and the relative humidity was 50%. It was found in montane evergreen forest at an elevation of ca. 2280 m asl according to the CAS specimen database (see http://portal.vertnet.org/o/cas/ herp?id=urn-catalogue-cas-herp-235254, accessed in May 2020). The forest habitat at the site of collection comprised montane evergreen forest with the predominance of trees from the families Dipterocarpaceae , Pinaceae , Lauraceae , Fagaceae and Magnoliaceae with dense bamboo ( Bambuseae , Poaceae ) undergrowth and Rhododendron spp. (Ericaceae) shrubs ( Fujikawa et al. 2008).

Figures

Figure 1. Map showing distribution of the Pareas monticola species complex and locations of the studied populations. Circles denote localities for which both DNA and morphological data were examined; diamonds denote localities for which only morphological data were available; triangles denote populations for which only DNA data were available; a dot in the centre of an icon indicates a type locality; question marks denote unconfirmed and historical records. Abbreviations: BAN. = Bangladesh; BHU. = Bhutan. Localities. Pareas monticola: BHUTAN: 1 – Bhutan, no exact locality (Lenz 2012); BANGLADESH: 2 – Lawachara NP, Moulvibazar, Sylhet (Das and Das 2017; Hakim et al. 2020); INDIA: 3 – Darjiling, West Bengal; 4 – Khasi Hills, Meghalaya; 5 – Jampui Hills, Tripura; 6 – Mizoram; 7 – Naga Hills, Assam (type locality of Dipsas monticola Cantor, 1839); 8 – Orang, Assam (Deepak et al. 2020); 9 – Abor Hills, Arunachal Pradesh; 10 – Mishmi Hills, Arunachal Pradesh; MYANMAR: 11 – Indawgyi NR, Myitkyina, Kachin; 12 – Banmauk, Sagaing; CHINA: 13 – ‘Medog’ (= Motuo), Xizang (Guo et al. 2011; Li et al. 2020; Wang et al. 2020); 14 – Linzhi, Motuo, Xizang; 15 – Longchuan, Yunnan (Yang and Rao 2008); 16 – Pingbian, Yunnan (Wang et al. 2020); VIETNAM: 17 – ‘Chapa’ (= Sa Pa), Lao Cai (Bourret 1936); 18 – Tam Dao, Vinh Phuc (Orlov et al. 2003); Pareas sp.: MYANMAR: 19 – Hkakabo Razi NP, Putao, Kachin; Pareas victorianus sp. nov.: MYANMAR: 20 – Nat Ma Taung Mt., Mindat, Chin (type locality). Photo showing P. monticola from Sagaing, Myanmar, by N.A. Poyarkov. Abbreviations: BAN. = Bangladesh; BHU. = Bhutan.

Figure 3. Holotype of Pareas victorianus sp. nov. in preservative (CAS 224415, adult male): a–b: Dorsolateral and ventral view of body, respectively; c–f: head in lateral right, lateral left, dorsal, and ventral aspects, respectively. Photos by G. Vogel.

Figure 4. Comparison of head scalation in lateral view of the type specimens of Pareas monticola complex members: a: Pareas monticola holotype (BM(NH) 1946.1.20.5, adult male); b: Pareas victorianus sp. nov. holotype (CAS 224415, adult male); c: Pareas sp. from Kachin State (CAS 235254, adult female). Drawings by L.B. Salamakha.