Dixonius pawangkhananti Pauwels & Chomngam & Larsen & Sumontha 2020, sp. nov.
Creators: name: Pauwels, Olivier S. G.
name: Chomngam, Nirut
name: Larsen, Henning
name: Sumontha, Montri
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Reptilia
Squamata
Gekkonidae
Dixonius
Dixonius pawangkhananti

description: Dixonius pawangkhananti sp. nov.
(Figures 1–5)
Holotype. THNHM 25606 (field no. MS 563), adult male caught at night by M. Sumontha, N. Chomngam and P. Pawangkhanant on 8 August 2015 on the foot of the hill (12°50’04.4”N, 99°56’10.3”E) behind Wat (= Temple) Nikhom Wachiraram, Khao Yai Subdistrict, Cha-am District, Phetchaburi Province, peninsular Thailand.
Paratypes (2). AUP-02001 (field no. MS 564), adult male, and PSUZC-R 728 (field no. MS 565), adult female. Same locality, collecting date and collectors as holotype.
Diagnosis. Dixonius pawangkhananti sp. nov. can be distinguished from all other congeneric species by the combination of its maximal known SVL of 42.6 mm; 16 longitudinal rows of dorsal tubercles; 30 to 32 paravertebral scales; 16 longitudinal rows of ventrals across the abdomen; six precloacal pores in males, no pores in females; a marked canthal stripe; and a dorsal pattern consisting of bands or blotches.
Description of holotype. Adult male (Figure 1). SVL 40.7 mm. Head relatively long (HL/SVL ratio 0.32), wide (HW/HL ratio 0.61), not markedly depressed (HD/HL ratio 0.37), distinct from neck. Lores and interorbital region weakly inflated. Canthus rostralis relatively prominent. Snout moderately short (SnOrb/HL ratio 0.39), rounded, slightly longer than orbit diameter (OrbD/SnOrb ratio 0.58). Scales on snout and forehead small, hexagonal to rounded, flattened, with smooth or slightly rugose surface. Scales on snout larger than those on occipital region. Eye of moderate size (OrbD/HL ratio 0.22). Pupil vertical with crenelated margins. Supraciliaries short, without spines. Ear opening rounded, moderate (EarL/HL ratio 0.05); orbit to ear distance greater than orbit diameter. Rostral about twice wider than high. Two enlarged supranasals in broad contact. Rostral in contact with supralabial I on each side, nostrils and both supranasals. Nostrils round, each surrounded by supranasal, rostral, supralabial I and two postnasals. Mental triangular, about as long as deep. Two pairs of enlarged postmentals, anteriormost approximately four times larger than posterior. Each anterior postmental bordered anteriorly by mental, medially by the other anterior postmental, anterolaterally by infralabial I, posterolaterally by the second postmental; the pair collectively bordered posteromedially by a row of four throat scales. Supralabials to mid-orbital position 6/6; enlarged supralabials to angle of jaws 8/8. Infralabials 7/7. Interorbital scales 7.
Body slender, elongate (TrunkL/SVL ratio 0.43), without ventrolateral folds. Dorsal scales heterogeneous, small, irregular, flattened to conical, distributed among large, strongly keeled tubercles arranged in 16 more-orless regular longitudinal rows at midbody. Flanks covered with irregular, smooth to slightly conical scales. Gular region with relatively homogeneous, granular scales. Ventral scales smooth, imbricate, their free margin rounded. Ventrals increasing in size from throat to chest to abdomen, somewhat smaller in precloacal region. Midbody scale rows across belly to lowest rows of tubercles 16. Six precloacal pores in a discontinuous series: a poreless scale is separating three pores on the left side from three pores on the right side. Pore-bearing scales not enlarged relative to adjacent scale rows. Scales in the row immediately posterior to the pore-bearing row about three times the size of other scales in precloacal region. No femoral pores or enlarged femoral scales.
Fore- and hind limbs short, slender (FAL/SVL ratio 0.15; TibL/SVL ratio 0.16). Digits slender, dilated distally, all bearing robust, slightly recurved claws. Basal subdigital lamellae narrow, without scansorial surfaces (6-9-12-11- 9 right manus; 8-14-14-15-15 right pes); setae-bearing lamellae restricted to enlarged, distal, ‘‘leaf-like’’ scansors. Scales on palm and sole small, smooth, rounded to oval. Interdigital webbing absent. Relative length of digits: III>IV>II>V>I (manus), IV>III>V>II>I (pes). Tail original; total length of tail 57.3 mm. Tail slender, tapering to tip, longer than snout-vent length (TailL/SVL ratio 1.41). Supracaudals markedly keeled in the anterior portion of the tail. Ventral tail scales enlarged into transverse plates; 59 subcaudals.
Coloration in life. Dorsal surface of head gray with several irregular black blotches. On each side of the head a black canthal stripe runs from the nostril through the eye and extends to the neck; it is bordered below and above by a light grey thin stripe. The supralabials are whitish with each a black spot. The dorsal surface of the neck shows two longitudinal blotches followed by one transversal irregular blotch. The dorsum shows a gray background color with five irregular bars between the anterior and posterior limb insertions (Figure 1C). The same gray background color extends to the base of the tail, with one black bar above sacrum and two above the base of the tail; posteriorly to these two supracaudal black bars the following bars are all orangish on a light gray background. In total two black bars and ten orangish bars alternate with the light gray background color from the base of the tail to its tip. Dorsal surfaces of members gray with black spots. Ventral surfaces of head, body, members and tail whitish. In preservative the colors strongly fade and become less contrasted (Figure 1 A–B).
Variation. Main morphometric and meristic characters of the type series are provided in Table 1. Morphological and coloration characters of the paratypes agree in most respects with the holotype. The paratype female has an original tail and shows a TailL/SVL ratio of 1.33; i.e., proportionally a bit shorter than in the holotype. Similarly to the holotype, the male paratype has three left precloacal pores separated from three right precloacal pores by a median poreless scale. Precloacal pores are absent in females. Depending on the individuals, the background color of the body is grey to light brown. The dorsal pattern shows a clear sexual dimorphism: while males have a banded pattern, females have a blotched one. The tail of older individuals, both males and females, often shows an orangish color (Figures 1C, 2C, 4 A–B). None of the newborn and juvenile individuals seen showed an orangish tail (Figure 5).
Distribution and natural history. The type-specimens and other individuals of Dixonius pawangkhananti sp. nov. were found at night at the type-locality of the new species, i.e., at the foot of the hill behind Wat Nikhom Wachiraram (Figure 6). Several other individuals were observed a few hundred meters east, on another hill closer to the sea side, in Khao Nang Phanthurat Forest Park (Figure 7). Both hills are separated by 300 meters and are covered with secondary forest. They are located at about 5 km from the beach, and are totally surrounded by urbanized and cultivated areas. Individuals of Dixonius pawangkhananti sp. nov. were locally abundant, and always found on lime stones, never on the ground where Dixonius siamensis individuals were common. Dixonius pawangkhananti sp. nov. individuals were much shier than the latter, and seemed to fear light, rapidly retreating in rock crevices when approached with a torch.
Besides Dixonius siamensis, squamates we found in the direct surroundings of the new species included Cyrtodactylus interdigitalis Ulber and C. sp., Gehyra fehlmanni (Taylor) and G. lacerata (Taylor), Gekko gecko (Linnaeus) (Gekkonidae), Ahaetulla nasuta Lacepède, Chrysopelea ornata (Shaw) and Lycodon capucinus (Boie) (Colubridae).
A gravid female caught at the type-locality along with the type-series laid two eggs which hatched after three months.
Etymology. The specific epithet honors the Thai zoologist Parinya Pawangkhanant (Agriculture University of Phayao, Phayao, and Rabbit in the Moon Foundation, Ratchaburi), for his contributions to the herpetology of Thailand, and who is one of the collectors of the type-series. We suggest the following common names: Djing-djok din Cha-am (Thai), Cha-am leaf-toed gecko (English), Dixonius de Cha-am (French), Cha-am Blattfingergecko (German).
Comparison to other species. Dixonius pawangkhananti sp. nov. is distinguished from the Vietnamese D. aaronbaueri Ngo & Ziegler, 2009 based on its larger SVL (42.6 vs. 38.6 mm), lower Ven number (16 vs. 18 or 19), much higher DTR number (16 vs. 11), sensibly lower PV number (30–32 vs. 45–50) and PV’ number (18–21 vs. 29–32), lower InterOrb number (7 vs. 8–10), and its dorsal pattern (Ba or Bl vs. U). Although they show similarities in their dorsal pattern, Dixonius pawangkhananti sp. nov. clearly differs from Dixonius hangseesom by its much lower Ven number (16 vs. 22–26), higher DTR number (16 vs. 12–14), lower InterOrb number (7 vs. 10) and lower IL number (6 or 7 vs. 8). It can be separated from Dixonius kaweesaki by its much lower Ven number (16 vs. 24), higher DTR number (16 vs. 12 or 13), lower SL number (7 or 8 vs. 10 or 11) and lower SLMOrb number (5 or 6 vs. 7 or 8), lower PrePo number (6 vs. 9–11) and by its dorsal pattern (Ba or Bl vs. St). It differs from the Laotian Dixonius lao Nguyen, Sitthivong, Ngo, Luu, Nguyen, Le & Ziegler, 2020 by its much smaller SVL (42.6 vs. 55.4 mm), much lower Ven number (16 vs. 23 or 24), lower DTR number (16 vs. 20–23), much lower PV number (30–32 vs. 40–43) and lower PV’ number (18–21 vs. 24 or 25), lower InterOrb number (7 vs. 8 or 9), lower SMLOrb number (5 or 6 vs. 7 or 8), lower PrePo number (6 vs. 8), its marked canthal stripe, and its dorsal pattern (Ba or Bl vs. U). It can be separated from Dixonius melanostictus Taylor, 1962 by its smaller SVL (42.6 vs. 50.0 mm), much lower Ven number (16 vs. 22), much higher DTR number (16 vs. 10 or 11), lower SL number (7 or 8 vs. 9) and SLMOrb (5 or 6 vs. 7), lower PrePo number (6 vs. 9), and by its dorsal pattern (Ba or Bl vs. St). It is distinguished from the Vietnamese Dixonius minhlei Ziegler, Botov, Nguyen, Bauer, Brennan, Ngo & Nguyen, 2016 by its lower Ven number (16 vs. 20–23), slightly higher DTR (16 vs. 14 or 15), much lower PV number (30–32 vs. 38–44) and lower PV’ number (18–21 vs. 23–26), lower PrePo number (6 vs. 7 or 8), and by its dorsal pattern (Ba or Bl vs. Sp). It differs from the sympatric Dixonius siamensis by its much smaller SVL (42.6 vs. 57.0 mm), lower Ven number (16 vs. 18–25), higher DTR (16 vs. 10–14), by its marked canthal stripe, and its dorsal pattern (Ba or Bl vs. Sp). It can be separated from the Vietnamese Dixonius taoi Botov, Phung, Nguyen, Bauer, Brennan & Ziegler, 2015 by its lower Ven number (16 vs. 21–23) and by its much higher DTR number (16 vs. 11 or 12). From Dixonius vietnamensis Das, 2004, it differs by its lower PV number (30–32 vs. 36), its lower InterOrb number (7 vs. 8–10) and by its dorsal pattern (Ba or Bl vs. Sp).
description: Published as part of Pauwels, Olivier S. G., Chomngam, Nirut, Larsen, Henning & Sumontha, Montri, 2020, A new limestone-dwelling leaf-toed gecko (Gekkonidae: Dixonius) from coastal hills in Cha-am, peninsular Thailand, pp. 97-108 in Zootaxa 4845 (1) on pages 98-102, DOI: 10.11646/zootaxa.4845.1.7, http://zenodo.org/record/4406394