A New Species of the Genus Scincella Mittleman, 1950 (Squamata: Scincidae) from Sichuan Province, Southwest China, with a Diagnostic Key of Scincella Species in China

Abstract

The genus Scincella Mittleman, 1950 of the family Scincidae currently includes 38 species. To date, however, taxonomic assessment remains challenging. Here, phylogenetic analyses based on DNA sequences of four mitochondrial genes supported a putative new species from Sichuan Province, Southwest China, as an independent lineage. Uncorrected genetic distance of 16S rRNA between the new species and closest congener was 8%, and the population was morphologically distinguishable from all other known congeners. We herein describe the Scincella population as a new species based on both phylogeny and comparative morphology. The new species can be distinguished from its congeners by a combination of the following morphological characters: (1) body slender, mediumsized, snout-vent length 35.0-62.1 mm; (2) infralabials seven, rarely eight; (3) supraciliaries 5-7; (4) tympanum deeply sunk without lobules; (5) midbody scale-row counts 27-30; (6) dorsal scales smooth and enlarged, paravertebral scale-row counts 60-75, ventral scalerow counts 46-59, gulars 25-30; (7) upper edge of lateral longitudinal stripes relatively straight with six rows of dorsal scales in middle; (8) number of enlarged, undivided lamellae beneath finger IV 9-11, number of enlarged, undivided lamellae beneath toe IV 13-16; (9) ventral side of tail densely ornamented with dark brown or black spots; and (10) grayish-brown discontinuous regular dorsal stripes 5-7, distinct black dorsolateral stripes, starting from posterior corner of eye and continuing to lateral side of tail. A diagnostic key to all Scincella members from China is also provided. The new species is currently only known from Wenchuan and Lixian counties, Sichuan Province, China, and brings the number of Scincella species in China to 12. This study emphasizes the incompleteness of knowledge on herpetodiversity in China.

Headnote

Abstract The genus Scincella Mittleman, 1950 of the family Scincidae currently includes 38 species. To date, however, taxonomic assessment remains challenging. Here, phylogenetic analyses based on DNA sequences of four mitochondrial genes supported a putative new species from Sichuan Province, Southwest China, as an independent lineage. Uncorrected genetic distance of 16S rRNA between the new species and closest congener was 8%, and the population was morphologically distinguishable from all other known congeners. We herein describe the Scincella population as a new species based on both phylogeny and comparative morphology. The new species can be distinguished from its congeners by a combination of the following morphological characters: (1) body slender, mediumsized, snout-vent length 35.0-62.1 mm; (2) infralabials seven, rarely eight; (3) supraciliaries 5-7; (4) tympanum deeply sunk without lobules; (5) midbody scale-row counts 27-30; (6) dorsal scales smooth and enlarged, paravertebral scale-row counts 60-75, ventral scalerow counts 46-59, gulars 25-30; (7) upper edge of lateral longitudinal stripes relatively straight with six rows of dorsal scales in middle; (8) number of enlarged, undivided lamellae beneath finger IV 9-11, number of enlarged, undivided lamellae beneath toe IV 13-16; (9) ventral side of tail densely ornamented with dark brown or black spots; and (10) grayish-brown discontinuous regular dorsal stripes 5-7, distinct black dorsolateral stripes, starting from posterior corner of eye and continuing to lateral side of tail. A diagnostic key to all Scincella members from China is also provided. The new species is currently only known from Wenchuan and Lixian counties, Sichuan Province, China, and brings the number of Scincella species in China to 12. This study emphasizes the incompleteness of knowledge on herpetodiversity in China.

Keywords Hengduan Mountain Region, mitochondrial DNA, morphology, Scincella wangyuezhaoi sp. nov., taxonomy

1. Introduction

The family Scincidae is one of the most diverse groups of lizards globally, currently containing 164 genera and 1743 species (Uetz et al., 2022). The smooth skink genus Scincella Mittleman in Scincidae contains 38 species, with fragmented distribution across the North American continent (five species) to Japan, Korean Peninsula, China, and Southeast Asia (Ouboter, 1986; Uetz et al., 2022). These terrestrial skinks are commonly found in forests among weeds near streams and in hillside fragments, as well as hot-dry valleys in the Hengduan Mountains. Species within the genus are characterized by their small size, elongated body, short limbs, relatively long tail, smooth subcycloid scales (most species), small oblong head with transparent disc in a movable lower eyelid, absence of supranasals, pentadactyl hindlimbs, one row of basal subdigital lamellae (most species), median preanals overlapping lateral ones, four or more scales bordering the parietals between the upper secondary temporals, and lower secondary temporal overlapping the upper one (Greer and Shea, 2003; Lim, 1998; Nguyen et al, 2010a; Nguyen et al., 2010b; Nguyen et al., 2010c).

The phylogenetic relationships between Scincella and many other Southeast Asian lygosomine skinks remain unresolved due to their many morphological similarities (e.g., Nguyen et al., 2010a, 2010b). Based on examination of museum specimens, Ouboter (1986) undertook a major revision of Scincella, resulting in many synonymies. Morphological similarity and taxonomic uncertainty have hindered progress in the systematics of smooth skinks, with only a few species described in the past two decades, including five taxa discovered from Vietnam (Darevsky et al, 2004; Nguyen et al, 2019, 2020; Nguyen et al, 2010a, 2010c), one from Cambodia (Neang et al., 2018), one from Mexico (García-Vázquez et al., 2010), and one from Japan (Koizumi et al, 2022). In China, the genus is currently represented by 11 species, including S. barbouri (Stejneger, 1925), S. doriae (Boulenger, 1887), S. formosensis (Van Denburgh, 1912), S. monticola (Schmidt, 1925), S. huanrenensis Zhao and Huang, 1982, S. modesta (Günther, 1864), S. potanini (Günther, 1896), S. przewalskii (Bedriaga, 1912), S. reevesii (Gray, 1838), S. schmidti (Barbour, 1927), and S. tsinlingensis (Hu, 1966). Although Wang and Zhao (1986) reviewed Scincella in China, generic diversity remains understudied.

From 2004 to 2020, a total of 14 Scincella specimens were collected from Wenchuan and Lixian counties in Sichuan Province, China (Figure 1). These specimens most closely resembled S. potanini, S. monticola, and S. tsinlingensis, but differed from the latter three species and all other known Scincella members. Phylogenetic analyses based on mitochondrial DNA and morphological comparisons suggested that the Scincella specimens from Wenchuan and Lixian counties in Sichuan Province were distinct, which we herein describe as a new species.

2. Materials and Methods

2.1. Sampling A total of 50 specimens were examined in this study. All newly collected specimens were fixed in 10% buffered formalin and later transferred to 75% ethanol for preservation. Liver and muscle tissues used for molecular analysis were preserved in 95% alcohol at -20°C. All specimens were deposited in the Herpetological Museum, Chengdu Institute of Biology (CIB), Chinese Academy of Sciences, Chengdu City, Sichuan Province, China.

2.2. DNA extraction, polymerase chain reaction (PCR), and sequencing Genomic DNA was extracted from liver and muscle tissues using a DNA extraction kit (Sangon Biotech, Shanghai, China). Partial fragments of mitochondrial noncoding regions (i.e., mitochondrial 16S rRNA (16S), 12S rRNA (12S), cytochrome b (Cyt b), and cytochrome oxidase I (COI) were amplified using the primers listed in Table 1. A 25-gl reaction was set for bi-directional PCR, containing 12.5 gl of Thermo Scientific DreamTaq PCR Master Mix, 9.5 gl of molecular grade water, 1 pl of each 10 pM primer, and 1 pl of template DNA, carried out using an Applied Biosystems ProFlex PCR System. Thermocycling profiles for amplification were as follows: initial denaturation step at 95°C for 5 min, 36 cycles of denaturation at 95°C for 40 s, annealing for 40 s (see Table 1 for annealing temperatures), extension at 72°C for 1 min, and final extension at 72°C for 10 min, with maintenance at 10°C. The PCR products were sequenced on an ABI Prism 3 730 automated DNA sequencer by Chengdu TSINGKE Biological Technology Co. Ltd. (Chengdu, China). All newly generated sequences were deposited in GenBank (Table 2). Homologous DNA sequences of voucher specimens of related species were downloaded from GenBank and included in phylogenetic analysis.

2.3. Phylogenetic analyses For molecular analysis, Sphenomorphus cryptotis Darevsky, Orlov, and Cuc, 2004 was selected as an outgroup to root the tree based on Pyron et al. (2013) (Table 2). Four mitochondrial genes from 11 muscle and liver samples were newly sequenced in this study, and 58 sequences were downloaded from GenBank, representing 42 individuals and 20 Scincella species (including our putative new species). Details on these materials are shown in Table 2.

Initial nucleotide sequences were manually verified using SeqMan (Skwor, 2012), then combined with data from GenBank. Sequences were aligned in MEGA X (Kumar et al, 2018) using ClustalW (Thompson et al, 1997) with default settings. The sequences were concatenated using PhyloSuite v.122 (Zhang et al, 2020). For optimal partitioning strategies and evolutionary substitution models, the aligned data were analyzed using PartitionFinder v.2.1.1 (Lanfear et al, 2012), implementing a greedy search algorithm under Akaike Information Criterion (AIC). Phylogenetic trees were constructed using both maximum-likelihood (ML) and Bayesian inference (BI) approaches. Analysis suggested that the best partition scheme was 12S/16S/COI/Cyt b fragments. The GTR + I + G model was selected as the best model for 12S rRNA, 16S rRNA, COI, and Cyt b. ML analysis was performed using RAxML v.82.10 (Stamatakis, 2014) with the above selected model and 1000 bootstrap pseudoreplicates. BI analysis was implemented in MrBayes v.3.2.6 (Ronquist and Huelsenbeck, 2003) and run for 600 million generations, with sampling every 100 generations. Once the standard deviation of split frequencies reached < 0.01, analysis was not continued. In total, 25% of generated trees were discarded as burn-in. Tree nodes were considered well supported at a Bayesian posterior probability (BPP) > 0.95 and ML ultrafast bootstrap support (BS) > 95 space (Felsenstein, 2004; Hillis and Bull, 1993). Trees were visualized using FigTree v.1.4.3 (Rambaut, 2012). Uncorrected p-distances for 16S were calculated using default parameters in MEGA X (Kumar et al, 2018).

2.4. Morphological analysis Morphometric data were taken from 46 well-preserved specimens (voucher information is provided in Table 2). Measurements were recorded to the nearest 01 mm with digital calipers by Ru-Wan Jia following Zhao et al. (1999), Wang and Zhao (1986), Nguyen et al. (2010c), Neang et al. (2018), and Nguyen et al. (2019). A total of 44 morphological characteristics were measured, including: SVL = snout-vent length (distance from tip of snout to posterior edge of vent); TaL = tail length (distance from posterior margin of vent to tip of tail); TaW = tail width (widest section of tail posterior to hemipenial bulge); TaD = tail depth (ventral to dorsal surface of tail); AGD = axilla-groin distance (distance between posterior edge of forelimb insertion and anterior edge of hindlimb insertion); MBW = midbody width (measured from lateral surface to opposing lateral edge at midpoint of axilla-groin region); MBD = midbody depth (measured from ventral surface to dorsal surface at midpoint of axilla-groin region); HL = head length (distance from the tip of the snout to the articulation of jaw); HW = maximum head width (greatest width between the left and right articulations of jaw); HD = head depth (measured from ventral to dorsal surface of head at jaw articulations); ED = eye diameter (maximum horizontal diameter of eye); PDD = palpebral disc diameter (maximum horizontal diameter of palpebral disc); TD = tympanum diameter (ear opening diameter, maximum diameter of ear); END = eye-narial distance (from anterior margin of eye to posterior margin of nare); SNL = snout length (distance from the tip of the snout to the anterior comer of eye); IND = intemasal distance (minimum distance between the inner margins of the external nares); IOD = interorbital distance (minimum distance between the inner edges of the upper eyelids); FLL = forelimb length (measured from forelimb insertion to tip of finger IV or longest digit); HLL = hind-limb length (measured from hind-limb insertion to tip of toe IV or longest digit); T4L = toe IV length (measured from the most basal part to tip of toe IV); F4L = finger IV length (measured from the most basal part to tip of finger IV); MBSR = midbody scale-row count (number of longitudinal scale rows measured around widest point of midbody); DBR = dorsal scale rows between dorsolateral stripes (number of dorsal scale rows at midbody between dark dorsolateral stripes, following Inger et al. (1990)); NU = enlarged, differentiated nuchal count (X pairs or absence); PVSR = paravertebral scale-row count (number of scale rows counted between parietals and the just posterior margin of hindlimbs); VSR = ventral scale-row count (number of scale rows counted between gulars and precloacals); L = loreal count (left/right); AGSR = axilla-groin scale-row count (number of scale rows counted between posterior edge of forelimb insertion and anterior edge of hind-limb insertion); SL = supralabial count (left/right); IfL = infralabial count (left/ right); SC = superciliary count (left/right); SO = supraocular count (left/right); TEM = enlarged temporal count (left/right); FTSR = scale-row on the dorsal surface of the finger and toe (single or paired); F4S = number of enlarged, undivided lamellae beneath finger IV (left/right); T4S = number of enlarged, undivided lamellae beneath toe IV (left/right); MT = maxillary teeth count (left only); LT = lower teeth count (left only); PF = prefrontals in contact with each other (Yes: in contact/No: not in contact/absence); FP = frontoparietals in contact with each other (Yes: in contact/No: not in contact/absence); P = parietals in contact with each other (Yes: in contact/No: not in contact/ absence); chin-shields = paired large scales behind mental or postmentals); gulars = many minor scales in the center of the ventral head (number of scale rows counted between the first scale behind the chin-shields and the middle of the forelimb); limbs adpressed = toes overlap/in contact/not in contact with fingers when limbs adpressed. Values of paired characters were recorded in left to right order. Nomenclature for head shields followed Smith (1935).

Morphological data used for comparisons were taken from previously published literature: i.e., Taylor (1963); Darevsky and Nguyen (1983); Ouboter (1986); Wang and Zhao (1986); Darevsky and Orlov (1997); Zhao et al. (1999); Gonzalez et al. (2005); Stuart and Emmett (2006); Stuart et al. (2006); Nguyen et al. (2010a); Nguyen et al. (2010c); Pham et al. (2015); Neang et al. (2018); and Nguyen et al. (2019). Some morphological data that have not been used prior to the study, such as PDD, F4L, VSR, gulars, AGSR, and F4S, are provided (Table 3). To reduce the impact of allometry, a size-corrected value of the ratio of each character to SVL was calculated for morphometric analyses. We conducted principal component analysis of size-corrected variables and simple bivariate scatterplots using our morphometric data with Origin 2021 (OriginLab, Northampton, USA) to test the morphological separation between taxa and assess major loading components SVL, HL/SVL, HW/SVL, AGD/SVL, FLL/ SVL, HLL/SVL, F4L/SVL, T4L/SVL, MBSR, DBR, PVSR, VSR, gulars, and AGSR were the major loading components recovered. These contributing characters were plotted using multivariate analysis. Differences were tested by comparing the new species to S. potanini and S. monticola. Statistical analysis was carried out with a normalized dataset using Z scores.

3. Results

3.1. Phylogenetic analyses and genetic divergence The ML and BI phylogenetic trees were constructed based on four mitochondrial genes (12S, 385 bp; 16S, 480 bp; Cyt b, 611 bp; COI, 556 bp) from 21 species, with a total length of 2 032 bp. Both the ML and BI analyses resulted in a largely identical topology (Figure 2).

Overall, four major matrilines were resolved. The skinks from Southwest China were nested within the genus Scincella and were distinct from their congeners, which formed a highly isolated and monophyletic clade with unresolved internal relationships. The new taxon was sister clade to ((S. vandenburghi + S. modesta) + (S. boettgeri + S. formosensis)), with relatively low node support (BPP = 29; BS = 051; Figure 2).

The uncorrected inter- and intraspecific p-distances are shown in Table 4. The Scincella specimens from Wenchuan and Lixian, Sichuan, showed low genetic distance, with intraspecific genetic divergences ranging from 0.0%-1.0%, but differed substantially from other congeners, with interspecific genetic divergences ranging from 8.0% (vs. S. monticola and S. vandenburghi) to 11.0% (vs. S. reevesii and S. rupicola) (Table 4). The 16S rRNA genetic distance between the putative new species and closely related S. monticola and S. vandenburghi was 8%, greater than the distance that typically represents species differentiation in lizards (> 3%) (V ences et al, 2005).

3.2. Morphological analyses The putative new species was most similar to S. potanini and S. monticola. However, based on morphological comparisons (Table 5), the new species differed significantly from S. potanini, S. monticola, and all other species, especially in the MBSR, DBR, gulars, and T4S characters. The new species was also distinguished based on PCA (Figure 3), with the PC1 and PC2 eigenvectors accounting for 42.6% and 16.2% of the variance, respectively (58.8% cumulatively). As illustrated in the PC1 and PC2 scatter plots, samples of each species were clustered together. The new species did not overlap with any other species, while S. potanini and S. monticola clustered together and could not be separated.

Our analysis demonstrated that the new species from Wenchuan and Lixian was distinct from all other described Scincella species based on both morphological characters and phylogenetic analysis. Thus, we describe the population from Wenchuan and Lixian, Sichuan, as a new species herein.

3.3. Taxonomic account

Scincella wangyuezhaoi sp. nov. Jia, Ren, Jiang, & Li (Figures 4-6, 7A)

Chresonymy Scincella potanini - Shi and Zhao 1980: 135 (in part); Zhao 2003: 115 (in part).

Holotype CIB 87244 (field no. ZL0013) (Figures 5-6), adult female, collected from Shapai Village, Caopo Town, Wenchuan County, Sichuan Province, China; coordinates 31°18.845' N, 103°19.364' E; elevation 1900 m ash, by Cheng Li on 30 May 2004.

Paratypes Six individuals were collected from the same locality as the holotype: CIB 87247 and CIB 87250, adult males, and CIB 87245, CIB 87246, CIB 87248, and CIB 87249, adult females; coordinates 31°18.845' N, 103°19364' E; elevation 1900 m a.s.l.; collected on 30-31 May 2004 by Cheng Li. Seven specimens were collected from Shuluogou, Lixian County, Sichuan Province, China; CIB 119509, CIB 119512, CIB 119515, and CIB 119518, adult males, CIB 119516 and CIB 119519, adult females, and CIB 119510, juvenile; coordinates 3Г23356' N, 103°49.154' E; elevation 2 818 m a.s.l.; collected on 30 May 2020 by Xiao-Mao Zeng, Jun Ping, Jin-Long Liu, Xing-Zhong Wang, and ZeZhong Li.

The holotype and 13 paratypes are preserved in the Herpetological Museum, Chengdu Institute of Biology (CIB), Chinese Academy of Sciences, Chengdu, Sichuan, China.

Etymology This species epithet "wangyuezhaoi" is named after Professor Yue-Zhao Wang in recognition of his research on Chinese amphibians and reptiles and his continuous support of young herpetologists in China. We propose "Wenchuan's Ground Skink" as the common English name and "wen chuān huá xī (ШI |?f?)" as the Chinese name.

Diagnosis Scincella wangyuezhaoi sp. nov. is assigned to the genus Scincella Mittleman, 1950 based on molecular phylogenetic analyses and the following morphological characteristics: (1) body slender, snout short and blunt; (2) prefrontals and frontoparietals normal but not healed; (3) eyelids developed, lower eyelids with transparent eyelid window, no postnasal; (4) first enlarged nuchals obliquely connected to parietals; (5) one pair of enlarged cloacal scales; and (6) scales with limbs, toes five, 4th toe dorsal surface rows two (Wang and Zhao, 1986; Zhao et al, 1999).

Scincella wangyuezhaoi sp. nov. can be distinguished from all other congeners by the following combination of morphological characters: (1) body slender, medium-sized, snout-vent length 35.0-62.1 mm; (2) infralabials seven, rarely eight; (3) supraciliaries 5-7; (4) tympanum deeply sunk without lobules; (5) midbody scale-row counts 27-30; (6) dorsal scales smooth and enlarged, paravertebral scale-row counts 60-75, ventral scale-row counts 46-59, gulars 25-30; (7) upper edge of lateral longitudinal stripes relatively straight with six rows of dorsal scales in middle; (8) number of enlarged, undivided lamellae beneath finger IV 9-11, number of enlarged, undivided lamellae beneath toe IV 13-16; (9) ventral side of tail densely ornamented with dark brown or black spots; and (10) grayish-brown discontinuous regular dorsal stripes 5-7, distinct black dorsolateral stripes, starting from posterior corner of eye and continuing to lateral side of tail. Description of holotype CIB 87244 (Figures 5-6): adult female, SVL 61.0 mm; snout short, obtuse; lower eyelid with undivided transparent disc; tympanum deeply sunk with prominent oblique edge; tail primary; head elongated, HL 9.7 mm (HL/SVL 0.16), longer than wide, HW 8.8 mm (HW/HL 0.90), slightly depressed, HD 6.4 mm (HD/HL 0.66); neck rather slender, slightly distinct from head; toes five, 4th toe dorsal surface rows two.

Head Snout rounded in profile and dorsal view, SNL 4.4 mm, more than twice as long as TD (1.8 mm); ear vertically oval, TD 1.8 mm; ED 25 mm; PDD 1.1 mm, proportion of palpebral disc and ear opening snout broad 058; END 3.1 mm; IND 2.9 mm, IOD 5.1 mm; snout broad, visible from above, in contact with 1st SL laterally, nasals and frontonasal posteriorly; MT 20, LT 16; supranasals absent; frontonasal broad, subtrapezoidal in shape, anterior side forming almost straight suture (0.6 mm) with rostral, posterior width 1.7 mm, as wide as rostral, slightly more than twice as wide as length (0.8 mm), in contact with nasals and 1st loreal laterally, posterior margin slightly touching prefrontals; prefrontals in slight contact, laterally bordered by two loreals, frontal posteriorly; frontal elongated, rhombus-shaped, posterior part much longer than anterior; frontal in contact with 1st and 2nd supraoculars laterally, frontoparietals posteriorly, anterior corner of rostral end slightly separating posterior portions of prefrontals medially, posterior corner of frontal slightly overlapping medial suture between frontoparietals; two frontoparietals in contact with each other, each diamond-shaped, together forming butterfly shape, in contact with 2nd, 3rd, and 4th supraoculars laterally, interparietal and parietals posteriorly; interparietal relatively small, rhombus-shaped, with posterior portion slightly longer than anterior, in contact with parietals posteriorly, anterior corner of interparietal acute, slightly intruding into median suture between frontoparietals; parietals large, in contact with each other posteriorly, narrowly contacting 4th supraocular and posterior supraciliary scale, in broad contact with upper secondary temporal laterally and enlarged nuchal scales posteriorly. Naris rounded, laterally pierced in nasal scale; nasals in contact with 1st SL ventrally, frontonasal dorsally, 1st loreal posteriorly; loreals two, anterior loreal rhomboidal, in contact with 2nd SL ventrally, frontonasals and prefrontals dorsally, posterior loreal subtrapezoidal, in contact with 2nd and 3rd SL ventrally, preocular and upper presubocular posteriorly, prefrontals and anterior supraciliary scale dorsally; supraciliaries seven, anterior two largest; supraoculars four, first two contacting frontal, 2nd to 3rd contacting frontoparietals; lower eyelid with distinct transparent disc (window) bordered above by small palpebral scales; supralabials seven, 1st smallest, 5th located ventral to window of eye, 6th largest; infralabials seven (left) and six (right), 1st smallest, 5th largest, rectangular or pentagonal; primary temporals two, lower larger, subrhomboid, ventrally in contact with 5th and 6th SL, posteriorly in contact with lower secondary temporal, upper primary temporal sub-rhomboid, posteriorly in contact with both secondary temporals; secondary temporals two, lower smaller, broadly touching upper, in contact with 7th SL ventrally, upper secondary temporal about twice as large as lower, in contact with parietals dorsally and nuchal scales posteriorly; nuchal scales three, bordering posterior edge of parietals, relatively enlarged in comparison with adjacent posterior scales. Mental rounded, in contact with 1st IfL laterally, postmental posteriorly; postmental large, in contact with 1st and 2nd IfL laterally, 1st chinshield posteriorly; chinshield pairs three, 1st pair in broad contact medially with each other, contacting 2nd-3rd IfL laterally, 2nd pair separated by sub-triangular gular scale, contacting 3rd4th IfL laterally, 3rd pair separated medially by three gular scales, in contact with 5th-6th IfL laterally, three gular scales posteriorly; gulars 28.

Body, limbs, and tail Body relatively stout, SVL 61.0 mm; axilla groin relatively long, AGD 34.9 mm (AGD/SVL 057); MBW 12.4 mm (MBW/SVL 020), MBD 10.6 mm (MBD/SVL 0.17); primary tail relatively long, TaL 71.7 mm, TaL/SVL 117; tail width approximately equal to tail height: TaW 5.8 mm (TaW/SVL 0.09), TaD 5.2 mm (TaD/SVL 0.09); forelimbs short, FLL 12.2 mm (FLL/SVL 020); hindlimbs longer than forelimbs, HLL172 mm (HLL/SVL 028).

Body scales smooth, cycloid, imbricate; dorsal scales significantly larger than ventral scales, slightly larger than those on lateral body and gular scales; scales on anterior flanks between tympanic region and posterior margin of axilla smaller than adjacent dorsal scales; MBSR 30; PVSR 63; VSR 43; AGSR 60; enlarged preanal scale pairs one, median scales overlapping outer scales; dorsal scale rows, longitudinal scale rows on dorsum between dorsolateral stripes 6+2(1/2); limbs pentadactyl, toes not in contact with fingers when limbs adpressed; digits slender, F4L 3.6 mm, T4L 6.4 mm; F4S 9 (left), F4S 10 (right), T4S 15 (left), T4S 14 (right).

Coloration in life In life, the female holotype CIB 87244 had the same color as male paratype CIB 119518 (Figure 4). Dorsal surface of head, dorsum, and base of tail dark bronze-brown, side of head between tip of snout and forelimb insertion light brown; dorsal surface of remaining tail reddish-brown. Dark broken irregular dorsal stripes anteriorly and on tail and posteriorly on body, formed by series of dark dots or elongated black spots, including wider dark paravertebral stripe; anterior part of dorsum with dorsal stripes formed by series of dots, posterior part of dorsum with dark dot-formed regular dorsal stripes reaching base of tail, continuing with dark stripes on dorsal surface of tail, extending about one-third of tail length; light laterodorsal stripes from behind eye, through temporals, along dorsolateral scale row to lateral sides of tail, and fading at one-third of tail length; large distinct irregular black longitudinal dorsolateral stripe on each side of body, covering two to three scale rows, starting as narrow stripe covering about one scale row, running from posterior corner of eye through upper temporals, above tympanum, expanding wider to two scale rows above axilla, running below light dorsolateral stripe, along upper flanks through upper angle of groin to lateral surface of tail, becoming indistinct at posterior lateral tail; body flanks ventrally with black longitudinal streaks on bluish-brown background; ventrolateral surfaces from below level of eye to axillary region with longitudinal whitish-grey streaks and dark marking on reddish-brown background; lateral surfaces of tail reddish-brown; dorsal surfaces of limbs with irregular dark blotches on dark brown background. Ventral surfaces of head, gular region, body, and limbs uniformly whitish-grey; ventral surface of tail uniform pinkishcream. Palmar surfaces of hands and thenar surfaces of feet dark grey. Iris light-grey.

Coloration in preservative In preservative, dorsal surfaces of holotype dark grayish-brown; upper margin of lateral longitudinal striation relatively straight. Ventral head with faint irregular dark spots, pineal ocellus present as single white dot on posterior part of interparietal; two wide dorsolateral black stripes distinctly present; lateral sides of tail with small dark spots; dark brown or black spots densely distributed on ventral tail; throat and ventral surface of body and limbs grayish-cream; ventral surface of tail lighter cream; palmar surfaces of hands, fingers, and toes brown (Figures 5-6).

Variation Para types (Table 3) resemble holotypes in most morphometric and meristic characters and coloration, with the following character variations: (1) MBSR: 27-30; (2) PVSR and VSR: 60-75 and 46-59, respectively; (3) gulars: 25-30; (4) AGSR: 53-78; (5) posterior temporals: three posterior temporals in CIB 87247 and CIB 87249; (6) nuchals: four nuchal scales on left in CIB 87248 and CIB 119519; two nuchal scales on left in CIB 87249, CIB 119509, CIB 119510, and CIB 119516; (7) infralabials: six scales in CIB 87247, CIB 87249, CIB 119516, and CIB 119518; (8) superciliary counts: five superciliaries in CIB 87246; seven superciliaries in CIB 87244, CIB 87247, CIB 87248, and CIB 87250; (9) F4S and T4S: 9-11 and 13-16, respectively; (10) MT and LT: 14-26 and 16-22, respectively; (11) prefrontals: prefrontals not in contact in CIB 119509, CIB 119512, CIB 119515, and CIB 119518; (12) parietals: parietals not in contact in CIB 87247; (13) limbs adpressed: toes in contact with fingers when limbs adpressed in CIB 87247; and (14) color pattern: denser black dots on head and dorsal in CIB 119509, CIB 119510, CIB 119512, CIB 119515, CIB 119516, CIB 119518, and CIB 119519. Moreover, TaW/ SVL, AGD/SVL, MBW/SVL, MBD/SVL, HL/SVL, HW/SVL, HD/SVL, PDD/SVL, END/SVL, SNL/SVL, IND/SVL, FLL/

SVL, HLL/SVL, T4L/SVL, and F4L/SVL are higher in CIB 87245 compared to other specimens. Other minor variations are shown in Table 3.

Distribution and natural history The new species is currently only known from Shapai Village, Caopo Town, Wenchuan County, Sichuan Province, and Shuluogou, Lixian County, Sichuan Province, China (Figure 1).

All specimens were collected in rocky areas with decaying leaf litter at elevations of 1 900-3100 m asl in both dry and wet seasons. The new species was mostly active during the day, observed on rocky walls or leaf litter surface in caves and between rocks. Sympatric lizards included Diploderma zhaoermii (Gao and Hou, 2002). The diet and reproductive biology of the new species remain unknown. However, four well-developed offsprings were found in a pregnant female, suggesting that the new species may be ovoviviparous, similar to S. tsinlingensis, S. huanrenensis, and S. reevesii, but different from S. potanini, S. monticola, S. modesta, and S. formosensis.

Ecology Wenchuan and Lixian Counties are located in Hengduan Mountain Region (HMR) of Sichuan Province. The most typical geomorphological feature of HMR is a series of north-south mountains and deep valleys arranged in parallel with each other. The terrain fluctuates greatly, with the highest altitude drop of 6 000 meters (Chen and Ai, 1983). The type series of S. wangyuezhaoi sp. nov. was collected in the shores of ditches and small ponds in HMR. These shores were covered by low (height usually less than 30 cm) halophilic vegetation (Figure 8). Comparisons The morphological characters distinguishing the new species from its Asian congeners are as follows: from S. apraefrontalis by more MBSR (27-30 vs. 18), more supralabials and infralabials (7 vs. 6 and 6-7 vs. 5, respectively), more T4S (14-15 vs. 8-9), and prefrontals present (vs. absent) (Nguyen et al, 2010c); from S. badenensis by greater number of TD/SVL (0.02 vs. 0.03), fewer MBSR (27-30 vs. 32-36), more nuchal pairs (2-4 vs. 0-1), fewer superciliaries (5-7 vs. 8-9), fewer T4S (14-15 vs. 18-20), and toes not in contact with fingers when limbs adpressed (vs. overlapping or separated) (Nguyen et al, 2019); from S. baraensis by fewer DBR (6 vs. 8), fewer VSR (46-59 vs. 64-66), fewer superciliaries (5-7 vs. 8), fewer F4S and T4S (9-11 vs. 12-13 and 14-15 vs. 18-20, respectively), weak auricular lobules absent (vs. present), and enlarged dorsal scales (vs. small) (Nguyen et al, 2020); from S. boettgeri by fewer T4S (14-15 vs. 15-16) (Ouboter, 1986); from S. capitanea by fewer MBSR (27-30 vs. 30-32), fewer T4S (14-15 vs. 15-17), and neck narrower than head (vs. neck wider than head) (Ouboter 1986); from S. darevskii by shorter SVL (301-62.1 mm vs. 88.6 mm), fewer supraoculars (4 vs. 5), weak auricular lobules absent (vs. present), and enlarged dorsal scales (vs. small) (Nguyen et al., 2010c); from S. devorator by fewer T4S (14-15 vs. 19) and prefrontals always in contact (vs. not in contact) (Darevsky et al., 2004; Nguyen et al., 2011); from S. dunan by upper margin of lateral longitudinal striation relatively straight (vs. wavy) and little (vs. large) dark irregular spots densely scattered under the dorsolateral stripes (Koizumi et al., 2022); from S. melanosticta by fewer MBSR (2730 vs. 30-32), fewer T4S (14-15 vs. 16-22), fewer superciliaries (5-7 vs. 8-9), and toes not in contact with fingers when limbs adpressed (vs. overlapping) (Bourret and Bour, 2009; Neang et al, 2018; Smith, 1935; Taylor, 1963); from S. nigrofasciata by greater number of TD/SVL (0.02 vs. 0.03), fewer MBSR (27-30 vs. 32-33), fewer DBR (6 vs. 8), fewer T4S (14-15 vs. 15-17), and toes not in contact with fingers when limbs addressed (vs. overlapping or separated) (Neang et al, 2018); from S. ochracea by more supralabials (7 vs. 5) and auricular lobules absent (vs. present) (Bourret and Bour, 2009; Neang et al, 2018; Pham et al, 2015); from S. punctatolineata Boulenger by more MBSR (27-30 vs. 24-26), more T4S (14-15 vs. 12-14), and nuchals present (vs. absent) (Smith 1935); from S. rara by more MBSR (27-30 vs. 24) and single row of lamellae beneath toes and fingers II-IV (vs. double) (Darevsky and Orlov, 1997); from S. rufocaudata by fewer MBSR (27-30 vs. 30-34), fewer DBR (6 vs. 10), fewer T4S (14-15 vs. 16-22), fewer superciliaries (5-7 vs. 8), and toes not in contact with fingers when limbs adpressed (vs. overlapping) (Darevsky and Nguyen, 1983; Neang et al, 2018); from S. rupicola by fewer MBSR (27-30 vs. 33-36), fewer DBR (6 vs. 8), fewer T4S (14-15 vs. 18-21), fewer superciliaries (5-7 vs. 7-9), and toes not in contact with fingers when limbs adpressed (vs. overlapping) (Smith 1935; Taylor 1963; Neang et al, 2018); from S. vandenburghi by more T4S (14-15 vs. 12) (Schmidt, 1927); and from S. victoriana by more MBSR (27-30 vs. 26), and smooth scales on dorsum and tail (vs. keeled) (Ouboter 1986).

Among Chinese species, Scincella wangyuezhaoi sp. nov. differs morphologically from S. potanini by more MBSR (27-30 vs. 24-27), more DBR (6 vs. 4), more gulars (25-30 vs. 23-25), more T4S (14-15 vs. 10-13), and greater F4L/SVL (0.06-0.10 vs. 0.03-0.06); from S. monticola by more MBSR (27-30 vs. 23-25), more DBR (6 vs. 4), more gulars (25-30 vs. 22-24), more T4S (14-15 vs. 10-12), and greater FLL/SVL (020-027 vs. 013-019), HLL/SVL (0.24-0.43 vs. 0.20-0.22), and F4L/SVL (0.06-0.10 vs. 0.03-0.05); from S. tsinlingensis by more DBR (6 vs. 4) and greater IND/SVL (0.04-0.07 vs. 0.03-0.04). Other morphological characteristics distinguishing the new species from S. potanini, S. monticola, and S. tsinlingensis are summarized in Table 5. For the remaining congeners in China, Scincella wangyuezhaoi sp. nov. differs from S. modesta by upper margin of lateral longitudinal striation relatively straight (vs. wavy) (Wang and Zhao, 1986); from S. formosensis Günther by upper margin of lateral longitudinal striation relatively straight (vs. wavy) (Wang and Zhao, 1986); from S. huanrenensis by fewer DBR (6 vs. 8) and prefrontals always in contact (vs. not in contact) (Chen et al., 2001; Zhao and Huang, 1982); from S. barbouri by fewer T4S (14-15 vs. 15-17) and fewer nuchals (2-4 vs. 4-5) (Ouboter, 1986; Stejneger, 1925); from S. przewalskii by more supralabials (7 vs. 6), more supraoculars (4 vs. 3), more superciliaries (5-7 vs. 4-5), and fewer T4S (14-15 vs. 17) (Wang and Zhao, 1986); from S. reevesii by postnasals absent (vs. one postnasal pair present), greater FLL/SVL (020-027 vs. 0.16-0.19), fewer MBSR (27-30 vs. 32), fewer DBR (6 vs. 8), more VSR (46-59 vs. 44-45), more gulars (25-30 vs. 23-25), fewer T4S (14-15 vs. 16-17), and upper margin of lateral longitudinal striation relatively straight (vs. wavy); from S. schmidti by more MBSR (27-30 vs. 26), more DBR (6 vs. 4), and more lamellae beneath toe IV (14-15 vs. 11) (Barbour, 1927); from S. doriae by fewer MBSR (27-30 vs. 34-37), fewer DBR (6 vs. 10), fewer T4S (14-15 vs. 15-18), toes not in contact with fingers when limbs adpressed (vs. overlapping), and upper margin of lateral longitudinal striation relatively straight (vs. wavy) (Boulenger, 1887; Bourret and Bour, 2009; Smith, 1935; Taylor, 1963).

4. Discussion

DBR is a conservative trait for identifying Scincella species Previous studies have found that the number of dorsal scale rows at the midbody between the dark dorsolateral stripes (DBR) is a relatively conservative trait with important taxonomic implications for Scincella (Neang et al., 2018; Nguyen et al, 2019; 2020; Wang and Zhao, 1986). The DBR is conserved in different populations of certain species, but distinguishable from other species groups. Here, although Scincella wangyuezhaoi sp. nov. was phylogenetically close to S. potanini and S. monticola, DBR comparisons among these species indicated clear morphological differences (Figure 7). As taxonomy and identification remain relatively elusive among Scincella species, the use of DBR could facilitate fast identification during field surveys. Therefore, our results agree with those of Wang and Zhao (1986), suggesting that Scincella could be divided into four groups based on DBR: i.e., DBR 4: S. potanini, S. monticola, 5. tsinlingensis, S. huanrenensis, and S. schmidti; DBR 6: Scincella wangyuezhaoi sp. nov., S. barbouri, S. darevskii, S. doriae, S. formosensis, S. modesta, S. ochracea, and S. przewalskii; DBR 8: S. baraensis, S. nigrofasciata, S. rupicola, and S. reevesii; DBR 10: S. badenensis, S. melanosticta, and S. rufocaudata.

Diversity and identification of Scincella species in China The description of Scincella wangyuezhaoi sp. nov. increases the current number of Scincella species to 39, with 12 recorded from China (Uetz et al, 2022; Zhao et al., 1999; this study), including Scincella wangyuezhaoi sp. nov., S. potanini, S. monticola, S. tsinlingensis, S. modesta, S. huanrenensis, S. reevesii, S. barbouri, S. doriae, S. formosensis, S. przewalskii, and S. schmidti. The discovery of a new Scincella species indicates that reptile fauna in China remains insufficiently studied and future field surveys are needed to more accurately assess herpetodiversity. Our study further highlights the importance of taxonomic research and biodiversity assessment for conservation. To facilitate future taxonomic work, we provide a key to the species of Scincella in China based on Wang and Zhao (1986).

Diagnostic key to Scincella species in China

1A Supraoculars 3_S. przewalskii

1B Supraoculars 4_2

2A Postnasal pairs 1_S. reevesii

2B Postnasals absent_3

3A Upper margin of lateral longitudinal striation relatively straight_.4

3B Upper margin of lateral longitudinal striation wavy_.8

4A DBR 6._Scincella wangyuezhaoi sp. nov.

4B DBR 4_5

5A T4S 10-13_6

5B T4S 13-16._7

6A MBSR 23-24_S. monticola

6B MBSR 24-27_S. potanini

7A Infralabials 6.S. huanrenensis

7B Infralabials 7-8.S. tsinlingensis

8A DBR 4_S. schmidti

8B DBR 6.._9

9A Toes and fingers overlap when limbs adpressed._S. doriae

9B Toes separated or in contact with fingers when limbs adpressed_.10

10A PVSR 70_S. barbouri

10B PVSR 53-69.._11

11A MBSR 26-28, rarely 30.S. formosensis

11B MBSR 28-30.S. modesta

Distribution of Scincella in HMR on eastern edge of Tibetan Plateau Despite its ecological and biogeographical importance, the biodiversity of HMR remains poorly understood. Five Scincella species have been recognized in HMR, including Scincella wangyuezhaoi sp. nov., S. potanini, S. monticola, S. tsinlingensis, and S. doriae (Günther, 1896; Schmidt, 1925; Hu and Zhao, 1966; Boulenger, 1887; this study). Based on recent findings, we speculate that the true biodiversity of HMR be seriously underestimated, and future herpetofaunal surveys and taxonomic revisions are needed for Scincella species in the region. For example, species of Diploderma (Lacertilia: Agamidae) in HMR have been widely misidentified as Diploderma flaviceps, while they were suggested to be different species out of hot-dry valley of Dadu River (Gao and Hou, 2002; Manthey et al, 2012; Wang et al, 2019a; Wang et al, 2019b). The distribution pattern of Scincella is similar to that of Diploderma, and they are difficult to distinguish morphologically due to a lack of previous research. Therefore, further studies should focus on the cryptic diversity and taxonomic revision of Scincella species in HMR.

For instance, all Scincella populations distributed in the Tianquan, Yuexi, Meigu, Yanbian, and Ganzi counties of Sichuan are currently identified as S. potanini, but no taxonomic study has been conducted for this widely distributed species (Wang and Zhao, 1986; Zhao et al, 1999). Furthermore, the systematic relationship between S. potanini and S. monticola is questionable, with no molecular data available for either S. potanini or S. monticola prior to this study. Based on topotypic materials, our results indicated that S. monticola was phylogenetically closest to S. potanini and could not be distinguished from the latter species. Specifically, the p-distance between S. potanini and S. monticola was only 3.0% and the two species could not be separated by PCA. Thus, further studies are required to clarify the taxonomy of Scincella species in HMR.

Acknowledgements We thank Dihao WU (CIB) for photograph editing; Xiaomao ZENG (CIB) and Li DING (CIB) for providing kind help and giving us access to examine specimens under their care; Jinlong LIU (CIB) for photographing; Ke LV (CIB) for the loan and examination of specimens. This research was funded by the Second Tibetan Plateau Scientific Expedition and Research Program (STEP) (2019QZKK0501); the Sichuan Science and Technology Program (2021JDJQ0002); Biological Resources Programme, Chinese Academy of Sciences (KFJ-BRP-017-65).

Sidebar

Received: 30 September 2022 Accepted: 28 November 2022

Scientific Editor: Bin WANG

How to cite this article:

Jia R. W., Gao Z. Y., Huang J. J., Ren J. L, Jiang K., Li D. Y., Li J. T. A New Species of the Genus Scincella Mittleman, 1950 (Squamata: Scincidae) from Sichuan Province, Southwest China, with a Diagnostic Key of Scincella Species in China. Asian Herpetol Res, 2023, 14(1): 24-40. DOI: 10.16373/j.cnki.ahr.220054

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Appendix

Specimens examined (n = 32)

Scincella monticola (n = 4): China: Yunnan, Weixi: CIB 6969, CIB 6970, CIB 6971, and China: Yunnan, Shangri-La: DL-YNJC2020824. Scincella potanini (n = 14): China: Sichuan, Kangding: CIB 85805, CIB 85806, CIB 85807, CIB 72253-60, DL-KD202109071, DLKD202109072, DL-KD2018070302.

Scincella reevesii (n = 4): China: Guangdong, Guangzhou: CIB 7215, CIB7216, CIB 7219, and China: Guangxi: CIB 7218.

Scincella tsinlingensis (n = 10): China: Shannxi, Zhouzhi: CIB 7226, CIB 7240, CIB 7246, CIB 7249, CIB 7251, CIB 7252, CIB 7253, CIB 7258, CIB 7259, CIB 7261.