Cyrtodactylus tayninhensis, Do & Nguyen & Nguyen & Le & Ho & Pham & Nguyen & Ziegler & Ngo, 2025

Cyrtodactylus tayninhensis sp. nov.

( Figs. 4-5 View FIGURE 4 View FIGURE 5 )

Holotype. IEBR R.6331 (Field number CT.TN2022. T04 .N14), adult male, collected on 29 September 2022 by H. T. Ngo, Q. H. Do, H.Q. Nguyen from the Ba Den MCHC, Tay Ninh Province, southern Vietnam.

Paratypes. Two adult males: IEBR R . 6332 (Field number CT.TN2022. T04 .N03), IEBR R . 6333 (Field number CT.TN2022. T04 .N11) ; two adult females: IEBR R . 6334 (Field number CT.TN2022. T04 .N09), IEBR R . 6335 (Field number CT.TN2022. T04 .N13), identical collection data and collectors as the holotype .

Diagnosis. The new species can be distinguished from other members of the Cyrtodactylus irregularis group by a combination of the following characters: size medium (SVL 73.4–80 mm); dorsal tubercles in 13 or 14 irregular rows; 36–39 ventral scale rows; enlarged femoral scales absent; precloacal pores absent in females, 4–6 in males, in a continuous row; femoral pores absent; postcloacal spurs 2 or 3 on each side; lamellae under toe IV 16–18; a U-shaped continuous neckband, dorsal pattern between limb insertions consisting two or three irregular yellow-brown bands and tail with 8–10 thin light bands (with 2 bands near vent light brown, others white); the absence of transversely enlarged median subcaudal scales.

Description of holotype. Adult male, medium size, snout-vent length (SVL) 76.4 mm. Head wider than body, relatively long (HL 22.9 mm, HL/SVL 0.3) and wide (HW 15.1 mm, HW/HL 0.66), relatively depressed (HH 8.5 mm; HH/HL 0.37; HH/HW 0.56), distinct from neck. Prefrontal and postnasal regions concave. Snout elongate (SE/ HL 0.4), round anteriorly, longer than orbit diameter (OD/SE 0.56). Scales on snout small, round to oval, granular to weakly conical, mostly homogeneous, larger than those on crown, interorbital and occipital regions. Orbit of moderate size (OD/HL 0.22), pupils vertical, supraciliaries short, forming conical spines, larger anteriorly. Ear opening vertically oval, small (ED/HL 0.1), eye to ear distance longer than orbit diameter (Eye-Ear/OD 1.25). Rostral much wider than deep with a medial suture, bordered by first supralabial on each side, nostrils, two supranasals and one internasal. Nostrils oval, each surrounded by supranasal, rostral, first supralabial and three postnasals. Two enlarged supranasals separated from each another anteriorly by one internasal. Mental triangular, wider than deep. A single pair of greatly enlarged postmentals in broad contact behind mental, bordered by mental anteriorly, first infralabial laterally, and six enlarged chin scales posteriorly. Supralabials 10/10; infralabials 7/8. Scales of labial area decrease in size towards jaw.

Body moderately slender, relatively long (TrunkL/SVL 0.43) with the presence of non-denticulate, ventrolateral skin folds. Dorsal scales granular; dorsal tubercles round, conical, present on occipital region and back, each surrounded by 9 or 10 granular scales, in 14 irregular longitudinal rows at midbody. Ventral scales larger than dorsal scales, smooth, oval, subimbricate, largest on posterior abdomen and in precloacal region. Midbody scale rows across belly between ventrolateral folds 36. Gular region with homogeneous, smooth, juxtaposed granular scales. Enlarged femoral scales, femoral pores and preanal groove absent. Precloacal scales arranged in a diamond shape, precloacal pores 6, in a continuous row, pore-bearing scales enlarged.

Fore and hind limbs moderately slender and long (ForeaL/SVL 0.16, CrusL/SVL 0.19); tubercles on dorsum of fore and hind limbs weakly developed. Fingers and toes without distinct webbing; subdigital lamellae on finger IV 14 and on toe IV 16.

Tail 79.6 mm, approximately the length of the snout-vent length (TaL/SVL 1.03); postcloacal spurs each bearing three much enlarged conical scales; subcaudals without enlarged plate row, flat, smooth, imbricate, about two times larger than scales on tail dorsum.

Coloration in life. Dorsal surface of head brown with irregular light brown markings; nuchal loop dark-brown, U-shaped, edged in yellow-brown, extending from posterior margin of orbit, crossing the upper edge of ear opening to neck; ground color on back dark brown, dorsal pattern between limb insertions consisting of two irregular yellow brown bands; tail with 8 thin light bands (with 2 bands near vent light brown, others white) and 8 thick dark bands; venter of body cream.

Coloration in preservative. In 70% alcohol, the color pattern is slightly faded. The yellow edges disappear and brown turns to whitish grey but the main characteristics are still clearly visible.

Sexual dimorphism and variation. Females differ from males in the absence of precloacal pores and hemipenial swellings at the tail base. The number of narrow light bands on the tail varies by one to two. For other morphological characters see Table 5.

Distribution. Cyrtodactylus sp. nov. is currently known only from the type locality in Ba Den MCHC, Tay Ninh Province, Vietnam ( Fig. 1 View FIGURE 1 ).

Etymology. The specific epithet of the new species refers to the type locality of the new species, Tay Ninh, a province in southern Vietnam. Suggested common names: Tay Ninh Bent-toed Gecko (English), Thằn lằn chân ngón tây ninh (Vietnamese).

Natural history. The type series was found between 19:00 and 24:00 in deep rocky caves with low light. More than 50 individuals were observed, but not collected, during our field surveys in September 2022 and August 2024. The microclimatic conditions of Cyrtodactylus tayninhensis sp. nov. were characterized by air microtemperatures ranging from 22.0 to 27.5°C and substrate temperatures varying between 19.8 and 30.7°C. The majority of individuals were discovered in habitats with high canopy coverage (≥ 80%) and elevated humidity levels (≥ 80%). The surrounding habitat was secondary forest of medium and small hardwoods mixed with shrubs. We also found C. badenensis in the same habitat. However, C. badenensis tends to stay near the cave entrance and outside the cave, while C. tayninhensis sp. nov. stays deep inside the cave (for more details see the discussion below).

Comparisons. We compared the new species with its 30 congeners from the Cyrtodactylus irregularis complex based on examination of specimens and data obtained from the literature ( Smith 1921; Heidrich et al. 2007; Orlov et al. 2007; Nazarov et al. 2008; Ngo & Bauer 2008; Rösler et al. 2008; Geissler et al. 2009; Ngo & Chan 2010; Nazarov et al. 2012; Ngo 2013; Nguyen et al. 2013; Ziegler et al. 2013; Schneider et al. 2014; Luu et al. 2017; Pauwels et al. 2018; Ngo et al. 2020; Neang et al. 2020; Ostrowski et al. 2020, 2021; Nguyen et al. 2021; Do et al. 2021, 2023; Ngo et al. 2023, 2024) ( Table 6).

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(* = regenerated or broken tail); bilateral meristic characters are given as (left/right).

Below, we compared the new species with the most phenotypically similar species. In particular, Cyrtodactylus tayninhensis sp. nov. differs from C. arndti Ngo, Hormann, Le, Pham, Phung, Do, Ostrowski, Nguyen & Ziegler by the absence of enlarged femoral scales ( versus 5–11), the absence of precloacal pores in females ( versus 6), the absence of transversely enlarged subcaudal plates ( versus present), and different dorsal color pattern (distinct bands with thin light bands; two bands nearest to vent light brown and the others white) versus irregular bands with thicker light brown bands; from C. badenensis by having more ventral scale rows (36–39 versus 25–28), the presence of precloacal pores in males ( versus absent), the absence of transversely enlarged subcaudal plates ( versus present), and different dorsal color pattern (thin light bands with two bands nearest to vent light brown and the others white versus four white bands across the back, the first at forelimbs, the last at hindlimbs and two others in the middle of the back); from C. bidoupimontis Nazarov, Poyarkov, Orlov, Phung, Nguyen, Hoang & Ziegler by having fewer dorsal tubercle rows (13 or 14 versus 18–24), the absence of enlarged femoral scales ( versus 8–10), and different tail color pattern (thin light bands with two bands nearest the vent light brown and the others white versus thicker having a light brown bands); from C. chumuensis Ngo, Hormann, Le, Pham, Phung, Do, Ostrowski, Nguyen & Ziegler by having a larger size (SVL 73.4–80.0 mm versus 67.5 mm), fewer ventral scale rows (36–39 versus 43–45), no enlarged femoral scales ( versus 4 or 5), and different dorsal color pattern (distinct bands with thin light bands, two bands nearest the vent light brown and others white versus irregular bands with thicker light brown bands and short longtitudinal stripes on the neck); from C. irregularis (Smith) by lacking enlarged femoral scales ( versus 7 or 8), difference in color pattern of dorsum (banded versus blotched), and different tail color pattern (thin light bands versus thicker light brown bands); from C. orlovi Do, Phung, Ngo, Le, Ziegler, Pham & Nguyen by having fewer dorsal tubercle rows (13 or 14 versus 16–20), the absence of enlarged femoral scales ( versus 3–8), and different tail color pattern (dark transverse bands of wider than light brown interspaces versus dark brown transverse bands narrower than interspaces); and from C. taynguyenensis Nguyen, Le, Tran, Orlov, Lathrop, Macculloch, Le, Jin, Nguyen, Nguyen, Hoang, Che, Murphy & Zhang by having more supralabial scales (10–12 versus 8 or 9), fewer ventral scale rows (36–39 versus 42–49), and different dorsal color pattern (banded versus blotched).

Discussion

The new species represents the fourth species of Cyrtodactylus from Ba Den MCHC ( Nguyen et al. 2006). The newly described species is clearly distinguishable from three previously known species, C. badenensis , C. dati and C. nigriocularis based on the morphological and molecular analyses presented in this study and Fig. 6 View FIGURE 6 . According to our field observations, C. badenensis , C. nigriocularis and C. tayninhensis are found only in the granite habitat of Ba Den, whereas C. dati occupies several different microhabitat types, including on the ground with leaf litter and soil, on dead branches and on granite rocks.

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In terms of altitudinal gradients, C. nigriocularis was found at elevations lower than 700 m asl., whereas C. badenensis and C. dati were encountered at elevations both lower and higher than 700 m asl. In contrast, Cyrtodactylus tayninhensis was only detected at elevations above 700 m asl. Moreover, although C. badenensis and Cyrtodactylus tayninhensis were observed in syntopy, they are morphologically divergent and genetically separated from each other. This study once again illustrates a high level of sympatry but not syntopy in bent-toed geckos. Several other localities in Vietnam and other countries harbor more than three co-occurring species of Cyrtodactylus , including Phong Nha - Ke Bang National Park and Ta Kou Nature Reserve ( Ngo & Bauer 2008; Ostrowski et al. 2021; Duong et al. 2024). The ability to co-exist in the same habitats might partly explain the stunning diversity of the genus and their habitat preference ( Grismer et al. 2020, 2021). Our discovery brings the species number of the C. irregularis species group to 32, including C. buchardi , which is still being investigated genetically ( Grismer et al. 2021; Ngo et al. 2023, 2024; Uetz et al. 2024; Do et al. 2025).

The population status of the new species and the other three bent-toed geckos, and the anthropogenic threats to their microhabitats in Ba Den MCMC still need to be further investigated. According to Nguyen et al. (2018a,b), Ba Den MCHC has become a popular tourist destination with rapid tourism development. Presently, C. nigriocularis is classified as Critically Endangered, C. badenensis as Vulnerable and Endangered, and C. dati as Data Deficient in the IUCN Red List and Vietnam Red List ( Nguyen et al. 2018a,b; IUCN Vietnam Red List 2024). Moreover, Ba Den MCHC receives a lower level of protection compared to a nature reserve. Therefore, further studies of the four species population status, all restricted to a single mountain surrounded by lowlands heavily used for agriculture and other infrastructural developments, should be performed and appropriate conservation measures should be designed to protect their natural habitat and populations.