We describe a new species of Scincella similar to Sphenomorphus tridigitus based on a single specimen from Lang Son Province, northeastern Vietnam. The new species differs from the latter by presence of lower eyelids with undivided opaque window, forelimbs with five digits, and by absence of prefrontals. Scincella apraefrontalis sp. n. is distinguished from all other species of Scincella and all other Asian limbreduced lygosomines by a combination of the following characters: no supranasals; no prefrontals; nasal and first supralabial fused; six supralabials; lower eyelid with undivided opaque disc; no external ear openings; 18 midbody scale rows; and pentadactyl limbs.
At present, a total of 34 species of the genus Scincella (Mittleman, 1950) have been reported, including 29 species from Asia and five species from southeastern North America (Greer 1974, Shea & Greer 2002). This genus is differentiated from other sphenomorphines by its small size, attenuate habitus, terrestrial behaviour, postorbital bone which is usually long and thin, and a transparent window in a moveable lower eyelid (Greer 1974).
The generic assignment of many Southeast Asian lygosomines including Scincella, however, is still uncertain, and their phylogenetic relationships remain unresolved. The lower eyelid with a transparent or opaque window is found in several genera of Asiatic skinks: Asymblepharus, Leptoseps, Lipinia, Paralipinia, and Vietnascincus (Darevsky & Orlov 1994, 1997, Greer 1997, Eremchenko 2002, Shea & Greer 2002). Darevsky & Orlov (1997) described a new genus of arboreal skinks, Paralipinia, with double rows of subdigital lamellae on basal fingers and toes. Subsequently, this genus was synonymized with Scincella by Greer & Shea (2003) based on the secondary temporal scale overlap pattern (lower scale overlapping upper one). This character was not included when Greer et al. (2006) allocated Siaphos tridigitus to Sphenomorphus, although it differs from most species of Sphenomorphus by having the upper temporal scale overlapping the lower one (instead of the opposite condition). Although we agree with Greer & Shea (2003) that the generic relationships of Paralipinia are likely closer to Scincella than to Lipinia, we advocate considering Paralipinia as a distinct genus until additional data is available. Greer (1997) erected Leptoseps for Siaphos poilani Bourret, 1937 and Larutia osellai Böhme, 1981. Although Greer mentioned the new genus as a member of the Sphenomorphus group of lygosomine skinks, he did not compare Leptoseps with Scincella. Scincella can be distinguished from Leptoseps by the number of digits on the hindlimbs: five versus four, respectively (Greer 1997). Therefore, in view of these uncertainties, we provisionally consider lygosomines with a transparent or opaque window on the lower eyelid, supranasals absent, hindlimbs with five digits, lamellae under the basal digits in one row, and dorsum without dark and light stripes as belonging to the genus Scincella, pending future studies, particularly molecular genetic analyses.
As a result of recent field work in northeastern Vietnam, we found a remarkable small skink which represents a member of the genus Scincella by the combination of characters as mentioned above. However, this specimen was not assignable to any of the lygosomine species known from Vietnam nor to species reported from neighbouring countries, so that we herein describe it as a new species.
Material and Methods
Field work was conducted in April 1998 within Huu Lien Nature Reserve, Huu Lung District, Lang Son Province. Specimens referred to within this paper are deposited in the collections of the Institute of Ecology and Biological Resources (IEBR), Hanoi, Vietnam and of the Muséum National d'Histoire Naturelle (MNHN), Paris, France.
Morphological analysis: Measurements were taken with a dial calliper to the nearest 0.1 mm. The following abbreviations were used: SVL: Snoutvent length, TaL: Tail length, AG: Distance from axilla to groin, HL: Maximum head length (from the tip of snout to the posterior margin of parietal), HW: Maximum head width, HH: Head height, SL: Snout length (from the anterior corner of eye to the tip of snout), STL: Distance from snout to anterior margin of tympanum (or vestige of tympanum), SFlL: Snout-forelimb length, END: Distance from the anterior corner of eye to nostril, EL: Eye length, ETL: Distance from anterior border of tympanum to the hind margin of eye, TYD: Maximum diamater of tympanum, FlL: Forelimb length, HlL: Hind limb length. Scalation: Nuchal scales: widened scales behind parietals, paravertebral scales: number of scales from posterior edge of parietals to the point above vent, ventrals in tranverse rows: number of scales from first gular row to precloacal scales. Altitude: a.s.l.: above sea level. Formula of dorsal scale rows between lateral stripes follows Inger et al. (1990) and Chen et al. (2001).
Scincella apraefrontalis sp. n.
Holotype: IEBR A.0832, an adult male collected in April 1998 by Nguyen Van Sang and Nguyen Quang Truong from the Huu Lien Nature Reserve, Huu Lung District, Lang Son Province (21°40′N, 106°20′E), at an altitude of ca. 200 m a.s.l.
Diagnosis: Small skink (36.1 mm SVL); supranasals absent; prefrontals absent; nuchals two or three pairs; nasal and first supralabial fused; loreal single; supralabials six; infralabials five; lower eyelid with undivided opaque window; external ear openings absent; midbody scales in 18 rows; limbs short, pentadactyl, widely separated when adpressed; subdigital lamellae in one row under the digits, numbering eight on fourth toe; dorsum and tail base bronze brown with some indistinct darker spots in anterior part of each scale; laterals paler with three or four longitudinal dark brown stripes.
Description of holotype: Size small (SVL 36.1 mm); tail lost; see Table 1 for further measurements; head longer than wide (ratio of SVL/HL 6.6); snout rounded anteriorly; rostral wider than high, visible from above; supranasals absent; frontonasal wider than long, in contact with rostral, nasals, loreals, anterior supraciliaries, and frontal; prefrontals absent; frontal narrowing posteriorly, as long as distance to the snout, in contact with frontonasal, anterior supraciliaries, first and second supraoculars, and frontoparietals; a pair of frontoparietals, in contact with each other anteriorly, and bordered with frontal, three posterior supraoculars, parietals and interparietal; interparietal lozenge, slightly wider than frontal, with a small transparent spot; parietals in contact posteriorly, posterior border covered by three enlarged scales; nuchal scales 2/3; nostril in single nasal; nasal and first supralabial fused; loreal single, in contact with nasal, second supralabial, preocular, anterior presubocular, and frontonasal; preocular single; presuboculars two, lower one in contact with second and third supralabials; supraciliaries six; supraoculars four, first and fourth longest, followed by a small postsupraocular; postocular in contact with fourth supraocular, postsupraocular, and upper postsubocular; postsuboculars three, lower one in contact with fifth supralabial; primary temporal single, in contact with fifth and sixth supralabials; secondary temporals two, upper very large, in contact with posterior border of parietal, and overlapped by lower one; lower eyelid with an undivided opaque window (central disc), separated from supralabials by a row of small scales; supralabials six (counting the first supralabial fused to nasal), fourth below the eye; external ear openings absent, its position indicated by scaly depression; mental wider than long, rounded anteriorly, in contact with anterior infralabials and postmental; infralabials five; postmental undivided, in contact with mental, anterior infralabials, and anterior pair of chinshields; three pairs of chinshields, anterior pair in contact medially, second pair separated from each other by a gular scale, and posterior pair separated from each other by three scales. Midbody scales in 18 rows; dorsal scales smooth, larger than lateral scales, in four rows; paravertebral scales 52; ventrals smooth, in 50 transverse rows; precloacals two, enlarged; tail thick at base, tail tip lost, medial subcaudals of tail base widened.
Limbs relatively short (ratio of FlL/SVL 14.1% and HlL/SVL 22.4%), pentadactyl, widely separated when adpressed, and adpressed forelimbs not reaching to eye; dorsal surface of digits covered by two scale rows on basal and by a single row on terminal phalanges; subdigital lamellae smooth, in one row under the digits, numbering seven under fourth fingers and 8/9 under fourth toes.
Colouration in alcohol: Free margins of upper and lower eyelids not edged in white; dorsum and tail base bronze brown with some indistinct darker spots in anterior part of each scale; laterals paler with three or four longitudinal dark brown stripes from behind the eye to hindlimb; infralabials and throat with dark spots; venter cream; underside of tail base with indistinct brown marbling.
Comparisons: Among the currently known species of Scincella from Asia, the following have a relatively low midbody scale count: S. barbouri (Stejneger, 1925) with 24–28 rows; S. beddomei (Boulenger, 1887) with 20–24; S. bilineata (Gray, 1846) with 22–26; S. modesta (Günther, 1864) with 24–32; S. monticola (Schmidt, 1925) with 22–26; S. punctatolineata (Boulenger, 1893) with 22–28; and S. travancorica (Beddome, 1870) with 22–30 (Boulenger 1887, Schmidt 1925, 1927, Smith 1935, Taylor 1963, Ouboter 1986, Inger et al. 1990, Chen et al. 2001, Shea & Greer 2002). According to Eremchenko (2002), two other Himalayan scincid taxa, Scincella himalayana (Günther, 1864) (with 24–32 midbody scale rows) and S. sikkimensis (Blyth, 1853) (with 21–29 midbody scale rows) were transferred to the genus Asymblepharus. Scincella apraefrontalis sp. n. differs from all afore mentioned species by having a midbody scale count of only 18 rows (versus 20 and more rows), by lacking prefrontals (versus present in the afore mentioned species), and by lacking external ear openings (which are present in the previously listed taxa).
Scincella apraefrontalis sp. n. is most similar to Sphenomorphus tridigitus (Bourret, 1939) by having midbody scales in 18 rows, adpressed limbs widely separated, and by the absence of external ear openings. However, the new species differs from the latter by lacking prefontals (which are very small but present in S. tridigitus), by having pentadactyl forelimbs (which only have three digits in S. tridigitus), lower secondary temporal overlapping upper one (upper secondary temporal overlapping lower one in S. tridigitus), and lower eyelid with an undivided opaque window (versus scaly lower eyelid in S. tridigitus) (Greer et al. 2006, per. obs.). Scincella apraefrontalis sp. n. also shares several diagnostic characters of Leptoseps such as supranasals absent; prefontals absent; only a single loreal; first supraciliary in contact with frontal; lower eyelid with an opaque window; supralabials six; infralabials five; external ear openings absent; midbody scales in 18 rows, and dorsal scales smooth. However, in comparison with Greer's (1997) description, the new species can clearly be distinguished from Leptoseps by having nasal and first supralabial fused (nasal and first supralabial not fused in Leptoseps spp.); both fore and hind limbs pentadactyl, more developed (ratio of FlL/SVL 14.1% and HlL/SVL 22.4% versus 6% and 7–8%, respectively, in Leptoseps spp.); ratio of SVL/HL 6.6 (versus 8.3–8.5 in Leptoseps spp.). Scincella apraefrontalis sp. n. further differs from Leptoseps poilani and L. osellai by having 52 paravertebral scales (versus 75–77 scales in L. poilani and 82 scales in L. osellai) (Bourret 1937, Böhme 1981, Greer 1997). Scincella apraefrontalis sp. n. is distinguishable from Leptoseps tetradactylus by having 18 midbody scale rows (versus 20 in L. tetradactylus), by lacking prefrontals (prefrontals very small in L. tetradactylus), and by having lower eyelid with opaque window (lower eyelid scaly in L. tetradactylus) (Darevsky & Orlov 2005). Distribution: Scincella apraefrontalis sp. n. is only known from the type locality in Lang Son Province, northeastern Vietnam (Fig. 2).
Natural history: The new species is currently known only from a single male specimen, which was found active during the daytime among leaf litter on the ground of secondary limestone forest at an altitude of 200 m a.s.l. The mode of life of Scincella apraefrontalis sp. n. in the Huu Lien Nature Reserve supports the supposition of Greer (2002): the loss of the external ear opening of skinks may help to reduce water loss and this character is strongly asscociated with two different features: fossoriality and small size. The holotype has two yellowish white testicles, each 3.3 mm in length.
Etymology: The species name derives from Latin: apraefrontalis — meaning “without prefrontals”. As common names we suggest Huulien ground skink (English), Scinque de terre d'Huulien (French), Huulien Bodenskink (German), and Thằn lằn cổ hữu liên (Vietnamese).
Measurements (in mm) and selected morphological characters of Scincella apraefrontalis sp. n. compared to Sphenomorphus tridigitus from Vietnam (F — Female, M — Male, * — regenerated tail or tip lost, for abbreviations see Material and Methods).
In the revision of Asian Scincella, Ouboter (1986) synonymized many species and recognized only 12 species from this region. He placed both Lygosoma rupicola (Smith, 1916) and Leiolopisma siamensis (Taylor & Elbel, 1958) in the synonymy of S. melanosticta. Subsequent to Shea & Greer (2002), Teynié et al. (2004) listed again Scincella rupicola as a distinct species, known from Laos, Vietnam, and Thailand. In the recent checklist of amphibian and reptiles of Vietnam, Nguyen et al. (2005) listed four species of Scincella: S. doriae (Boulenger, 1887), S. melanosticta (Boulenger, 1887), S. reevesii (Gray, 1838), and S. rufocaudata (Darevsky & Nguyen, 1983). However, previous records of S. melanosticta in northern Vietnam were replaced by Livorimica bacboensis, a new genus and species described in 2003 by Eremchenko. Bourret (1937) described Leiolopisma ochraceum without precise locality for the type specimen. Bourret (2009) noted a female collected from “Indochine française (ou Yunnan?)”. Ouboter (1986) considered Leiolopisma ochraceum to be a synonym of Scincella reevesii. Shea & Greer (2002) mentioned the syntypes (MNHN 48.57) of Scincella ochracea from Southeast Asia. The record of this species from Vietnam was subsequently followed by Eremchenko (2003), Bobrov & Semyonov (2008), David & Ineich in Bourret (2009). The discovery of Scincella apraefrontalis sp. n. from Lang Son Province brings the total species number of currently recognized Vietnamese Scincella to seven (S. doriae, S. monticola, S. ochracea, S. reveesii, S. rufocaudata, and S. rupicola) (Nguyen et al. 2009, 2010).
We are grateful to X.C. Le and N.C. Dang (IEBR, Hanoi) for their support and encouragement. We wish to thank the directorate of the Forest Protection Department, Department of Science and Technology, and the Huu Lien Nature Reserve (Lang Son Province) for issuing relevant permits. We gratefully acknowledge R.H. Bain (AMNH, New York), N. Ananjeva and N.L. Orlov (ZISP, St. Petersburg), V.V. Bobrov (Moscow) for providing literature and comments on the manuscript. Furthermore, we thank the Nature Reserve staff and M.L. Hoang (Huu Lien, Huu Lung) for their assistance during field work in Lang Son Province. This research was partially funded by the Institute of Ecology and Biological Resources (IEBR) and the German Academic Exchange Service (DAAD).