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Two new genera of freshwater crabs (Potamidae) are recorded from northern Vietnam, Tortomon Huang, Wang & Shih, 2020, and Aiyunamon Pan, Ng & Sun, 2022. These genera had previously only been reported from southern China and eastern Myanmar. Each genus is represented by a new species. Tortomon distinctum n. sp. is markedly different from its two Chinese congeners in its proportionately wider carapace, more elongate third maxilliped, the carpus of the cheliped being armed only with a low tubercle, possessing relatively more slender and longer ambulatory legs, a gently curved male first gonopod and a more elongate male second gonopod. Aiyunamon vietnamicum n. sp. is distinct from its five congeners in its proportionately less convex dorsal surface of the carapace, relatively lower epigastric cristae, lower rugosities of the postorbital cristae, wider median lobe of the posterior margin of the epistome, relatively narrower male pleon, and a male first gonopod that has the terminal segment more distinctly curved with a wider concavity on the outer margin of the subterminal segment.

A new species of insular Bent-toed Gecko, Cyrtodactylus culaochamensis sp. nov. of the C. irregularis group is described from Cu Lao Cham Mountain, from Hon Lao Island, Hoi An City, Quang Nam Province, Cham Islands, central Vietnam. Cyrtodactylus culaochamensis sp. nov. is the sister species of C. pseudoquadrivirgatus from Ba Na Nui Chua from Danang City, central Vietnam. It differs from all congeners by having a maximum SVL of 79.8 mm (n=5); dark spots on the head edged in white; a fragmented nuchal loop; irregularly shaped, broad, completed or broken dorsal bands; 19–21 interorbital scales across the frontal bone; 28–32 scales between the eye and nostril; 45–50 rows of ventral scales between the ventrolateral folds; scattered, smooth tubercles; 20–22 irregular, longitudinal rows of weakly keeled tubercles at midbody between the ventrolateral folds; seven or eight precloacal pores in a chevron pattern in males; no enlarged femoral scales, no femoral pores; 13–15 subdigital lamellae on first toe; 20–23 subdigital lamellae on fourth toe; and very slightly enlarged subcaudal scales.

An integrative taxonomic analysis using color pattern, morphology, and 1449 base pairs of the ND2 mitochondrial gene and its five flanking tRNAs demonstrated that eight species-level lineages occur within the Cyrtodactylus intermedius complex ( Cyrtodactylus intermedius sensu stricto , C. phuquocensis and related populations) of the Cardamom mountains and associated highlands that have a sequence divergence ranging 3.4–8.9%. Additionally, each lineage is discretely diagnosable from one another based on morphology and color pattern and most occur in specific geographic regions (upland areas, karst formations or islands) that prevent or greatly restrict interpopulation gene flow. Six of these lineages were masquerading under the nomen C. intermedius and are described as the following: Cyrtodactylus auralensis sp. nov. endemic to Phnom Aural, the highest mountain in Cambodia; C. bokorensis sp. nov. endemic to the Bokor Plateau, Cambodia; C. cardamomensis sp. nov. from the main block of the Cardamom mountains; C. thylacodactylus sp. nov. endemic to Phnom Dalai the northernmost peak of the Cardamom mountains; C. laangensis sp. nov. endemic to the Phnom Laang karst formation, Cambodia; and C. septimontium sp. nov. from the Bảy Nui Hills of southwest Vietnam.

A new species of Bent-toed Gecko, Cyrtodactylus dati sp. nov. is described from the secondary evergreen forests of Bu Dop District, Binh Phuoc Province, Vietnam. It differs from all other species of Indochinese and Thai-Malay Cyrtodacty-lus by having a maximum SVL of 70.1 mm (n=6); no distinct dark blotches on the head in adults; no continuous nuchal loop; a blotched dorsal pattern; 17–19 interorbital scales across the frontal bone; 23–26 scales in a straight line between eye and nostril; 42–48 rows of ventral scales between ventrolateral folds; 20–22 irregular, longitudinal rows of keeled tu-bercles at midbody between the ventrolateral folds; a series of five or six precloacal pores medially interrupted by one poreless scale in males; three or four femoral pores on each thigh in males; 4–7 enlarged scales beneath thighs; 12–13 subdigital lamellae on first toe; 18–19 subdigital lamellae on fourth toe; and small subcaudal scales.

A new species of Gekko Laurenti is described from Tà Kóu Mountain, an isolated granitic peak in Tà Kóu Nature Reserve, Ham Thuan Nam district, Binh Thuan province, southern Vietnam. The species is distinguished from its congeners by its moderate size, with snout to vent length (SVL) reaching a maximum 107.0 mm; dorsal pattern of 5–8 white vertebral blotches between the nape and sacrum and 6–8 pairs of short white bars on the flanks; 11–14 precloacal pores in males; 14–17 longitudinal rows of smooth dorsal tubercles; and 18–20 broad lamellae beneath the fourth toe. Gekko takouensis sp. nov. is the second endemic gekkonid discovered in the Tà Kóu Nature Reserve, Cyrtodactylus takouensis Ngo & Bauer being the first.

A new endemic cave-dwelling species of gekkonid lizard, Cyrtodactylus hontreensis sp. nov., is described from Hon Tre Island in Kien Giang Biosphere Reserve in southwestern Vietnam and differentiated from all other species by a unique suite of the following characters: SVL of 79.7 ± 4.9 mm, three broad transverse dorsal body bands edged in white between limb insertions, very low smooth dorsal body tubercles, the absence of a precloacal groove, 7–8 precloacal pores arranged in a chevron in males, a shallow dorsal groove on the tail, absence of caudal tubercles, and various aspects of color pattern.

Two new cave-dwelling species of Cyrtodactylus from mainland southwestern Vietnam and an offshore island are differentiated from all other congeners in lacking a precloacal groove and precloacal pores, presence of enlarged femoral scales beneath thigh, and in having a color pattern consisting of four or five narrow white bands on the body dorsum and one on the tail. Cyrtodactylus grismeri sp. nov. is reddish brown, has a mean SVL of 87.6 ± 3.8 mm (n = 9), 18–22 irregular longitudinal rows of weakly-keeled tubercles at midbody between the lateral folds, 33–38 ventral scales between ventrolateral folds, 0–3 enlarged scales beneath thighs, and 20–24 subdigital lamellae under the first toe. Cyrtodactylus eisenmani sp. nov. is chocolate brown, has a mean SVL of 81.3 ± 5.0 mm (n = 5), 14 irregular longitudinal rows of weakly keeled tubercles at midbody between ventrolateral folds, 44–45 ventral scales between ventrolateral folds at midbody, 4–6 enlarged femoral scales beneath each thigh, and 22–25 subdigital lamellae under the first toe. This discovery increases the total number of Cyrtodactylus found in Vietnam to fifteen.

An integrative taxonomic analysis of the distantly related Cyrtodactylus condorensis and intermedius species complexes of the Mekong Delta revealed that C. paradoxus is a junior synonym of C. condorensis and that C. thochuensis is a junior synonym of C. leegrismeri. Additionally, the analysis revealed that a cave-dwelling ecomorpholgy has evolved independently early on in the evolution of both complexes (represented by C. hontreensis in the intermedius complex and C. grismeri and C. eisenmani in the condorensis complex) and cave ecomorphs exist in sympatry-but not syntopy-with general scansorial ecomorphs. Multiple, recent, cyclical, glacioeustatic driven changes in sea levels across the Sunda Shelf are hypothesized to account for the evolution and distribution of the widely separated, conspecific insular populations of C. condorensis and C. leegrismeri. The independent evolution of cave ecomorphology is proposed to have been driven by competition avoidance. Habitat islands across the Mekong Delta are an important source of endemism and in need of protection.

A new species of the genus Gekko Laurenti is described from central Laos. The species is distinguished from its congeners by its moderate size, i.e. maximum SVL 80.0 mm, dorsal pattern of five to six dirty white vertebral spots alternating with yellowish-edged, W-shaped blotches between nape and sacrum and six to seven pairs of dirty white spots interspersed with yellowish-edged dark blotches on the flanks between limb insertions, 0-1 internasal, 39-43 ventral scale rows between the weakly developed ventrolateral folds, 3-4 precloacal pores in males, sometimes separated by one poreless scale, 98-104 smooth dorsal scale rows around the body, 16 broad lamellae beneath digit I of pes, 15-16 broad lamellae beneath digit IV of pes, and enlarged subcaudal scales.

A new species of the gekkonid Hemiphyllodactylus banaensis sp. nov. is described from Ba Na-Nui Chua Nature Reserve in central Vietnam. Previously included within H. yunnanensis, the new species is distinguished from all other congeners by having the unique combination of a maximum SVL of 48.2 mm in males and 51.0 mm in females; seven chin scales extending transversely from the union of the first and second infralabials and posterior margin of mental; enlarged postmental scales; 9-12 supralabials; 9-11 infralabials; 18-20 longitudinally arranged dorsal scales at midbody contained within one eye diameter; 20-21 precloacal and femoral pore-bearing scales contiguous in males and 0-20 contiguous pore-bearing precloacal scales in females; dorsal pattern on body composed of transverse blotches and two whitish stripes across shoulder extending to sacrum; postsacral mark whitish brown and bearing anteriorly projecting arms; and caecum and oviducts unpigmented.

An integrative taxonomic analysis of the distantly related Cyrtodactylus condorensis and intermedius species complexes of the Mekong Delta revealed that C. paradoxus is a junior synonym of C. condorensis and that C. thochuensis is a junior synonym of C. leegrismeri. Additionally, the analysis revealed that a cave-dwelling ecomorpholgy has evolved independently early on in the evolution of both complexes (represented by C. hontreensis in the intermedius complex and C. grismeri and C. eisenmani in the condorensis complex) and cave ecomorphs exist in sympatry—but not syntopy—with general scansorial ecomorphs. Multiple, recent, cyclical, glacioeustatic driven changes in sea levels across the Sunda Shelf are hypothesized to account for the evolution and distribution of the widely separated, conspecific insular populations of C. condorensis and C. leegrismeri. The independent evolution of cave ecomorphology is proposed to have been driven by competition avoidance. Habitat islands across the Mekong Delta are an important source of endemism and in need of protection.

A new species of the genus Gekko Laurenti is described from central Laos. The species is distinguished from its congeners by its moderate size, i.e. maximum SVL 80.0 mm, dorsal pattern of five to six dirty white vertebral spots alternating with yellowish-edged, W-shaped blotches between nape and sacrum and six to seven pairs of dirty white spots interspersed with yellowish-edged dark blotches on the flanks between limb insertions, 0–1 internasal, 39–43 ventral scale rows between the weakly developed ventrolateral folds, 3–4 precloacal pores in males, sometimes separated by one poreless scale, 98–104 smooth dorsal scale rows around the body, 16 broad lamellae beneath digit I of pes, 15–16 broad lamellae beneath digit IV of pes, and enlarged subcaudal scales.

A new species of the gekkonid Hemiphyllodactylus banaensis sp. nov. is described from Ba Na-Nui Chua Nature Reserve in central Vietnam. Previously included within H. yunnanensis, the new species is distinguished from all other congeners by having the unique combination of a maximum SVL of 48.2 mm in males and 51.0 mm in females; seven chin scales extending transversely from the union of the first and second infralabials and posterior margin of mental; enlarged postmental scales; 9-12 supralabials; 9-11 infralabials; 18-20 longitudinally arranged dorsal scales at midbody contained within one eye diameter; 20-21 precloacal and femoral pore-bearing scales contiguous in males and 0-20 contiguous pore-bearing precloacal scales in females; dorsal pattern on body composed of transverse blotches and two whitish stripes across shoulder extending to sacrum; postsacral mark whitish brown and bearing anteriorly projecting arms; and caecum and oviducts unpigmented.

A new crevice dwelling species, Cyrtodactylus phuquocensis sp. nov. from Phu Quoc National Park on Phu Quoc Island in Kien Giang Biosphere Reserve in southwestern Vietnam is differentiated from all other species by the following combination of characteristics: SVL 62.2–85.8 mm; no precloacal groove; 7–9 precloacal pores arranged in an angular series; a series of enlarged femoral scales contacting a wide patch of enlarged precloacal scales; 2–5 intersuparanasals in contact with rostrum; 16–18 weakly keeled, longitudinal rows of tubercles on body; 38–43 transverse rows of ventral scales between ventrolateral folds; and dorsal caudal tubercles extending 57.8–75% down length of tail. This species most closely resembles C. intermedius Smith, 1917 to which it was previously referred. The description of this species has elevated the number of endemic species of gekkonids of this region to eight within the last three years.

A new genus and new species of pinnotherid crab, Solenotheres prolixus, is described from the razor clam, Solen corneus (Solenidae), in Vietnam. The new genus is characterised by its broad and subquadrate carapace, a spatuliform third maxilliped dactylus that is inserted near the base of the propodus, and asymmetrical third ambulatory legs.

A new species of endemic, insular Cnemaspis is described from Hon Khoai Island, Ca Mau Province, Ngoc Hien District, 18 km off the southern tip of the Ca Mu Peninsula in southern Vietnam. Cnemaspis psychedelica sp. nov. is the most uniquely colored of all southeast Asian Cnemaspis in that both sexes and all age classes have bright orange forelimbs, forelegs, hands and feet; a bright orange tail; a dense, yellow reticulum on the neck overlying thick, black, longitudinal lines; and a blue-gray to light purple trunk bearing yellow transverse bars on bright-orange flanks. It also differs from all other species of Cnemaspis in aspects of size and squamation. Cnemaspis psychedelica is the third insular endemic species of Cnemaspis from Vietnam and brings the total number of species in Vietnam to six. Its occurrence on one of the 92 islands in Rach Gia Bay underscores the necessity for continued surveys of these poorly known islands that are beginning to show a surprising degree of endemism and diversity.

We describe a new species of pitviper Cryptelytrops honsonensis sp. nov. from Hon Son Island in Rach Gia Bay, Kien Giang Province of southern Vietnam based on it having unique aspects of scalation, body proportions, and color pattern. It is similar to C. venustus in morphology and color pattern and the putative close relationship between these species would corroborate a biogeographical link across southern Indochina seen in a number of other taxa. The presence of this newly discovered insular endemic in Rach Gia Bay and other insular endemics of Rach Gia Bay addressed herein, underscores the understudied nature of these islands and the need for their continued conservation.

Two new species of the gekkonid lizard genus Cyrtodactylus Gray, 1827 are described on the basis of voucher specimens collected in isolated mountains separated from the Truong Son Mountain Range, southern Vietnam. Both species were collected from shallow caves, as have been many of the recently described Cyrtodactylus from across Southeast Asia. Both species, C. takouensis sp. nov. from Ta Kou Nature Reserve, Binh Thuan Province and C. huynhi sp. nov. from Chua Chan Mountain, Dong Nai Province, are characterized by a small number of enlarged femoral scales separated from the precloacal scales by a large diastema. They may be distinguished from one another and from all other congeners by differences in rows of tubercles and ventral scales, subcaudal scalation and dorsal color pattern. These new taxa bring the number of currently recognized Cyrtodactylus species in Vietnam to twelve.