Dixonius lao Nguyen & Sitthivong & Ngo & Luu & Nguyen & Le & Ziegler 2020, sp. nov.
Creators: name: Nguyen, Thuong Huyen
name: Sitthivong, Saly
name: Ngo, Hanh Thi
name: Luu, Vinh Quang
name: Nguyen, Truong Quang
name: Le, Minh Duc
name: Ziegler, Thomas
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Reptilia
Squamata
Gekkonidae
Dixonius
Dixonius lao

description: Dixonius lao sp. nov.
(Figs. 2–5)
Holotype. Adult male, VNUF R.2016.2 (Field no. TK16.2) in Na Ngua village, Thakhek Town, Khammouane Province (17 o 32N, 104 o 51E, at an elevation of 145 m a.s.l.), collected by V. Q. Luu and N. Schneider on 24 February 2016.
Paratypes. IEBR A.2019.5 (Field no. TK16.3), adult female; IEBR A.2019.6 (Field no. TK16.1), subadult female; the same data as the holotype.
Diagnosis. A species of the genus Dixonius that can be distinguished from its congeners by a combination of the following characters: maximum SVL 55.4 mm; 20–23 longitudinal rows of dorsal tubercles at midbody; 23 or 24 longitudinal rows of ventrals across the abdomen; 8–10 supralabials, 7 or 8 in mid-orbital position; 7 or 8 infralabials; 8 precloacal pores in male; the male without femoral pores; precloacal and femoral pores absent in females; uniformly pebble brown dorsum.
Description of the holotype. Adult male, SVL 50.1 mm with dorsolaterally flattened body, TaL 69.0 mm, trunk length 20.6 mm. Head longer than wide, depressed, distinct from neck. Head length 14.1 mm, head width 9.2 mm, eye of moderate size 3.6 mm, ear-opening oblique (EL 1.4 mm), snout-eye length 5.6 mm, internarial distance 1.7 mm.
Rostral very large, wider than high (width 2.2 mm, height 1.2 mm), with distinct suture; supralabials 10/9 (8/ 7 in midorbital position); nostril in contact with rostral, first supralabial, supranasal, and two nasals posteriorly on each side; supranasals in broad contact; without intersupranasals; snout flat, covered with granular scales; pupil vertical; ear opening oblique, oval, approximately one third of the eye diameter, without bordering enlarged scales; infralabials 8/8, decreasing gradually in size; mental triangular, wider than high (width 2.5 mm, height 1.7 mm); two pairs of enlarged postmentals, first pair very large and in contact with each other, second pair about one third to one half size of first, in contact with the first and second infralabials and separated from each other by four gular scales; dorsal tubercle rows at midbody 22, keeled and separated from each other by one smaller scale which is keeled or at least almost conical shaped; ventral scales larger than dorsal scales, in 23 rows at midbody; dorsal surface of fore- and hind limbs covered with shallowly keeled scales, area around limb insertions covered with small granular scales; paravertebral scales, number of scales in a paravertebral row from first scale posterior to parietal scale to last scale at the level of vent opening 43; paravertebral scales in a row between limb insertions 25; lamellae on fourth toe 15; precloacal pores 8, in an angular series; tail covered with smooth scales, in different sizes; subcaudals 42, enlarged and undivided.
Coloration in life. In life, dorsum of the holotype pebble brown (Fig. 2); head with brownish olive spots; canthal stripe absent; ventral surface light beige to uniformly whitish as the belly and the throat; supralabials grey with dark grey spots; upper surface of fingers and toes uniformly light grey; dorsal surface of the tail light brownish grey, with uniformly distributed light spots along the tail tip.
Sexual dimorphism. Morphologically, the female paratypes corresponded well with the holotype, except for the lack of precloacal pores.
Comparisons. We compared the new species from Laos with all other known Dixonius species (see Table 4 for a comparison with most similar species). Morphologically, the new species is most similar to Dixonius minhlei from Vietnam in the number of precloacal pores and ventral scale rows. However, the new species can be distinguished from the latter by having more dorsal tubercle rows at midbody (20–23 versus 14 or 15), the absence of canthal stripe (versus canthal stripe continuing behind orbit to back of head), and by a different color pattern (pebble brown dorsum versus olive grey ground color on dorsum, with more or less discernible brownish olive blotches in D. minhlei); from D. siamensis, which is known from Laos, Cambodia, Thailand and Vietnam, by having more dorsal tubercle rows (20–23 versus 10–14), more precloacal pores (8 versus 6 or 7), and generally more supralabials (8–10 versus 7 or 8); from D. hangseesom from Thailand by having more dorsal tubercle rows (20–23 versus 12–14), more paravertebral scales in a row from first scale posterior to parietal scale to last scale at the level of vent opening (PV 40–43 versus 26), and coloration of tail almost the same as the dorsum (versus orange tail); from D. kaweesaki from Thailand by its larger size (maximum SVL 55.4 mm versus 41.6 mm), having more dorsal tubercle rows at midbody (20–23 versus 12 or 13), and in dorsal head and body pattern (back pebble brown and head with brownish olive spots versus dorsal surface of head gray in D. kaweesaki); from D. melanostictus from Thailand and Vietnam by having more dorsal tubercle rows (20–23 versus 10 or 11), more paravertebral scales in a row between limb insertions (PV’ 24–25 versus 10 or 11), and the absence of canthal stripe (versus canthal stripe extending along flanks in D. melanostictus); from D. aaronbaueri from Vietnam by having more ventral scale rows at mid-body (23 or 24 versus 18 or 19), more dorsal tubercle rows at midbody (20–23 versus 11), more precloacal pores in males (8 versus 5), and different dorsal pattern (back pebble brown versus dorsal yellowish-orange to bright orange color from head to tail tip); from D. taoi from Vietnam by its larger size (maximum SVL 55.4 mm versus 43.9 mm), having more dorsal tubercle rows (20–23 versus 11 or 12), more precloacal pores (8 versus 5 or 6) and different dorsal pattern (back pebble brown versus one or two irregular rows of yellowish marks running from head along flanks in D. taoi); from D. vietnamensis from Vietnam and Cambodia in having more dorsal tubercle rows at mid-body (20–23 versus 16), more supralabials (8–10 versus 5 or 6), more ventral scale rows at midbody (23 or 24 versus 20), more lamellae under fourth toe (15 versus 13), and more precloacal pores (8 versus 5–7).
Natural history notes. The type series was found between 20:00 and 21:00h on the forest floor or on karst cliffs, about 0.3 m above the ground. The surrounding habitat was secondary karst forest on the mountain (Fig. 6). The relative humidity ranged from 58% to 70%, and air temperature was 25–26 oC.
Distribution. Dixonius lao sp. nov. is currently known only from the type locality in Khammouane Province, central Laos (Fig. 7).
Etymology. The specific epithet “ lao ” is derived from both the official name of Laos, the Lao People’s Democratic Republic in which the species was discovered, and the Lao, the main group of people inhabiting Laos.
description: Published as part of Nguyen, Thuong Huyen, Sitthivong, Saly, Ngo, Hanh Thi, Luu, Vinh Quang, Nguyen, Truong Quang, Le, Minh Duc & Ziegler, Thomas, 2020, A new species of Dixonius (Squamata: Gekkonidae) from the karst forest of Khammouane Province, central Laos, pp. 530-542 in Zootaxa 4759 (4) on pages 532-538, DOI: 10.11646/zootaxa.4759.4.4, http://zenodo.org/record/3741047