Dixonius taoi, Botov, Andreas, Phung, Trung My, Nguyen, Truong Quang, Bauer, Aaron M., Brennan, Ian G. & Ziegler, Thomas, 2015

Botov, Andreas, Phung, Trung My, Nguyen, Truong Quang, Bauer, Aaron M., Brennan, Ian G. & Ziegler, Thomas, 2015, A new species of Dixonius (Squamata: Gekkonidae) from Phu Quy Island, Vietnam, Zootaxa 4040 (1) : -

Dixonius taoi sp. nov.

Holotype: IEBR A.2014.26 collected on 2nd of June 2013 by Trung My Phung, Phu Quy Island, Phu Quy District, Binh Thuan Province, Vietnam.

Paratypes: CAS 257300, IEBR A.2014.27, VNMN A.2014.4, ZFMK 96680, the same data as the holotype.

Diagnosis. A small gecko with up to 44 mm SVL; 7 or 8 supralabials; 11 or 12 rows of keeled tubercles on dorsum; 21–23 ventral scale rows; 5 or 6 precloacal pores in males; a canthal stripe running from rostrum through the eye and terminating at back of head; lateral second pair of postmentals about one third to one half size of first pair; brown dorsal ground color with light yellowish/orange spots in one or two rows along flanks, and irregular bands or a reticulated network of dark marks on dorsum.

Description of holotype. Adult male, snout-vent length 41.5 mm with dorsolaterally flattened body, total tail length 46.4 mm with regenerated tip (10 mm), trunk length 17.5 mm. Head longer than wide, depressed, distinct from slender neck. Head length 7.5 mm, head width 6.6 mm, eye of moderate size 2.8 mm, ear opening oblique (EL 0.9 mm), nare-eye length 3.5 mm, snout-eye length 4.8 mm, internarial distance 1.5 mm.

Rostral very large, wider (1.3 mm) than high (1.8 mm), with distinct suture; supralabials 7 (fifth in midorbital position), smaller in subocular rictus; nostril in contact with rostral, first supralabial, supranasal, and two nasals posteriorly on each side; supranasals in broad contact and without internasals; snout flat, covered with granular scales; pupil vertical; ear opening oblique, oval, approximately one third of the eye diameter, without bordering enlarged scales; mental triangular, as wide as long; infralabials 7/6, decreasing gradually in size; mental triangular, wider (2.2 mm) than high (1.6 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 first and second infralabials and separated from each other by four gular scales; dorsal scale rows at midbody 12, keeled and separated from one another by one or two smaller scales which are keeled or at least conical shaped; three to four rows of small scales along vertebrae; ventral scales larger than dorsal scales, in 21 rows at midbody, with distinct serration posteriorly; dorsal surface of fore- and hind limbs covered with shallowly-keeled scales, area around limb insertions covered with small granular scales; lamellae on fourth toe 12/12; femoral pores absent; precloacal pores six, in an angular series; pore bearing scales not enlarged; precloacal depression absent; tail covered with keeled scales, in different sizes; subcaudals 38, enlarged and undivided.

Coloration. In life, dorsum olive gray ( Fig. 3 ) with irregular brownish olive blotches. A brownish olive stripe running from rostrum through eyes, ending at back of head, edged above by a thin yellowish stripe. Dorsal head with brownish olive bands or blotches. Four to seven round yellowish spots, arranging in one or two irregular rows from back of head and continuing along tail. Venter cream. In preservative, dorsum grey with irregular dark greyish brown blotches on forehead and body. Yellowish blotches faded to whitish marks in preservative.

Variation of paratypes: Coloration of all paratypes corresponds with the description of the holotype. Variation in scalation and morphometry is shown in Table 4 .

nov. For abbreviations see Table 1. Measurements in mm; measurements taken on right side; SPL/IFL/MO given in right/

left order; Min = minimum; Max = maximum; + = present.

Character IEBR A.2014.26 CAS 257300 VNMN ZFMK IEBR Min Max (holotype) A.2014.4 96680 A.2014.27

Comparisons. The new species from Phu Quy differs from all known Dixonius species as follows: from D. aaronbaueri by having more ventral scale rows at midbody (21–23 versus 18–19 in D. aaronbaueri ) and different color pattern (dorsum brown with light yellowish/orange spots and dark irregular bands versus unpatterned in D. aaronbaueri ); from D. hangseesom by having fewer ventral scale rows at midbody (21–23 versus 22–26 in D. hangseesom ), fewer precloacal pores in males (5–6 versus 6–8 in D. hangseesom ), coloration of tail the same as the dorsum (versus orange tail in D. hangseesom ); from D. melanostictus in having a smaller size (max. SVL 44 mm versus 50 mm in D. melanostictus ), fewer supralabials (7–8 versus 9 in D. melanostictus ), fewer precloacal pores in males (5–6 versus 9 in D. melanostictus ), and canthal stripe continues behind orbit to back of head (versus canthal stripe extending along flanks in D. melanostictus ); from D. siamensis in having a smaller size (max. SVL 44 mm versus 57 mm in D. siamensis ), the presence of a distinct canthal stripe (absent in D. siamensis ); from D. vietnamensis in having more ventral scale rows at midbody (21–23 versus 20 in D. vietnamensis ), fewer enlarged dorsal scale rows at midbody (11–12 versus 16 in D. vietnamensis ), and the presence of one or two irregular rows of yellowish marks running from head along flanks and meeting at base of tail in adults (versus scattered orange tubercles in D. vietnamensis in juveniles only) ( Tab. 5 ).

Etymology. The new species is named in honor of our colleague and friend Dr. Nguyen Thien Tao from the Vietnam National Museum of Nature in Hanoi, in recognition of his numerous and groundbreaking scientific contributions towards a better understanding of the herpetofauna of Vietnam.

Distribution. Phu Quy Island, Binh Thuan Province, Vietnam ( Fig. 4 ).

Natural history. The type series were found in secondary forest just above sea level ( Fig. 5 ). The predominant vegetation, which is interspersed with large volcanic stones, consists of small prickly shrubs and species of the families Pandanaceae , Ebenaceae , and Fabaceae . The geckos were collected during a rainy night, when they had left their shelters between stones and shrubs. A few specimens were found in the small shrubs in agricultural lands. Most of the forests in this area have been destroyed, and only a few small patches are left along the coast.

Figures

FIGURE 3. Dorsolateral view of Dixonius taoi sp. n. from Phu Quy Island, Vietnam. Adult male holotype (A: IEBR A. 2014.26) and adult female paratype with partially regenerated tail (B: IEBR A 2014.27). Photos: Trung My Phung.

FIGURE 4. Map showing the type locality of Dixonius taoi sp. n. (encircled) in southern Vietnam.

FIGURE 5. Natural habitat of Dixonius taoi sp. n. on Phu Quy Island, Vietnam. Photos: Trung My Phung.

Tables

TABLE 4. Selected morphometric measurements and morphological characters of the type series of Dixonius taoi sp.

Sex male male SVL 41.5 42.1	male 42.8	male 43.9	female 36.6	36.6	43.9
TL 46.4 (tip regenerated broken 10 mm)	broken	54.1	regenerated	46.4	54.1
TW 4.3 4.2 BW 9.2 8.5	4.4 8.1	4.3 8.4	2.8 8.0	2.8 8.0	4.4 9.2
HL 7.5 6.7 HW 6.6 6.1	7.8 6.5	7.5 7.3	6.6 5.4	6.6 5.4	7.8 7.3
HD 4.8 4.6	4.9	4.9	3.7	3.7	4.9
EL 0.9 0.8 ED 2.8 2.6	1.0 2.9	1.2 2.7	0.9 2.4	0.8 2.4	1.2 2.9
EN 3.5 3.6 ES 4.8 4.7	3.8 5.1	3.4 4.7	3.2 4.1	3.2 4.1	3.8 5.1
EE 4.0 3.6 IN 1.5 1.6	3.8 1.7	3.6 1.5	3.1 1.2	3.1 1.2	4.0 1.7
IO 4.1 3.8	3.7	3.9	3.1	3.1	4.1
FA 5.4 5.7 TBL 6.8 6.4 AG 17.5 18.8	6.2 7.4 17.6	5.3 7.7 18.3	4.9 6.0 17.2	4.9 6.0 17.2	6.2 7.7 18.8
AG/SVL 0.42 0.45 EL/ED 0.32 0.31	0.41 0.34	0.42 0.44	0.47 0.38	0.41 0.31	0.47 0.44
SPL 7/7 8/8	8/7	7/7	8/8	7	8
IFL 7/6 7/7 MO 6/5 6/6	6/6 6/6	5/6 6/6	6/7 5/6	5 5	7 6
IOS 9 7 ICS 31 26	10 26	9 30	10 28	7 26	10 31
V 21 22 DTR 12 11	22 11	21 11	23 12	21 11	23 12
PVtub 36 42 PV'tub 18 25	31 20	35 20	33 24	31 18	42 25
T4 r/l 12/12 13/12	14/13	14/12	13/12	12	14
PP 6 6 Canthal stripe + +	5 +	6 +	0 +	5	6

TABLE 5. Comparison of selected morphometrical and morphological characters of Dixonius taoi sp. n. and its congeners. For abbreviations see Table 1. Measurements in mm; Min = minimum; Max = maximum; + = present, - = absent; * 6 – 9 precloacal pores in D. vietnamensis are reported from Cambodia (Stuart et al., 2006).

Character	Dixonius taoi D. aaronbaueri sp. nov.	D. hangseesom	D. melanostictus	D. siamensis	D. vietnamensis
Max SVL	43.9 38.6	42.1	50.0	57.0	42.4
Max TL SPL IFL	54.1 37.1 7–8 8–9 5–7 6–8	51.5 8 6+2	56.0 9 7	58.0 7–8 6–7	37.8 7 6–7
MO IOS ICS	5–6 6–7 7–10 8–10 26–31	6 10	7 29		5–6 8–10
V DTR PVtub	21–23 18–19 11–12 11 31–42 45–50	22–26 12–14	22 10–11	18–25 10–14	20 16
PV'tub T4 r/l PP in males	18–25 29–32 12–14 13–15 5–6 5	13 6–8	15 9	12–16 6–7	13 5–6*
Canthal stripe	+ +	+	+	-	+