Hemiphyllodactylus yenchauensis, Luu & Sitthivong & Hoang & Ha & Ha & Xayasith & Ziegler & Grismer, 2025

Luu, Vinh Quang, Sitthivong, Saly, Hoang, Tuoi Thi, Ha, Hong Bich, Ha, Huan Van, Xayasith, Santi, Ziegler, Thomas & Grismer, L. Lee, 2025, Two more new species of Hemiphyllodactylus Bleeker, 1860 (Squamata: Gekkonidae) from Laos and Vietnam identified using an integrative taxonomic approach, Zootaxa 5686 (2), pp. 211-238 : 231-234

Hemiphyllodactylus yenchauensis sp. nov.

Yenchau Slender Gecko ( Fig. 8 ).

Holotype. Adult male VNUF R.2025.05 (Field no. Sonla05) collected on 04 October 2023 at 21:10 hrs by Vinh Q. Luu, Le P. Duc, Vilay Phimpasone at the entrance of karst cave of Pa Kha 1 Village, Chieng Tuong Commune, Yen Chau District , Son La Province, Vietnam (20°51'41.2"N 104°24'03.6"E; 1228 m in elevation).

Paratypes. Subadult male VNUF R.2025.06 (Field no. Sonla06) bears the same collection data as the holotype .

Diagnosis. Hemiphyllodactylus yenchauensis sp. nov. can be distinguished from all other species of Hemiphyllodactylus by possessing the unique combination of having a maximum SVL of 39.1 mm; chin scales 7 – 10; postmentals enlarged; circumnasal scales two or three; intersupranasals (=postrostrals) two; supralabials 10 or 11; infralabials 10 or 11; dorsal scales 21 and ventral scales 11 or 12; subdigital lamellae on the first finger four or five; subdigital lamellae on the first toe five or six; no femoral or precloacal pores in males; no plate - like subcaudal scales; dorsal surfaces of head, body, and limbs light brown with irregular dark blotches and marbling throughout; dark and light pre and postorbital stripes in parallel extends from posterior nares to forelimb insertion; dorsolateral light - colored spots on trunk; paravertebral region with a series of dark, irregular blotches from nape to base of tail; forming a chevron pattern along the midbody; ventral surface of trunk pale yellowish to cream with faint darker margins; ventral surface of original tail bright orange with ventrolaterally dark pigmentation. Three selective color pattern characters (DorBodPatrn, VenBodPatrn, and VenTalPatrn as montioned above) are scored across closely related Hemiphyllodactylus species in Tables 3 and 4.

Description of holotype. Adult male SVL 39.1 mm; triangularly shaped head in dorsal view, depressed, distinguish from neck; lores flat; rostrum moderate in length (SnEye/SVL 0.09); prefrontal region slightly concave; canthus rostralis smoothly rounded, barely discernable; snout moderate, rounded when viewed from above; eye large; ear opening small and elliptical, small; eye to ear distance greater than diameter of eye; rostral wider than high, bordered posteriorly by large supranasals; two intersupranasals; external nares bordered anteriorly by rostral, dorsally by supranasal, posteriorly by two postnasals, ventrally by first supralabial; rectangular supralabials tapering to below posterior margin of eye 10/11 (L, R); rectangular infralabials tapering to below posterior margin of eye 10 (L, R); scales of rostral, loreal, cranial, and occipital scales small, elevated, rostral scales largest; dorsal superciliaries flat, mostly square, subimbricate, largest anteriorly; mental triangular, bordered laterally by first infralabials and posteriorly by two enlarged postmentals; each postmental in contact with first infralabial and bordered laterally by a smaller sublabial; chin scales seven; gular scales small, subimbricate, grading posteriorly into slightly larger, subimbricate throat and even larger pectoral scales which grade into slightly larger, subimbricate ventrals.

Body somewhat elongate (Trunk/SVL 0.53), vertically flattened body shape; dorsal scales small, granular, dorsal scales at midbody contained within one eye diameter 21; ventral scales flat, subimbricate much larger than dorsal scales, ventral scales contained within one eye diameter 11; precloacal scales slightly larger than abdominal scales; no pore-bearing femoral or precloacal scales; enlarged tubercle on lateral margin of tail base single; forelimbs short, robust in stature, covered with flat, subimbricate scales dorsally and ventrally; palmar scales slightly raised, subimbricate; all digits except digit I well - developed; digit I vestigial, clawless bearing five subdigital lamellae; distal subdigital lamellae of digits II–V undivided, angular and U - shaped, lamellae proximal to these transversely expanded; distal lamellar formula of digits II–V (left) 4-5-5-4; claws on digits II–V well developed, unsheathed; distal portions of digits strongly curved, terminal joint free, arising from central portion of lamellar pad; hind limbs short, more robust than forelimbs, covered with slightly raised, juxtaposed scales dorsally and by larger, flat subimbricate scales anteriorly and ventrally; plantar scales slightly raised, subimbricate; all digits except digit I well - developed; digit I vestigial, clawless bearing five subdigital lamellae; distal subdigital lamellae of digits II–V undivided, angular and U - shaped, lamellae proximal to these transversely expanded; distal lamellar formula of digits II–V (left) 4-5-5-4; bearing five subdigital lamellae claws on digits II–V well - developed, unsheathed; distal portions of digits strongly curved, terminal joint free, arising from central portion of lamellar pad; tail partially regenerated, 30.2 mm in length; caudal scales in ring-like whorls; dorsal caudal scales larger than dorsal body scales, flat, nearly circular, slightly overlapping; ventrolateral caudals slightly enlarged, weak anterior flare, fringelike appearance; subcaudals flat, moderately larger than dorsal caudals, non-plate-like. Morphological characters are presented in Table 9.

Coloration in life ( Fig . 8). Dorsal surfaces of head, body, and limbs light brown with irregular, dark blotching and marbling throughout; top of head with faint, dark markings forming a Y-shaped pattern; parallel dark and white stripes from posterior nares, through eye, to forelimb insertion; eye large with vertical pupil and coppery-brown iris interspersed with black reticulations; paravertebral region with a series of dark, irregular blotches from nape to base of tail; forming a chevron pattern along the midbody, followed by a distinct black post-sacral band; cream post-sacral marking present immediately behind the black band; bearing faint, light-colored, anteriorly projecting arms; dorsolateral region of trunk with diffuse dark flecking and scattered light spots laterally; upper body with numerous light brown spots irregularly arranged; limbs mottled with irregular dark markings; original portion of tail with alternating, poorly defined dark and light brown bands; regenerated portion of tail grey-brown with dark markings and flecks extending to the tip; gular region pale pinkish-cream; ventral surface of trunk pale yellowish to cream with faint darker margins; ventral surface of limbs similar in tone to trunk; ventral surface of original tail bright orange with lateral dark pigmentation; subcaudal area of regenerated tail light grey with scattered dark markings.

Variation ( Fig. 8 ). The color patterns of the paratype generally match that of the holotype, though the dark dorsal markings are less bold and narrower than those of the holotype. Variation in morphometric and meristic data are presented in Table 9.

Distribution. Hemiphyllodactylus yenchauensis sp. nov. is known only from Pa Kha 1 Village, Chieng Tuong Commune, Yen Chau District, Son La Province, Vietnam ( Fig. 1 ).

Natural History. Hemiphyllodactylus yenchauensis sp. nov. is an upland species and the type series was collected at night between 20:00 and 20:30 hrs on trees approximately 0.5 m above the ground at the entrance of a karstic cave ( Fig. 9 ). The surrounding habitat consisted of disturbed forest, with the lower area converted to agricultural land ( Fig. 10 ).

Etymology. The specific epithet is a toponym derived from the type locality of Yen Chau District, Son La Province, Vietnam.

Comparisons. The molecular analyses indicate that Hemiphyllodactylus yenchauensis sp. nov. is the sister species to H. bonkowskii + H. vanhoensis ( Fig. 2 ) with mean uncorrected pairwise sequence divergences of 4.7% and 4.8%, respectively ( Table 2). However, H. yenchauensis sp. nov. differs significantly from H. bonkowskii in mean values of Trunk (1.26 vs. 1.34, p <0.001), HeadW (0.8 vs. 0.93, p <0.001), SnEye (0.53 vs. 0.67, p <0.001), NarEye (0.43 vs. 0.52, p <0.001), EyeD (0.35 vs. 0.45, p <0.006), SnW (0.16 vs. 0.31, p <0.001), VS (11.5 vs. 14.33, p = 0.022), DS (21 vs. 25.17, p = 0.009), the presence of a chevron pattern on the trunk (vs. a yellowish-grey dorsal trunk pattern in H. bonkowskii ), and an orange venter of the original tail (vs. cream-colored in H. bonkowskii ); differs from H. vanhoensis in mean values of Trunk (1.26 vs. 1.34, p <0.001), HeadL (1.00 vs. 1.04, p = 0.005), HeadW (0.8 vs. 0.86, p <0.001), NarEye (0.43 vs. 0.50, p = 0.018), CN (2.5 vs. 5.17, p <0.001), and the presence of a chevron pattern on the trunk (vs. semi-reticulate dorsal markings in H. vanhoensis ), and an orange venter of the original tail (vs. dull yellow with black and white spots in H. vanhoensis ). Raw morphometric, meristic, and categorical data used in the statistical analyses are provided in Tables 3 and 4. Statistically significant and discrete categorical differences between H. yenchauensis sp. nov. and all other closely related species are presented in Tables 6 and 7.

Figures

FIGURE 1. Type localities of the species of Hemiphyllodactylus of clade 6 (Edited after Luu et al. 2024).

FIGURE 2. Bayesian inference consensus tree of clade 6 of Hemiphyllodactylus (not including H. harterti) with Bayesian posterior probabilities (BPP) and Ultrafast Bootstrap support (UFB) values at the nodes, respectively.

FIGURE 8. Dorsal (A) view of the male holotype (VNUF R.2025.05) and dorsal (B) and ventral (C) views of the male paratype (VNUF R.2025.06) of Hemiphyllodactylus yenchauensis sp. nov. from Pa Kha 1 Village, Chieng Tuong Commune, Yen Chau District, Son La Province, Vietnam. Photos: Vinh Quang Luu.

FIGURE 9. Habitat of Hemiphyllodactylus yenchauensis sp. nov. at Pa Kha 1 Village, Chieng Tuong Commune, Yen Chau District, Son La Province, Vietnam. Photo: Vinh Quang Luu.

FIGURE 10. Negative impact to habitat of Hemiphyllodactylus yenchauensis sp. nov. at Pa Kha 1 Village, Chieng Tuong Commune, Yen Chau District, Son La Province, Vietnam. Photo: Vinh Quang Luu.