ZooKeys | 163: 143—| 76 (2023) A peer-reviewed open-access journal doi: 10.3897/zookeys. | 163.101230 RESEARCH ARTICLE #$Zookey S https:/ / ZOO keys. pensoft.net Launched to accelerate biodiversity research Two new species of Dixonius from Vietnam and Laos with a discussion of the taxonomy of Dixonius (Squamata, Gekkonidae) Vinh Quang Luu'”, Thuong Huyen Nguyen', Minh Duc Le?*°, Jesse L. Grismer’, Hong Bich Ha’, Saly Sitthivong’, Tuoi Thi Hoang', L. Lee Grismer?® | Faculty of Forest Resources and Environmental Management, Vietnam National University of Forestry, Xuan Mai, Chuong My, Hanoi, Vietnam 2. Herpetology Laboratory, Department of Biology, La Sierra University, 4500 Riverwalk Parkway, Riverside, California 92505, USA 3 Faculty of Environmental Sciences, University of Science, Vietnam National University, Hanoi, 334 Nguyen Trai Road, Hanoi, Vietnam 4 Central Institute for Natural Resources and Environmental Studies, Vietnam National University, Hanoi, 19 Le Thanh Tong, Hanoi, Vietnam 5 Department of Herpetology, American Museum of Natural History, Central Park West at 79” Street, New York, New York 10024, USA 6 College of Forestry Biotechnology, Vietnam National Uni- versity of Forestry, Hanoi, Vietnam 7 Faculty of Forestry, National University of Laos, Dong Dok Campus, Vientiane, Lao PDR 8 Department of Herpetology, San Diego Natural History Museum, PO Box 121390, San Diego, California, 92112, USA Corresponding authors: Vinh Quang Luu (vinhlq@vnuf.edu.vn); L. Lee Grismer (lgrismer@lasierra.edu) Academic editor: Thomas Ziegler | Received 2 February 2023 | Accepted 18 April 2023 | Published 23 May 2023 https./zoobank.org/9D07C5 9D-7AF6-4428-BB1LA-79D029368CA9I Citation: Luu VQ, Nguyen TH, Le MD, Grismer JL, Ha HB, Sitthivong S, Hoang TT, Grismer LL (2023) Two new species of Dixonius from Vietnam and Laos with a discussion of the taxonomy of Dixonius (Squamata, Gekkonidae). ZooKeys 1163: 143-176. https://doi.org/10.3897/zookeys.1163.101230 Abstract Integrated analyses using maximum likelihood (ML), Bayesian inference (BI), principal component anal- ysis (PCA), discriminate analysis of principal components (DAPC), multiple factor analysis (MFA), and analysis of variance (ANOVA) recovered two new diagnosable species of gekkonid lizards in the genus Dixonius, one from the Central Highlands, Gia Lai Province, Vietnam and another from the Vientiane Province, Laos. Phylogenetic analyses based on the mitochondrial NADH dehydrogenase subunit 2 gene (ND2) and adjacent tRNAs showed that Dixonius gialaiensis sp. nov. is the sister species of D. minhlei from Dong Nai Province, Vietnam and is nested within a clade that also includes the sister species D. siamensis and D. somchanhae. Dixonius muangfuangensis sp. nov. is the sister species to D. /ao from Kham- mouane Province, Laos and is embedded in a clade with D. vietnamensis, D. taoi, and undescribed species from Thailand. Multivariate (PCA, DAPC, and MFA) and univariate (ANOVA) analyses using combina- Copyright Vinh Quang Luu et al. This is an open access article distributed under the terms of the CCO Public Domain Dedication 144 Vinh Quang Luu et al. / ZooKeys 1163: 143-176 (2023) tions of 15 meristic (scale counts), six morphometric (measurements), and five categorical (color pattern and morphology) characters from 44 specimens encompassing all eight species of Dixonius from Vietnam and Laos clearly illustrate Dixonius gialaiensis sp. nov. and Dixonius muangfuangensis sp. nov. are statisti- cally different and discretely diagnosable from all closely related species of Dixonius. These integrative analyses also highlight additional taxonomic issues that remain unresolved within Dixonius and the need for additional studies. The discovery of these new species further emphasizes the underappreciated herpe- tological diversity of the genus Dixonius and illustrates the continued need for field work in these regions. Keywords Gekkota, Indochina, integrative taxonomy, molecular phylogeny, morphology, new species, Southeast Asia Introduction The genus Dixonius was established by Bauer et al. (1997) to contain two species, D. melanostictus (Taylor, 1962) and D. siamensis (Boulenger, 1898), with a distribution range through Myanmar, Thailand, Laos, Vietnam, and Cambodia. Currently, thirteen species have been recognized worldwide (Nguyen et al. 2020, 2021; Pauwels et al. 2021; Uetz et al. 2022). In Vietnam, six species of Dixonius have been documented, including four originally described from the country, i.e., D. vietnamensis (Das 2004) from Khanh Hoa and Binh Thuan provinces, D. aaronbaueri (Ngo and Ziegler 2009) from Ninh Thuan and Binh Thuan provinces, D. taoi (Botov, Phung, Nguyen, Bauer, Brennan & Ziegler, 2015) from Binh Thuan Province, D. minhlei (Ziegler, Botov, Nguyen, Bauer, Brennan, Ngo & Nguyen, 2016) from Dong Nai Province, and two from outside Vietnam, D. siamensis from Thailand and Cambodia and D. melanostictus from Thailand (Uetz et al. 2022). Lastly, in Laos, there are three species (D. siamensis, D. lao (Nguyen, Sitthivong, Ngo, Luu, Nguyen, Le & Ziegler, 2020), D. somchanhae (Nguyen, Luu, Sitthivong, Ngo, Nguyen, Le & Ziegler, 2021)) two of which, D. lao from Vientiane Capital and D. somchanhae from Khammouane Province, were de- scribed within the last five years (Fig. 1). During a recent herpetofaunal surveys in Chu Se Mountain Pass, Hbong Com- mune, Gia Lai Province in Vietnam and Vientiane Province in Laos, new populations of Dixonius were found at each location (Fig. 1). Based on phylogenetic evidence from the mitochondrial NADH dehydrogenase subunit 2 (ND2) gene and adjacent tRNAs, morphometric, meristic, and color pattern data, neither can be ascribed to any known species and as such they are described below as new species. Materials and methods A total of six Dixonius specimens were caught by hand from Gia Lai Province, Viet- nam and Vientiane Province, Laos. The specimens were fixed in approximately 80% ethanol and then transferred to 70% ethanol for permanent storage. Tissue samples taken before the specimens were preserved were stored separately in 95% ethanol. ‘Two new Dixonius from Vietnam and Laos 145 200 km (1) aaronbaueri (6) pawangkhananti (a1) somchanhae (2) dulayaphitakorum (7) lao (12) taoi (3) mekongensis (8) melanostictus (13) vietnamensis (4) hangseesom (9) minhlei muangfuangensis sp. NOV. - () kaweesaki siamensis (15) gialaiensis sp. nov. Figure |. Location of the type localities of all known species of Dixonius. The inset delimits the study area. 1 Dixonius aaronbaueri from Ninh Thuan Province, Vietnam; 2 D. dulayaphitakorum from Ra- nong Province, Thailand; 3 D. mekongensis from Ubon Ratchathani Province, Thailand; 4 D. hangseesom from Kanchanaburi Province, Thailand; 5 D. kaweesaki from Prachuap Khiri Khan Province, Thailand; 6 D. pawangkhananti from Phetchaburi Province, Thailand; 7 D. dao from Khammouane Province, Laos; 8 D. melanostictus from Nakhon Ratchasima Province, Thailand; 9 D. minhlei from Dong Nai Province, Vietnam; 10 D. siamensis from SaraBuri and Nakhon Ratchasima provinces, Thailand; 11 D. somchanhae from Vientiane Capital, Laos; 12 D. taoi from Binh Thuan Province, Vietnam; 13 D. vietnamensis from Khanh Hoa Province, Vietnam; 14 D. muangfuangensis sp. nov. from Vientiane Province, Laos; 15 D. gi- alaiensis sp. nov. from Gia Lai Province, Vietnam. 146 Vinh Quang Luu et al. / ZooKeys 1163: 143-176 (2023) The specimens have been deposited in the collection of the Vietnam National Uni- versity of Forestry (VNUF), Hanoi, Vietnam and the National University of Laos (NUOL), Vientiane, Laos. Species delimitation The general lineage concept (GLC: de Queiroz 2007) adopted herein proposes that a species constitutes a population of organisms evolving independently from other such populations owing to a lack of, or limited gene flow. By “independently,” it is meant that new mutations arising in one species cannot spread readily into another species (Barra- clough et al. 2003; de Queiroz 2007). Molecular phylogenies recovered multiple mono- phyletic mitochondrial lineages of individuals (populations) that were used to develop initial species-level hypotheses, the grouping stage of Hillis (2019). Discrete color pat- tern data and univariate and multivariate analyses of morphological data were then used to search for characters and morphospatial patterns consistent with the tree-designated species-level hypotheses, the construction of boundaries representing the hypothesis- testing step of Hillis (2019), thus providing independent diagnoses to complement the molecular analyses. In this way, delimiting (phylogeny) and diagnosing (taxonomy) species are not conflated (Frost and Hillis 1990; Frost and Kluge 1994; Hillis 2019). Molecular data and phylogenetic analyses Four samples of the newly collected specimens were analyzed, two from Gia Lai Prov- ince, Vietnam (VNUF R.2020.22 — field number GL.02, VNUF R.2020.33 — field number GL.03) and two from Vientiane Province, Laos (VNUF R.2022.42 — field number ME.02, VNUEF R.2022.52 — field number ME03). We used the protocols of Nguyen et al. (2021) for DNA extraction, amplification, and sequencing. The com- plete NADH dehydrogenase subunit 2 (ND2) gene with six partial or complete adja- cent tRNAs, approximately 1200 bp long, respectively, were amplified and sequenced using the primer pair, MetF1(5’-AAGCTTTCGGGCCCATACC-3’) and COIRI(5’- AGRGTGCCAATGTCTTTGTGRITT-3’) (Macey et al. 1997). Genomic DNA was extracted from all liver tissues stored in ethanol following the standard protocols of DNeasy blood and tissue kit, Qiagen (California, USA). The PCR volume consisted of 20 wl (1 pl each primer, 7 ul water, 10 pl of Taq mastermix and 1 pl DNA template). PCR conditions were: 95 °C for 5 min, followed by 42 cycles: 95 °C for 30 s, 50 °C for 45 sand 72 °C for 60 s with a final elongation step for 6 min at 72 °C. PCR products were visualized using electrophoresis through a 1.2% agarose gel, marker 100 bp, 1X TAE and stained with RedSafe Nucleic Acid Staining Solution and photographed under UV light of Geldoc system (Quantum CX5, Villber, France). Successful amplifications were purified using innuPREP Gel Extraction Kit (Analytik Jena, Germany). Cleaned PCR products were sent to 1* Base (Malaysia) for sequencing in both directions. We obtained 1,444 base pairs of NADH dehydrogenase subunit 2 gene (ND2) sequence data and the flanking tRNAs from 29 ingroup individuals of Dixonius Two new Dixonius from Vietnam and Laos 147 representing 13 nominal species including the new samples from Vietnam and Laos. Heteronotia spelea was used as an outgroup to root the tree based on the phylogenetic re- sults generated by Gamble et al. (2015). Sequence data for other species were acquired from GenBank. Newly generated sequences were deposited in GenBank (Table 1). Maximum likelihood (ML) and Bayesian inference (BI) were used to estimate phy- logenetic 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 F81+F was the best-fit model of evolu- tion for the tRNAMET and K2P+I, and HKY+F+G4 were the best models of evolu- tion for tRNAs2 and ND2, 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) us- ing MrBayes v. 3.2.4 (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 MCMCMC chains were run for 80,000,000 gen- erations with the cold chain sampled every 8000 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 v. 3.2.4 (Ronquist et al. 2012). Stationarity was checked with Tracer v. 1.6 (Rambaut et al. 2014) to ensure 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 11 (Kumar et al. 2016) using the complete deletion option to remove gaps and missing data from the alignment prior to analysis. A time-calibrated Bayesian phylogenetic tree was estimated using BEAST 2 (Bayesian Evolutionary Analysis by Sampling Trees) v. 2.7.3 (Drummond et al. 2012) implemented in CIPRES (Cyberinfrastructure for Phylogenetic Research; Miller et al. 2010) where the ingroup node subtending the split between Dixonius aaronbaueri and the remaining species was given a 24.04 mya prior with an offset range of 20.23—27.68 mya following Gamble et al. (2015). The split between Heteronotia and Dixonius was set at 45.0 mya with an offset range of 33.3-56.8 mya (Gamble et al. 2015). An input file was constructed in BEAUti (Bayesian Evolutionary Analysis Utility) v. 2.7.3. An optimized relaxed clock with unlinked site models, linked clock models and linked trees, and a calibrated Yule prior were employed for the species level. BEAST Model Test (Bouckaert and Drummond 2017), implemented in BEAST, was used to numeri- cally integrate over the uncertainty of substitution models while simultaneously esti- mating phylogeny using Markov chain Monte Carlo (MCMC). MCMC chains were run for 80 million generations and logged every 8,000 generations. The BEAST log file was visualized in Tracer v. 1.7.2 (Rambaut et al. 2014) to ensure effective sample sizes (ESS) were above 200 for all parameters. A maximum clade credibility tree using mean heights at the nodes was generated using [reeAnnotator v. 2.7.3 (Rambaut and 148 Vinh Quang Luu et al. / ZooKeys 1163: 143-176 (2023) Table |. List of specimens used for the phylogenetic analyses. Species Catalog no. Location GenBank no. Dixonius aaronbaueri ZFMK87274 Nui Chua NP, Ninh Thuan Province, southern Vietnam | HM997152 Dixonius gialaiensis sp. nov. VNUE R.2020.22 Chu Se District, Gia Lai Province, Vietnam 0Q819041 (Field no. GL.02) VNUEF R.2020.33 Chu Se District, Gia Lai Province, Vietnam OQ8190412 (Field no. GL.03) Dixonius lao VNUEF R.2016.2 Khammouane Province, Laos MT024681 IEBR A.2019.5 Khammouane Province, Laos MT024683 IEBR A.2019.6 Khammouane Province, Laos MT024682 Dixonius melanostictus VU 022 Captive, Thailand HM997153 Dixonius minhlei ZEMK 97745 Vinh Cuu, Dong Nai Province, Vietnam KX379194 Dixonius muangfuangensis sp. nov. | VNUF R.2020.42 | Muangfuang District, Vientiane Province, Central Laos | OQ818586 (Field no. MFO2) VNUF R.2020.52 | Muangfuang District, Vientiane Province, Central Laos | OQ818587 (Field no. MF03) Dixonius cf. siamensis VU 023 Captive, Thailand KX379195 Dixonius siamensis LSUHC 7328 Phnom Aural, Purset Province, Cambodia EU054299 FMNH 263003 Keo Seima District, Mondolkiri- Province, Cambodia EU054298 LSUHC 7378 Phnom Aural, Purset Province, Cambodia KP979732 Dixonius somchanhae VNUEF R.2020.2 Nasaithong District, Vientiane Capital, Laos MW605166 VNUEF R.2020.1 Nasaithong District, Vientiane Capital, Laos MW605165 VNUEF R.2020.3 Nasaithong District, Vientiane Capital, Laos MW605167 VNUEF R.2020.55 Vientiane Capital, Laos OQ818589 (Field no. VT05) VNUEF R.2020.54 Vientiane Capital, Laos OQ818588 (Field no. VT04) VNUEF R.2020.59 Vientiane Capital, Laos OQ818591 (Field no. VT09) VNUEF R.2020.56 Vientiane Capital, Laos OQ818590 (Field no. VTOT06) Dixonius sp. LSUHC 9466 Sai Yok, Kanchanaburi Province, Thailand KX379196 Dixonius taoi ZEMK 96680 Phu Quy Island, Binh Thuan Province, Vietnam KP979733 CAS 257300 Phu Quy Island, Binh Thuan Province, Vietnam KP979734 IEBR A 2014-26 Phu Quy Island, Binh Thuan Province, Vietnam KP979735 IEBR A 2014-27 Phu Quy Island, Binh Thuan Province, Vietnam KP979736 Dixonius cf. vietnamensis ZEMK 87273 Nui Chua, Ninh Thuan Province, Vietnam KX379201 Dixonius vietnamensis IEBR R.20163 Nha Trang, Khanh Hoa Province, Vietnam KX379198 Drummond 2013) with a burn-in of the first 10% of each run. Nodes with Bayesian posterior probabilities (BPP) of 0.95 and above were considered strongly supported (Huelsenbeck et al. 2001; Wilcox et al. 2002). Morphological data and analysis The morphological data set comprised six closely related species including six type specimens of Dixonius minhlei from Dong Nai Province, Vietnam (IEBR A.0801-02, VNMN R.2016.1-2, ZFMK 97745-46), three type specimens of D. dao from Kham- mouane Province, Laos (VNUF R.2016.2, IEBR A.2016.5-6), eight specimens of D. siamensis from Pursat Province, Cambodia (LSUHC 07328, 07378, 08420, 08487, Two new Dixonius from Vietnam and Laos 149 08491, 08522, 09284, 09289), five type specimens of D. somchanhae from Vientiane Capital, Laos (VNUF R.2020.1-5), four specimens of D. sp. from Gia Lai Province, Vi- etnam, and 12 specimens of D. vietnamensis from Nha Trang Province, Vietnam (ZRC 2.6024-27, IEBR R.2016.1, 2016.3, 2016.4, VNMN R.2016.3-4, ZFMK 97747-49). Morphological data included both meristic and morphometric characters. Mor- phological characters were taken from the 44 specimens following Bauer et al. (2004) and Ngo and Ziegler (2009). Morphometric characters were taken after preservation with a digital caliper to the nearest 0.1 mm under a zoom stereomicroscope on the right/left of the body. Recorded data included: SVL: snout-vent length (taken from the tip of the snout to the vent), TaL: tail length (taken from the vent to the tip of the tail, original or partially regenerated), TW: tail width (taken at the base of the tail immediately posterior to the postcloacal swelling), BW: body width (greatest width of torso, taken at the level of midbody), HL: head length (the distance from the posterior margin of the retroarticular process of the lower jaw to the tip of the snout), HW: head width (the distance from the posterior margin of the retroarticular process of the lower jaw to the tip of the snout), HD: head depth (the maximum height of head measured from the occiput to base of the lower jaw), EL: ear length (greatest oblique length across the auditory meatus), TBL: Tibia length (taken on the ventral surface from the posterior surface of the knee while flexed 90° to the base of the heel), AG: ax- illa to groin length (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), FA: forearm length (taken on the ventral surface from the posterior margin of the elbow while flexed 90° to the inflection of the flexed wrist), ED: eye diameter (the greatest horizontal diameter of the eye-ball), EN: eye nostril distance (measured from the anterior margin of the bony orbit to the posterior margin of the external nares), ES: eye snout distance (measured from anteriormost margin of the bony orbit to the tip of snout), EE: eye ear distance (measured from the anterior edge of the ear opening to the posterior edge of the bony orbit), IN: internarial distance (measured between the external nares across the rostrum), IO: interorbital distance (measured between the dorsal-most edges of the bony orbits). Meristic data taken were: V: ventral scales (counted transversely across the abdomen midway between limb insertions from one ventrolateral fold to the other), DTR: longi- tudinal rows of dorsal tubercles (counted transversely across the body midway between the limb insertions from one ventrolateral body fold to the other), PV: paravertebral scales (counted in a paravertebral row from first scale posterior to parietal scale to last scale at the level of vent opening), PV’: paravertebral scales (counted in a row be- tween limb insertions), T4: lamellae under fourth toe (counted from the distal scale containing claw to basal scale that broadly contacts adjacent fragmented scales), IOS: Interorbital scales (counted at narrowest point between orbits), ICS: interciliary scales (counted between supraciliaries at midpoint of orbit), SPL: supralabials (counted from the largest scale at the corner of the mouth to the rostral scale), IFL: infralabials (count- ed from termination of enlarged scales at the corner of the mouth to the mental scale), MO: number of supralabial at midorbital position, PP: precloacal pores in males. 150 Vinh Quang Luu et al. / ZooKeys 1163: 143-176 (2023) Color pattern on dorsum including the presence or absence of canthal stripes (CanthStrp), the presence or absence of strong darkly barred lips (LipBar), the pres- ence or absence of dark-colored round blotches on the top of the head (RdHdBlch) and dorsum (RdBodBlch), and the presence or absence of two regularly arranged whitish tubercles on flanks (Tub). The raw morphological data for all characters and specimens are presented in Tables 2, 3. All statistical analyses were performed using R v. 4.2.1 (R Core Team, 2021). Mor- phometric characters used in the statistical analyses were SVL, BW, HL, HW, HD, EL, ED, EN, ES, EE, IN, IO, FAr, TBLr, and AGr. Tail metrics were not used due to the high degree incomplete sampling (i.e., regenerated, broken, or missing). To remove potential effects of allometry on morphometric traits (sec. Chan and Grismer 2022), we used the following equation: Xadj = log(X) — B[log(SVL) — log(SVLmean)], where Xadj = adjusted value; X = measured value; 8 = unstandardized regression coefficient for each population; and SVLmean = overall average SVL of all populations (Thorpe 1975, 1983; Turan 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 into a single data set so as not to conflate potential intra- with interspecific variation (Reist 1986; McCoy et al. 2006). All data were scaled to their standard deviation to ensure they were analyzed on the basis of correlation and not covariance. Meristic characters (scale counts) used in statistical analyses were SPLr/l, IFLr/l, MO, IOS, ICS, V, DTR, and T4r/l. Precloacal and femoral pores were omitted from the analyses due to their absence in females. Cat- egorical characters analyzed were CanthStrp, LipBar, RdHdBlch, RdBodBlch, and Tub. A Levene’s test for normalized morphometric and meristic characters was con- ducted to test for equal variances across all groups. Analyses of variance (ANOVA) were conducted on meristic and normalized morphometric characters (see below) with statistically similar variances to search for the presence of statistically significant mean differences (p < 0.05) among species across the data set. Characters bearing statistical differences were subjected to a TukeyHSD test to ascertain which species pairs differed significantly from each other for those particular characters. Boxplots were generated for discrete meristic characters in order to visualize the range, mean, median, and de- gree of differences between pairs of species bearing statistically different mean values and violin plots were generated for continuous morphometric characters to visualize the same. Morphospatial positions were visualized using principal component analysis (PCA) from the ADEGENET package in R (Jombart et al. 2010) to determine if their posi- tioning was consistent with the putative species boundaries delimited by the molecular phylogenetic analyses and defined by the univariate analyses (see above). PCA, imple- mented using the “prcomp()” command in R, is an indiscriminate analysis plotting the overall variation among individuals (i.e., data points) while treating each individual independently (i.e., not coercing data points into pre-defined groups). Subsequent to the PCA, a discriminant analysis of principle components (DAPC) was used to test Two new Dixonius from Vietnam and Laos 151 Table 2. Sex and raw meristic and categorical data used in the analyses from specimens of Dixonius from Vietnam and Laos. m = male; f = female; j = juvenile; r/l = right/left. Species Museum no. | Sex Categorical data mali IOS | V | T4 | Canthal Blotches | Blotches | Two regularly r/l | rfl r/l strong | on the head | on dorsum disposed round round whitish tubercles on each side of the flanks minhlei IEBRA.0802. | m]| 8 | 6 | 6 | 10 |22} 14 | present | no yes yes absent IEBR A.0801 £185] 7 | 6 12 | present absent ZFMK 97745 | f | 7.5} 6 | 5.5} 10 13 | present absent VNMN R.2016.1} f | 8 | 6 15.5] 8 15 | present absent VNMN R.2016.2| f | 8 |65] 6 | 7 |20] 13 | present) no absent Sp. Nov. VNUF R.2020.33| f | 7 | 6 | 6 14 | present present VNUEF R.2020.44| mj | 8 | 7 | 6 14.5] present present vietnamensis ZRC 2.6024 |m]} 5 | 6] 5 13 | present present ZRC 2.6025 m/| 5 | 6] 5 | 9 |20} 13 | present} no present 8 |20] 13 | present] no no no present IEBR R.2016.3. | mJ] 8 | 6 | 5.5] 10 | 19] 13.5] present | no no no present 5.5] 9 |19]13.5] present] no no no present TEBRR.2016.1 | f | 7 | 6 | 5.5] 8 | 18] 13.5] present | no no no present 9 |20) 13 | present] no no no present 8 | 20] 14 | present) no no no present ZFMK 97747 | mj| 7.5 | 6 | 5.5 | 10 | 15] 13.5] present | no no no present 7 | 6 | 7 |21}12.5] present] no no no present ZFMK 97749 | ff | 7 | 6.5] 5.5] 8 | 19] 13.5] present] no no no present sp. 6 | 9 | 24) 14 | present] no no yes present VNUEF R.2022.82} £ | 7.5]5.5] 6 | 8 | 23] 14.5] present] no no yes present 8 | 23] 14 | present] no no yes present somchanhae VNUF R.2020.3 | m| 7 | 5 | 6 | 8 | 24] 14 | present | yes no no present VNUF R.2020.2 8 6 | 8 | 23) 15 | present | yes no no present VNUF R.2020.1 | m] 8 | 5.5] 6 15 | present no no present VNUF R.2020.4 | f | 8 |5.5] 6 15 | present no no present VNUF R.2020.5 | f | 8 | 6 | 6 13 | present no no present siamensis LSUHC09284 | f | 8 | 7 | 6 | 9 | 19] 14 | absent | yes no yes present 10 |22}14.5] absent | yes no yes present asuncoeae7 [Fe [7 [6 [10 [z0fra5|atene| ye [vo [ye | pr LSUHC08420 | mJ| 85] 7 | 6 | 10 |21] 13 | absent | yes no yes present f 6 | 9 |20}14.5] absent | yes no yes present LSUHC07328 | j | 7.5 | 6 | 5.5 absent no yes present LSUHC07378 | mJ] 8 | 6 | 6 14.5] absent no yes present LSUHC09289 | m|7.5] 6] 6 absent no yes present muangfuangensis | NUOL R.2022.01] m| 7 |65] 6 | 7 |21] 15 | absent | yes no no present Sp. Nov. 7 |20) 15 | absent | yes no no present | VNUF R.2020.52| f | 8 [65] 6 | 7 |21] 15 | absent | yes no no present lao | VNUF R.2016.2 | m | 9.5 | 8 | 7.5| 9 |23] 15 | absent | yes no no absent TEBR A.2019.5 | f | 85] 8 | 7 | 8 |23) 15 | absent | yes no no absent 7.5 8 | 24] 15 | absent | yes no no absent 143-176 (2023) Vinh Quang Luu et al. / ZooKeys 1163 152 SIZ UL C€ LI ran ra 91 SC ze | ert | cor | ogp j L8¥800HNST ZZ p= Ch — — ZZS80O0HNST 61 EL £9 Z y LG LG ¢ j ¥8760DHNST sasuawuunts £61 2 ee | 3 | S0zocwdNNA CSI He Gz. lle SZ a — ¥0Z07U ANNA rLI re GZ w =| [0z07u ANNA S61 C€ ae w =| z0z07 uw ANNA soz | €Z re re w | ¢0z07Y ANNA avyunyouios eC] oF 67 (y | p8'7ZOTU ANNA aval SZ 41 €8'7ZOTU ANNA ze | 79 Ze J | 787707 ANNA Z'07 | wel | | ow | 18°7z07 A AONA ‘ds Fie lee E G 6bLL6 MINAZ GIT SF VT ly POLOTU UPA ra pt fw L¥LL6 WAZ Z'61 eS g'¢ Cz j ShLL6 MINAZ 781 | iy | ve | wz | re | ze | ee | ce | 98 | cee | 3 [votocwNwna Z'61 Sy (ee = ie. V9107Y Ul 991 EZ w | €-9107N NWNA SFI pe i C9107 U UAAI Sore s' ( LT9T OUZ El | rz | 90 y ws || ¥S | FE ood | 9709'S OUZ IZ EN a SZ09'T OUZ Ic OT uw ¥C09'T OUZ susuaupujaia a = Pr OCOT ANNA SIZ ae €€0Z07U ANNA 8ST oa ZC'0COTM ANNA ‘sou “ds sysuaivn13 C-0€ a — Z'9L07U NWNA 907 SZ jy. | V9L07 A NWNA Gig r¢ J ShLL6 MINAZ Z1Z e€ j 1080°V UdAI Z'81 ra ui 9FLL6 NWAZ £81 ¢ ze | ce | st | zy | ze | ez [| xo | oy | = | cosovuaa saqquy IDV sa | na | aa | ta | aH | wa | TH | ma | Tas | *&S ‘ou unas] sapedg ‘gyrusan( = { Sopeuray = J Sopeur = WT ‘sory pue WeUIdIA WOIJ sazuoxig Jo susuTIDods WoOIF sosATeUR dy) UT pasn eIep sINoWOYdIow Mes pur x9¢ *¢ BIqeL 153 Two new Dixonius from Vietnam and Laos vu 60° TT OCI €S'Tl 60°F OZ OT 66'1T 10°€T (auc €T IT 91ST yO'Eel O¢ ET STAIESQUIIOUL 00°0 L0°6 £901 YCCI LTTI Ov'cl Ov'cl LOI 06°TI €LZI1 99°CI Teel FRG UBY ULES 00°0 99°01 yO TI 96'IT OL TI COTI €E TI yLIT YT OL €8 FI IZ 1 SESUBUADIS 00°0 09°€ 06°01 IT€l Sel OVE! 8Z IT ELSI LTFL IS€T ‘sou “ds sesuatnyp1s vu VTE ET ET TOE €lyl Cee] ‘OS LT €eST L6'€T di hed 00°0 Ole 6E TT 06'TT 060I 99°91 976 948 OPT 00°0 0S'7I 6Z°71 OC TT ZV'8I Z1'8 8Z 01 ‘aou “ds sesuadurn{suvnus vu LOT 9EL Test ara (awa SESUIUUDUIIIA “JO Ld Aad 8o°9 8 81 LET (awa SISUIUUBUIIIA T0°0 L091 OTE oy Il 1004 eu LET ZS'8I LONVQUOLDD eu rereaze) SISUIULDIS “JD vyju ‘ds snzuoxiqT ‘sou ‘ds ‘aou ‘ds SHIIYSOULJAUL avgUYYIULOS sisumUvIs sisumvIIS aquiU ov] sisuasuvnfsuvniu sisuauvujaia ‘yO sisuaupvujala 10¥1 = taanvquolvy sisuaumis yo ‘ds sniu0oxIg ‘ajqeordde jou eiep = e/U UOJ Ppjog ul are souvasIp-d oyoodseU] ‘suzuox1qZ Jo soidads ay) Suow (s2ouvIsIp-d) sduaSIaArIp aduanbes astmsted paydors09UN Jo saseyUaoIod URdVl *p BIGeL TST 9°610¢'V Uda TCT C6107 V Uda 9°07 C9LOCU ANNA GET YLT cS 0C0TU ANNA Ve? cy 0c0T UN SNA COT : : ul LO'ZZOTU TONN | “Aou “ds szsuadurn{suvnu 68T 68760)HNST UV9T 8ZEZOOHNST CI 87EZOOHNST 6l l6V800HNST <0 OcY80DHNST susuauunis INy ‘ou Umasny, sarsadg 154 Vinh Quang Luu et al. / ZooKeys 1163: 143-176 (2023) for corroboration and further discrimination of morphospatial differences among the putative species. DAPC a priori groups the individuals of each predefined population inferred from the phylogeny into separate clusters (i.e., plots of points) bearing the smallest within-group variance that produce linear combinations of centroids having the greatest between-group variance (i.e., linear distance; Jombart et al. 2010). DAPC relies on standardized data from its own PCA as a prior step to ensure that variables analyzed are not correlated and number fewer than the sample size. Principal compo- nents with eigenvalues accounting for 90-95% of the variation in the data set were retained for the DAPC analysis according to the criterion of Jombart et al. (2010). To test and further corroborate the PCA and DAPC analyses, we conducted a mul- tiple factor analysis (MFA) on the above-mentioned morphological characters plus the categorical color pattern differences for a near total evidence data set (see Tables 5, 6). The MFA was implemented using the m/fa() command in the R package FactorMineR (Husson et al. 2017) and visualized using the Factoextra package (Kassambara and Mundt 2017). MFA is a global, unsupervised, multivariate analysis that incorporates qualitative and quantitative data (Pagés 2015), making it possible to analyze different data types simultaneously in a nearly total evidence environment. In an MFA, each in- dividual is described by a different set of variables (i.e., characters) which are structured into different data groups in a global data frame, in this case, quantitative data (i.e., meristics and normalized morphometrics) and categorical data (i.e., color pattern). In the first phase of the analysis, separate multivariate analyses are carried out for each set of variables, principal component analyses (PCA) for the quantitative data sets and multiple correspondence analysis (MCA) for categorical data. The data sets are then normalized separately by dividing all their elements by the square root of their first eigenvalues. For the second phase of the analysis, the normalized data sets are concat- enated into a single matrix for a global PCA of the data. Standardizing the data in this manner prevents one data type from overleveraging another. In other words, the nor- malization of the data in the first phase prevents data types with the highest number of characters or the greatest amount of variation from outweighing other data types in the second phase. This way, the contribution of each data type to the overall variation in the data set is scaled to define the morphospatial distance between individuals as well as calculating each data type’s and each character's contributions to the overall variation in the data set (Pagés 2015; Kassambara and Mundt 2017). Results Molecular results The results of ML, BI, and BEAST analyses produced trees with identical topologies and strong support at nearly every node (Figs 2, 3). The molecular analyses suggest that Dixonius aaronbaueri is the sister species to a clade containing all other species of Dixonius. Additionally, all analyses recovered the newly discovered population from Two new Dixonius from Vietnam and Laos 155 Table 5. Summary statistics of the principal component analysis of Dixonius species. Abbreviations are listed in the Materials and methods. PCl PC2 PC3 PC4 PCS PC6 PC7 Standard deviation 3.01003227 1.685877698 1.23949927 1.189032683 1.136318219 0.950656207 0.922402779 Proportion of Variance 0.43144 0.13534 0.07316 0.06732 0.06149 0.04304 0.04052 Cumulative Proportion 0.43144 0.56678 0.63994 0.70727 0.76875 0.81179 0.85231 eigen 9.060294267 2.842183612 1.53635844 1.413798721 1.291219096 0.903747223 0.850826887 SVL -0.183137642 0.011423135 -0.069418522 0.076025214 -0.119546371 0.451176774 -0.589642945 BW -0.287276767 0.064974951 0.187163981 -0.199453201 0.019777911 -0.133068566 -0.114357041 HL -0.222534372 0.251387029 0.23514022 0.300194841 0.119329084 -0.056134295 0.150350725 HW -0.264923454 0.100856053 0.274888978 0.257153297 -0.193697896 -0.025433828 0.20364848 HD -0.239223187 -0.126312635 0.224210506 -0.024761051 -0.413575793 0.029259717 0.233903564 EL -0.2480955 0.169750915 0.178082873 0.002208353 0.210266124 0.137233441 -0.232577889 ED -0.202876478 0.122593123 0.079950567 -0.239727042 -0.47584928 0.235373894 -0.048044975 EN -0.265593548 -0.130857091 -0.293077474 0.03772842 0.029146276 -0.105240363 0.142115916 ES -0.267303156 -0.128737264 -0.102433066 -0.036514974 -0.068578553 -0.009743264 0.195931987 EE -0.276238196 -0.150072094 -0.016576264 0.149081788 0.006956725 -0.271219422 -0.084638951 IN -0.239210846 -0.181935095 0.070874242 0.114696597 0.170327297 0.022503069 0.138746934 10 -0.131045671 -0.460675273 -0.164479294 -0.032535496 0.242758327 -0.169473493 -0.152061581 FAr -0.279019143 -0.171574811 -0.122828868 -0.090763378 0.096076353 -0.023168457 0.04857391 TBLr -0.256167278 -0.099347048 -0.096744886 -0.219547386 0.043230096 0.332696024 0.101539921 AGr -0.262180808 -0.1304743 0.000207287 -0.261650023 -0.044763987 -0.216118201 -0.26353247 SPL«.l -0.138456955 0.383331303 -0.225322477 0.206591458 0.113507526 0.110869199 -0.176892801 IFL«.1 -0.089464182 0.168661032 -0.585083828 0.180041929 -0.237863864 -0.199925005 -0.127174583 MO -0.156905954 0.393579439 -0.305813247 0.010226561 -0.089299256 -0.164453012 0.254918394 IOS -0.068091843 -0.230600144 0.078301763 0.673617186 0.047911701 0.164434462 -0.062199104 Vv -0.140473075 0.310134826 0.27924011 -0.11493361 0.255279707 -0.405751544 -0.23957707 T4r1 -0.152382721 0.157971329 -0.130436885 -0.183960387 0.490226326 0.396201891 0.316382072 PC8 PC9 PC10 PCl11 PC12 PC13 PC14 Standard deviation —_0.843138943 0.710443326 0.614017867 0.525772586 0.515133085 0.463343505 0.418149629 Proportion of Variance 0.03385 0.02403 0.01795 0.01316 0.01264 0.01022 0.00833 Cumulative Proportion 0.88616 0.91019 0.92815 0.94131 0.95395 0.96417 0.97249 eigen 0.710883277 0.50472972 0.37701794 0.276436812 0.265362095 0.214687204 0.174849113 SVL 0.265288193 -0.446853384 0.196416397 -0.110376596 0.139472173 -0.13673416 0.085656549 BW 0.09057594 -0.129906618 -0.173199899 0.177854897 0.108703018 -0.085524495 -0.103253386 HL -0.070645969 -0.213980283 -0.087846741 -0.389903504 -0.321747003 -0.17842853 -0.021701889 HW 0.039378469 -0.022086396 0.070374143 0.022285485 0.134276418 -0.209651757 0.058151643 HD 0.139854316 -0.180680891 -0.127550531 0.157737189 -0.027411952 0.137530567 -0.134451774 EL -0.203202698 0.278604397 -0.198153958 0.402630535 -0.109054652 -0.264792874 0.164044114 ED -0.319474696 0.251272882 -0.008164379 0.059050615 -0.034208937 0.225488518 0.158104491 EN 0.295981088 0.09576584 0.048312128 0.019723407 0.172978909 0.06220716 —-0.41905017 ES 0.426919556 0.259878689 -0.007215665 -0.131144367 0.25121175 -0.129629771 0.403591724 EE 0.038959782 -0.113710926 -0.227904855 0.339050813 -0.133303008 -0.064748891 -0.201696035 IN -0.469863359 -0.267676841 -0.188020288 -0.317994993 0.412756086 0.253021631 0.111955286 IO -0.122814373 0.056652546 -0.125361847 0.03792394 0.095742055 -0.182302581 0.359575483 FAr -0.057154891 0.014271255 0.303625758 -0.210415667 -0.567849769 -0.191700829 -0.00332367 TBLr -0.266800377 0.279797707 0.228807449 -0.14978157 0.145371473 -0.238209022 -0.413156342 AGr 0.069118103 0.008227511 -0.004079106 -0.18336757 -0.303043068 0.52714368 —0.090386865 SPLrl 0.178898959 0.359957261 -0.462995625 -0.293841774 0.004054536 0.173258047 -0.103413131 IFLrl -0.352501894 -0.193922056 0.002786908 0.157568267 0.04772871 -0.046397338 -0.113553524 MO -0.000619521 -0.057816313 0.271775541 0.090085724 0.002030737 -0.003433238 0.40989474 IOS -0.02790961 0.257813239 0.336314946 0.217437021 -0.064780745 0.352986111 0.03220845 Vv -0.010841335 0.086524979 0.460243812 -0.002655612 0.309267431 0.129809552 -0.119165889 T4r1 0.091314647 -0.276112686 0.005762572 0.333431445 -0.07395688 0.301989669 0.038025431 156 Vinh Quang Luu et al. / ZooKeys 1163: 143-176 (2023) PC15 PC16 PC17 PC18 PC19 PC20 PC21 Standard deviation 0.376199721 0.365477475 0.339179752 0.282916626 0.236187037 0.171149685 0.149480188 Proportion of Variance 0.00674 0.00636 0.00548 0.00381 0.00266 0.00139 0.00106 Cumulative Proportion 0.97923 0.98559 0.99107 0.99488 0.99754 0.99894 1 eigen 0.14152623 0.133573785 0.115042904 0.080041817 0.055784316 0.029292215 0.022344327 SVL -0.083499418 0.052323475 -0.106015238 0.003344968 -0.031996278 0.03916795 -0.019457555 BW -0.178247777 -0.058497317 0.597846907 -0.255954135 0.379366422 -0.199217481 0.221418054 HL 0.08265144 -0.13083192 -0.024132742 0.014837636 0.131660321 0.479388229 0.2891919 HW 0.244724903 -0.059011694 0.113956101 -0.074931386 0.04577337 -0.069612504 -0.732492773 HD 0.050630806 0.316234183 0.16660119 0.299515683 -0.49781424 0.046244883 0.219619924 EL 0.296740909 0.376559691 -0.260809485 -0.089676204 -0.027290387 -0.071210438 0.140852117 ED -0.231235089 -0.168155577 -0.115371244 0.284151752 0.361474786 0.202917841 -0.049017145 EN 0.022603597 0.420837275 -0.236893263 0.02900181 0.436157574 0.238920063 -0.045962367 ES 0.248024801 -0.355459446 -0.140327076 0.068202164 0.014098586 -0.168841736 0.325882917 EE -0.393037351 -0.425564191 -0.418495874 -0.066368342 -0.173649977 -0.04666024 -0.080329 IN -0.081626216 0.152259274 -0.192312604 -0.041856001 0.036286384 -0.306664296 0.054524547 IO -0.115305892 0.069986307 0.310505175 0.23842857 -0.096262685 0.459593261 -0.180632462 FAr -0.116757716 0.126720851 0.055407627 0.30600813 0.081267972 -0.470097472 -0.064137815 TBLr -0.021197578 -0.178071358 0.100589652 -0.310374261 -0.331807871 0.142300685 0.047913831 AGr 0.334353255 -0.016725971 -0.026314358 -0.397995653 -0.105887039 0.100382932 -0.137085205 SPLr.l -0.184269598 0.036899566 0.194841372 0.163667167 -0.204455175 -0.121267207 -0.156153276 IFLr.l 0.428551026 -0.165166993 0.155004291 0.142458525 0.008969802 -0.065554124 0.111490515 MO -0.391157106 0.255079755 -0.004834981 -0.342258191 -0.175496507 0.081476947 0.028734251 IOS -0.059743664 -0.04851249 0.20733712 -0.095515858 0.057436279 -0.015186946 0.173384569 V 0.002458015 -0.062420243 -0.039680685 0.361422477 -0.145522506 0.02608135 0.040083497 T4rl 0.117972701 -0.206198025 0.0622901 0.17118706 0.012651195 0.069479213 -0.122746338 Chu Se District, Gia Lai Province, Vietnam as the strongly supported (1.00/100) sister species of D. minhlei and the newly discovered population from Muangfuang District, Vientiane Province, Laos as the strongly supported (1.00/100) sister species of D. lao (Figs 2, 3). Uncorrected pairwise sequence divergences among Dixonius species ranged from 2.57—18.84% (Table 4). Ranges for the new species described (see below) are as follows: new species from Vietnam 3.60—15.73%, being most similar to D. minhlei and most distant to D. aaronbaueri and new species from Laos 3.10—18.17%, being most similar to D. dao and most distant to D. aaronbaueri. The time-calibrated BEAST analysis places the divergence between Dixonius aar- onbaueri and the remaining species of Dixonius at approximately 24.04 mya (20.23- 27.68 highest posterior density [HPD]). Within the Vietnam’s lineages, D. gialaiensis sp. nov. and D. minhlei diverged from each other at approximately 3.19 mya (0.79- 5.78 HPD) and within the Lao lineages, D. muangfuangensis sp. nov. and D. lao di- verged approximately 3.47 mya (1.37—6.16 HPD) (Fig. 3). Statistical analyses The first two principal components (PC1 and PC2) of the PCA analysis recovered 56.6% of the variation in the morphometric and meristic data set (Fig. 4A) and load- ed most heavily for body width (BW), head width (HW), eye nostril distance (EN), eye snout distance (ES), and eye ear distance (EE) along PC1 and interorbital dis- ‘Two new Dixonius from Vietnam and Laos 15:7 Heteronotia spelea HQ840102 D. aaronbaueri HM997 152 D. metanosticitus HM997 153 D. minhlei KX379194 Dixonius gialaiensis sp. nov. (VNUF R.2020.22) P| Dixonius gialaiensis sp. nov. (VNUF R.2020.33) D. siamensis EU054299 D. siamensis EU054298 D. siamensis KP979732 D. somchanhae MW605166. ioar.00) 2. somehanhae MW605165 D. somchanhae MW 605167 881.00 D. somchanhae VNUF R.2020.55 soar100| |. somchanhae VNUF R.2020,59 D. somchanhae VNUF R.2020.54 .D. somchanhae VNUF R.2020.56 D. vieinamensis KX379198 D. ef. vietnamensis KX379201 D. taai KP979733 Pp. taoi KP979736 rT, Hoor'. D. taoi KP979735 D. sp. KX379196 D. cf. siamensis KX379195 Dixonius muangfuangensis sp. Dixonius muangfuangensis sp. nov. (VNU! D, lao MT024682 D. lao MT024681 0.04 Figure 2. Maximum likelihood topology of the Dixonius species from Vietnam and Laos with ultrafast bootstrap values (UFB) and Bayesian posterior probabilities (BPP) at the nodes, respectively. ‘Heteronotia spelea HQ840102 D. aaronbaueri HM997 152 D. melanostictus HM997153 ‘DD, minhlei KX379194 is EU0S4299 is EU054298 is KP979732 hae MW605166 .D. somchanhae MW605 165 5; Somchanhae MW605167 ‘D, somehanhae VNUF R.2020.55 2.817) somchanhae VNUF R.2020.54 oD. somchanhae VNUF R.2020.59 D. somchanhae VNUF R.2020.56 D. vietnamensis KX379198 ‘D. cf. viemamensis KX379201 D, taoi KP979733 ny D. taoi KP979734 Pe oD. taoi KP979735 D. taoi KP979736 D. of. siamensis KX379195 D. sp. KX379196. Dixonius muangfuangensis sp. n0 a -Dixonius muangfuangensis sp. nov, (VN D. lao MT02468 1a ia 286), lao MT024683 9331), Jao MT024681 D. fao MT024682 -40 30 20 -10 n) Figure 3. BEAST chronogram of the Dixonius species from Vietnam and Laos. Numbers at the nodes are mean ages in millions of years. Bars represent 95% highest posterior densities. tance (IO), supralabials (SPLr/I), number of supralabial at midorbital position (MO), and ventral scales (V) along PC2 (Table 5). The PCA recovered D. gialaiensis sp. nov. and D. muangfuangensis sp. nov. to be widely separated from most other species with D. muangfuangensis sp. nov. only overlapping with the distantly related D. siamensis. The two distantly related new species are well-separated from most other species in the DAPC but each overlaps with one other species in their 67% inertia ellipses (Fig. 4B). The MFA analysis recovered all species to be separated from one another including Dixonius muangfuangensis sp. nov. and D. siamensis (Fig. 5A). The morphometric data 143-176 (2023) Vinh Quang Luu et al. / ZooKeys 1163 158 9 8 Te T y8'0 c8'0 €S°0 67°0 yS'0 89°0 $s'0 TS°0 0c'0 yL0 c6°0 80'1 10'T £9" roddy, yl 08°0 89°0 €T0 8600 ZY70 c9'0 cy'0 0r'0 O10 99°0 06°0 Sol £60 S| TACT 807v0 syd L700 9100 0500 OSTO €Z400 €700 yc00 1700 ¢700 FE00 97200 6000 <€100 <€€0'0 $F0'0 ds LOS SLL ITT €8°0 €Z°0 €70 810 0S°0 $90 870 970 L10 02°0 16'0 LOT £60 col uPoyW (9 =) avgquvqoumos ‘q OT 9C OI €1 17 Z €COT €€9T £860 LO¥T €eEetT LTB 9 © O) 9 wn KR ST €7 OI 9 L 8 vy 68°0 €8'0 09°0 1c0 6S°0 020 LS'0 670 810 120 680 Z80 L860 89T reddy, €1 0c Z G'S 9 L ETI 680 8Z°0 €S°0 yT0 €S°0 90 (650) cy'0 80°0 690 620 680 S60 19'T TOMOTT ces'0 =— 190T = 8TS'0) 0 ZZT0)=—967'0—s«*OTE|D-—s«dTZO'|O-=— ZT0'0— ss 8@0'N-—s—«*OTN'DN-—s—s«*9HO'0—s«édT€N';O = 1700 POO E00 8700 6700 F100 6000 ZS¢0'0 Z40°0 ds SEF €90T £96 yO'S 9S°9 GOL ZT1 y8 0 08°0 S50 S70 8¢°0 89°0 yS'0 €V'0 €1°0 020 8060 60°1 €6°0 c9'T Urey (Q = %) stsuamuis ‘q CVI €T OI 9 L c'8 Sel 180 8Z0 C0 070 99°0 69°0 yS'0 oS) S70 8Z'0 66°0 OTT €0'T SLT reddy, cl CT OI 9 9 8 TeT 18°0 8Z0 TE0 810 69'0 £90 yS'0 vv 0 810 ZL0 £60 €lT €O'T 8ST TMOT ewe tT LLG°0 0 0 a0) 6870 ceood 1000 000 9000 T1100 sooo 1100 ¢€000 000 I€00 S000 9000 9100 1000 960°0 ds Sel €€°CT Or 9 S9 L1'8 Sel 18°0 8Z°0 €¢'0 610 99'0 89'0 yS'0 L¥‘0 170 8Z'0 660 cI €O'T 69'T ue (¢€ =u) ‘aou ‘ds stsuasuvnf{suvnu sniuoxiq ST €T Ol 9 L 8 vy'l 68°0 €8°0 09°0 1c0 6$°0 020 LS'0 670 810 1Z'0 68°0 Z8°0 86°0 89'T reddy, €1 0c z G'S 9 L 8c 680 8Z°0 €S°0 YT 0 €S'0 y9'0 cS'0 cyv'0 80°0 690 620 680 S60 19'T MOT: €cOT 99€T II? 8670 92€0 8170 0900 ZI00 0700 S700 €700 7700 S700 1700 7700 00 7700 ZE00 8000 7zI00 sz0'0 ds CCPL Celt LIL €8°S cy9 CLL eel 98°0 08°0 LS°0 L1‘0 9S°0 89°0 cc’0 Sv'0 (an) £90 c8'0 98°0 £60 SOT ues (9 = &) gajquim ‘q cI vC 6 8 8 56 6vgr 80 180 170 ovo 8s0 7to0 70 #0 LI0 %@0 60 €1T 660 FZ rddy cI €7 8 ZL CL C8 671 980 8Z0 zo Zt0 950 2490 60 160 70 020 €60 601 960 SGI TOMOT 0 4L¢0 LLS0 $0 6870 $0 €000 000 ZI00 ZOO €10'0 ZIOO 8700 70 9100 7200 €100 S000 ZI00 F100 660°0 as cI CET EES eer ESL 6 6cgI 2480 640 O10 sto L460 690 Lg0 wo 86SIO0)61Z006F60)ChCUdITTTSCO 860s LT ueoy (€=4) oy ‘qd Sv IZ ZL 9 Z 8 cul 6P80—Ct:C«CLDs—C(‘iééE'O—C“‘“CSKC'OsCiTSS'O—Cia|Ds—C‘—“osd CLOCSD—C‘iELZ'ONW:«CBOCLOLC EGO «89'T soddq, va 61 ZL 9 9 ZL ocr 70 €Z0 800 zo s0 ¢90 670 Z¥0 00 7@0 680 90T 0 96'I TOMOT 6870 SSI'I 0 0 4LS0 $0 Sz0'0 €10°0 ¥€0'0 6700 8100 S000 7000 4000 7000 QN_aeeoeeeoeeeeee 1 2 ' = : Q Se = ‘gialaiensis sp. nov. ae : £ a ‘ somchanhae ‘ eel : laa® © -2 =1 0 2 3 B Dim1 (31.6%) Contribution of groups to Dim-2 x 30 2 60 2 g 2 3 = 20 = 40 = — were $10 © 20 oO 0 a) mensural categorical meristic categorical mensural metistic pre Contribution of groups to Dim-3 _. Contribution of groups to Dim-4 = Ss uw wn c 2 =| 2 ra [2] O meristic mensural categorical meristic categorical mensural Figure 5. A MFA scatter plot showing the morphospatial relationships among the Dixonius species based on normalized morphometric, meristic, and color pattern characters B bar graphs showing the percent contribution of each data type to the overall variation in the data dimensions 1—4. The dashed red line in the bar graphs indicates the expected average value if the contributions of each data type were equal. neck; prefrontal region concave; canthus rostralis rounded; snout elongate (ES/HL 0.37), rounded in dorsal profile; eye moderate size (ED/HL 0.25); ear opening oval, obliquely oriented, moderate in size; diameter of eye slightly smaller than eye to ear distance (ED/EE 0.88); rostral rectangular, partially divided dorsally by straight rostral groove, bordered posteriorly by large left and right supranasals, bordered laterally by first supralabials; external nares bordered anteriorly by rostral, dorsally by large supra- nasal, posteriorly by two smaller postnasals, bordered ventrally by first supralabial; 8,7 (R,L) rectangular supralabials extending to below and slightly past posterior margin of 164 Vinh Quang Luu et al. / ZooKeys 1163: 143-176 (2023) SPLr.! IFLr.l Mo 8 - 8 . or 0) 8 - i : es 0 7. 0 0 6 j 6 - ¢e+4+ 6 + 6- 9) 5 - 5 : ts) Beh sa Satan we eae ary a oo es ek Siow Sees 262827 88 s7 25838528 eee ge e78 Se se S S98 28 SS aS . rk * = Ss bo P S& ES § 3 § FEES s fe ges & 2 = 4 Rc S = 4 25 = ee ee OS 2 2 is 4 i) — mH Ke} & a 3 = 5 a = a us s 5 <3 4 & Sy) = Sb DS oo aS 2 aS s 3 8 8 3 3 3 ¢ % § SS Se = : : T4r.l 8 los = V = i § 10- 0 a Cm «(16 | 0 at gee 15 - ~0- * y® 14. : eo oe >) qo Og 18 - 0 13 - 0 ! ie 15 (ee — 12 © dag) Sees eae Sons Se See aS ae as seve Soe fee. ese 2S @sees8 2672 Ses § ets 3 = Ss = S @ &§ ' ¢ = Sg aes es 4. se SS % . Soe ae 3 ¥ Ss £ 8 g®F 5 § § ¢ Sf § & & = E& ¢ BE 8 2 a = = 25 S a = § S 5 < Sa 8 Bo ~ 8 3 2 = i = ~ 3 3 3 $ 8 3 2 = bp 50 S 5 ® 2 : 8 3 5 = = s Figure 6. Boxplot comparisons of meristic characters among the Dixonius species where interspecific statistical differences were recovered (see Table 7). Pale blue circles are means and the black horizontal bars are medians. eye, sixth in midorbital position; 6,6 (R,L), infralabials tapering smoothly to just below midpoint of eye, decreasing gradually in size; scales of rostrum and lores flat to domed, larger than granular scales on top of head and occiput; scales of occiput intermixed with distinct, small, conical tubercles; superciliaries elongate, largest anteriorly; mental triangular, bordered laterally by first infralabials and posteriorly by large left and right trapezoidal postmentals contacting medially for 60% of their length posterior to men- tal; gular and throat scales small, granular, grading anteriorly into slightly larger, flatter, smooth, imbricate, pectoral and ventral scales. Body relatively short (AG/SVL 0.38); dorsal scales small, granular interspersed with larger, conical, regularly arranged, keeled tubercles; tubercles extend from top 165 ‘Two new Dixonius from Vietnam and Laos .e) -"Aou “ds sa nele eac -OD] © “AOU ‘ds sIsuaiDjv1 - SISUAUIDIS <> -OD] -‘AoU ‘ds sisuasupn{supnu =< - DYUDYIUIOS - 12] YUulul <= _p- - SISUDUUDIS <> 4 ri ace sat => - 1a] Yul 6 - AOU “dS s7suaipjpI1s QE - SISUQUIDUJAIA n - SISUAWUDUJAIA In ar -s uw — a — --(/s roe) ar ce) re) = ao ye & Hb + OM fo) o o oO oO a ro = oe ces ~Aou ‘ds sisuasupn{suvnu - OD] .e3 -OD] <= -layyulu

- ADYUDYIWOS g -Aou ‘ds sisuasupn{sunnu <> - SISUOUIDIS - SISUDUIDIS le) --Aou ‘ds sisuaipjpis rey ~Aou ‘ds sisuaipjpis => > lajyuiu — =| = ? -aou “ds sisua8unnfSuonu

is -OD]

-OD] =< -"Aou ‘ds sisuasupn{supnus <> - SISUAUIDIS —= OS - IDYUDYIUOS Q -“Aou ‘ds sisuamjnis fe) ~aou “ds sisuaipjp1s <> -apyunyouos - lajyulu © a “ds - SISUBUUDIS - 1a] Yulul ——— 0S - sisuatupujaia 5 > <> - sisuawpujaia TT > --ds mn N — Oo a ioe) Ww) t .) | - > = oS (=) =) °o (=) 2 -aou ‘ds sisuaSupnfsupnut MOPaS “Aou ‘ds sisuaSupn{suonut ~<==- - ADYUDYIUIOS - IDYUDYIWUOS <> -OD <> -OD] <> - lajyulul = SS - SISUBWUDIS =< ~Aou ‘ds sisuammjnis =a -layyulut Fe} - SISUAUIDIS == -‘ds aS “ds . re) - AOU ‘ds sisuaipjpis = SSS - SiSuaupujaia TT POL a= -SISUIUIDUJAIA = 2 23 so 8 Sa a => <> veer - apyUunYyauios =O 0.90 - -*Aou ‘ds sisuasupn{suvnu “1a, Yul - OD] -SISUDUIDIS - IDYUDYIWOS "AOU “ds sisuampjpis - SISUAWUIDUJAIA -ds - OD] 5 fojyuia - SISUAUIDIS "AOU ‘ds sisuaipjpis -aou ‘ds sisuasupn{supnu Figure 7. Violin plots of the normalized morphometric characters overlain with box plots showing the range, frequency, mean (white dot), and 50% quartile (black rectangle) of characters where interspecific statistical differences were recovered (see Table 7). New species in bold italics. 166 Vinh Quang Luu et al. / ZooKeys 1163: 143-176 (2023) holotype VNUF R.2020.22 (Field no. GLO2) B adult female paratype VNUF R.2020.33 (Field No. GLO3) C juvenile male paratype VNUF R.2020.44 (Field No. GL04) in Chu Se Mountain Pass, Hbong Commune, Chu Se District, Gia Lai Province. Two new Dixonius from Vietnam and Laos 167 of head onto posterior haft of tail forming longitudinal rows, terminating at last por- tion of tail; smaller tubercles extend anteriorly onto nape and occiput, diminishing in size and distinction on top of head; 19 longitudinal rows of tubercles at midbody; 33 paravertebral scales, number of scales in a paravertebral row from first scale posterior to parietal scale to last scale at the level of vent opening; 23 paravertebral scales in a row between limb insertions; 21 flat, imbricate, ventral scales much larger than dorsal scales; 7 enlarge, pore-bearing, precloacal scales in an angular series; and no deep pre- cloacal groove or depression. Forelimbs moderate in stature, relatively short (FA/SVL 0.15); granular scales of forearm slightly larger than those on body, interspersed with small tubercles; hind limbs more robust than forelimbs, moderate in length (TBL/SVL 0.17), covered dor- sally by granular scales interspersed with large, and small conical tubercles; ventral scales of thigh flat, imbricate, larger than dorsals; subtibial scales flat, imbricate; proxi- mal femoral scales smaller than distal femorals; femoral pores absent; digits relatively long with 14 lamellae on fourth toe; and claws well developed. Tail 108.4 mm in length, 4.5 mm in width at base, tapering to a point; dorsal scales of flat, square with conical, keeled tubercles in anterior part; median row of transversely expanded subcaudal scales, significantly larger than dorsal caudal scales on original portion; base of tail bearing hemipenal swellings; and postcloacal scales flat, imbricate. Coloration in life (Fig. 8). Ground color of dorsal head and dorsum grey brown with rounded black-brown blotches, decreasing gradually in size from head to body; canthal stripe continues behind orbit to back of head; dark bars on the lips; uneven light spots running from postorbital along the flanks to tip tail; upper surface of fore- and hindlimbs uniformly light grey with black-brown spots; dorsum of tail covered with some small rounded black-brown blotches; ventral surface beige uniformly as the belly and the throat. Variation (Fig. 8). Ihe female paratype (VNUF R.2020.33) generally has more dark brown blotches on head and dorsum, and uniformly black on the new regener- ated tail. The dorsum of the of head and body of the juvenile male paratype (VNUF R.2020.44) pale brown with pale-colored blotches on granulose skin arranged along its sides extending from the flanks to the tail tip. Further measurements are summarized in Tables 2-4, Suppl. material 1: table S1. Distribution. Dixonius gialaiensis sp. nov. currently is only known from the type locality of Chu Se Mountain Pass, H’ Bong Commune, Chu Se District, Gia Lai Prov- ince, Central Highlands, Vietnam (Fig. 1). Natural history. The specimens were found at night, between 19:45 and 21:00 h, on the ground in an area along the National Highway 25. The surrounding habitat was secondary montane forest with woody trees. The temperature and humidity were approximately 32.6 °C and 57% (Fig. 9). Etymology. The new species is named after the type locality of Gia Lai Province, Central Highlands, Vietnam. Comparisons. Dixonius gialaiensis sp. nov. is the sister species to D. minhlei (Fig. 2) from which it differs by an uncorrected pairwise sequence divergence of 3.60% (Table 4). It is differentiated from it morphologically by having a significantly higher 168 Vinh Quang Luu et al. / ZooKeys 1163: 143-176 (2023) Figure 9. Habitat of Dixonius gialaiensis sp. nov. HBong Commune, Chu Se District, Gia Lai Province, Central Highlands, Vietnam. mean number of head length (HL), head width (HW), and axilla to groin length (AG). In addition, it differs from D. minhlei in color pattern (grey-brown dorsum with more round black-brown blotches versus olive gray dorsum with round brownish olive blotches). Statistically significant and discrete categorical differences between Dixonius gialaiensis sp. nov. and all other species and populations are presented in Tables 5—7. Dixonius muangfuangensis sp. nov. https://zoobank.org/A447 ECO 1-F653-4FE5-A616-5FBD25F027C6 Fig. 10 Muangfuang leaf-toed gecko Material examined. Holotype. Adult male, VNUF R.2020.42 (Field no. ME02) in Sinxay Temple, Nadan Village, Muangfuang District, Vientiane Province, Central Laos (18°32'52"N, 101°58'31"E; 276 m a.s.l.), collected by Saly Sitthivong and Thuong Huyen Nguyen on 05 December 2020. Paratypes. NUOL R.2022.01 (Field no. ME. 01), juvenile male, and VNUF R.2020.52 (Field no. ME. 03), adult female; the same data as given for the holotype. Diagnosis. Dixonius muangfuangensis sp. nov. can be separated from all other spe- cies of Dixonius by possessing the unique combination of having a maximum SVL of 56.7 mm; 21-23 longitudinal rows of dorsal tubercles at midbody; 20 or 21 longitudi- nal rows of ventrals across the abdomen; 7 or 8 supralabials, sixth in at midorbital posi- tion; 6 or 7 infralabials; 7 interorbital scales; 7 or 8 precloacal pores in males, femoral pores lacking; precloacal and femoral pores absent in female; 15 lamellae on fourth toe; Two new Dixonius from Vietnam and Laos 169 dorsum olive grey color with numerous small and irregular black blotches; head with brown spots; light spots irregularly arranged from the back of the head to base of tail; lips with dark bars; two regularly disposed whitish tubercles on each side on each side. ‘These characters are scored across all Dixonius species from Vietnam and Laos in Tables 6, 7. Description of the holotype. Adult male, SVL 55.6 mm; head moderate in length (HL/SVL 0.28), wide (HW/HL 0.71), depressed (HD/HL 0.45), distinct from neck; prefrontal region concave; canthus rostralis rounded; snout elongate (ES/HL 0.39), rounded in dorsal profile; eye moderate size (ED/HL 0.20); ear opening oval, oblique- ly oriented, moderate in size; diameter of eye much smaller than eye to ear distance (ED/EE 0.59); rostral rectangular, partially divided dorsally by straight rostral groove, bordered posteriorly by large left and right supranasals, bordered laterally by first su- pralabials; external nares bordered anteriorly by rostral, dorsally by large supranasal, posteriorly by two smaller postnasals, bordered ventrally by first supralabial; 8,8 (R,L) rectangular supralabials extending to below midpoint of eye, sixth in midorbital posi- tion; 7,7 (R,L), infralabials tapering smoothly to be just slightly past posterior below midpoint of eye, decreasing gradually in size; scales of rostrum and lores flat to domed, larger than granular scales on top of head and occiput; scales of occiput intermixed with distinct, small, conical tubercles; superciliaries elongate, largest anteriorly; mental triangular, bordered laterally by first infralabials and posteriorly by large left and right parallelogram postmentals contacting medially for 60% of their length posterior to mental; gular and throat scales small, granular, grading anteriorly into slightly smaller, flatter, smooth, imbricate, pectoral and ventral scales. Body relatively short (AG/SVL 0.42) with well-defined ventrolateral folds; dorsal scales small, granular interspersed with moderate, conical, regularly arranged, keeled tubercles; tubercles extend from top of head onto interior haft of tail forming longi- tudinal rows, terminating at regenerated portion of tail; smaller tubercles extend an- teriorly onto nape and occiput, diminishing in size and distinction on top of head; 23 longitudinal rows of tubercles at midbody; 45 paravertebral scales, number of scales in a paravertebral row from first scale posterior to parietal scale to last scale at the level of vent opening; 24 paravertebral scales in a row between limb insertions; 20 flat, imbri- cate, ventral scales much larger than dorsal scales; 8 enlarge, pore-bearing, precloacal scales in an angular series; and no deep precloacal groove or depression. Forelimbs moderate in stature, relatively short (FA/SVL 0.12); granular scales of forearm slightly larger than those on body, interspersed with small tubercles; hind limbs more robust than forelimbs, moderate in length (TBL/SVL 0.13), covered dor- sally by granular scales interspersed with large, and small conical tubercles; ventral scales of thigh flat, imbricate, larger than dorsals; subtibial scales flat, imbricate; proxi- mal femoral scales smaller than distal femorals; femoral pores absent; digits relatively long with 15 lamellae on fourth toe; and claws well developed. Tail 37.8 mm in length, first 17.1 mm original, 6.1 mm in width at base, taper- ing to a point; dorsal scales of flat, square with conical, keeled tubercles, regenerated portion covered with small, smooth subcircular scales; median row of transversely ex- panded subcaudal scales, significantly larger than dorsal caudal scales on original por- tion; base of tail bearing hemipenal swellings; and postcloacal scales flat, imbricate. 170 Vinh Quang Luu et al. / ZooKeys 1163: 143-176 (2023) ME02) B adult female paratype VNUF R.2020.52 (Field no. ME 03) C juvenile male paratype NUOL R.2022.01 (Field no. ME 01) in Nadan Village, Muangfuang District, Vientiane Province, Central Laos. ‘Two new Dixonius from Vietnam and Laos Al Figure ||. Habitat of Dixonius muangfuangensis sp. nov. Nadan Village, Muangfuang District, Vientiane Province, Central Laos. Coloration in life (Fig. 10). Ground color of dorsal head and dorsum dark grey with numerous small and irregular black blotches; lips with dark bars; two regularly disposed whitish tubercles on each side on each side running from postorbital along the flanks to tail, terminating at regenerated portion of tail; upper surface of fore and hind limbs uniformly dark brown with round black-brown spots; dorsum of tail cov- ered with some large black-brown blotches; ventral surface beige uniformly as the belly and the throat. Variation (Fig. 10). The female paratype (VNUF R.2020.52) generally match- es that of the holotype in all characteristics. The juvenile male paratype (NUOL R.2022.01) has fewer black blotches on head and dorsum and two regularly disposed whitish tubercles on each side on each side of the head extending from the postorbital region, along the flanks, to the tail tip. Further measurements are summarized in Ta- bles 2-4 and Suppl. material 1: table S2. Distribution. Dixonius muangfuangensis sp. nov. currently is only known from the type locality of Nadan Village, Muangfuang District, Vientiane Province, Central Laos (Fig. 1). Etymology. ‘The specific epithet of the new species refers to the type locality of the new species in Muangfuang District, Vientiane Province, Central Laos. Natural history. The type series was collected between 19:10 and 19:30 h, on the ground inside Sinxay Temple, at an elevation of 276 m a.s.l. The surrounding habitat was disturbed lowland karst forest (Fig. 11). 172. Vinh Quang Luu et al. / ZooKeys 1163: 143-176 (2023) Comparisons. Dixonius muangfuangensis sp. nov. is the sister species to D. lao (Fig. 2) from which it differs by an uncorrected pairwise sequence divergence of 3.10% (Table 4). It is differentiated morphologically by having a significantly higher mean number of head length (HL), infralabials (IFL), and numbers of supralabial at midor- bital position (MO). In addition, it differs from D. /ao in dorsal pattern (dorsal pebble brown versus dorsal dark gray with black blotches). Statistically significant and discrete categorical differences between Dixonius muangfuangensis sp. nov. and all other species and populations are presented in Tables 5—7. Discussion Morphological comparisons indicated that Dixonius gialaiensis sp. nov. is most similar to its sister species D. minhlei, but can be differentiated from the latter species by the number of dorsal tubercle scale rows and differences in color pattern. The results of the molecular analysis show the uncorrected pairwise sequence divergence between the two taxa is 3.60%. Additionally, the two species are widely separated geographi- cally being in different mountain systems and separated by the Dong Nai River system (Fig. 1). Collectively, these data suggest these are separate and distinct species. Dixonius gialaiensis sp. nov. was discovered in a protected forest near the National Highway 25. The construction of new infrastructure at this site strongly impacts the habitat of D. gialaiensis sp. nov., including range fragmentation and forest degradation. Further investigations on conservation status is urgently required to develop effective conservation measures. Dixonius muangfuangensis sp. nov. is most closely related to D. /ao, but can be dis- tinguished from it by head shape and color pattern differences. The molecular analysis indicated these two species differ by a 3.1% uncorrected pairwise genetic distance. In addition, the two species evolved separately in geographically isolated regions. The type locality of D. muangfuangensis sp. nov. is approximately 500 km south of the type locality of D. /ao and the type localities are separated by the Nam Ngiap and Xebangfai river network systems (Fig. 1). The BEAST analysis indicates that the divergence between Dixonius gialaiensis sp. nov. and D. minhlei and that between D. muangfuangensis sp. nov. and D. lao may have been the result of cyclical climatic events during the recent interglacial periods of the Pliocene as noted for several other Indochinese species (see Grismer and Grismer 2017 and references therein). D. muangfuangensis sp. nov. and D. lao diverged from one another at approximately 3.47 mya. Relatively soon after, at approximately 3.19 mya, Dixonius gialaiensis sp. nov. and D. minhlei separated from one another, thus allowing sufficient time for them to evolve significant differences between them in a number of characteristics. During this time period, the formation of separate karstic habitats and granitic mountains and hills may have prevented gene flow between these populations, placing each species on separate evolutionary trajectories (Grismer and Grismer 2017). Two new Dixonius from Vietnam and Laos 173 Acknowledgements For supporting field work and issuing relevant permits, we are grateful to Chu Se Protection Forest’s ranger station and The People’s Committee of Chu Se District, Gia Lai Vietnam, and National University of Laos. We thank Oanh Van Lo and Khanh Quoc Nguyen for his assistance in the field in Vietnam. Many thanks to Thomas Zie- gler (Cologne) and Truong Quang Nguyen (Hanoi) for providing comments on the manuscript. Field surveys in Laos were financially supported by Rufford Foundation (ID: 31189-1) to THN and SS. Field surveys in Vietnam were partially funded by the Mohamed bin Zayed Species Conservation Fund (Project Number: 192521666) and the Vietnam National Foundation of Science and Technology Development (NA- FOSTED, Grant No. 106.06-2021.28) to VQL. Equipment was supported by IDEA WILD. Research of THN was funded by the Master, PhD Scholarship Programme of Vingroup Innovation Foundation (VINIF), code VINIF.2022.TS125. 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Zootaxa 4136(3): 553-566. https://doi.org/10.11646/zootaxa.4136.3.7 Supplementary material | Measurements and morphological characters of the type series of Dixonius gialaiensis sp. nov. Authors: Vinh Quang Luu, Thuong Huyen Nguyen, Minh Duc Le, Jesse L. Grismer, Hong Bich Ha, Saly Sitthivong, Tuoi Thi Hoang, L. Lee Grismer Data type: tables (Excel spreadsheet) Explanation note: table S1: Measurements (in mm) and morphological characters of the type series of Dixonius gialaiensis sp. nov. (for abbreviations see Material and methods). Measurements taken on right side; FA is given in the left side; SPL/IFL/ T4 given in right/ left order; -absence; * tail regenerated; table S2: Measurements (in mm) and morphological characters of the type series of Dixonius muangfuan- gensis sp. nov. (for abbreviations see material and methods). Measurements taken on right side; FA and T4 are given in the left side; SPL/IFL given in right/ left order; -absence, * tail regenerated; ** tail lost. Copyright notice: This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0/). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this Dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited. Link: https://doi.org/10.3897/zookeys. 1163.101230.suppl1