Cyrtodactylus hangvaensis, Duong & Vu & Vu & Mulcahy & Bragin & Poyarkov & Grismer, 2024

Duong, Tang Van, Vu, Lien Van, Vu, Hien Thi Thu, Mulcahy, Dan, Bragin, Andrey M., Poyarkov, Nikolay A. & Grismer, L. Lee, 2024, Another new species of Cyrtodactylus Gray, 1927 (Squamata: Gekkonidae) of the angularis group from the karstic landscape of Phong Nha-Ke Bang National Park, central Vietnam, Zootaxa 5471 (5), pp. 555-571 : 562-567

Cyrtodactylus hangvaensis sp. nov.

Figs. 4 , 5 ; Table 2

Holotype. Adult male ( VNMN_DBN000132 ) collected from a cliff near the Hang Va cave ( Phong Nha-Ke Bang National Park ), Tan Trach Subdistrict, Bo Trach District, Quang Binh Province, Vietnam (17.489279 oN, 106.285529 oE; elevation 165 m a.s.l.) on 30 May 2022, at 19:30h by Duong Van Tang.

Diagnosis. Cyrtodactylus hangvaensis sp. nov. can be separated from all other species of the angularis group by the combination of having a maximum SVL = 59.2 mm (male); seven supralabials, nine infralabials, 36 paravertebral tubercles, 20 rows of longitudinally arranged tubercles, 33 longitudinal rows of ventrals, 163 transverse rows of ventrals, five expanded subdigital lamellae on the fourth toe, 13 unmodified subdigital lamellae on the fourth toe, 18 total subdigital lamellae on the fourth toe; seven expanded subdigital lamellae on the fourth finger, 12 unmodified subdigital lamellae on the fourth finger, 19 total subdigital lamellae on the fourth finger; 24 total number of enlarged femoral scales, 12 total femoral pores; 14 enlarged precloacals; eight precloacal pores in males (n=1); three rows of large post-precloacal scales; eight enlarged precloacal scales; enlarged femorals and enlarged precloacals continuous; proximal femorals same size as distal femorals; femoral pores restricted to proximal scales; five(R) and six(L) postcloacal tubercles; body tubercles moderatly keeled; small tubercles on forelimbs and flanks; tubercles do not extend beyond base of tail; medial subcaudals 2–3 times wider than long but not extending onto lateral surface of tail; nuchal loop wide divided medially; dark-colored band on nape absent; dark-colored dorsal bands lack paravertebral elements, lack lightened centers, are edged with light-colored tubercles, faintly jagged in shape, and the same width as interspaces; dark-colored markings in dorsal interspaces; dorsal tubercles not brightly colored; top of head in adults diffusely mottled; five dark-colored transverse body bands; four thin light-colored caudal bands on an original tail not bearing dark-colored markings and not encircling tail (n=1); five dark-colored caudal bands on an original tail much wider than light-colored caudal bands (n=1), posterior one-half of tail unicolor brown to beige ( Table 2 ).

Description of holotype ( Fig. 4 ). Adult male SVL 59.2 mm; head moderate in length (HL/SVL 0.29), width narrow (HW/HL 0.59), flattened (HD/HL 0.35), distinct from neck, triangular in dorsal profile; lores weakly concave anteriorly, weakly inflated posteriorly; prefrontal region concave; canthus rostralis rounded; snout elongate (ES/HL 0.40), flat, rounded in dorsal profile; eye large (OD/HL 0.23); ear opening elliptical, vertically oriented, moderate in size; eye to ear distance slightly greater than diameter of eye; rostral rectangular, partially divided dorsally by inverted Y-shaped furrow, bordered posteriorly by large left and right supranasals, bordered laterally by first supralabials; external nares bordered anteriorly by rostral, dorsally by large supranasal, posteriorly by two moderately sized postnasals, bordered ventrally by first supralabial; seven (R,L) rectangular supralabials tapering abruptly to below midpoint of eye, first–fifth supralabials largest; nine (R,L) infralabials tapering smoothly to slightly past the termination of enlarged supralabials to corner of mouth; scales of rostrum and lores flat, same size as than granular scales on top of head and occiput; scales of occiput weakly intermixed with small, rounded, tubercles; superciliaries squarish, largest dorsally; mental triangular, bordered laterally by first infralabials and posteriorly by large left and right trapezoidal postmentals contacting medially for ~85% of their length posterior to mental; one row of enlarged, sublabials extending posteriorly to third infralabial (L), fourth infralabial (R); gular and throat scales small, granular, grading posteriorly into slightly larger, flatter, smooth, imbricate, pectoral and ventral scales.

Body relatively long (AG/SVL 0.46) with small ventrolateral folds; dorsal scales small, granular, interspersed with moderately sized, weekly keeled, rounded, semi-regularly arranged tubercles extending from occiput to slightly beyond base of tail; ~ 20 longitudinal rows of tubercles at midbody; ~ 36 paravertebral tubercles; 33 flat, imbricate, ventral scales much larger than dorsal scales; 14 enlarged precloacal scales, eight bearing pits; no deep precloacal groove or depression; and three rows of large post-precloacal scales on midline.

Forelimbs moderate in length and stature (FL/SVL 0.16); granular scales of forelimbs slightly larger than those on body, no tubercles on dorsal surface of forearms; palmar scales flat, juxtaposed; digits well-developed, inflected at basal interphalangeal joints, slightly narrower distal to inflections; subdigital lamellae transversely expanded, those proximal to joint inflections much wider than nearly unmodified lamellae distal to inflections; seven expanded subdigital lamellae on the fourth finger, 12 unmodified subdigital lamellae on the fourth finger, 19 total subdigital lamellae on the fourth finger; claws well-developed, sheathed by a dorsal and ventral scale; hind limbs robust, wider and longer than forelimbs (TBL/SVL 0.19), covered dorsally by granular scales interspersed with moderately sized tubercles, larger and flat scales anteriorly; ventral scales of thighs flat, imbricate, slightly larger than dorsals; subtibial scales moderate in size, flat, imbricate; one row of six (R,L) enlarged femoral scales terminating midway to knee, continuous with enlarged precloacal scales; proximal femorals larger than distal femorals, all femorals forming an abrupt union with smaller, granular, ventral scales of posteroventral scales of thigh; femoral pores six (R,L) restricted to proximalmost femorals; plantar scales flat, juxtaposed; digits well-developed, inflected at basal interphalangeal joints; claws well-developed, sheathed by a dorsal and ventral scale at base; seven (R,L) wide subdigital lamellae on fourth toe proximal to joint inflection, five expanded subdigital lamellae on the fourth toe, 13 unmodified subdigital lamellae on the fourth toe, 18 total subdigital lamellae on the fourth toe.

Original tail long (TL/SVL 1.15), thin, 67.9 mm in length, 5.9 mm wide at base, tapering to a point, posterior onethird regenerated; dorsal caudal scales small, generally square, juxtaposed; median row of subcaudals significantly larger than dorsal caudals, transversely expanded, not extending dorsally onto lateral side of tail; body tubercles extending slightly beyond base of tail; hemipenal swellings at base of tail, 5(R),6(L) postcloacal tubercles on both sides; and postcloacal scales flat, imbricate.

Coloration prior to preservation ( Figs. 5 ). Ground color of top of head, limbs, and dorsum brownish-grey; top of head bearing faint poorly defined, irregularly shaped, dark-brown markings; dark-brown, nuchal loop bearing bifurcated medially; four dark-brown, immaculate, weakly jagged, dorsal body bands terminating above the ventrolateral folds extending from shoulders to groin same width as interspaces, edged with light-colored tubercles; one dark-colored sacral band; dorsal interspaces not mottled; forelimbs faintly mottled; hind limbs more darkly mottled; one post-sacral and five wide, dark-brown caudal bands much wider than four thin caudal bands; whitish caudal bands do not encircle tail, not bearing dark-brown markings; iris greenish with thin black reticulations, pupil bordered in gold; venter generally beige with faint, dark shadowing on belly and limbs; subcaudal region dark-brown, nearly unicolor.

Etymology. The species name “ hangvaensis ” is in reference to the type locality at Hang Va cave, Quang Binh Province, Vietnam ( Fig. 1 ).

Distribution. The species is known only from the type locality.

Comparisons ( Fig. 5 ; Tables 2, 2s ). Cyrtodactylus hangvaensis sp. nov. is similar in morphology to its close relatives C. roesleri and C. sommerladi . It differs from the former in having 12 versus 17–19 subdigital lamellae beneath the fourth finger, thin versus thick light-colored caudal bands, absence of tubercles on the dorsal surface of the tail versus their presence, and a more bold markings on the top of the head. It is most similar to C. sommerladi but differs in having a brownish-grey versus a yellowish-grey ground color and more bold markings on the top of the head. Despite the close geographic proximity of these species their uncorrected pairwise sequence divergence is high—9.5% from C. sommerladi ~ 25 km to the southwest and 11.7% from C. roesleri 50 km to the northwest ( Fig. 1 ). Cyrtodactylus hangvaensis sp. nov. is well separated from the distantly related C. phongnhakebangensis and C. cryptus which also occur in the PNKB. From the former it differs by having a SVL of 59.2 mm versus 78.5–96.3 mm, having a total of 20 versus 32–42 combined femoral and precloacal pores, having a narrow versus a wide nuchal band, and thin versus wide light-colored caudal bands. From C. cryptus it differs by having a SVL of 59.2 mm versus 74.0– 86.6 mm, having 33 versus 47–50 ventral scales, having femoral pores versus their absence, having 20 versus 10 enlarged precloacal scales, having 12 subdigital lamellae on the fourth finger versus 18 or 19, having enlarged versus small subcaudals, thin versus a wide nuchal band, and thin versus wide light-colored caudal bands. We are well aware that with only a single specimen, some of the characters listed as potentially diagnostic may prove not to be with additional specimens. Just as other characters not listed as potentially diagnostic may turn out to be diagnostic.

Natural history. Cyrtodactylus hangvaensis sp. nov. was recorded in the Va Forest, located deep in Phong Nha-Ke Bang National Park, distance about 115 meters from the back door of the Son Doong Cave in the western part of Quang Binh Province ( Fig. 6 ), in the northern Truong Son range, Vietnam. The Va Forest is located on limestone mountains with primeval forests.The Specimen of C. hangvaensis sp. nov. was found on a karst cliff of a small mound at 1.5 m height from the trail surface, in a forest with many shrubs and small trees. The specimen was collected at night (at about 19h30). It seems that C. hangvaensis sp. nov. occurs in sympatry with C. phongnhakebangensis and C. cryptus , while its sympatric relationship with C. roesleri has not been determined. The site where C. hangvaensis sp. nov. was found (Va Forest) is 5.6 km from Hang En Cave in a straight line, where C. phongnhakebangensis was recorded by previous studies and 28.9 km from Cha Noi where all three species bent-toed geckos of Phong Nha-Ke Bang National Park ( C. phongnhakebangensis , C. cryptus , and C. roesleri ) were recorded. However, the microhabitat of C. hangvaensis sp. nov. seems to be more similar to C. phongnhakebangensis than to C. cryptus because it was found on a cliff, and has not been recorded on trees.

Figures

FIGURE 1. Location of the clade composed of Cyrtodactylus hangvaensis sp. nov. and C. roesleri from Phong Nha-Ke Bang National Park (PNKB) and C. sommerladi from Hin Nam No NPA, Khammouane Province, Laos. Red dot in the inset denotes the location of the PNKB.

FIGURE 4. Holotype of Cyrtodactylus hangvaensis sp. nov. A. Lateral view of head. B. Gular region. C. Dorsal view of head. D. Dorsal view of the specimen. E. Ventral view of the specimen. F. Ventral view of the right hand. G. Ventral view of the right foot. H. Precloacal and proximal thigh region. I. Midsection of the subcaudal region.

FIGURE 5. Species comparisons.A. Holotype of Cyrtodactylus hangvaensis sp. nov. from HangVa cave, Quang Binh Province, Vietnam. Photograph by Tang Duong. B. C. cryptus from Phong Nha-Ke Bang National Park (PNKB). Photograph by Thomas Ziegler. C. C. roesleri VNUH 220509 from PNKB. Photograph by Thomas Ziegler. D. C. sommerladi VNUF R.2013.22 from Hin Nam No NPA, Khammouane Province, Laos. Photograph by Vinh Quang Luu. E. C. phongnhakebangensis from PNKB. Photograph by Thomas Ziegler.

FIGURE 6. A. karst microhabitat near the Hang Va cave. B. Forest habitat for the Hang Va cave region. Photographs by Tang Duong.

Tables

TABLE. 2. Data are from Sitthivong et al. (2019) for species of the angularis group plus Cyrtodactylus cryptus from Heidrich et al., (2007). Abbreviations are as follows: / = characters unobtainable from literature; * = tail regenerated; max. = maximal; SVL = snout–vent length; TaL = tail length; V = ventral scales; FS = enlarged femoral scales; FP = femoral pores; PP = precloacal pores; LD4 = subdigital lamellae on fourth finger; TL4 = subdigital lamellae on fourth toe. Shaded cells denote possible diagnostic differences from Cyrtodactylus hangvaensis sp. nov. All measurements in millimeters.

Taxon	SVL	TaL	VS	FS	FP	FP+PP (males)	PP (females)	LD4	LT4	Dorsal pattern	Enlarged subcaudals
C. hangvaensis sp. nov.	59.2	67.9*	33	24	12	20	/	12	18	banded	present
C. angularis	80.0–92.0	92–95.2	40–45	present	absent	3	3	18–19	18–19	banded	present
C. bansocensis	71.0–74.0	98.5–103.5	34–35	present	present	34	unknown	16–19	18–21	banded	present
C. calamei	75.0–89.3	86.1–107.5	39–42	present	present	35–39	38	16–18	18–20	banded	present
C. chanhomeae	69.9–78.8	74.4–74.7	36–38	present	present	32	34	18–20	21–23	banded	present
C. cryptus	74.0–86.6	75.8–88.4	47–50	16–27	absent	10	0	18–19	20–23	banded	absent
C. darevskii	84.6–100.0	95.0–113.0	38–46	present	present	38–44	24–34	17–20	18–22	banded	present
C. hinnamnoensis	83.6–100.6	76.1–108.3*	35–48	present	present	36–44	0–28	16–21	19–22	banded	present
C. jaegeri	60.0–68.5	82.4–83.4	31–32	17–19	present	44	21	17–19	20–23	banded	present
C. jarujini	85.0–90.0	105.0–116.0	32–38	present	present	52–54	0	15–17	18–19	blotched	present
C. lomyenensis	57.7–71.2	72.2–86.1	35–36	17–18	present	/	32	16–19	19–23	banded	present
C. muanfuangensis	79.6–83.9	81.9*–102.6	31–37	present	present	21	5–9+6+5–8	16–19	18–23	banded	present
C. multiporus	81.0–98.0	97.0–105.0	30–38	present	present	58–60	0	18–20	18–22	banded	present
C. nigriocularis	82.7–107.5	70.6–121	42–49	absent	absent	/	0	–	17–21	uniformly	present
C. pageli	76.2–81.8	85.4*–113.2*	41–44	absent	absent	4	4	19–23	19–23	banded	present
C. phongnhakebangensis	78.5–96.3	98.0–110.0	32–42	present	present	32–42	0–41	15–20	18–26		present
C. roesleri	51.1–75.3	63.4–101.0	34–40	7–10	present	20–28	17–22	17–19	17–21	banded	present
C. sommerladi	58.8–80.3	58.8*–89.4	31–39	present	present	20–26	17–21	16–19	17–24	banded	present
C. soudthichaki	69.2–70.0	95.1*–95.2	32–33	present	present	29	absent	16–18	18	banded	present
C. teyniei	89.9	ca. 110.0	38	23	absent	unknown	13	17–18	19–20	blotched	present