Gekko nadenensis Luu, Nguyen, Le, Bonkowski & Ziegler, 2017, sp. nov.

Gekko nadenensis sp. nov.

(Fig. 2)

Holotype. VNUF R.2016.1, adult male, on a karst cliff, near the entrance of Nang Log cave (17°30’N, 105°23’E, elevation 178 m a.s.l.), Naden Village, Gnommalath District, Khammouane Province, central Laos, collected by Vinh Quang Luu and Kieusomphone Thanabuaosy on 20 February 2016.

Paratype. NUOL-R.2016.2, adult male, the same data as the holotype; ZFMK 98741, gravid adult female, collected on a karst cliff inside Nang Log cave by Vinh Quang Luu, Thomas Calame, and Kieusomphone Thanabuaosy on 29 March 2015.

Diagnosis. Gekko nadenensis sp. nov. differs from its relatives by a combination of the following characters: a medium-sized gecko species (SVL 61.0– 77.1 mm); nares bordered with rostral; internasals absent; postmentals enlarged; interorbital scales between anterior corners of the eyes 28–30; dorsal tubercles absent; ventral scales between mental and cloacal slit 175–185; midbody scale rows 123–140; ventral scale rows 38–40; subdigital lamellae on first toes 13–15, on fourth toes 14–16; finger and toe webbing present at base; tubercles on upper surface of fore and hind limbs absent; precloacal pores six (3+3 or 5+1) in a discontinuous row in males and absent in the female; postcloacal tubercles 1 or 2; tubercles absent on dorsal surface of tail base; subcaudals distinctly enlarged; dorsal surface of body with greyish brown blotches.

Description of holotype. An adult male with a total length of 134.1 mm (SVL 61.0 mm, TaL 73.1 mm); body slender, elongate (AG/SVL ratio 0.46); head longer than wide (HW/HL ratio 0.70); rostral quadrangular, nearly twice wider than high (RH/RW ratio 0.56) and wider than mental (MW/RW ratio 0.78 mm), bordered with first supralabial and supranasal on each side; nostrils round, touching rostral, first supralabial, supranasal, and two enlarged nasals posteriorly; posterior nasal region concave; internasal absent; preorbitals 22/22, preorbital region deeply concave; interorbitals 30; eye large (OD/HL ratio 0.24), pupil vertical; ear opening oval, oblique, smaller than eye (TD/OD ratio 0.44); mental triangular, wider than long (ML/MW ratio 0.86); enlarged postmentals two, hexagonal, twice as long as wide, and longer than length of mental, touching mental, first infralabial on both sides and seven gular scales posteriorly, outer gular scales larger than inner scales; supralabials 12/14; infralabials 10/10; dorsal scales on body smooth, round or oval, granular, juxtaposed; lateral fold distinct; ventrals distinctly larger than dorsal scales, smooth, imbricate, and largest in the middle of belly; ventral scales at midbody 40; scale rows around midbody 140; ventral scales in a row between mental and cloacal slit 175; scales on dorsal surface of forelimbs slightly enlarged; tubercles on dorsal surface of limbs absent; scales on anterior and ventral parts of femur larger than those on posterior and dorsal parts; enlarged femoral scales absent; fingers and toes basally webbed; subdigital lamellae under first fingers 15/15, under fourth finger 15/14, under first toe 13/14, under fourth toe 15/16; precloacal pores six (3+3), in a discontinuous row, precloacal scales enlarged; postcloacal tubercles 1/1; base of tail thickened, without tubercles on dorsal surface; subcaudals enlarged, smooth, imbricate.

Coloration in life. Dorsal surface of head dark grey with grey blotches and brownish spots; posterior part of the orbit with a grey stripe; labials with grey and dark bars; crown region with a grey star aniseed shape; neck with three grey oval-shaped blotches; dorsal surface of body dark grey with grey blotches and brownish spots, largest blotches on the midbody; dorsal surface of fore and hind limbs brownish grey with light transverse bars; ventral surface of head, belly, and limbs cream with black dots; dorsal surface of tail with eight grey transverse bands, more distinct posteriorly; ventral tail grey-brown in forepart and with nearly closed bands in hindpart.

Sexual dimorphism. Measurements and scalation of the female paratype are shown in Table 2. The female paratype has a larger size (SVL 77.1 mm versus 61.0– 74.3 mm in males) and without precloacal pores.

TABLE ³. Morphological comparisons among the species of the Gekko japonicus group (mođifieđ after Luu et al. 2015, abbreviations đefineđ in text, - = đata unavailable).

......continued on the next page TABLE ³. (continueđ) ......continued on the next page TABLE ³. (continueđ) Comparisons. Based on examination of specimens and data obtained from the literature (Boulenger 1907; Ota et al. 1995; Rösler et al. 2005, 2010, 2011; Yang et al. 2012, Nguyen et al. 2013; Luu et al. 2014; Ngo et al. 2015; Yang 2015; Luu et al. 2015) we compared the new species from Laos with the remaining members of the Gekko japonicus group (Rösler et al. 2011; Luu et al. 2015) (see Table 3).

Morphologically, the new Gekko species can be distinguished from the species of the G. japonicus group (following Rösler et al. 2011; Luu et al. 2015) as follows:

Gekko nadenensis sp. nov. does not have dorsal tubercles and thus differs from the following species which have tubercles on the back: G. adleri, G. auriverrucosus, G. canhi, G. chinensis, G. japonicus, G. hokouensis, G. kwangsiensis, G. liboensis, G. palmatus, G. scabridus, G. shibatai, G. similignum, G. swinhonis, G. vertebralis, and G. wenxianensis.

The new species can be distinguished from G. aaronbaueri by having fewer interobital scales (28–30 versus 34–37), more scale rows around midbody (123–140 versus 98–104), and more precloacal pores in males (6 versus 3–4); from G. melli by its smaller size (SVL reaching 77.1 mm versus 84.6 mm), fewer interorbitals (28–30 versus 34–40), internasals absent (versus present), postmentals enlarged (versus not enlarged), and fewer precloacal pores in males (6 versus 9–11); from G. subpalmatus by having fewer interorbitals (28–30 versus 32), postmentals enlarged (versus not enlarged), the absence of internasals (versus present), having fewer ventral scales (38–40 versus 48), and precloacal pores in a discontinuous row in males (versus in a continuous row); from G. taibaiensis by its larger size (SVL reaching 77.1 mm versus 69 mm), having more supralabials (12–14 versus 9–10), and more lamellae under first and fourth toes (13–15 versus 6¯7 and 14–16 versus 7 or 8, respectively); from G. tawaensis by the lack of internasals (versus 2), having postmentals enlarged (versus not enlarged in G. tawaensis), and precloacal pores present (versus absent); from G. truongi by its smaller size (SVL reaching 77.1 mm versus 95.9 mm), having fewer interobital scales (28–30 versus 45–48), more scales from mental to cloacal slit (175–185 versus 160–172), and fewer precloacal pores in males (6 versus 10–11); and from G. yakuensis by lacking internasals (versus having), having postmentals enlarged (versus not enlarged), fewer precloacal pores in males (6, in a discontinuous row versus 6–8, in a continuous row), and the absence of tubercles on dorsal surface of tail (versus presence).

Gekko nadenensis sp. nov. is similar to G. bonkowskii, G. thakhekensis, G. scientiadventura, and G. sengchanthavongi in body size and dorsal pattern. However, the new species can be distinguished from G. bonkowskii by having more interorbitals (28–30 versus 26–27), precloacal pores in a discontinuous row in males (versus in a continuous row), more scales from mental to cloacal slit (175–185 versus 154–169), and more scale rows at midbody (123–140 versus 117); from G. thakhekensis by having more interorbitals (28–30 versus 22–26), more precloacal pores in males (6, in a discontinuous row versus 1–5, in a continuous row), more scales from mental to cloacal slit (175–185 versus 165–174), and more scale rows at midbody (123–140 versus 110–116); from G. scientiadventura by having fewer interorbitals (28–30 versus 41–51), and precloacal pores in a discontinuous row in males (versus in a continuous row), and more scales from mental to cloacal slit (175–185 versus 118–140); from G. sengchanthavongi by having more precloacal pores in males (6 versus 4–5), more supralabials and infralabials (12–14 versus 8¯10 and 10–12 versus 6–7, respectively), dorsal head pattern with light grey blotches and a grey stripe behind the orbit (versus dark and grey spots), and dorsal body pattern with light grey blotches and brown flecks (versus irregular transverse dark brown bars). For more details see Table 4.

Distribution. Gekko nadenensis sp. nov. is currently known only from the type locality in the karst forest of Nang Log cave, Naden Village, Gnommalath District, Khammouane Province, central Laos (Fig. 3).

Etymology. We name this species after its type locality, Naden Village, to underscore the importance of the limestone forest in terms of biodiversity and nature conservation. From this site another new gecko species (Cyrtodactylus rufford) was described recently (Luu et al. 2016). We suggest as common names: Naden Gecko (English), Kap Ke Naden (Laotian), and Naden Gecko (German).

Natural history. Specimens of the new species were collected between 19:30 and 22:00, on a karst cliff near the entrance of and inside Nang Log Cave, from 0.3 m to 3 m above the ground, at elevations between 158 and 178 m a.s.l. (Fig. 4). The humidity was approximately 70–80% and the air temperature ranged from 18 to 26o C. The new species co-occurs with the recently described bent-toed gecko Cyrtodactylus rufford (Luu et al. 2016). The female paratype, which was collected in March 2015 contained two eggs. In February 2016, we found a mass egglaying site (about 2 m above the ground) in a dark and narrow corner of a rock crevice system at the mouth of the Nang Log cave. Some of the eggs had not yet hatched (Fig. 5).