Scincella dunan, Koizumi & Ota & Hikida, 2022

Koizumi, Yuki, Ota, Hidetoshi & Hikida, Tsutomu, 2022, A new species of the genus Scincella (Squamata: Scincidae) from Yonagunijima Island, Southern Ryukyus, Japan, Zootaxa 5128 (1), pp. 61-83 : 68-71

Scincella dunan sp. nov.

[New Japanese name: Yonaguni-subetokage]

( Figs. 5 , 6 )

Scincella boettgeri: Ota 1983, p. 15 ; Chigira 1989, p. 38; Okada et al. 1992, p. 51; Chen et al. 2001a, p. 116; Maenosono & Toda 2007, p. 39; Koizumi et al. 2014, p. 229.

Holotype. KUZ R 47494, adult male from Yonagunijima Island (24°26'43.8'' N, 122°57'34.4'' E) of the Yaeyama Group, Ryukyu Archipelago, collected on 29 July 1998 by T. Yamasaki.

Paratypes. 33 specimens collected from Yonagunijima Island ; KUZ R412–3 , 444 and 1364, adult female, on 22–25 March 1983 ; KUZ R1365 , subadult male, on 22–25 March 1983 ; KUZ R1366 , juvenile, female, on 22–25 March 1983 ; KUZ R 13052, 13054 , 13058 , 13060–61 , 13064 , 13068 and 13070–72, adult male, on 22–25 March 1983 ; KUZ R 13053, 13055–57 , 13059 , 13062–63 , 13065–67 , 13069 and 13073, adult female, on 22–25 March 1983 ; KUZ R 13133, adult male, on 14 March 1984 ; KUZ R13134–36 , adult female, on 14 March 1984 .

Diagnosis. Scincella dunan sp. nov. can be distinguished from other congeners by a combination of the following morphological characteristics: small size in adults (SVL up to 51.8 mm, AGL up to 29.9 mm); 26–29 smooth midbody scale rows; 55–67 ventral scale rows; 57–70 paravertebral scale rows; usually six, sometimes seven supraciliaries; prefrontals conditions (contacted, contacting at a point, and separated) appear about the same; tympanum deeply recessed, and no ear lobules; forelimb and hindlimb length to SVL with 0.19–0.26 and 0.28–0.37, respectively; smooth lamellae beneath toe IV with 13–17 lamellae; dorsolateral stripes often broken up by light spots and the width of which is uncertain, some clearly defined and 2–3.5 scale rows of dorsolateral stripes, both margins of the stripes are wavy; large, dark irregular spots densely scattered under the dorsolateral stripes ( Fig. 7 ).

Description of holotype. Adult male: SVL 34.4 mm, snout short and rounded; lower eyelid with an undivided transparent disc; body rather slender; tympanum deeply sunk with a prominent oblique edge; no ear lobules in earopening; limbs pentadactyl, contact between adpressed limbs. Head scalation smooth; rostral partly visible from above, in broad contact with frontonasal; frontonasal broader than long; no supranasals; prefrontals contacting at a point;; four supraoculars; frontal large, about the 1.48 times its distance from tip of snout, narrowing posteriorly, longer than wide, bordered laterally by first two supraoculars, anteriorly by prefrontals and frontonasal, and posteriorly by frontoparietals; pair of frontoparietals in contact with the second to fourth supraoculars; interparietal longer than wide, narrowed posteriorly; pair of parietals large, in contact posteriorly, behind the interparietal; parietal eye in posterior part of interparietal; one prenuchal on only right side; three pairs of nuchals. Nostril in center of nasal; nasal in contact with the first supralabial, rostral, anterior loreal, and frontonasal; two loreal; six supraciliaries on the left side and seven on right side; two small preocular, contacting first presubocular; two presuboculars; two postsuboculars; three pretemporal in contact with fourth supraocular and last supraciliary; one primary, two secondary and three tertiary temporals on each side, lower secondary temporal overlapping upper one and in contact with seventh supralabials; seven supralabials, fifth below center of the eye, sixth largest; six infralabials, first two in contact with postmental; three pairs of chin shields laterally in contact with inflalabials; first chin shield medially in contact with each other. Dorsal and ventral scales about the same size, slightly larger than lateral ones; 28 midbody scale rows; paravertebral scales smooth, in 59 rows; ventral scales smooth, in 58 rows; six scale rows between dorsolateral stripes; dark dorsolateral stripe without very definite lower border, broken up by some light spots, upper margin are wavy; small scales between the original part of tail base; first to fourth subcaudal paired, followed by unpaired wide subcaudals; two enlarged precloacals, left one overlapping right one. Limbs well developed, scales smooth; hands with five distinct fingers, subdigital lamellae 11/10 on left/right finger IV; feet with five distinct toes, subdigital lamellae 17/17 on left/right toe IV.

Variation. The squamation of Scincella dunan sp. nov. showed substantial intraspecific variation in these points; six to seven supralabials; five to six infralabials; none or one prenuchals and two to five nuchals; six to seven supraciliaries; two or three presuboculars; various condition of prefrontals (contacted, contacted at a point and separated); contact or separate between adpressed limbs; 26–29 midbody scale rows; 8–12 subdigitals of finger IV; one to five small scales between the original part of tail base; two enlarged precloacals, the overlap of scales is variable (left side up, or right side up). All specimens had various sizes of light spots, and in more than half of the specimens the stripes were broken up by light spots. The relatively large black spots scattered under the stripes, and some were indistinguishable from the broken stripes. Some individuals have a dark bronze body color and others bronze color. For some quantitative characters, there were differences between female and male; ratio of limbs to SVL, 0.21–0.26 in males and 0.19–0.24 in females for forelimbs, 0.30–0.37 in males and 0.28–0.34 in females for hindlimbs; 55–65 ventral scales in males and 58–67 in females; 57–64 prevertebral scales in males and 57–70 in females; subdigital scales of toe IV, 13–17 in males and 13–16 in females.

Distribution. Yonagunijima Island, Yaeyama Group, Ryukyu Archipelago, Japan. This species was collected only from its type locality ( Fig. 1 ).

Natural history. Scincella dunan sp. nov. is often found on the floor of broad-leaved forests, it is diurnal, and hides beneath leaf litter when approached ( Ota 1983; Koizumi personal observation). Okada et al. (1992) noted the reproductive traits of S. boettgeri sensu lato at that time, with a positive correlation between female body size and clutch size (4– 11 eggs), and that gravid females were present in March.

Etymology. The specific name “dunan” is derived from an old local name of Yonagunijima Island, which is not commonly used as a place name now. This term refers to the difficulty involved in accessing the island because of the cliffs.

Comparisons. Morphological comparisons of Scincella species found in the Southeast Asia and East Asia are given in Table 3–4 . Among the Asian species, Scincella dunan sp. nov. can be distinguished from S. reevesii of southern China by the lack of ear lobules (none vs. yes), its lower number of SRBDLS (6 vs. 8), VS (55–65 vs. 63–72 in males, 58–67 vs. 67–75 in females) and PVS (57–64 vs. 66–73 in males, 57–70 vs. 69–78 in females), T4S (13–17 vs. 16–18 in males, 13–16 vs. 15–19 in females), and MBSR (27–29 vs. 31–33 in males, 26–29 vs. 32–34 in females); from S. modesta of China by its lower number of VS (55–65 vs. 60–68 in males, 58–67 vs. 63–72 in females) and PVS (57–64 vs. 60–67 in males, 57–70 vs. 65–69 in females), its large number of T4S (13–17 vs. 11–16 in males, 13–16 vs. 12–14 in females), and its greater number of SRB (≥ 2 or uncountable in all vs. <2 in almost all), dark dorsolateral stripes with light spots (present in all vs. none); from S. huanrenensis of Korea by its large FLL/SVL (0.21–0.26 vs. 0.21–0.22 in males, 0.19–0.24 vs. 0.18–0.20 in females) and HLL/SVL values (0.30–0.37 vs. 0.29–0.31 in males, 0.28–0.34 vs. 0.27–0.29 in females), lower number of VS (55–65 vs. 74–78 in males, 58–67 vs. 74–81 in females), PVS (57–64 vs. 74–79 in males, 57–70 vs. 76–83 in females), relatively large number of MBSR in females (26–29 vs. 24–26), greater number of SRBDLS (6 vs. 4), shape of upper margins of dorsolateral stripes (wave in almost all vs. straight in all), its pattern (with light spots vs. uniformly black); from S. vandenburghi in Korea and Tsushima Island by comparatively its greater number of SRB (≥ 2 or uncountable in all vs. <2 in all), fewer number of VS (55–65 vs. 67–76 in males, 58–67 vs. 69–78 in females), PVS (57–64 vs. 63–72 in males, 57–70 vs. 65–78 in females). Phylogenetically, Scincella dunan sp. nov. is closely related to S. formosensis and S. boettgeri ( Fig. 2 ), but can be distinguished from S. formosensis in Taiwan by a combination characters: its statistically larger SVL in males (34.4–51.8 mm vs. 38.5–44.5 mm), AGL (15.6–28.2 mm vs. 19.0–22.0 mm in males, 21.6–29.9 mm vs. 19.9–26.3 mm in females), statistically small FLL/SVL and HLL/SVL values in females (0.19–0.24 vs. 0.21–0.26, 0.28–0.34 vs. 0.30–0.37, respectively), statistically fewer T4S (13–17 vs. 13–18 in males, 13–16 vs. 14–19 in females), condition of PF (vs. separated in almost all), its comparatively greater number of SRB (≥ 2 or uncountable in all vs. <2 in almost all), and dark dorsolateral stripes with light spots (present in all vs. none). Morphologically, Scincella dunan sp. nov. is most similar to S. boettgeri in the southern Ryukyus (Miyako and Yaeyama Group excluding Yonagunijima Island), but can be distinguished by a combination of: PF (vs. contacted with each other in almost all in the two Islands Group population), the dorsolateral stripes pattern. The condition of the dorsolateral stripes differ from other islands populations, especially from the axilla to the groin as a whole, or from the middle or further posterior to the groin (broken vs. not); often dark in color (vs. basically light dark brown), below the lateral stripes have many dark spots (vs. few dark pale brown spots), broken up by many scattered light spots, with less definite lower border, and cannot distinguish between stripe broken up by light spots and dark spots that are usually under the stripe (vs. even if light spots in the stripes, both upper and lower borders are clear, and in some cases, with a white line at the upper and/or lower border) ( Fig. 7 ). In each Islands Group populations, it can be statistically distinguished by a combination of: larger SVL in females with Miyako Group population (37.8–50.8 mm vs. 37.4–47.6 mm), and AGL in males with Miyako Group (15.6–28.2 mm vs. 17.9–25.4 mm) and in females with Miyako and Yaeyama Group (21.6–29.9 mm vs. 20.9–26.9 mm vs. 19.7–31.1 mm, respectively); smaller FLL/ SVL values in females (0.19–0.24 vs. 0.20–0.25), its fewer number of T4S (13–17 vs. 14–18) with Miyako Group population; larger AGL in females (21.6–29.9 mm vs. 19.7–31.1 mm), smaller FLL/SVL in males (0.21–0.26 vs. 0.21–0.28) and HLL/SVL values (0.30–0.37 vs. 0.30–0.38 in males and 0.28–0.34 vs. 0.27–0.35 in females), its fewer number of PVS (57–64 vs. 55–73 in males, 57–70 vs. 57–72 in females) and MBSR in females (26–29 vs. 27–30) with Yaeyama Group (excluding Yonagunijima Island) population.

Figures

FIGURE 1. Map of the Southern Ryukyus, Japan, and Taiwan showing the geographic location of Yonagunijima Island. The black circles and arrows indicate the sample localities used in this study.

FIGURE 2. The Bayesian inference (BI) tree based on the COI and cytb sequences for Scincella species used in this study. Maximum likelihood (ML) ultrafast bootstrap values (UFB) and Bayesian posterior probability (PP) are shown from left to right at each node (UFB/PP). Asterisks shows strong support by ML (UFB ≥95%) and BI (PP ≥0.95).

FIGURE 5. Dorsal (A) and lateral (B) views of the Scincella dunan sp. nov. holotype (KUZ R47494).

FIGURE 6. Lateral (A), dorsal (B), and ventral (C) views of head scalation on the Scincella dunan sp. nov. holotype (KUZ R47494). Abbreviations for scale characters: IL, infralabial; L, loreal; NU, nuchal; PNU, prenuchal; POS, postsubocular; PRO, preocular; PRSO, presubocular; SC, supraciliary; SL, supralabial; SO, supraocular.

FIGURE 7. Comparison of the dorsolateral stripes pattern in Scincella dunan sp. nov. (A), S. boettgeri (B), S. formosensis (C).