Morphological characters of specimens (n = 2 males) from Son La Province agreed with the descriptions of Yang et al. (1983) and Ho et al. (1999): SVL 71.4–75.8 mm; head wider than long (HL 26.1–28.1 mm, HW 28.5–31.8 mm, HL/SVL 37%; HW/SVL 40.0–42.0%); snout round (SL 11.0–11.3 mm), longer than horizontal diameter of eye (EL 9.5–9.9 mm); canthus rostralis distinct; loreal region oblique, moderately concave; nostril lateral, closer to tip of snout than to eye (NS 4.8–4.9 mm, EN 5.2–5.5 mm); interorbital space flat, broader than upper eyelid and internarial distance (IOD 9.5–9.8 mm, UEW 7.3–7.4 mm, IN 5.0–5.2 mm); tympanum indistinct; vomerine teeth absent; tongue heart-shaped, notched posteriorly; vocal openings absent.

Forelimb long (FLL 58.0–62.8 mm); relative finger lengths II < I < IV < III; fingers without dermal fringe, free of webbing; tips of fingers rounded, slightly swollen; subarticular tubercle indistinct; palmar tubercles two, oval; nuptial pads absent.

Hindlimb slender, long (HLL 105.0–106.7 mm); thigh longer than tibia (FL 34.8–36.6, TL 31.3–34.0 mm); tips of toes slightly swollen; webbing formula I1–2II1–21/2III2–3/1/2IV4–2V; inner metatarsal tubercle distinct, shorter than length of toe I; tibiotarsal articulation reaching to posterior margin of orbit when limb adpressed along body.

Skin. Dorsal surface with fine network of ridges, tubercles present in the posterior region of tympanum; upper lip with 46–78 keratinised spines; supratympanic fold present, from posterior edge of eye to axilla; flanks, belly, chest, throat, underside of forelimbs and thighs with small white pustules.

Colouration in life. Dorsal surface of the head light brown or reddish-brown, with dark brown spots on medial side of upper eyelid; back with irregularly dark brown spots; ventral surface with light brown pustules, more concentrated in chest area (Fig. 2).

In Vietnam, this species was recorded from Lao Cai Province (Nguyen et al. 2009). Our new record is approximately 70 km distant from Lao Cai Province. Elsewhere, this species is known from China (Frost 2019).

The specimens of L. ailaonicum were found on the edge of small streams and on forest paths between 20:00 and 21:00 h. The surrounding habitat was mixed secondary forest of large hardwood and shrub.

The male specimens from Son La have more keratinied spines than those in the previous studies: 46–78 versus 20–48 (Yang et al. 1983) and 50–59 (Ho et al. 1999).

Morphological characters of the specimens (n = 3 females) from Son La Province agreed with the description of Lathrop et al. (1998): SVL 55.9–56.8 mm; head longer than wide (HL 22.2–23.0 mm, HW 21.4–22.0); snout distinctly pointed in dorsal view, longer than eye diameter (SL 8.6–8.9 mm, ED 6.8–7.0 mm); nostrils oval, on lateral side, closer to the tip of snout than to eye (NS 3.8–4.1 mm, EN 4.5–5.0 mm); canthus rostralis distinct, loreal region concave; interorbital distance wider than upper eyelid width and internarial distance (IOD 6.5–6.8 mm, UEW 4.6–5.0 mm, IN 4.0–4.4 mm); eye large, approximately twice diameter of tympanum (TD 3.2–3.5 mm); tympanum round; vomerine teeth absent; tongue notched posteriorly.

Forelimbs. Forearm robust; relative finger lengths I = II = IV < III, tips of fingers not enlarged into discs; webbing absent; subarticular tubercles indistinct; palmar tubercles round, in contact, inner one very large.

Hindlimbs. Tibia longer than thigh (FL 22.0–23.9 mm, TL 23.0–24.2 mm); relative toe lengths I < II < V < III < IV; webbing rudimentary between toes I–IV and absent between IV and V; subarticular tubercles indistinct; inner metatarsal tubercle oval; outer metatarsal tubercle absent; tibiotarsal articulation reaching to orbit when limb adpressed along body.

Skin. Dorsal surface of head and body, upper part of flanks with tubercles; upper eyelid granular; supratympanic fold distinct, extending from posterior corner of eye to a point behind articulation of jaw; dorsolateral fold absent; ventral surface smooth.

Colouration in life. Dorsal surface of head brown grey with a dark brown marking between eyes; canthus and supratympanic fold dark brown; upper lip with dark brown bars; limbs with dark brown transverse bars; ventral surface orange (Fig. 3).

In Vietnam, this species has been recorded from Lao Cai, Dien Bien, Yen Bai, and Vinh Phuc provinces (Nguyen et al. 2009). Our new record in Son La Province filled the distribution gap of the species in northwestern Vietnam. Elsewhere, this species is known from China (Frost 2019).

The specimens were found at night, between 19:00 and 22:00 h, on the side of the streams in the secondary forest.

Morphological characters of the specimen (n = 1 male) from Son La Province agreed with the descriptions of Boulenger (1887), Inger et al. (1999) and Fei et al. (2009): SVL 96.5 mm; head wider than (HL 37.6 mm, HW 44.8 mm, HL/SVL 39%, HW/SVL 46%); snout round (SL 10.9 mm), longer than horizontal diameter of eye (EL 8.1 mm); canthus rostralis feeble; nostril lateral, slightly closer to eye than to tip of snout (NS 5.8 mm, EN 5.5 mm); interorbital space flat, broader than upper eyelid and internarial distance (IOD 12.0 mm, UEW 5.7 mm, IN 9.5 mm); tympanum indistinct; vomerine teeth present; tongue heart–shaped, slightly notched posteriorly; vocal sac present.

Forelimb short (FLL 47.2 mm); relative finger lengths I < II < IV < III; fingers dermal fringe absent, free of webbing; tips of fingers round, not swollen; subarticular tubercles indistinct; palmar tubercles indistinct; nuptial pads present.

Hindlimb (HLL 127.0 mm); tibia shorter than thigh (TL 41.1 mm, FL 42.3 mm); relative toe lengths I < II < V < III < IV; tips of toes round; toes without dermal fringe; webbing rudimental; inner metatarsal tubercle distinct; subarticular tubercles indistinct; tibiotarsal articulation reaching to commissure of the jaws.

Skin. Dorsal surface smooth with some small warts; upper eyelid with tubercles, one of which being larger; supratympanic fold present, from posterior edge of eye to axilla; ventral surface smooth.

Colouration in life. Dorsal surface brown olive; supratympanic fold edged in dark brown below; upper lip light brown; ventral surface dark brown with some whitish dots (Fig. 4).

In Vietnam, this species has been recorded from Lao Cai, Yen Bai, Ha Giang, Cao Bang, Lang Son, Vinh Phuc and Bac Giang provinces (Nguyen et al. 2009). Our new record in Son La Province filled the distribution gap of the species in northwestern Vietnam. Elsewhere, this species has been recorded from southern China, Myanmar and Thailand (Frost 2019).

The specimen was found at 20:15 h on a rock in a stream. The surrounding habitat was mixed secondary forest composed of medium hardwoods and shrubs.

Morphological characters of the specimens (n = 4) from Son La Province agreed with the descriptions of Fei et al. (2009) and Nguyen et al. (2016): SVL 49.0–50.0 mm in males (n = 2), 58.5–59.7 mm in females (n = 2); head wider than long (males: HL 17.5–17.7 mm, HW 18.0 mm, HL/SVL 35–36%, HW/SVL 36–37%; females: HL 19.5–20.4 mm, HW 19.9–21.0 mm, HL/SVL 33–35%, HW/SVL 33–36%); snout pointed (SL 6.3–6.5 mm in males, 7.1–7.5 mm in females), longer than horizontal diameter of eye (EL 5.9–6.1 mm in males, 6.9–7.0 mm in females); loreal region concave; nostril lateral, closer to eye than to tip of snout (NS 3.2 mm, EN 2.5–2.6 mm in males; NS 3.6–3.7 mm, EN 2.7–2.9 mm in females); interorbital space flat, slightly broader than upper eyelid and internarial distance (IOD 4.9–5.1 mm, UEW 4.2–5.0 mm, IN 4.8–5.0 mm in males; IOD 6.0 mm, UEW 4.9–5.3 mm, IN 5.7–5.9 mm in females); tympanum distinct (TD 2.8–2.9 mm in males, 3.0–3.1 mm in females) less than half of eye diameter (TD/EL 47–48% in males, 43–45% in females); vomerine teeth present; tongue heart–shaped, round posteriorly; vocal sacs present in males.

Forelimb slender (FLL 29.0–29.3 mm in males, 31.9–34.0 mm in females); relative finger lengths IV ≤ II < I < III; fingers without dermal fringe, free of webbing; tips of fingers round, not swollen; subarticular tubercle indistinct; palmar tubercles indistinct; nuptial pads weak and nuptial spines on first and second fingers.

Hindlimb slender, long (HLL 84.9–87.3 mm in males, 100.3–103.0 mm in females); tibia longer than thigh (TL 27.2–27.7 mm, FL 25.0–25.8 mm in males; TL 30.3–31.6 mm, FL 29.2–29.8 mm in females); relative toe lengths I < II < V < III < IV; tips of toes round, slightly swollen; webbing formula I ¼ – 1II 1/3 – 2III1 ½ – 2IV2 – ½ V; toes with weak dermal fringe; inner metatarsal tubercle distinct; subarticular tubercles indistinct; tibio-tarsal articulation reaching to anterior corner of eye.

Skin. Dorsal surface of head and body smooth; supratympanic fold extending from posterior edge of eye to axilla; upper lips, around tympanum and upper eyelid with small spines; flanks with some tubercles; surrounding of cloaca with tubercles; dorsolateral folds present; and ventral surface smooth.

Colouration in life. Dorsal surface brown to light yellowish-brown; a darker brown triangular marking with a yellow central blotch between eyes; chin, chest and anterior part of belly dark brown in males or light brown with erratic dark brown blotches in females, a round white spot on each side of the chest present; posterior part of belly and ventral surface of thighs cream to dirty white; posterior part of thighs dark brown with some light blotches (Fig. 5).

In Vietnam, this species has been recorded from Lao Cai and Ha Giang provinces (Nguyen et al. 2009, Nguyen et al. 2016). Our new record in Son La Province is approximately 70 km and 150 km distant from Lao Cai and Ha Giang provinces, respectively. Elsewhere, this species is known from China (Frost 2019).

The specimens were found on the edge of streams, between 19:00 and 21:30. The surrounding habitat was secondary forest, composed of larger hardwoods and shrubs.

Morphological characters of specimens (n = 2 males) from Son La Province agreed with the descriptions of Ohler (2003) and Hecht et al. (2013): SVL 37.2–39.0 mm; head small, wider than long (HL 10.4–10.6 mm, HW 10.8–11.0 mm, HL/SVL 27–28%, HW/SVL 28–29%); snout truncate, protruding, projecting beyond upper jaw (SL 3.9–4.1 mm), shorter than horizontal diameter of eye (EL 4.3–4.6 mm); loreal region vertical, concave; nostril lateral, closer to tip of snout than to eye (NS 1.4 mm, EN 2.0–2.3 mm); interorbital space flat, narrower than upper eyelid and internarial distance (IOD 2.4–2.6 mm, UEW 3.5–3.9 mm, IN 2.9–3.2 mm); tympanum round, distinct (TD 2.9–3.0); vomerine teeth absent; tongue round; vocal sacs present in males.

Forelimb slender (FLL 23.5–24.5 mm); relative finger lengths I < II = IV < III, tips of fingers round, not enlarged; fingers free of webbing; subarticular tubercles absent; palmar tubercles indistinct.

Hindlimbs slender (HLL 52.9–57.1 mm); tibia longer than thigh (TL 16.9–18.0 mm, FL 16.6–17.1 mm); relative toe lengths I < II < V < III < IV; tips of toes round, slightly swollen; webbing rudimentary; subarticular tubercles indistinct; metatarsal tubercle indistinct; tibio-tarsal articulation reaching to eye.

Skin. Dorsal surface shagreened, with symmetric glandular ridges; flanks shagreened covered with granules; ventral surface smooth.

Colouration in life. Dorsum greyish or light brown, upper surface of limbs with transverse dark brown bars; flanks with some small black spots; ventral surface cream with dark brown marbling (Fig. 6).

In Vietnam, this species has been recorded from Lao Cai and Ha Giang in the North southwards to Dak Lak and Lam Dong provinces (Nguyen et al. 2009, Hecht et al. 2013). Our new record in Son La Province filled the distribution gap of the species in northwestern Vietnam. Elsewhere, the species is known from China, Laos, Thailand and Cambodia (Frost 2019).

The specimens were found between 19:30 and 22:00 h on branches or stones near rocky streams. The surrounding habitat was secondary forest composed of medium hardwoods and shrubs.

Morphological characters of the specimens (n = 4) from Son La Province agreed with the descriptions of Boulenger (1893), Bourret (1942), and Fei et al. (2009): SVL 44.5–46.7 mm in males (n = 2), 55.4–56.7 mm in females (n = 2); head longer than wide (males: HL 15.4–16.5 mm, HW 14.8–16.2 mm, HL/SVL 35%, HW/SVL 33–35%; females: HL 18.7 mm, HW 18.0–18.5 mm, HL/SVL 33–34%, HW/SVL 32–33%); snout obliquely truncate, projecting beyond upper jaw (SL 5.9–6.7 mm in males, 6.7–7.0 mm in females), longer than horizontal diameter of eye (EL 5.3–5.9 mm in males, 5.8 mm in females); loreal region concave; nostril lateral, slightly closer to eye than to tip of snout (NS 2.8–3.2 mm, EN 2.7–2.9 mm in males; NS 3.2–3.3 mm, EN 3.1–3.2 mm in females); interorbital space flat, broader than upper eyelid and narrower than internarial distance (IOD 4.6–4.7 mm, UEW 4.1–4.2 mm, IN 5.0–5.5 mm in males; IOD 5.0–5.2 mm, UEW 4.2–4.7 mm, IN 5.5–5.6 mm in females); tympanum distinct (TD 3.5–3.7 mm in males, 4.5 mm in females); vomerine teeth present; tongue heart–shaped, round posteriorly; vocal sacs present in males.

Forelimb slender (FLL 27.0–28.9 mm in males, 31.0–34.1 mm in females); relative finger lengths I ≤ II < IV < III; fingers dermal fringe absent, free of webbing; tips of fingers round, not swollen; subarticular tubercles indistinct; palmar tubercles indistinct; nuptial pads absent in males.

Hindlimb slender, long (HLL 69.1–75.6 mm in males, 85.0–94.0 mm in females); tibia longer than thigh (TL 22.2–23.7 mm, FL 20.5–20.6 mm in males; TL 27.0–29.8 mm, FL 24.4–24.6 mm in females); relative toe lengths I < II < V < III < IV; tips of toes round, slightly swollen; webbing rudimentary; toes without dermal fringe; metatarsal tubercle indistinct; subarticular tubercles indistinct; tibiotarsal articulation reaching to anterior margin of eye.

Skin. Dorsal surface smooth; flanks with small glandular warts; supratympanic fold present, from posterior edge of eye to axilla; around cloaca with small tubercles; ventral surface smooth.

Colouration in life. Dorsal surface light yellowish-brown; a darker brown triangular marking between eyes; upper lips with vertical dark brown bars; ventral surface whitish, a round white spot on each side of the chest present; ventral surface of limbs reddish (Fig. 7).

In Vietnam, this species has been recorded from Lao Cai, Lai Chau, Dien Bien, and Ha Giang provinces (Nguyen et al. 2009, Orlov et al. 2015, Luong et al. 2019). Our record in Son La Province is the southernmost record of this species in Vietnam. Elsewhere, this species is known from Nepal, India, Bangladesh, Myanmar, Thailand, China, and Laos (Nguyen et al. 2009, Frost 2019).

The specimens were found on the edge of streams, between 19:00 and 22:00 h. The surrounding habitat was mixed secondary forest of medium hardwoods and shrubs.