A review of the genus Sphenomorphus Fitzinger, 1843 (Squamata: Scincidae) in southern Vietnam, with additional data on S. sheai and S. tridigitus

Use your smartphone to scan this QR code and download this article ABSTRACT Introduction: Among 14 species of forest skinks (genus Sphenomorphus) in Vietnam, seven were recorded from southern part of the country. Shea's forest skink, S. sheai, was described from Kon Tum Plateau based on a single female. Similarly, the tridigital forest skink, S. tridigitus, was also described based on a single putrid and desiccated specimen found dead on a road in Bach Ma; specimens collected recently in Laos did not fully agree with the original description. Hence, additional specimens from type localities of both poorly known species are necessary to discern their morphological variation. In addition, little is known about hemipenis and distribution of the other forest skinks in southern Vietnam. Our study seeks to (1) confirm the occurrence of all known species in the area and access their distributions, (2) provide additional morphological data on poorly known S. sheai and S. tridigitus, and (3) describe hemipenial structure of known species. Methods: We analyzed themorphology of 47 specimens of forest skink collected from southern Vietnam to identify species. Scales were observed and counted under a zoom stereo microscope and measurements were taken with a digital caliper. Results: Analyses confirmed the occurrence of seven species of Sphenomorphus in southern Vietnam, including S. annamiticus, S. buenloicus,S. indicus,S.maculatus, S. sheai, S. tridigitus, and S. yersini. New specimens of S. sheai had one enlarged anterior temporal and eight or nine lamellae under fourth toe, which differed from the original description. Additional specimens of S. tridigitus from the type locality verified that the holotype has 20 mid-body scale rows and first supralabial and nasal fused, but they differed from the holotype in having upper temporal overlapped or overlapping the lower one. Fieldwork discovered 20 new localities for all seven species. The hemipenes of four species involved those with symmetric and asymmetric lobes. Conclusion: We confirm the occurrence of seven species of Sphenomorphus in southern Vietnam with 20 additional distribution records. Hemipenial structures of known species form two groups. New specimens of S. sheai and S. tridigitus differ slightly from the holotypes.


INTRODUCTION
With 112 species, Sphenomorphus Fitzinger 1 is one of the most diverse genera of the family Scincidae. The genus has a wide distribution extending from India throughout Southeast Asia and associated islands to Australia 2-4 . The following morphological characters diagnose the genus: lower eyelid scaly, supranasals absent, prefrontals present, parietals in contact behind interparietal, tympanum usually sunk, dorsal scales usually smooth, medial pair of precloacals enlarged, inner precloacals overlapping outer ones, hind limbs with five digits, and symmetrical or asymmetrical forked hemipenis 2 . Nguyen et al. 5  tonkinensis, S. tridigitus, and S. tritaeniatus, and provided a key to the species in Vietnam and China. Subsequently, Nguyen et al. 6,7 added S. incognitus from Bac Giang Province and described the new species, S. sheai, from the border area between Quang Ngai and Kon Tum provinces. Nguyen et al. 2 described another new species, S. yersini, from Khanh Hoa Province. Uetz et al. 3 added S. malayanum into the faunal list of Vietnam based on the checklist of Bobrov 8 . However, Bobrov & Semenov 9 removed this species from the Vietnamese herpetofauna, and when reviewing Sphenomorphus in Vietnam and describing new species, Nguyen et al. 5,7 did not include it. Recently, S. annamiticus was resurrected for the populations in southern Vietnam and S. stellatus was reported to be restricted to Peninsular Malaysia 4 . Therefore, Vietnam has 14 species of Sphenomorphus.
Seven species of Sphenomorphus, including S. annamiticus, S. buenloicus, S. indicus, S. maculatus, S. sheai, S. tridigitus, and S. yersini, occur in southern Vietnam from Bach Ma-Hai Van Mountains southward. Most of these species are documented from a series of specimens 2,10 , but two are the most poorly known species of skinks in Vietnam. Sphenomorphus sheai was described from the female holotype only 7 and, hence, more samples are necessary to assess its morphological variation. Similarly, S. tridigitus was described from a single specimen collected at Bach Ma, Thua Thien-Hue Province 11 . The second specimen was reported from Bolaven Plateau, Champasak Province, Laos 12 , and subsequently Greer et al. 13 13 . These samples have a frontonasal, two widely separated prefrontals, fusion of nasal and first "infralabial" (it should be "supralabial") scales, and 18 and 20 mid-body scale rows 16 . Because the holotype was in a poor state of preservation having been found dead on a road 13 and the additional specimens collected out of the type locality do not fully agree with the original description, more specimens from Bach Ma (type locality) are necessary to clarify the status of this skink. Our recent field surveys in southern Vietnam yielded additional specimens of S. sheai near its type locality, S. tridigitus from its type locality, and all other congeners from southern Vietnam. Therefore, we review the species of Sphenomorphus in southern Vietnam and provide additional data on the morphology of S. sheai and S. tridigitus.

MATERIAL AND METHODS
A total of 47 specimens deposited in the Institute of Tropical Biology Collection of Zoology (ITBCZ, Vietnam Academy of Science and Technology, Ho Chi Minh City) were examined. Scales were observed and counted on the right side under a zoom stereo microscope at 7X-45X (Akeiyo, Hong Kong). Measurements were also taken on the right side with a digital caliper (Exploit 150 mm, China) to the nearest 0.1 mm. Elevation (above see level -a.s.l.) was measured using GPS Garmin 64S (Taiwan). Common English and Vietnamese names followed Nguyen et al. 2,7,17 . The following morphological characters modified from Nguyen et al. 2,7 were used: snout-vent length (SVL) measured from the tip of the rostral to the vent; tail length (TaL) measured from the vent to the tip of tail; axilla-groin length (AxGnL) measured from the posterior margin of the forelimb insertion to the anterior margin of the hind limb insertion; snout to forelimb length (SnForeL) measured from the anterior margin of the forelimb insertion to the tip of the rostral; head length (HL) measured from the posterior margin of parietal to the tip of the rostral; head width (HW) measured at the widest portion of the temporal region; supralabials (SL); infralabials (IL); loreals; supraoculars (SO); enlarged temporals (L/U -the lower secondary temporal overlapping the upper one, U/L -the upper secondary temporal overlapping the lower one); nuchal (pair); midbody scale rows (MBS) counted as the number of longitudinal scale rows encircling the body at a point midway between the limb insertions; paravertebral scale rows (ParaVert) counted as the number of scales in a line from the parietal scales to a point on the dorsum opposite the vent; ventral scale rows (Ven) counted as a row of scales between the postmentals and the cloacal plate; enlarged cloacal plate (L/R -the left plate overlapping the right one, R/L -the right plate overlapping the left one); subcaudal scales (SC) counted as a row of subcaudals between the vent and the tip of tail (paired + single plate); and lamellae beneath the fourth toe (Toe IV) counted from the first scale whose posterior margin extending into the body of the foot. Values of paired characters were recorded in order of left and right. Nomenclature for head shields followed Smith 10 , Ouboter 18 , and Greer 13 .

RESULTS
Examination of our 47 specimens confirmed the occurrence of seven species of the genus Sphenomorphus in southern Vietnam as follows:

Sphenomorphus buenloicus Darevsky & Nguyen, 1983
Buonluoi forest skink, thằn lằn phê-nô buôn lưới ( Figure 1G Diagnosis. Relatively small size (SVL up to 56 mm); depressed limbs overlap; prefrontals in contact with each other; four supraoculars; parietals shields contacting behind interparietal; one enlarged anterior temporal, two posterior temporals, the lower scale overlapping the upper one; no enlarged dorsal scale rows, 32-34 mid-body scale rows, all smooth; two enlarged precloacal shields; limbs well developed, pentadactyl, 16-19 lamellae beneath fourth toe; hemipenis smooth, forked at the middle point of its length with two developing lobes and the outer lobe is slightly longer than the inner one. These characters agree with the previous descriptions 2, 21

Sphenomorphus indicus (Gray, 1853)
Indian forest skink, thằn lằn phê-nô ấn độ ( Figure 1E). Diagnosis. Large-sized skink (SVL up to 90 mm); depressed limbs overlap; rostral convex, in broad contact with the frontonasal; prefrontals always separated from one another; no nuchals; four large supraoculars; ear oval, no projecting lobules; no enlarged dorsal scale rows, 30-38 mid-body scale rows, all smooth; two enlarged precloacal shields; limbs well developed, pentadactyl, 16-22 lamellae beneath fourth toe; hemipenis smooth, forked at about half of its length with two long lobes. These characters agree with the previous description 10 . Data on hemipenis are new. Distribution. In southern Vietnam, S. indicus has been recorded from the following provinces: Thua

Sphenomorphus maculatus (Blyth, 1853)
Spotted forest skink, thằn lằn phê-nô đốm ( Figure 1B). Diagnosis. Medium-sized skink (SVL up to 62 mm); depressed limbs overlap; rostral concave, in broad contact with the frontonasal; prefrontals rather small, separated from one another; no nuchals; five supraoculars, first longest, fifth smallest; ear without projecting lobules; 38-42 mid-body scale rows, all smooth; dorsal scales larger than lateral ones; two enlarged precloacal shields; limbs well developed, pentadactyl, 16-22 lamellae beneath fourth toe; hemipenis smooth, forked at the middle point of its length with two long lobes. These characters agree with the previous description 10  All specimens were collected at night and in daytime under rotting leaf layer or rocky area in evergreen, semi-deciduous or disturbed forests and in hilly habitats near resident area.

Sphenomorphus sheai Nguyen, Nguyen, Devender, Bonkowski & Ziegler, 2013
Shea's forest skink, thằn lằn phê-nô shea ( Figure 1D). Type locality: border area between Quang Ngai and Kon Tum provinces, Vietnam 7 . Specimens examined (n = 3). ITBCZ 4563, 4564, and 6036, sex unknown, Tram Lap, K'Bang Dist., Gia Lai Prov., 997 m a.s.l. Diagnosis. Small-sized skink (SVL up to 34.6 mm); limbs short, pentadactyl, depressed limbs separated from each other; rostral concave, in broad contact with the frontonasal; prefrontals separated from one another; enlarged nuchals in two pairs; four, rarely three, supraoculars; supralabials six, the sixth largest, the first fused with nasal; infralabials five; primary temporal one; secondary temporals two, the lower scale overlapping the upper one; external ear openings absent; 20 mid-body scale rows, all smooth; paravertebral scales 54-58, slightly larger than lateral ones; two enlarged precloacal shields, the left shield overlapping the right one; 8 or 9 lamellae beneath fourth toe; tail longer than snout-vent length (TaL/SVL = 1.6), 88 transversally enlarged subcaudals; dorsolateral light stripe present on neck, shoulder, and anterior part of dorsum. Detailed morphological characters for the additional samples were showed inTable 1. These characters essentially agree with the original description 7 . Distribution. In southern Vietnam, S. sheai has been recorded from the following provinces: Quang Ngai-Kon Tum border 7 and Gia Lai: Tram Lap [this study]. Natural history. All specimens were collected at night under rotting leaf layer in evergreen forests.

Distribution.
In southern Vietnam, S. tridigitus has been recorded from the following provinces: Thua Thien-Hue: Bach Ma Mountains 11 , [this study]; Quang Nam: Ngoc Linh 5,15 ; Kon Tum: Ngoc Linh [this study]. Natural history. All specimens were collected in the morning under leaf litter in mixed evergreen and pine forests around the Bach Ma summit and in evergreen forest in Ngoc Linh.