Morphological Characteristics of the Vietnamese Adult Human Acetabulum Using Multiplanar Reconstruction Computed Tomography in Total Hip Replacement Surgery.

Background: The anatomical parameters of the acetabulum vary among races and geographical regions. Multislice Computed Tomography (CT) has proven to be a practical approach to assess morphological parameters of the acetabulum. The purpose of this study was to explore morphological characteristics of the acetabulum measured by CT scans in Vietnamese adults. Methods: Thirty-five consecutive patients aged 18 years and older received indications and eligibility for total hip replacement surgery. Sixty-three acetabulum were examined with multislice computed tomographic system (CT) with multiplanar reconstruction (MPR). Measured morphometric parameters of acetabulum included acetabular inclination angle (AIA), acetabular anteversion angle (AAA), acetabular angle of sharp (AAS), sagittal acetabular angle (SAA), acetabular horizontal offset (AHO), transverse acetabular ligament anteversion (TALA), transverse acetabular ligament inclination (TALI), acetabular depth (ADe), acetabular depth ratio (ADr) and acetabular diameter (ADi). Results: The mean values of acetabular diameter, femoral head diameter, AIA, AAA, AAS, SAA, TALA, TALI, AHO, ADe, ADr were 50.22±3.56 mm, 43.54±3.68 mm, 40.27±5.09 mm, 13.30±5.54 mm, 39.46±5.41 mm, 26.38±9.01 mm, 9.49±3.92 mm, 47.70±6.73 mm, 3.06±0.37 mm, 18.62±2.95 mm and 309.60±41.87 mm. Conclusion: Our initial data has showed morphological characteristics of the acetabulum in Vietnamese adults, different from the populations from other parts of world. Also, significant correlation between the orientation of the acetabulum and the transverse acetabular ligament was documented.

A new species of the Cyrtodactyluschauquangensis species group (Squamata, Gekkonidae) from Lao Cai Province, Vietnam.

We describe a new species of the genus Cyrtodactylus based on five adult specimens from Bac Ha District, Lao Cai Province, northern Vietnam. Cyrtodactyluslucisp. nov. is distinguished from the remaining Indochinese bent-toed geckos by a combination of the following morphological characteristics: medium size (SVL up to 89.5 mm); dorsal tubercles in 17-19 irregular transverse rows; ventral scales in 32-34 longitudinal rows at midbody; precloacal pores present in both sexes, 9 or 10 in males, 8 or 9 in females; 12-15 enlarged femoral scales on each thigh; femoral pores 9-12 in males, 5-10 in females; postcloacal tubercles 2-4; lamellae under toe IV 21-23; dorsal pattern consisting of 5 or 6 irregular dark bands, a thin neckband without V-shape or triangle shape in the middle, top of head with dark brown blotches; subcaudal scales transversely enlarged. Molecular phylogenetic analyses recovered the new species as the sister taxon to C.gulinqingensis from Yunnan Province, China, with strong support from all analyses and the two taxa are separated by approximately 8.87-9.22% genetic divergence based on a fragment of the mitochondrial ND2 gene. This is the first representative of Cyrtodactylus known from Lao Cai Province.

A new species of Hemiphyllodactylus (Squamata, Gekkonidae) from Ha Giang Province, Vietnam.

An integrative analysis recovered a new species of the Hemiphyllodactylustypus group from a karst formation in Lung Cu Commune, Dong Van District, Ha Giang Province, northeastern Vietnam. Hemiphyllodactyluslungcuensissp. nov. is embedded within clade 6 of the typus group, bearing an uncorrected pairwise sequence divergence of 4.6-20.2% from all other species based on a 1,038 base pair segment of the mitochondrial NADH dehydrogenase subunit 2 gene (ND2). It is diagnosable from other species in clade 6 by statistically significant mean differences in normalized morphometric, meristic, and categorical characters. A multiple factor analysis using the three aforementioned character types recovered its unique, non-overlapping placement in morphospace as statistically significantly different from that of all other species in clade 6. The description of this new Hemiphyllodactylus species contributes to a growing body of literature underscoring the high degree of herpetological diversity and endemism in karst landscapes in Vietnam as well as in the genus Hemiphyllodactylus.

A new species of Cyrtodactylus (Squamata: Gekkonidae) from Phu Yen Province, Vietnam.

We describe a new species of the genus Cyrtodactylus based on six adult specimens from Lac Dao forests, Phu Yen Province, southern Vietnam. Cyrtodactylus tayhoaensis sp. nov. is distinguished from the remaining Indochinese bent-toed geckos by a combination of the following characters: medium size (SVL up to 94.2 mm); nasal scales 5-6; internasal single or double; ciliaria 29-34; dorsal tubercles in 20-22 irregular transverse rows; ventral scale in 37-41 longitudinal rows at midbody; ventrolateral folds present without interspersed tubercles; precloacal pores absent in females, precloacal pores 4 or 5 in males; 10 or 11 enlarged femoral scales on each thigh; femoral pores 3-7 in males, absent in females; postcloacal tubercles 3 or 4; lamellae under toe IV 22-24; dorsal pattern consisting of unclear transverse bands formed by irregularly shaped dark-brown blotches, a discontinuous neckband with V-shape or triangle shape in the middle, dorsal head surface with dark-brown blotches; subcaudal scales transversely enlarged. In the phylogenetic analyses, the new species is recovered as a sister taxon to C. kingsadai with approximately 4% genetic divergence between the two species based on a fragment of the COI gene. This is the second species of Cyrtodactylus known from Phu Yen Province located in southern Vietnam.

Achalinus quangi, a new odd-scaled snake species from Vietnam.

Based on morphological and molecular analyses, we herein describe a new species of Achalinus from northern Vietnam. Achalinus quangi sp. nov. differs from its sister taxon, A. emilyae, and other members of the genus Achalinus by at least 4% in terms of genetic divergence based on fragments of the mitochondrial COI and Cytb genes and a combination of the following morphological characters: (1) maxillary teeth 27-29; (2) suture between the internasals distinctly longer than that between the prefrontals; (3) loreal not fused with prefrontal, extending from the nasal to the eye; (4) supralabials six; (5) infralabials five; (6) postocular absent, temporals 2+2, only the upper one in broad contact with eye; (7) dorsal scales in 25(23)-23-23(21) rows, keeled; (8) ventrals 139-141 in males, 141-154 in females; (9) subcaudals 75-84 in males, 69 in the female, all unpaired; (10) cloacal entire; (11) dorsum reddish brown to brown. Achalinus quangi sp. nov. consists of two subclades, the first one occurring on the northern side of the Da River in Son La and Tuyen Quang provinces and another subclade found on the southern side in Thanh Hoa, Nghe An, and Ha Tinh provinces. These two subclades are separated from each other by 1.8 to 2.3% genetic divergence and are slightly differing in ventral scalation.

Two new species of Dixonius from Vietnam and Laos with a discussion of the taxonomy of Dixonius (Squamata, Gekkonidae).

Integrated analyses using maximum likelihood (ML), Bayesian inference (BI), principal component analysis (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 Dixoniusgialaiensissp. 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. Dixoniusmuangfuangensissp. nov. is the sister species to D.lao from Khammouane 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 combinations 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 Dixoniusgialaiensissp. nov. and Dixoniusmuangfuangensissp. nov. are statistically 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 herpetological diversity of the genus Dixonius and illustrates the continued need for field work in these regions.

A new species of Gracixalus (Anura, Rhacophoridae) from northwestern Vietnam.

A new species of small tree frog is described from northwestern Vietnam based on morphological differences and molecular divergence. Gracixalustruongisp. nov. is distinguishable from its congeners and other small rhacophorid species on the basis of a combination of the following characters: size relatively small, SVL 32.2-33.1 mm in males, 37.6-39.3 mm in females; head slightly wider than long; vomerine teeth absent; snout round and long RL/SVL 0.17-0.19 in males, 0.16-0.17 in females; spines on upper eyelid absent; supratympanic fold distinct; tympanum distinct; dorsal skin smooth; throat smooth and venter granular; tibiotarsal projection absent; webbing of fingers rudimentary, toes with moderately developed webbing; dorsum moss-green, with an inverse Y-shaped dark green marking extended from interorbital region to posterior region of dorsum; external vocal sac absent in males; males with a nuptial pad on finger I. In the molecular analyses, the new species has no clear sister taxon and is at least 4.5% divergent from other congeners based on a fragment of the mitochondrial 16S rRNA gene.

A new species of the genus Achalinus (Squamata: Xenodermidae) from Son La Province, Vietnam.

A new snake of the genus Achalinus Peters, 1869 is described based on an adult male specimen from Son La Province, Vietnam. Achalinus vanhoensis sp. nov. can be distinguished from its congeners by a combination of the following characters: 1) maxillary teeth 32; 2) suture between the internasals distinctly longer than that between the prefrontals; 3) loreal fused with prefrontal, prefrontals stretch towards the supralabials; 4) dorsal scales in 252323 rows, keeled; 5) supralabials six (left) and seven (right); 6) infralabials six; 7) temporals 2+2, the two anterior temporals in broad contact with eye; 8) ventrals 176; 9) subcaudals 84, entire; 10) cloacal entire; 11) dorsum in preservative dark purple grey above; 12) venter somewhat lighter with yellow-edged scales in the chin region, including infralabials; 13) posterior edges of ventrals and subcaudals with yellow margin. In the molecular analysis, the new species is recovered as a sister taxon of Achalinus timi, a species endemic to Vietnam, and genetically the two species are around 5% divergent from each other based on a fragment of the mitochondrial COI gene. This discovery brings the number of Achalinus species known from Vietnam to nine.

How many more species are out there? Current taxonomy substantially underestimates the diversity of bent-toed geckos (Gekkonidae, Cyrtodactylus) in Laos and Vietnam.

Cyrtodactylus is the most diverse genus of the family Gekkonidae and the world's third largest vertebrate genus. The number of species has increased more than fourfold over the last two decades. Indochina, especially Vietnam and Laos, has witnessed a surge in new species discoveries over the last three decades. The species number reported from Laos and Vietnam has remarkably increased from five in 1997 to 71 species in 2021. However, within the genus, several taxonomic issues have not yet been fully resolved. Based on recently collected samples from Laos and Vietnam, we conducted a comprehensive molecular review of Cyrtodactylus occurring in Laos and Vietnam. Our molecular analysis with support from morphological comparisons showed that C.thuongae is a junior synonym of C.dati and C.rufford is a junior synonym of C.lomyenensis. In total, 68 described species distributed in Laos and Vietnam are undisputed with strong support from both molecular and morphological evidence. On the other hand, the molecular analyses revealed that there are at least seven undescribed species in Vietnam and Laos, one in the C.angularis group, one in the C.chauquangensis, and five in the C.irregularis group. This number will likely increase significantly, as previous work suggested that the C.angularis and C.irregularis groups harbor three and six unnamed lineages, respectively. Based on survey gaps identified in our study, it is clear that additional new species will be discovered in poorly studied regions of central Vietnam and northern and southern Laos. As many species in the genus are facing high extinction risks, several undescribed populations might already be severely threatened by human activities in both countries. Therefore, urgent taxonomic research is needed before conservation assessments of newly discovered taxa can be undertaken to protect them from anthropogenic threats.

A new species of Cyrtodactylus (Squamata: Gekkonidae) from Ninh Thuan Province, southern Vietnam.

A new species of the Cyrtodactylus irregularis group is described from Ninh Thuan Province, southern Vietnam based on molecular divergence and morphological differences. Cyrtodactylus orlovi sp. nov. is distinguished from the remaining Indochinese bent-toed geckos by having the unique combination of the following characters: size medium (SVL 61.077.7 mm); dorsal tubercles in 1620 irregular rows; 3639 ventral scale rows; precloacal pores absent in females, 5 or 6 in males, in a continuous row; femoral pores absent; 38 enlarged femoral scales; postcloacal spurs 1 or 2; lamellae under toe IV 1619; a continuous neckband; a highly irregular transverse banded dorsal pattern; the absence of transversely enlarged median subcaudal scales. In phylogenetic analyses, the new species was revealed to be the sister taxon to a clade consisting of Cyrtodactylus cattienensis and the most recently described species from Vietnam, C. chungi, with 12.112.4% and 11.7 % pairwise genetic divergence from the two species, respectively, based on a fragment of the mitochondrial COI gene.

A new species of Hemiphyllodactylus Bleeker, 1860 (Squamata: Gekkonidae) from Da Lat Plateau, Vietnam.

We describe a new species of the genus Hemiphyllodactylus on the basis of four specimens from Bidoup - Nui Ba National Park, Da Lat Plateau, Lam Dong Province, Vietnam. The new species, Hemiphyllodactylus dalatensis sp. nov., is distinguished from the remaining congeners by a combination of the following characters: a bisexual taxon; maximum SVL of 45.9 mm; dorsal scale rows 16; ventral scale rows 8 or 9; chin scales 710; postmental scales enlarged; femoral and precloacal pores in a continuous series, 2325 in total in males, absent in the female; digital lamellae formula 4-5-5/6-5 (forefoot) and 5-6-6-6/5 (hind foot); cloacal spurs 2 or 3 on each side in both males and female; subcaudal scales not enlarged; dorsal trunk pattern with two paravertebral stripes, formed by two rows of dark spots; dark lateral head stripe distinct; postsacral mark cream or orange and bearing anteriorly projecting arms. In phylogenetic analyses, the new species is recovered as the sister taxon to a clade including all species from India although support values are low from all analyses.

First record of the Cyrtodactylus brevipalmatus group (Squamata: Gekkonidae) from Vietnam with description of a new species.

A new species of the genus Cyrtodactylus is described from Dien Bien Province, northwestern Vietnam based on morphological and molecular data. Cyrtodactylus ngati sp. nov. can be distinguished from remaining congeners by the following combination of characters: maximum SVL 69.3 mm; dorsal pattern consisting of six dark irregular transverse bands between limb insertions; inter-supranasals one; dorsal tubercles present on occiput, body, hind limbs and on first half of tail; 1722 irregular dorsal tubercle rows at midbody; lateral folds clearly defined, with interspersed tubercles; 3238 ventral scales between ventrolateral folds; 13 precloacal pores separated by a diastema of 5/5 poreless scales from a series of 7/7 femoral pores in enlarged femoral scales; precloacal and femoral pores absent in females; 13 postcloacal tubercles on each side; transversely enlarged median subcaudal scales absent. In the molecular analyses, the new species is shown to be the sister taxon to C. interdigitalis from Thailand. This is the 47th species of the genus Cyrtodactylus and the first member of the C. brevipalmatus species group recorded from Vietnam.

A new species of Dixonius (Squamata: Gekkonidae) from Vientiane Capital, Laos.

A new species of the gekkonid genus Dixonius is described from Huaysorn-Huaysua village, Nasaithong District, Vientiane Capital, Laos. The new species can be distinguished from all other species by a combination of the following characters: maximum SVL 47.1 mm; 1921 longitudinal rows of dorsal tubercles at midbody; 2326 longitudinal rows of ventrals across the abdomen; 7 or 8 supralabials, 6 in mid-orbital position; 5 or 6 infralabials; 5 or 6 precloacal pores in males, femoral pores lacking; precloacal and femoral pores absent in females; a canthal stripe running from rostrum through the eye and terminating at back of head; dorsum brown with irregular dark marks. In phylogenetic analyses, the species is recovered as the sister taxon to D. siamensis, which occurs in Laos, Thailand, and Vietnam. Genetically, the two species are approximately 9.4% divergent from each other based on the complete mitochondrial ND2 gene with six partial or complete adjacent tRNAs. It is the 12th species known in the genus Dixonius and the second Dixonius species described from Laos.

A new species of the Gekko japonicus group (Squamata: Gekkonidae) from Khammouane Province, central Laos.

A new species of the Gekko (Japonigekko) japonicus group from Khammouane Province, central Laos is described based on morphological characters and molecular evidence. Morphologically, Gekko khunkhamensis sp. nov. can be distinguished from the remaining congeners by a combination of the following characters: size moderate (SVL 69.775.2 mm); nares in contact with rostral; internasals absent; postmentals enlarged; interorbital scales between anterior corners of the eyes 31 or 32; dorsal tubercles absent; ventrals between mental and cloacal slit 181185; midbody scales 127138; ventral scales 4245; subdigital lamellae on first toe 13 or 14, on fourth toe 14 or 15; tubercles on upper surface of fore and hind limbs absent; precloacal pores absent in the male and females; postcloacal tubercles 2; tubercles absent on dorsal surface of tail base; subcaudals distinctly enlarged; dorsal surface of body with five dark grey bands, which become irregular posteriorly. Genetically, the new species is placed in a clade, consisting of G. bonkowskii, G. nadenensis, G. scientiadventura, G. sengchanthavongi, and G. thakhekensis and differs from other congeners by at least 13% in terms of pairwise distance based on a fragment of the mitochondrial ND2 gene.

A new species of Limnonectes (Amphibia: Anura: Dicroglossidae) from Vietnam.

A new species of Limnonectes from Phu Yen Province, South-central Vietnam is described based on morphological and molecular differences. Morphologically, the new species is distinguishable from its congeners on the basis of a combination of the following diagnostic characters: SVL 49.8-77.9 mm in males, 40.8-61.8 mm in females; males with moderately enlarged head (HL/SVL 0.47, HW/SVL 0.48); head slightly broader than long (HL/HW 0.97 in males, 0.95 in females); vomerine teeth present; external vocal sacs absent; rostral length short (RL/SVL 0.15); tympanum invisible; dorsal surface of head, body and flanks with ridges and tubercles; dorsal surface of tibia and foot distinctly tuberculate, covered with moderately dense, small, low tubercles; supratympanic fold present; dorsolateral fold absent; Finger I with nuptial pad, composed of minute spines on dorsal surface and medial edge in males; toes webbed to distal of terminal phalanx, webbing formula I0-0II0-0III0-0IV0--0V0; in life, dorsum yellowish brown with dark brown markings; ventral surface white with brown markings. In phylogenetic analyses, the new species from Vietnam and Limnonectes fastigatus as well as L. kiziriani form a clade, which is sister to L. fragilis from China, although the nodal support values for the set of relationships are insignificant from all analyses.

A new species of Achalinus (Squamata: Xenodermidae) from Trang An Landscape Complex, Ninh Binh Province, Vietnam.

We describe a new snake of the genus Achalinus based on an adult female specimen from Ninh Binh Province, Vietnam. Achalinus tranganensis sp. nov. is differentiated from its congeners genetically and by a unique combination of the following characters: 1) maxillary teeth 29; 2) suture between the internasals distinctly longer than that between the prefrontals; 3) loreal distinctly wider than high, extending from the nasal to the eye; 4) dorsal scales in 25-23-23 rows, keeled; 5) two pairs of prefrontals; 6) supralabials six; 7) infralabials six; 8) temporals 2+3, the two anterior temporals in contact with eye; 9) ventrals 171; 10) subcaudals 73+, unpaired; 11) cloacal plate entire; 12) dorsum in preservative reddish to greyish brown above; 13) the lower part of head side and chin region somewhat paler than the dorsum; 14) venter greyish cream, with the anterior region of each ventral and subcaudal somewhat darker. Based on molecular comparisons using a fragment of the mitochondrial cytochrome c oxidase subunit I (COI), the new species differs from other members of the genus by at least 11.8%. This discovery increases the number of Achalinus species known from Vietnam to seven.

Two new species of Cyrtodactylus (Squamata: Gekkonidae) from northern Laos, including new finding and expanded diagnosis of C. bansocensis.

Two new Cyrtodactylus species are described from Houaphan and Luang Prabang provinces in Laos based on morphological and molecular data. Cyrtodactylus houaphanensis sp. nov. differs from all other Cyrtodactylus in the C. wayakonei species group by at least 3.3 % genetic divergence in the COI gene and can be diagnosed in morphology as follows: SVL 75.8 mm; supralabials 9 or 10; infralabials 8 or 9; ventral scales 35; dorsal tubercles in 20 rows at midbody; precloacal pores 6 in the male; femoral pores absent; subcaudals enlarged; five irregular, brown bands between limb insertions. The new species morphologically resembles C. chauquangensis and revealed to be a sister taxon to C. puhuensis according to our genetic analyses, from which it mainly differs in the absence of enlarged femoral scales. Cyrtodactylus ngoiensis sp. nov. differs from other closely related congeners by at least 11.6 % genetic divergence in the COI gene and can be diagnosed in morphology as follows: maximum SVL 95.3 mm; supralabials 6-9; infralabials 8-11; ventral scales 38-43; dorsal tubercles in 15-21 rows at midbody; enlarged femoral scales present; precloacal pores 7 in the male, 7 pitted scales in females; femoral pores 14 in the male, absent in females; five bright yellowish transverse dorsal bands; subcaudals enlarged. The new species is shown to be a member of the C. wayakonei species group, but morphologically resembles C. dumnuii from Thailand. According to our phylogenetic analyses, it is a basal taxon to a clade comprising C. spelaeus, C. chauquangensis, C. vilaphongi, C. cucphuongensis, C. puhuensis, C. houaphanensis, C. otai and C. bobrovi. Based on a new record of C. bansocensis from central Laos, which represents the first recorded female we provide a redescription of C. bansocensis including expanded diagnosis. In addition, an updated identification key for the Cyrtodactylus known from Laos is provided.

A new species of Hemiphyllodactylus (Squamata: Gekkonidae) from Tuyen Quang Province, Vietnam.

A new species of the gekkonid genus Hemiphyllodactylus is described from limestone karst forest of Tuyen Quang Province, northern Vietnam based on morphological differences and molecular divergence. Hemiphyllodactylus nahangensis sp. nov. is distinguished from the remaining congeners by having the unique combination of the following characters: a bisexual taxon; SVL of adults 41.4-43.6 mm; dorsal scale rows 18-23; ventral scale rows 9-13; chin scales bordering mental and first infralabial distinctly enlarged; 22-24 pore-bearing femoral and precloacal scales, in a continuous row, absent in females; digital lamella formula 3-4-5-4 (forefoot) and 4-5-5-5 (hindfoot); cloacal spur single, present in both sexes; dark lateral head stripe indistinct; postsacral mark cream and bearing anteriorly projecting arms. In phylogenetic analyses, the new species is placed in a clade that includes H. dushanensis, H. hongkongensis, H. huishuiensis, H. ngocsonensis and H. zugi. In terms of pairwise genetic distance, the new species is at least 5.9%-6.6% divergent from other congeners based on a fragment of the mitochondrial gene ND2.

A new species of Cyrtodactylus (Squamata: Gekkonidae) from southern Vietnam.

We describe a new species of Cyrtodactylus on the basis of four specimens collected from Phu My, Binh Dinh Province, southern Vietnam. Cyrtodactylus phumyensis sp. nov. is distinguished from the remaining Indochinese bent-toed geckos by a combination of the following characters: size small (SVL up to 66.8 mm); two internasals; dorsal tubercle rows 18 or 19 at midbody; ventral scale rows 33-41; ventrolateral folds slightly developed; each thigh with 5-7 enlarged femoral scales; femoral pores absent in males and female; a series of 5-7 precloacal pores plus a pitted, enlarged precloacal scale in males; 6 pitted, enlarged precloacal scales in female; paravertebral tubercles 20-23; lamellae under toe IV 18-21; small subcaudal scales, not transversely enlarged; two irregular dark longitudinal stripes on shoulder. In phylogenetic analyses, the new species is recovered as a member of the Cyrtodactylus irregularis species group, and strongly supported as a sister taxon of C. cucdongensis from Khanh Hoa Province.