Tropidophorus sebi, Pui, Yong Min, Karin, Benjamin R., Bauer, Aaron M. & Das, Indraneil, 2017

Pui, Yong Min, Karin, Benjamin R., Bauer, Aaron M. & Das, Indraneil, 2017, A new species of Tropidophorus Duméril & Bibron, 1839 (Squamata: Sauria: Scincidae) from Sarawak, East Malaysia (Borneo), Zootaxa 4258 (6), pp. 539-550 : 541-547

Tropidophorus sebi sp. nov.

( Figs. 1–2 )

Holotype. Museum of the Institute of Biodiversity and Environmental Conservation , UNIMAS P1167, from a small stream located at the First Count Logging Camp (01.35.644°N; 113.47.377°E; datum WGS84), Putai , upper Baleh, Kapit district, Sarawak, East Malaysia (Borneo), altitude 117 m ASL, coll. Pui Yong Min and Mohamad Paisal bin Wahab, 19 May 2015. Adult female. The type locality is shown in Fig. 3 .

Paratype. UNIMAS P 1166, same locality as holotype. Collected 20 May 2015. Adult female.

Diagnosis. A large-sized (SVL 83.8 mm and 85.9 mm in the two specimens known, both adult females); upper head shields, dorsal and lateral scales smooth; parietal scales in two pairs; presuboculars three; supraciliaries eight, first largest; supraoculars four, fourth contacting orbit; supralabials seven (supralabial five contacting orbit); infralabials four, second longest; postmental undivided; longitudinal scale rows 58; ventrals 53; transverse scale rows at midbody 34; subcaudals 98; preanals enlarged, single; and subdigital lamellae on Toe IV 19.

Etymology. The species name, sebi derives from the acronym ‘SEB’, for Sarawak Energy Berhad, with a genitive ending. We are pleased to name the new species after this organisation in acknowledgement of support received for our long-term research of the herpetofauna of the Upper Baleh region. Suggested common name: Baleh Water Skink.

Description of holotype. Adult female. Large size, SVL 83.8 mm, TL 121.4 mm; snout acute (IN:IO ratio 0.37), projecting beyond lower jaws; nostril laterally oriented; oval, situated closer to snout-tip than to orbit; eye– nostril distance 4.83 mm, eye–snout distance 6.58 mm (E-N:E-S ratio 0.73); head long, much longer than wide, HL 13.60 mm, HW 12.48 mm (HL:HW ratio 1.09); head shape slightly flattened, HD 8.91 mm (HL:HD ratio 1.53); upper head shields smooth; supranasals absent; frontonasal trapezoidal, as long as wide; prefrontals trapezoidal, in narrow contact medially; frontal elongated, trapezoidal, wider anteriorly; frontoparietals joined; interparietal single, with small transparent spot; parietal scales in two pairs; large posterior parietals, in contact posteriorly; small anterior parietal, in contact with frontoparietal and supraocular IV; nuchal scales in two pairs; nostrils on nasal located closer to anterior loreal; postnasal absent; supranasals absent; loreals two, anterior lower than posterior; preoculars two; presuboculars three, anterior large, second in contact with third and fourth supralabials, and third in contact with fourth and fifth supralabials; supraciliaries eight, first largest; supraoculars four, fourth contacting orbit; postsupraocular present; two postocular; pretemporal single; six postsuboculars, lower one contact with fifth and sixth supralabials; six primary temporals, lower one in contact with sixth and seventh supralabials; five secondary temporals; seven supralabials (supralabial five contacting orbit); four infralabials, second longest; mental smaller than rostral; rostral broad, projecting onto snout; posterior border of rostral straight; postmental undivided; genials in three pairs, first and second pair in broad contact, and third pair separated by three scales; auricular opening scaleless, ovoid and smaller than orbit of eye, its location indicated by a shallow depression; eyes relatively small; pupil discernable in preserved specimen; moveable eyelids; upper palpebrals 14; lower palpebrals 14; tongue short; undivided anteriorly, tip obtuse, not pointed; teeth relatively small and somewhat pointed.

Body slender, BW 12.52 mm (BW:SVL ratio 0.15); head distinct from neck and body; 58 longitudinal scale rows from parietal to above level of anterior margin of hind limb; dorsal and lateral scales smooth; ventrals 53, counted from first postgular to last scale before preanals; transverse scale rows at midbody 34; subcaudals 98; preanals enlarged, single; tail laterally compressed, relatively long, longer than snout-vent length (TL:SVL ratio 1.45); tail tip acute; tail base wider than rest of tail; tail gradually tapering to a point; median row of subcaudals enlarged. Visceral fat bodies absent in abdomen.

Limbs short and pentadactyl, digits short and clawed; lamellae smooth, enlarged; adpressed limbs touching; lamellae under Finger I-8; II-12; III-11; IV-9; V-5 and lamellae under Toe I-7; II-11; III-15; IV-19; V-12.

Colouration in life. Dorsum chocolate brown, with dark greyish-brown transverse bars on trunk and tail; bars on nape fused to form collar-like pattern; blackish-grey postocular band, starting from posterior corner of orbit and broadening to axillary region, and narrowing thereafter along the flanks of torsi; forehead unpatterned chocolate brown; temporal region grey with cream-coloured flecks; axilla and lower flanks with scattered yellow flecks; labials brown with greyish-black bars; dorsal surface of tail greyish-brown with darker areas forming incomplete bands; dorsal surface of fore- and hindlimbs chocolate brown with darker variegation; digits brown with darker bands; gular region pale grey, the chin with dark grey variegation, forming about 10 lines that extend to the pectoral region; upper two-thirds of pectoral region pale yellow with indistinct grey stripes; lower third orange, each scale edged with yellow; cloacal region deep orange; lowest edge of anal scale dark grey; tail base grey with large, orange-coloured scales; rest of tail dark grey; lower parts of forearm unpatterned pale grey; hindlimbs unpatterned pale orange; manus and pes dark grey; pupil rounded, black, with a narrow, orange ring; iris grey with an orange cast; oral cavity pale cream-coloured; tongue dark grey, not pale apically.

Measurements (in millimeters; holotype with paratype, in parentheses). SVL 83.8 (85.9); HL 13.6 (14.7); HW 12.5 (13.6); HD 8.9 (9.8); BW 12.5 (13.5); TBL 11.3 (11.9); ED 4.1 (4.3); IN 3.1 (3.2); E– S 6.9 (6.9); E– N 4.8 (5.3); N– S 1.7 (1.7); A–G 36.7 (41.5) and TL 121.4 (87.2).

Squamation (holotype with paratype in parentheses). Transverse scale rows at midbody 34 (33); longitudinal scale rows 58 (57); ventral scale rows 53 (53); supralabials 7 (7); infralabials 4 (4); subcaudals 98 (22 +; regenerated tail) and lamellae under toe IV 19 (19).

Ecological Notes and Distribution. The type series was collected from narrow crevices of rocky banks of small streams at the headwaters of Sungei Baleh. Currently, the new species is only known from its type locality, Putai, Upper Baleh, central Sarawak ( Fig. 4 ).

Phylogenetic relationships. The ML and BI topologies were identical with respect to relationships within Tropidophorus . Phylogenetic analysis of mitochondrial l2s and 16s provide strong support for Tropidophorus beccarii as the closest relative of the new species (see Fig. 5 ). This sister relationship suggests a single origin of smooth dorsal scales among Tropidophorus on Borneo (see Comparison), assuming an ancestral state of keeled dorsal scales for the genus. The phylogenetic results presented here are generally concordant with results of Honda et al. (2006), though we recover much weaker support for the paraphyly of Tropidophorus with respect to the Sphenomorphus group (ML bootstrap 36 vs. 73). The ML and BI topologies were identical with respect to relationships within Tropidophorus .

Raw pairwise sequence divergence between T. beccarii and the new species is 6.8–7.0% for 12s and 5.4–5.6% for 16s. Genetic divergence between the two type specimens of the new species is low, with raw distances of 0.2% and 0.3% for 12s and 16s, respectively. However, this measure of genetic diversity within the new species may be an underestimate as the two type specimens were collected from the same locality, and increased genetic divergence would likely exist across a larger spatial area.

Comparison. We initially compare the new species with Bornean congeners here. Tropidophorus sebi sp. nov. differs from T. brookei (distribution: widespread on Borneo), T. iniquus (distribution: upper Sungei Kajan, central Kalimantan, Indonesia), T. micropus (distribution: Long Bloe in upper Sungei Mahakkam, Kalimantan, Indonesia and Putai, Sarawak, Malaysia) and T. perplexus (distribution: Sungei Tinjar, Sarawak, Malaysia) in having smooth dorsal scales (versus keeled in these four species). The new species is further distinguished from another two smooth dorsal scales congeners, T. beccarii (widespread on Borneo) and T. mocquardii (distribution: northern Sabah, Malaysia; treated as a synonym of T. beccarii by some authors but considered valid here; see below) from Borneo, in showing a higher count of midbody scale rows (33–34) versus lower in T. beccarii (28–30), in having four supraoculars versus five supraoculars, and in lacking a thick, dark, dorsolateral stripe along flanks, that are with light transverse bands in T. mocquardii .

The presence of smooth dorsal scales distinguishes the new species from the following extra-Bornean congeners that possess keeled dorsal scales: T. assamensis Annandale, 1912 (distribution: north-eastern Bangladesh and north-eastern India, including Mizoram and Assam states); T. baconi Hikida, Riyanto & Ota, 2003 (distribution: Patunuang Natural Reserve, southern Sulawesi, Indonesia) ; T. baviensis Bourret, 1939 (distribution: Mount Ba Vi , Ha Tay Province, northern Vietnam and possibly, adjacent Thailand) ; T. berdmorei (Blyth, 1853) (distribution: Yunnan in southern China, Myanmar, Thailand and Vietnam) ; T. cocincinensis Duméril & Bibron, 1839 (distribution: Thailand, southern Vietnam and Cambodia) ; T. davaoensis Bacon, 1980 (distribution: southcentral Mindanao, Philippines); T. grayi Günther, 1861 (distribution: Panay, Luzon, Polillo, Leyte, Negros, Mastabe, Cebu, Philippines) ; T. guangxiensis Wen, 1992 (distribution: Guangxi and Hunan, China) ; T. hainanus Smith, 1923 (distribution: Hainan, Guangxi, Jiangxi, Hunan, Guangdong and Guizhou in China, and Bac Kan, Cao Bang, Dak Lak, Ha tay, Hai Duong, Hoa Binh, Kon Tum, Lai chau, Ninh binh, Phu Tho, Quang Ninh, Vinh Phuc and Nam Dinh in Vietnam) ; T. hangnam Chuaynkern, Nabhitabhata, Inthara, Kamsook & Somsri, 2005 (distribution: Chaiyaphum Province, north-easten Thailand), T. latiscutatus Hikida, Orlov, Nabhitabhata & Ota, 2002 (distribution: Phu Wua Wildlife Sanctuary, Nong Kai Province , eastern Thailand) ; T. matsuii Hikida, Orlov, Nabhitabhata & Ota, 2002 (distribution: Phu Pa Namtip, Roi Et Province, eastern Thailand) ; T. microlepis Günther, 1861 (distribution: southern Thailand, Vietnam, Laos and Cambodia); T. misaminius Stejneger, 1908 (distribution: Basilan, Camiguin and Mindanao, Philippines) ; T. murphyi Hikida, Orlov, Nabhitabhata & Ota, 2002 (distribution: Cao Bang Province, northern Vietnam) ; T. noggei Ziegler, Thanh & Thanh, 2005 (distribution: Phong Nha - Ke Bang National Park, Quang Binh Province, Vietnam) ; T. partelloi Stejneger, 1910 (distribution: Mataling River Falls , Cotabato Province, Mindanao, Philippines) ; T. robinsoni Smith, 1919 (distribution: Myanmar and Thailand); T. sinicus Boettger, 1886 (distribution: Guangxi, Guangdong, Hong Kong in China and Vietnam) and T. thai Smith, 1919 (distribution: Myanmar and northern and north-eastern Thailand) .

Two extra-Bornean congeners possess smooth scales: T. boehmei Nguyen, Nguyen, Schmitz, Orlov & Ziegler, 2010 (distribution: Hoang Lien Mountain, Lao Cai Province, northern Vietnam) and T. laotus Smith 1923 (distribution: Pak Lai district in Laos and Thailand). Tropidophorus boehmei differs from the new species in showing tiny, reduced prefrontals vs. trapezoidal prefrontals that are in contact, supralabials six vs. seven, longitudinal scale rows 60–69 vs. 58, and transverse scale rows at midbody 30–32 vs. 34 in the new Bornean species. Tropidophorus laotus differs from the new species in showing a frontonasal that is divided vs. fused, supralabials six vs. seven, and anterior loreal divided vs. undivided in the new species.

Finally, to aid field identification, we present below a dichotomous identification key to the Bornean species of the genus Tropidophorus .

Figures

FIGURE 1. Female holotype of Tropidophorus sebi sp. nov. (UNIMAS P 1167) in life. (SVL = 83.8 mm).

FIGURE 2. Female holotype of Tropidophorus sebi sp. nov. (UNIMAS P 1167), showing head in a. lateral; b. ventral; and c. dorsal views (scale markers = 10 mm); and d. pes and e. manus. (scale markers = 1 mm).

FIGURE 3. Map showing type locality of Tropidophorus sebi sp. nov., at Putai, Upper Sungei Baleh, Kapit District, Sarawak, Malaysia (Borneo). Inset: Map of the Indo-Pacific, showing the location of Borneo.

FIGURE 4. Habitat of Tropidophorus sebi sp. nov. at Putai, Upper Sungei Baleh, Sarawak, Malaysia (Borneo).

FIGURE 5. Concatenated ML phylogram of the mitochondrial 12 s and 16 s genes for Tropidophorus and close relatives with ML bootstraps (left number) and BI posterior probabilities (right number) shown at the nodes. Nodes with ML bootstrap ± 70 and BI posterior probability ± 0.95 are denoted with a black dot. The new species is indicated in bold.