A new cryptic arboreal species of the Cyrtodactylus brevipalmatus group (Squamata: Gekkonidae) from the uplands of western Thailand

The first integrative taxonomic analysis of the Cyrtodactylus brevipalmatus group of Southeast Asia recovered two newly discovered populations from the Tenasserim Mountains in Suan Phueng District, Ratchaburi Province, Thailand as a new species described here as C. rukhadeva sp. nov. Based on 1397 base pairs of the mitochondrial gene NADH dehydrogenase subunit 2 (ND2), C. rukhadeva sp. nov. is the well-supported sister species to a clade containing three undescribed species, C. ngati, and C. cf. interdigitalis with a large uncorrected pairwise sequence divergence from other species in the brevipalmatus group ranging from 15.4–22.1%. Cyrtodactylus elok and C. brevipalmatus are recovered as poorly supported sister species and the well-supported sister lineage to the remainder of the brevipalmatus group. Cyrtodactylus rukhadeva sp. nov. is putatively diagnosable on the basis of a number of meristic characters and easily separated from the remaining species of the brevipalmatus group by a number of discrete morphological characters as well as its statistically significant wide separation in multivariate morphospace. The discovery of C. rukhadeva sp. nov. continues to underscore the unrealized herpetological diversity in the upland forests of the Tenasserim Mountains and that additional field work will undoubtedly result in the discovery of additional new species. Vertebrate Zoology 71, 2021, 723–746 | DOI 10.3897/vz.71.e76069 Copyright L. Lee Grismer et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. L. Lee Grismer et al.: New arbroeal Cyrtodactylus from western Thailand 724


Introduction
Taxonomic partitioning of closely related, highly specialized, cryptic species has always been challenging because strong selection pressures on morphological characters can result in high degrees of parallel evolution. This is especially true for the Cyrtodactylus brevipalmatus group of continental Southeast Asia (Grismer 2008;Grismer et al. 2021a). Most members of this group are generally slow moving, cryptically colored species with prehensile tails ( Fig. 1) and partially webbed digits and spend most of their time above ground level-often in dense vegetation, beneath exfoliating bark, in root tangles, or within tree trunk crevices (Smith 1923;Ulber 1993;Grismer 2011;Nurngsomsri et al. 2014;Grismer et al. 2021b). The group currently contains four nominal species and at least three undescribed species (Chomdej et al. 2021;Grismer et al. 2021a) that range from northwestern Vietnam, Laos and Thailand, then southward along the Thai-Malay Peninsula to southern Peninsular Malaysia (Fig. 1). A recent molecular phylogeny of the group recovered the new species, C. ngati Le, Sitthivong, Tran, Grismer, Nguyen, Le, Ziegler & Luu from northwestern Vietnam (Le et al. 2021), as the sister species of C. interdigitalis Ulber of Thailand and Laos (Ulber 1993). However, this study did not have sufficient material to address many of the taxonomic issues surrounding the brevipalmatus group and the genetic sample of C. interdigitalis (LSUHC 11006) is of unknown provenance. In the most recent taxonomic study, Grismer (2008) noted a number of errors and misinterpretations in the literature based on misidentifications between C. interdigitalis and C. brevipalmatus Smith (Smith, 1923(Smith, , 1930(Smith, , 1935Welch 1990;Ulber 1993;Manthey and Grossmann 1997;Nabhitabhata et al. 2004). These errors stemmed from the fact that these two species are extremely similar in morphology and color pattern, and if not examined carefully across a broad range of characters, are easily confused with one another. The discovery of two new populations of the brevipalmatus group from Suan Phueng District, Ratchaburi Province in the Tenasserim Mountains of western Thailand within the currently proposed range of C. brevipalmatus (Grismer 2008), prompted us to initiate the first integrative taxonomic analysis of the group. To do so, we examined a suite of morphometric and meristic characters from specimens representing three of the four nominal species combined with a molecular phylogenetic analysis using the mitochondrial gene NADH dehydrogenase subunit 2 (ND2). Our analyses confirmed the specific recognition of C. brevipalmatus from the type locality, C. elok Dring, and C. ngati from its type localities, and that the newly discovered populations from Suan Phueng District comprise a new species described below. Furthermore, we provide molecular evidence strongly indicating that C. brevipalmatus does not range north of the Isthmus of Kra on the Thai-Malay Peninsula and reports of this species from western Thailand (Smith 1935;Welch et al. 1990;Ulber 1993;Manthey and Grossmann 1997;Nabhitabhata et al. 2004;Grismer 2008;Ellis and Pauwels 2012;Pauwels and Chan-ard 2014) comprise perhaps, as many as three undescribed species. We were not, however, able to examine specimens or acquire sequence data from C. interdigitalis from the type locality in Nam Nao National Park, Petchabun Province, Thailand. Therefore, populations from Laos and Thailand outside the type locality generally referred to as C. interdigitalis (e.g. Manthey and Grossmann 1997;Cox et al. 1998;Chan-ard et al. 1999Chan-ard et al. , 2015Stuart 1999;Nabhitabhata and Chan-ard 2005;Ellis and Pauwels 2012;Nurngsomsri et al. 2014;Grismer and Davis 2018;Chomej et al. 2021) are treated here as C. cf. interdigitalis pending further investigations.

Sampling
Specimens were collected in Suan Phueng District, Ratchaburi Province, Thailand by Parinya Pawangkhanant, Platon V. Yushchenko, Mali Naiduangchan, Chatmongkon Suwannapoom, and Nikolay A. Poyarkov during several field surveys in 2019 (Fig. 2). Geographic coordinates and elevations were obtained using a Garmin GPSMAP 60CSx and recorded in WGS 84 datum. Specimens were collected by hand, anaesthetized and euthanized with 20% benzocaine solution, femoral muscle or liver tissue samples removed, and then fixed in 10% buffered formalin before preserving in 70% ethanol. The tissue samples were stored in 95% ethanol. Specimens and tissues were subsequently deposited in the herpetological collections of the School of Agriculture and Natural Resources, University of Phayao (AUP, Phayao, Thailand) and of the Zoological Museum of Moscow University (ZMMU, Moscow, Russia).
Specimen collection and animal use protocols were approved by the Institutional Ethical Committee of Animal Experimentation of the University of Phayao, Phayao, Thailand (certificate number UP-AE61-01-04-022, issued to Chatmongkon Suwannapoom) and were strictly complacent with the ethical conditions of the Thailand Animal Welfare Act. Field work, including collection of animals in the field and specimen exportation, was autho-rized by the Institute of Animals for Scientific Purpose Development (IAD), Bangkok, Thailand (permit numbers U1-01205-2558 and UP-AE59-01-04-0022, issued to Chatmongkon Suwannapoom).

Morphological data and analyses
Morphological data included both meristic and morphometric characters. Measurements were taken on the left side of the body when possible to the nearest 0.1 mm using dial calipers under dissecting microscope following Murdoch et al. (2019). Measurements taken were: snout-vent length (SVL), taken from the tip of the snout to the vent; tail length (TL), taken from the vent to the tip of the tail, original or partially regenerated; tail width (TW), taken at the base of the tail immediately posterior to the postcloacal swelling; humeral length (HumL), taken from the medial end of the humerus at its insertion point in the glenoid fossa to the distal margin of the elbow while flexed 90°; forearm length (ForL), taken on the ventral surface from the posterior margin of the elbow while flexed 90° to the inflection of the flexed wrist; femur length (FemL), taken from the medial end of the femur at its insertion point in the acetabulum to the distal margin of the knee while flexed 90°; tibia length (TibL), Figure 1. Distribution of the species of the Cyrtodactylus brevipalmatus group. Stars = type localities and squares refer to literature records. White squares denote unexamined specimens of uncertain taxonomic status. Localities with specimen numbers denote individuals in the phylogeny (Fig. 2). No topotypic material (red) from the western Phetchabun massif was examined. NP = National Park and WS = Wildlife Sanctuary. taken on the ventral surface from the posterior surface of the knee while flexed 90° to the base of the heel; axilla to groin length (AG), taken from the posterior margin of the forelimb at its insertion point on the body to the anterior margin of the hind limb at its insertion point on the body; head length (HL), the distance from the posterior margin of the retroarticular process of the lower jaw to the tip of the snout; head width (HW), measured at the angle of the jaws; head depth (HD), the maximum height of head measured from the occiput to base of the lower jaw; eye diameter (ED), the greatest horizontal diameter of the eye-ball; eye to ear distance (EE), measured from the an-terior edge of the ear opening to the posterior edge of the bony orbit; eye to snout distance or snout length (ES), measured from anteriormost margin of the bony orbit to the tip of snout; eye to nostril distance (EN), measured from the anterior margin of the bony orbit to the posterior margin of the external nares; interorbital distance (IO), measured between the dorsal-most edges of the bony orbits; internarial distance (IN), measured between the nares across the rostrum; and ear length (EL), greatest oblique length across the auditory meatus.
Meristic characters evaluated were the number of supralabial scales (SL), counted from the largest scale im- mediately below the middle of the eyeball to the rostral scale; infralabial scales (IL), counted from the mental to the termination of enlarged scales just after the upturn of the mouth; the number of paravertebral tubercles (PVT), between limb insertions counted in a straight line immediately left of the vertebral column; the number of longitudinal rows of body tubercles (LRT), counted transversely across the center of the dorsum from one ventrolateral fold to the other; the number of longitudinal rows of ventral scales (VS,) counted transversely across the center of the abdomen from one ventrolateral fold to the other; the number of transverse rows of ventral scales (VSM), counted along the midline of the body from the postmentals to the cloacal opening; the number of expanded subdigital lamellae on the fourth toe proximal to the digital inflection (TL4E), counted from the base of the first phalanx where it contacts the body of the foot to the largest scale on the digital inflection-the large contiguous scales on the palmar and plantar surfaces were not counted; the number of small, generally unmodified subdigital lamellae distal to the digital inflection on the fourth toe (TL4U), counted from the digital inflection to the claw including the claw sheath (see Murdoch et al. 2019: Fig. 2); the total number of subdigital lamellae (TL4T) beneath the fourth toe (i.e. TL4E + TL4U = TL4T); the number of expanded subdigital lamellae on the fourth finger proximal to the digital inflection (FL4E) counted from the base of the first phalanx where it contacts the body of the foot to the largest scale on the digital inflection-the large contiguous scales on the palmar and plantar surfaces were not counted; the number of small, generally unmodified subdigital lamellae distal to the digital inflection on the fourth finger (FL4U) counted from the digital inflection to the claw including the claw sheath (see Murdoch et al. 2019: Fig. 2); the total number of subdigital lamellae (FL4T) beneath the fourth toe (i.e. FL4E + FL4U = FL4T); the total number of enlarged femoral scales (FS) from each thigh combined as a single metric; the number of enlarged precloacal scales (PCS); the number of precloacal pores in (PP) in males; the number of femoral pores in (FP) in males; the number of rows of post-precloacal scales (PPS) on the midline between the enlarged precloacal scales and the vent; and the number of dark body bands (BB) between the nuchal loop (the dark band running from eye to eye across the nape) and the hind limb insertions. Other morphological characters evaluated were the presence or absence of paravertebral tubercles, enlarged femoral scales, small tubercles on the forelimbs and flanks, paried or single enlarged subcaudal scales; large or small dorsolateral and ventrolateral caudal fringe scales (i.e. fringes), and the cross-section of the tail round or more square in shape.
Small sample sizes (n=1-3) from some of the populations/species precluded meaningful statistical analyses. However, the morphospatial clustering among the species for the meristic, morphometric, and concatenated datasets was visualized using principal component analysis (PCA) and discriminant analysis of principal components (DAPC) from the ADEGENET package in R (Jombart et al. 2010). We analyzed each data type (i.e. meristic and morphometric) separately in order to visualize the contribution of each to the variation in the group and then we concatenated the data types to visualize their overall contribution to the variation of the group. Previous studies have demonstrated that concatenated data sets generally outperform single data sets in capturing the overall morphological variation among closely related species (Grismer et al. , 2020a. Morphometric characters analyzed were SVL, AG, HumL, ForL, FemL, TibL, HL, HW, HD, ED, EE, EN, IO, EL, and IN. To remove potential effects of allometry in the morphometric dataset, size was normalized using the following equation: X adj =log(X)-β[log(SVL)-log(SV L mean )], where X adj =adjusted value; X=measured value; β=unstandardized regression coefficient for each population; and SVL mean =overall average SVL of all populations (Thorpe 1975(Thorpe , 1983Turan 1999;Lleonart et al. 2000, accessible in the R package GroupStruct (available at https://github.com/chankinonn/GroupStruct). The morphometrics of each species were normalized separately and then concatenated so as not to conflate intra-with interspecific variation (Reist 1986). All data were scaled to their standard deviation to insure they were analyzed on the basis of correlation and not covariance.
Meristic characters analyzed were SL, IL, LRT, VS, VSM, TL4E, TL4U. TL4T, FL4E, FL4U, FL4T, PCS, PPS, and BB. Paravertebral tubercles (PVT), enlarged femoral scales (FS) were not included due to their absence in Cyrtodactylus elok. Precloacal and femoral pores were also omitted due to their absence in females. For corroboration of the PCA, a discriminant analysis of principal components (DAPC) was performed on the same data sets. DAPC is a supervised analysis that relies on scaled data calculated from its own internal PCA as a prior step to ensure that variables analyzed are not correlated and number fewer than the sample size. Dimension reduction of the DAPC prior to plotting, is accomplished by retaining the first set of PCs that account for 90-99% of the variation in the data set (Jombart and Collins 2015) as determined from a scree plot generated as part of the analysis. The ranges, means, medians, and 50% quartiles were visualized using boxplots for the meristic data and violin plots with embedded boxplots for the mensual data. All analyses were performed in R [v3.4.3].

Genetic data
For the molecular phylogenetic analyses, we extracted the total genomic DNA from ethanol-preserved femoral muscle tissue of six specimens of the new Thai populations using standard phenol-chloroform-proteinase K extraction procedures with consequent isopropanol precipitation, for a final concentration of about 1 mg/ml (protocols followed Hillis et al. (1996) and Sambrook and David (2001)). We visualized the isolated total genomic DNA in agarose electrophoresis in the presence of ethidium bromide. We measured the concentration of total DNA in 1 μl using NanoDrop 2000 (Thermo Scientific), and consequently adjusted to ca. 100 ng DNA/μL.
PCR products were loaded onto 1.5% agarose gels in the presence of ethidium bromide and visualized in agarose electrophoresis. When distinct bands were produced, we purified the PCR products using 2 μl of a 1:4 dilution of ExoSapIt (Amersham) per 5 μl of PCR product prior to cycle sequencing. A 10 μl sequencing reaction included 2 μL of template, 2.5 μl of sequencing buffer, 0.8 μl of 10 pMol primer, 0.4 μl of BigDye Terminator version 3.1 Sequencing Standard (Applied Biosystems) and 4.2 μl of water. The cyclesequencing used 35 cycles of 10 sec at 96°C, 10 sec at 50°C and 4 min at 60°C. We purified the cycle sequencing products by ethanol precipitation. We carried out sequence data collection and visualization on an ABI 3730xl Automated Sequencer (Applied Biosystems).

Phylogenetic analyses
Ingroup samples consisted of 14 individuals of the brevipalmatus group representing three nominal species including a sample from one of the new populations in Suan Phueng District plus five individuals of Cyrtodactylus cf. interdigitalis from Thailand and Laos. Four species of the linnwayensis group were used to root the tree following Grismer et al. (2021b). Sequence data for some specimens were acquired from GenBank and newly generated sequences were deposited in GenBank (Table 1).
Maximum Likelihood (ML) and Bayesian Inference (BI) were used to estimate phylogenetic trees. Best-fit models of evolution determined in IQ-TREE (Nguyen et al. 2015) using the Bayesian information criterion (BIC) implemented in ModelFinder (Kalyaanamoorthy et al. 2017) indicated that TNe+I+G4 was the best-fit model of evolution for the tRNAs and HKY+F+G4, TIM3+F+G4, and TPM3u+F+I+G4 were the best models of evolution for codon positions 1, 2, and 3, respectively. The ML analysis was performed using the IQ-TREE webserver (Trifinopoulos et al. 2016) with 1000 bootstrap pseudoreplicates using the ultrafast bootstrap (UFB) analysis (Minh et al. 2013;Hoang et al. 2018). The BI analysis was performed on CIPRES Science Gateway (Miller et al. 2010) using MrBayes v3.2.4 (Ronquist et al. 2012. Two independent runs were performed using Metropolis-coupled Markov Chain Monte Carlo ( MCMCMC), each with four chains: three hot and one cold. The MC-MCMC chains were run for 15,000,000 generations with the cold chain sampled every 1500 generations and the first 10% of each run being discarded as burn-in. The posterior distribution of trees from each run was summarized using the sumt function in MrBayes v3.2.4 (Ronquist et al. 2012). Stationarity was checked with Tracer v1.7 (Rambaut et al. 2018) to be sure effective sample sizes (ESS) for all parameters were well above 200. We considered Bayesian posterior probabilities (BPP) of 0.95 and above and ultrafast bootstrap support values (UFB) of 95 and above as an indication of strong nodal support (Huelsenbeck et al. 2001;Minh et al. 2013). Uncorrected pairwise sequence divergences (p-distance) were calculated in MEGA 7 (Kumar et al. 2016) using the complete deletion option to remove gaps and missing data from the alignment prior to analysis.

Phylogenetic data
The ML and BI analyses recovered trees with identical topologies ( Fig. 2A). Cyrtodactylus elok and C. brevipal matus of the Thai-Malay Peninsula were recovered as poorly supported sister species (BPP 0.57/UFB 59) and the strongly supported (1.00/100) sister lineage to a strongly supported clade (1.00/100) containing the remaining taxa. Within that clade, the individual of the new population from Suan Phueng District was recovered as the sister lineage to a monophyletic group bearing the phylogenetic sequence of sp. 9, sp. 10, sp. 11, and terminating with the strongly supported (1.00/100) sister species C. ngati and C. cf. interdigitalis. Support values for these nodes in are shown in Figure 2A. The phylogenetic analyses strongly supported the recognition of the Suan Phueng population as a new species, which bears a 15.4-22.1% uncorrected pairwise sequence divergence from the other species in the brevipalmatus group ( Table 2). The phylogenetic analyses also supported the separate species status of sp. 9 and sp. 10 as previously recovered by Chomdej et al. (2021).
The phylogeny indicates species recognition for ZMMU R-16492 from Phu Hin Rong Kla National Park, Phitsanulok Province, Thailand ( Fig. 1; referred to here as sp. 11) in that it is recovered as the sister species to the strongly supported (1.00/99) lineage comprised of C. ngati and C. cf. interdigitalis (Fig. 2). Although the locality of ZMMU R-16492 at 1147 m in elevation is only 45 km to the northwest of the type locality of C. interdigitalis at 700 m in Nam Nao National Park, Petchabun Province (Ulber 1993), these upland sites are separated by a 20 km wide low-lying river basin of 136 m in elevation at its lowest point with no intervening hilly terrain ( Fig. 1). Similarly, C. cf. interdigitalis FMNH 265806 from the Phu Luang Wildlife Sanctuary occurs at 850 m in elevation and is 65 km north of the type locality of C. interdigitalis but separated from it by an approximately15 km wide low-lying river basin at approximately 200 m at its lowest point. ZMMU R-16492 lies 50 km to the south-west of FMNH 265806 and it too is separated by a lowlying river basins. Given the close geographic proximity of these three topographically separated upland localities and the fact that ZMMU R-16492 and FMNH 265806 are not each other's closest relatives, makes it premature to consider either as conspecific with C. interdigitalis in the Table 1. Specimens, locality, and GenBank accession numbers of specimens used in the phylogenetic analyses.

Species/specimens
Locality GenBank no.   absence of genetic data from the type locality or at least morphological data from the type series. Both options are currently being explored.
Although the monophyly of Cyrtodactylus cf. interdigitalis and C. ngati is strongly supported, the monophyly of each of them is not. Although it is difficult to conceive that C. ngati would not be monophyletic given that all specimens were found on the same karst formation approximately 200 km north of the nearest population of C.cf. interdigitalis (Fig.1), nodal support for its monophyly is only 0.62/82. That of C. cf. interdigitalis ranging from northern Laos to central Thailand is even less-0.51/52. If these nodes were collapsed on the basis of low support values, it would be phylogenetically conceivable to consider C. ngati and C. cf. interdigitalis as conspecific. However, these two species are trenchantly different in morphology (see below) and again, the absence of any data from the type locality of C. interdigitalis, makes any taxonomic proposal premature.

Multivariate data
The PCA of the concatenated meristic and adjusted morphometric data sets corroborated the phylogenetic analyses in that the Suan Phueng individuals are not embedded within the cluster of any other species along the combined ordination of principal component (PC) 1 and PC2 (Fig. 2B). PC1 accounted for 36.8% of the variation and loaded most heavily for AG, FemL, HW, HD, EL and FS. PC2 accounted for 15.3% of the variation and loaded most heavily for FL4T and BB (Table 3). These results were mirrored in the DAPC of the concatenated data (Fig.  2C). The PCA of the morphometric data also recovered separation of the Suan Phueng individuals along both axes but very close to C. cf. interdigitalis. In the DAPC, however, the Suan Phueng individuals were within the 66% confidence ellipsoid of C. cf. interdigitalis (Fig. 3). PC1 accounted for 50.2% of the variation and loaded most heavily for ES, HD, AG, FemL, and HL ( Fig. 4) and PC2 accounted for an additional 16.2% of the variation, loading most heavily for IO, IN, and EN. The meristic data also recovered separation of the Suan Phueng populations along the combined axes in the PCA and DAPC but again, closest to C. cf. interdigitslis (Fig. 5). PC1 accounted for 35.0% of the variation and loaded most heavily for AG, FemL, HW, HD, EL and FS (Fig. 6) and PC2 accounted for 20.1% of the variation, loading most heavily for FL4E, TL4T, and BB.

Taxonomy
Based on the phylogenetic relationships, PCA, DAPC, and several discrete morphological differences between the Suan Phueng individuals and all other species of the brevipalmatus group (see comparisons below and Table 4), we hypothesize that they comprise a discretely diagnosable lineage that is not reticulating with any other lineage and as such, should be accorded species status.

Description of holotype. (Figs. 7 and 8)
Adult male SVL 74.9 mm; head moderate in length (HL/SVL 0.27), width (HW/HL 0.72), depth (HD/HL 0.46), distinct from neck, triangular in dorsal profile; lores concave slightly anteriorly, weakly inflated posteriorly; prefrontal region slightly concave; canthus rostralis rounded; snout elongate (ES/HL 0.41), rounded in dorsal profile; eye large (ED/HL 0.23); ear opening round, small; eye to ear distance greater than diameter of eye; rostral rectangular, partially divided dorsally by inverted Y-shaped furrow, bordered posteriorly by large left and right supranasals and one small azygous internasal, bordered laterally by first supralabials; external nares bordered anteriorly by rostral, dorsally by large supranasal, posteriorly by two smaller postnasals, bordered ventrally by first supralabial; 11(R,L) rectangular supralabials extending to below Table 3. Summary statistics and principal component analysis scores for meristic characters of the Cyrtodactylus brevipalmatus group. Abbreviations are listed in the Materials and methods.   large left and right trapezoidal postmentals contacting medially for 60% of their length posterior to mental; one row of slightly enlarged, elongate sublabials extending posteriorly to fifth infralabial; gular and throat scales small, granular, grading posteriorly into slightly larger, flatter, smooth, imbricate, pectoral and ventral scales. Body relatively short (AG/SVL 0.46) with defined ventrolateral folds; dorsal scales small, granular interspersed with larger, conical, semi-regularly arranged, moderately keeled tubercles; tubercles extend from interorbital region onto base of tail; smaller tubercles extend anteriorly onto nape and occiput, diminishing in size and distinction in interorbital region; approximately 19 longitudinal rows of tubercles at midbody; approximately 27 paravertebral tubercles; 34 longitudinal rows of flat, imbricate, ventral scales much larger than dorsal scales; 153 transverse rows of ventral scales; 17 large, pore-bearing, precloacal scales; no deep precloacal groove or depression; and nine rows of post-precloacal scales on midline.
Forelimbs moderate in stature, relatively short (ForL/ SVL 0.11); granular scales of forearm slightly larger than those on body, interspersed with small tubercles; palmar scales rounded, slightly raised; digits well-developed, relatively short, inflected at basal interphalangeal joints; digits narrower distal to inflections; subdigital lamellae wide, transversely expanded proximal to joint inflections, narrower transverse lamellae distal to joint inflections; claws well-developed, claw base sheathed by a dorsal and ventral scale; nine expanded and 11 unexpanded lamellae beneath first finger; hind limbs more robust than forelimbs, moderate in length (TibL/SVL 0.13), covered dorsally by granular scales interspersed with moderately sized, conical tubercles and anteriorly by flat, slightly larger scales; ventral scales of thigh flat, subimbricate, larger than dorsals; subtibial scales flat, imbricate; one row of 9,8(R,L) enlarged femoral scales not continuous with enlarged precloacal scales, terminating distally at knee; proximal femoral scales smaller than distal femorals, the latter forming an abrupt union with smaller, rounded, ventral scales of posteroventral margin of thigh; 8,9(R,L) femoral pores; plantar scales flat; digits relatively long, well-developed, inflected at basal interphalangeal joints; 8(R,L) wide, transversely expanded subdigital lamellae on fourth toe proximal to joint inflection that extend onto sole; nine expanded and 10 unexpanded lamellae beneath first toe; and claws well-developed, sheathed by a dorsal and ventral scale at base.
Tail long (TL/SVL 1.29) 6.8 mm in width at base, tapering to a point; dorsal scales flat, square bearing tubercles forming paravertebral rows and slightly larger tubercles forming a dorsolateral longitudinal row; enlarged, posteriorly directed semi-spinose tubercles forming small  but distinct ventrolateral caudal fringe; median row of paired, transversely expanded subcaudal scales, larger than dorsal caudal scales; base of tail bearing hemipenal swellings; three conical postcloacal tubercles at base of hemipenal swellings; and postcloacal scales flat, imbricate.
Coloration in life (Fig. 8). Ground color of the head body, limbs, and tail brown; faint, diffuse mottling on the top of the head; wide, dark-brown post-orbital stripe; lores dark-brown; nuchal band faint, bearing two posterior projections; three wide faint body bands edged in darkbrown between limb insertions; band interspaces bearing irregularly shaped, dark markings; faint dark speckling on limbs and digits; five wide slightly darker caudal bands separated by five lighter caudal bands; posterior tip of regenerated tail unbanded; ventral surfaces beige, generally immaculate; gular region lacking pigment; poaterior subcaudal region faintly banded; iris orangish gold in color.  Variation (Fig. 8). The female paratype differs significantly from the male holotype in coloration and pattern. The holotype has a much less contrasting dorsal pattern with only faint indications of dorsal body and caudal bands whereas the paratype is boldly marked, bearing a one dark jagged-edged nuchal band and three dark jagged-edged body bands, all with darkened borders. The caudal pattern of the paratype consists of six dark and seven light-colored contrasting bands on a full original tail whereas the holotype has four dark and light-colored weakly contrasting bands and a regenerated tail tip. The top of the head of the holotype is essentially unicolor whereas that of the paratype is darkly mottled. With only one specimen of each sex we cannot say if these differences in color pattern are sexually dimorphic. An uncataloged juvenile had a generally unicolor tan dorsal ground color overlain with a dark-brown nuchal loop bearing two posteriorly oriented projections, four complete to incomplete dark-brown body bands, and nine dark-brown caudal bands separated by eight tan to white caudal bands (Fig. 8) Distribution. Cyrtodactylus rukhadeva sp. nov. is known only from the type locality from Khao Laem Mountain, Suan Phueng District, Ratchaburi Province, Thailand and Hoop Phai, Suan Phueng District, Ratchaburi Province, approximately 7.7 km to the west of the type locality ( Fig. 1).
Etymology. The specific epithet "rukhadeva" is given as a noun in apposition and refers to the spirits or gods residing in trees in Thai mythology, known as Rukha Deva (literally "Tree Nymphs"). According to Thai folklore, these sylvan spirits live on tree branches and on large older trees wearing traditional Thai attire, usually in reddish or brownish colours, and are believed to protect the forest. The new arboreal species of Cyrtodactylus resides in one of the remaining fragments of the north Tenasserim montane forests. We want to underscore the need for the immediate assessment of herpetofaunal diversity surveys and implementation of adequate conservation measures for these relic forests.
Comparisons. Given the low sample size (n=2) of Cyrtodactylus rukhadeva sp. nov., meaningful statistical comparisons of meristic were not possible. However, some character ranges-at this point-are diagnostic in that they are widely separated from one another. We are      well aware that a larger sample size may preclude some of these characters as being diagnostic but it is equally probable that they will demonstrate that they are truly diagnostic. Cyrtodactylus rukhadeva sp. nov. can be separated from C. ngati in having fewer paravertebral tubercles (PVT; 27-30 vs 38-40), from C. elok in having more longitudinal rows of dorsal tubercles (LRT; 19 or 20 vs 4-7), from C. brevipalmatus and C. elok in having fewer transverse rows of ventral scales (VSM; 152-154 vs 172-180 and 190-234, respectively), from C. brevipalmatus in having more enlarged femoral scales (FS; 16 or 17 vs 10-16), from all species in having more femoral pores in males (FP; 20 vs 0-17 collectively), from C. cf. interdigitalis, C. brevipalmatus, and C. elok in having males having more precloacal pores (PP; 17 vs 13, 7, and 8, respectively), and from all species except C. elok in having more post-precloacal scales (PPS; 16 vs 2-10, cllectively. All ranges are presented in Table 5. Summary statistics and comparisons among the adjusted morphometric characters are presented in Table 6. Cyrtodactylus rukhadeva sp. nov. can be readily separated from all other species on the basis of discrete morphological differences (Table 4). Cyrtodactylus rukhadeva sp. nov. has paravertebral tubercles and enlarged femoral scales which are absent in C. elok. Cyrtodactylus rukhadeva sp. nov. has small tubercles on the forelimbs which are absent in C. cf. interdigitalis, C. ngati, and C. elok. Cyrtodactylus rukhadeva sp. nov. has small tubercles on the flanks, femoral pores in males, enlarged dorsolateral tubercles, and a large ventrolateral caudal fringe that are absent in C. elok. Cyrtodactylus rukhadeva sp. nov. has a square tail in cross-section versus a round tail in C. cf. interdigitalis, C. ngati, and C. brevipalmatus. Cyrtodactylus rukhadeva sp. nov. has single enlarged subcaudal scales versus paired enlarged subcaudal scales in C. cf. interdigitalis and C. brevipalmatus. Cyrtodactylus elok and C. ngati lack distinctly enlarged subcaudal scales. Cyrtodactylus rukhadeva sp. nov. has a prehensile tail apparently lacking in C. ngati. Figure 9 illustrates the general morphological and color pattern similarity of the other members of the brevipalmatus group to C. rukhadeva sp. nov. Natural History. Cyrtodactylus rukhadeva sp. nov. inhabits montane and submontane evergreen polydominant tropical forests, and was most often recorded in bamboo forests mixed with dry dipterocarp forests at elevations ranging from 600 to 1100 m a.s.l. and dominated by the large trees Anisoptera costata Korth, 1841 and Dipterocarpus gracilis Blume, 1825 (Dipterocarpaceae) (Fig. 10A). Lizards were usually observed near large tree holes or hiding among the roots of strangler fig trees (Ficus sp.; Moraceae) (Fig. 10B). All were active from approximately 19:30-23:50 hrs and approximately 2 m above the ground. One lizard was observed ca. 6 m above the ground on the branch of Syzygium sp. (Myrtaceae) above a rocky streambed. Given its morphology, we believe C. rukhadeva sp. nov. is an arboreal specialist that generally resides in the upper canopy, but may be forced down to lower portions of the canopy or to the

Discussion
The tangled taxonomic history among the species of the brevipalmatus group revolves around their general morphological similarity (Fig. 9)-likely resulting from selection pressures from their unique, secretive, arboreal life style-and the fact that no detailed morphological analysis incorporating genetic data had ever been conducted. Smith's (1935) report of C. brevipalmatus from Ban Pa Che, Raheang (Umphang in Ellis and Pauwels 2012) Tak Province in western Thailand (not listed by Taylor 1963) was based on material he did not examine and his account merely re-described his specimens from the type locality at Khao Luang, Nakon Sri Thammarat Province (Smith 1923(Smith , 1930. Ban Pa Che is the same locality as Chao Doi Waterfall, Mae Moei National Park, Tha Song Yang District from where Chomdej et al. (2021) report sp.10. and it is highly likely this is the species reported by Smith (1935) as C. brevipalmatus. Ulber (1993) examined a specimen he referred to as C. brevipalmatus from Kaeng Krachen National Park, Petchaburi Province, approximately 400 km north of the type locality of C. brevipalmatus which was repeated by Nabhitabhata et al. (2004) and Pauwels and Chan-ard (2006). Kaeng Krachen National Park is 85 km across continuous upland habitat south of the type locality of C. rukhadeva sp. nov. and based on data from Ulber (1993) and a photograph of a living specimen from Kaeng Krachen National Park (Fig. 9), this population shares with C. rukhadeva sp. nov.
a yellow-orange iris; enlarged, unpaired, subcaudal scales; and a tail that is generally square in cross-section-character states that separate it from C. brevipalmatus (Table  4). Thus, although its species status remains uncertain, it is referred to here as C. cf. rukhadeva sp. nov. Chomdej et al. (2021) reported an undescribed species (sp. 9) in their phylogeny from Thong Pha Phum National Park, Thong Pha Phum District, Kanchanaburi Province, Thailand and government reports from Nabhitabhata et al. (2004) and Nabhitabhata and Chan-ard (2005) list C. interdigitalis from Huai Kha Khaeng, Uthai Province. These records have been repeated as both C. brevipalmatus and C. interdigitalis in a number of popular field and pocket guides and web sites on Thai reptiles. Based on the fact that all sequenced specimens from western Thailand north of the Isthmus of Kra are more closely related to C. ngati and C. cf. interdigitalis than they are to the sequenced specimen of C. brevipalmatus from its type locality in southern Thailand (Figs. 1 and 2), we hypothesize that none of specimens from the western Thailand are C. interdigitalis or C. brevipalmatus and that the Huai Kha Khaeng population may also be a new species. The type locality of Cyrtodactylus interdigitalis, Tham Yai Nam Nao (Ulber 1993) occurs within the Nam Nao National Park that is part of an isolated upland massif in the eastern section of the Phetchabun Mountains. Within this upland region, C. interdigitalis has been reported from Tat Mak National Park (https://www.thainationalparks.com/species/cyrtodactylus-interdigitalis), Phu Kiew Wildlife Sanctuary (Chan-ard et al. 2015), and Phu Kraden National Park (Chan-ard et al. 2015) ranging from ~700-1000 m in elevation (Fig. 1). Given that these are geographically proximate localities across continuous upland habitat we have no reason to believe at this point these populations are not conspecific.
The ND2 phylogenies (Fig. 2) were consistent with the CO1 phylogeny of Le et al. (2021) in that Cyrtodactylus ngati was recovered as the strongly supported sister species of their C. interdigitalis of unknown provenance. The ND2 trees recovered C. brevipalmatus and C. elok as sister species whereas the CO1 tree recovered C. elok as the sister species to the remaining brevipalmatus group. Although neither of these trees had strong nodal support for either topology, the sister group relationship was consistent with the strongly supported topology recovered in genus-wide analyses (Grismer et al. 2021a,b). Despite the low amount of uncorrected pairwise sequence divergence between Cyrtodactylus ngati and C. cf. interdigitalis (1.0-3.5%), C. ngati consistently plots as the most well-separated species in the multivariate analyses (Figs. 2, 3, and 5). We hypothesize that this difference in overall body shape may relate to a difference in microhabitat preference-as the type series was found on karst. However, C. interdigitalis has been reported to occur near karst formations and within cracks on a concrete bridge. The fact that the entire type series of C. ngati was found on limestone cliffs and in limestone crevices (Le et al. 2021) may represent the first transition of an arboreal species to a karst-dwelling species (Grismer et al. , 2021b. It is becoming a well-established observation that karst-adapted species in gekkotans depart significantly in ecomorphology from their closely related non-karst-adapted species (Neilson and Oliver 2017; Grismer et al. 2020b;2021c;Kaatz et al. 2021) as a result of different selection pressures on their morphology (Kaatz et al. 2021).
The discovery of Cyrtodactylus rukhadeva sp. nov. continues to underscore the unrealized herpetological diversity in the upland forests of the Tenasserim Mountains and that additional species have yet to be discoveredespecially given that the borderlands between Thailand and Myanmar are renowned for their high degree of range-restricted endemism (Matsui 2006;Sumontha et al. 2012Sumontha et al. , 2017Wilkinson et al. 2012;Connette et al. 2017;Grismer et al. 2017c;Matsui et al. 2018Mulcahy et al. 2018Suwannapoom et al. 2018;Lee et al. 2019). Additional field surveys followed up with appropriately conducted, statistically defensible integrative taxonomic analyses are necessary to continue increasing our understanding of this region's exceptional herpetofaunal diversity and endemism if we are to effectively initiate science-based conservation management programs. collection protocols and animal use were approved by the Institutional Ethical Committee of Animal Experimentation of the University of Phayao, Phayao, Thailand (certificate number UP-AE61-01-04-0022 issued to Chatmongkon Suwannapoom). We also would like to express our gratitude to the Rabbit in the Moon foundation for help during the field work, and especially to Charnchai Bindusen and Juthamas Wangaryattawanich for organizing our fieldwork; and to Kawin Jiaranaisakul, Krarok Wohde, Torn Wohde, Jo Wohde, Maiday Ta-Au for assistance in the field; we thank Kanokwan Yimyoo for constant support and Vladislav A. Gorin, Pattarawhich Dawwrueng, Thiti Ruengsuwan, Akkrachai Aksornneam for help during the work in the field and in the lab. We thank Valentina F. Orlova (ZMMU, Russia) for support and letting us examine specimens under her care. We thank Bryan L. Stuart (NCSM) for the loan of specimens, photographs, and for generating and providing sequence data. Fieldwork, specimen collection, morphological examination, molecular phylogenetic analyses and data analyses for this paper were conducted with the financial support of the Russian Science