Dixonius noctivagus, Grismer & Sinovas & Quah & Thi & Chourn & Chhin & Hun & Cobos & Ching & Murdoch & Gregory & Nguyen & Hernandez & Kaatz & Grismer, 2025

Grismer, L. Lee, Sinovas, Pablo, Quah, Evan S. H., Thi, Sothearen, Chourn, Phyroum, Chhin, Sophea, Hun, Seiha, Cobos, Anthony, Ching, Christian, Murdoch, Matthew L., Gregory, Jeren J., Nguyen, Eddie, Hernandez, Alex P., Kaatz, Amanda & Grismer, Jesse L., 2025, A new species of Dixonius Bauer, Good, & Branch, 1997 (Squamata: Gekkonidae) from a karstic archipelago in Western Cambodia, Zootaxa 5653 (4), pp. 501-523 : 509-518

Dixonius noctivagus sp. nov.

Suggested common names: Battambang Leaf-toed Gecko (English) and Khmer name ជ*ងចក់hv្លឹកប)ត់ដំបង (English transcription: Jing Jork Sloek Battambang).

https:// zoobank.org:pub: 44F544B5-5177-4790-BDF1-C5F49E98DB75

Figures 2–6

Holotype. Adult male ( LSUHC 15154 ) from Phnom Takriem , Banan District, Battambang Province, Cambodia (13.066612°N 103.03819°E; 58 m) collected at 2130 on 20 March 2024 by Matthew L. Murdoch, L. Lee Grismer, Evan S. H. Quah, Pablo Sinovas, Phyroum Chourn, Sothearen Thi, and Anthony Cobos.

Diagnosis. Dixonius noctivagus sp. nov. can be diagnosed from all other species of Dixonius by having a maximum adult SVL of 53.4 mm (female) and 49.8 mm (male); 7–9 supralabials; five or six supralabials to the midorbital position; six or seven infralabials; 8–13 interorbital scales; 14–26 interciliary scales; 14–21 ventral scales; 14–20 longitudinal rows of dorsal tubercles; 20–26 paravertebral tubercles; 11–13 subdigital lamellae on the 4 th toe; 12–17 subdigital lamellae on the 4 th finger; 5–7 precloacal pores in males; 10–13 enlarged precloacal scales; no femoral pores; no dark canthal stripe; dark barring on labials; irregularly shaped dark markings on the head and dorsum; and a row of light-colored tubercles on the flanks ( Table 6 ; Supplementary Material 1).

Description of the holotype. Adult male, SVL 44.6 mm; TaL 45.0 mm, axilla-groin length 19.9 mm; head longer than wide, depressed, distinct from neck; 12.1 mm in length, 8.7 mm in width; eye moderate in size, 2.8 mm diameter; ear opening oblique, 1.3 mm in length; orbit-snout 4.6 mm; internarial distance 1.6 mm; supralabials eight (six in midorbital position); nares contacting rostral, first supralabial, supranasal, two postnasals on each side; supranasals in point contact; no intersupranasals; snout flat, covered with granular scales; scales on top of head granular intermixed with small keeled tubercles; pupil vertical; ear opening obliquely oriented, oval, not bordered by enlarged scales; infralabials seven, decreasing gradually in size posteriorly; two enlarged postmentals, first pair in contact with each other for approximately 70% of their length, each bordered laterally by a single enlarged sublabial; gular scales granular grading posteriorly into larger imbricate pectorals and larger imbricate ventrals; body dorsoventrally flattened; dorsal tubercle rows at midbody 14, keeled, paravertebral rows separated from each other by one row of smaller keeled scales; paravertebral scales in a row between limb insertions 23; ventral scales larger than dorsal scales, in 16 rows at midbody; dorsal surface of forelimbs bear flat to weakly keeled scales; underside of forelimbs bearing small granular (brachial region) and slightly larger subimbricate (forelimb) scales; dorsal surface of hind limbs covered with strongly keeled scales; underside of hind limbs bearing enlarged, flat, imbricate scales abruptly transitioning into granular postfemoral scales; digits relatively short; all lamellae subdigital transversely expanded; distal lamellae divided, slightly enlarged forming small toe pad; 11 subdigital on fourth toe; 16 subdigital lamellae on fourth finger; contiguous pore-bearing precloacal scales in an angular series; two slightly enlarged postcloacal tubercles on each side at base of tail; dorsal caudals weekly keeled; and subcaudals flat, midventral row transversely expanded.

Coloration and pattern ( Fig. 4 ). Ground color of the dorsal surfaces of the head, body, limbs, and tail lightbrown; top of head bearing irregularly shaped, poorly defined dark markings with a chevron-shaped marking in occipital region, hourglassed-shaped marking on nape, followed by two paravertebral markings; iris gold bearing reddish and black variegations; labial region barred, bearing alternating dark and light markings; dorsum overlain with irregularly shaped poorly defined dark markings of varying size beginning with a dark transverse band between forelimbs, terminating with a medial sacral marking; series of seven light-colored groups of keeled scales on both sides of body, partly edged with dark markings, beginning in lower temporal region extending to hind limbs insertions, then down length of tail terminating in two bands; forelimbs bearing irregularly spaced dark stippling; hind limbs bearing widely separated, irregularly shaped, dark blotches; tail bearing irregularly shaped dark blotches of differing sizes; gular region and chest beige, faintly stippled; more distinct stippling on underside of limbs and abdomen; and subcaudal region grayish.

Variation ( Fig. 5 ). Dixonius noctivagus sp. nov. has a variable color pattern being covered in dark blotches of differing sizes and configurations (compare LSUHC 15146 [similar to the holotype] and 15155), to being nearly unicolor as in LSUHC 15147 . Three specimens have broken tails and seven specimens have complete or partially regenerated tails. The color pattern of the latter lack dark blotching but instead have small, faded, irregularly shaped markings. Variation in meristics, raw morphometrics, and categorical characters are illustrated in Table 6 .

Distribution. Dixonius noctivagus sp. nov. is only known reported from the Banan District, Battambang Province, Cambodia ( Fig. 1 ) but no doubt undoubtedly extends farther in all directions.

Etymology. The specific epithet “ noctivagus ” comes from the Latin “ nox ” meaning night and “ vagus ” meaning vagrant or wandering and refers to this species nocturnal activity.

Natural History. All specimens were collected from 2000–0100 hrs in typical karstic habitat ( Fig. 7 ). Dixonius noctivagus sp. nov. is primarily scansorial being found on karstic boulders below 1 m above the ground. One specimen ( LSUHC 15128 ) was found on a cement wall. Others were found in the leaf litter among the karstic boulders. LSUHC 15129 from P. Sampeu is a juvenile ( SVL = 35.5 mm) and LSUHC 15146 , 15148 , 15152–53 , 15190 [in FFI collection], and 15220 were gravid carrying two eggs, indicating that breeding probably occurs in February and March. No hatchings were observed.

Comparisons. Dixonius noctivagus sp. nov. is readily diagnosable from all species of Dixonius analyzed herein ( Tables 3 , 4 , Supplemental material 1). It is separated from its sister population from eastern Cambodia and southwestern Vietnam by being significantly different in morphospace (p -adjusted = 0.0047999) and having a significantly larger in SVL, AG, and EL (p =00.0185, p =0.00188, and p =0.0041, respectively). Significantly different morphospatial and univariate character values separating D. noctivagus sp. nov. and the other species are presented in Tables 3 and 4 .

Figures

FIGURE 1. Location of the karstic hills surveyed in Battambang Province, Cambodia and the location of Dixonius noctivagus sp. nov., from Phnom Kamping Poi, Phnom Khpoh, Phnom Kul, Phnom Sampeu, and Phnom Takriem.

FIGURE 2. Maximum Likelihood consensus tree of Dixonius based on 1,396 bp of ND2 and its flanking tRNAs (BBP and UFB values, respectively are labeled at the nodes) and MFA plots of nearly all species of Dixonius based on the nearly total evidence morphological data set.

FIGURE 3. Character contribution bar graphs of the first five dimensions of the MFA based on the nearly total evidence morphological data set.

FIGURE 4. Adult male holotype (SVL = 44.6 mm) of Dixonius noctivagus sp. nov. LSUHC 15154.A Dorsal view. B. Ventral view. C. Ventral view of the pelvic region, hind limbs, hind feet and anterior region of the tail. D. Ventral view of gular region, pectoral region, forelimbs and forefeet.

FIGURE 5. Dorsal view showing color pattern variation in the type series of Dixonius noctivagus sp. nov. Catalog numbers are above and below the specimens.

FIGURE 6. A–C Living specimens of Dixonius noctivagus sp. nov. A. Adult female (LSUHC 15128, SVL = 53 mm, in collection of FFI) from Phnom Sampeu. B. Juvenile (LSUHC 15129, SVL = 35.5 mm) from Phnom Sampeu. C. Adult female (LSUHC 15144 SVL = 51.1 mm) from Phnom Khpoh. Photographs by Evan S. H. Quah. D. Adult female Dixonius sp. from Che Teal Chrum Village, Pursat Province, Cambodia. Photograph by L. Lee Grismer.

FIGURE 7. Habitat at Phnom Sampeu. A. Vertical face microhabitat of a low karstic ridge. B. Boulder microhabitat within open karst vegetation. C. Vertical microhabitat. D. Typical deciduous karst vegetation. Paratype LSUHC 15131 was found on the trail.

Tables

TABLE 3. Significant p-values from the PERMANOVA analysis demonstrating that Dixonius noctivagus sp. nov. differs from all other species in MFA morphospace. sp. = the eastern Cambodia-southwestern Vietnam population.

species pairs	p -value	p -adjusted
gialaiensis vs noctivagus sp. nov.	0.00109998	0.13199736
lao vs noctivagus sp. nov.	0.00093998	0.11279774
muangfuangensis vs noctivagus sp. nov.	0.00105998	0.12719746
minhlei vs noctivagus sp. nov.	4.00E-05	0.0047999
sp. vs noctivagus sp. nov.	4.00E-05	0.0047999
somchanhae vs noctivagus sp. nov.	2.00E-05	0.00239995
fulbrighti vs noctivagus sp. nov.	0.00025999	0.03119938
vietnamensis vs noctivagus sp. nov.	2.00E-05	0.00239995
cf. siamensis vs noctivagus sp. nov.	0.00605988	0.72718546
dulayaphitakorum vs noctivagus sp. nov.	2.00E-05	0.00239995
mekongensis vs noctivagus sp. nov.	0.00093998	0.11279774
aaronbaueri vs noctivagus sp. nov.	0.00016	0.01919962
chotjuckdikuli vs noctivagus sp. nov.	2.00E-05	0.00239995
pawangkhananti vs noctivagus sp. nov.	0.00111998	0.13439731
kaweesaki vs noctivagus sp. nov.	0.00025999	0.03119938

TABLE 4. Adjusted p-values of significantly different (p<0.05) character means between Dixonius noctivagus sp. nov. and all other species. Shaded cells denote species bearing insignificantly different means from D. noctivagus sp. nov.

	aaronbaueri	chotjuckdikuli	dulayaphitakorum	fulbrighti	gilaiensis	hangseesom	kaweesaki	lao	mekongensis	minhlei	maungfuangensis	pawangkhananti	cf. siamensis	somchanhae	taoi	vietnamensis	sp. E Cambodia-SW Vietnam
Meristics
SL							2.45E-06									0.00040
IL														0.01868	0.00739
IOS		0.00019			0.00030	5.14E-07				0.00019		0.00030		0.00188		0.03031
VS			1.12E-06	3.06E-08			5.36E-12	1.69E-07	5.24E-06	1.48E-05	2.77E-05		0.00048	0
T4		0	0.00204	0.00034	0.00082		4.96E-08	1.45E-06	0.02143	3.84E-07		2.01E-05	0.00189	1.25E-06		0.00042
Morphometrics
SVL																	0.00185
AG		0	0.02232	0	0.00028		4.17E-07					0.00873	3.40E-07	0.01073		0	0.00118
FA	0		1.39E-07	1.17E-07			0.00267							0.00053		0
TBL	0			1.31E-10												0
HL	0			5.03E-06					0	0	3.33E-06					0.00E+00
HW	0			0			0.00021			0	0.04957					0
HD	0			0						0.00298						1.90E-07
ES	0			2.51E-09												2.86E-07
EN	0			0.00386										0.01913		0.00013
EE	2.94E-07								9.65E-05		2.31E-07						0.00410