Ateuchosaurus pellopleurus (Hallowell, 1861)

Makino, Tomohisa, Nakano, Takafumi, Okamoto, Taku & Hikida, Tsutomu, 2023, Taxonomic revision and re-description of Ateuchosaurus pellopleurus (Hallowell, 1861) (Reptilia, Squamata, Scincidae) with resurrection of A. okinavensis (Thompson, 1912), Zoosystematics and Evolution 99 (1), pp. 77-91 : 77

Ateuchosaurus pellopleurus (Hallowell, 1861)

Figs 3 , 4 Japanese name: Heriguro-Hime-Tokage

Lygosaurus pellopleurus Hallowell, 1861: 496-497 (part); Stejneger 1907: 222-224 (part); 1927: 2; Sclater 1950: 114.

Lygosoma pellopleurum : Boulenger 1887: 319; Okada 1891: 70 (part).

Lygosoma (Homolepida) pellopleurus : Boettger 1895: 107.

Lygosaurus pellopleurus browni Van Denburgh, 1912a: 7; Van Denburgh 1912b: 240-241.

Ateuchosaurus pellopleurus : Smith 1937: 231; Tanaka 1979: 37 (part); Hikida 1996: 81 (part); Ota et al. 1999: 106 (part); Goris and Maeda 2004: 155-156 (part); Austin and Arnold 2006: fig. 2, table 1; Pyron et al. 2013: fig. 7; Hedges 2014: 322; Zheng and Wiens 2016: figs 1-2; Okamoto 2017: table 5.2; Makino et al. 2020: 6 ("northern lineage"); Okamoto and Kurita 2021: 142-143 (part).

Lygosoma pellopleurus : Okada 1939: 206-209 (part).

Lygosoma (Ateuchosaurus) pellopleurum : Nakamura and Uéno 1963: 123-125 (part).

Lectotype designation.

One of the existing syntypes, USNM 42110, was designated as the lectotype for A. pellopleurus .

Lectotype. USNM 42110 collected from Amamioshima Island, Amami Group, Ryukyu Archipelago, Japan, in the United States North Pacific Surveying and Exploring Expedition in 1853-1856.

Paralectotype. USNM 42114. The locality of this specimen is the same as USNM 42110. Missing syntype(s) collected from Loo-Choo is also automatically fixed as the paralectotype(s) of A. pellopleurus . However, the specimen(s) may belong to A. okinavensis .

Material examined.

Japan • Kagoshima Prefecture, Mishima Village, Takeshima Island ; KUZ R54830 to 54834, 70451, 70453 to 70456, 70458, 70461 • Kagoshima Prefecture, Mishima Village, Iojima Island ; KUZ R70413 to 70417, 70420, 70422 to 70425, 70442 to 70443, 70445 to 70450 • Kagoshima Prefecture, Mishima Village, Kuroshima Island ; KUZ R47185 to 47202 • Kagoshima Prefecture, Toshima Village, Kuchinoshima Island ; KUZ R66811 to 66812, 68678 • Kagoshima Prefecture, Toshima Village, Nakanoshima Island ; KUZ R66815 , 66834 to 66835, OMNH R3024 to 3028, 6880 • Kagoshima Prefecture, Toshima Village, Suwanosejima Island ; KUZ R69905 to 69910, OMNH R3022 to 3023, 6886, 6889 • Kagoshima Prefecture, Toshima Village, Akusekijima Island ; KUZ R66781 to 66782, OMNH R3018 to 3019 • Kagoshima Prefecture, Toshima Village, Kodakarajima Island ; KUZ R34983 to 34986, 70147 to 70151, 70153 to 70155, 70162 • Kagoshima Prefecture, Toshima Village, Takarajima Island ; KUZ R13169 to 13207, OMNH R1 to 4, 2217, 3014 to 3016, 6890 • Kagoshima Prefecture, Kikai Town, Kikaijima Island ; OMNH R3029 to 3036 • Kagoshima Prefecture, Amamioshima Island ; KUZ R62708 , 66187 to 66190, 69075, 69901 to 69904, 70700, 72543, 72545, 77679 to 77682, 77686, 77689 to 77690, 77692, 77694 to 77698, 77700, 77702 to 77708, OMNH R245 to 246, 248 to 249, 260, 621 to 623, 2777, 3077 to 3094, 3096 to 3100, 3102, 3105 to 3112, 6876, 6878 to 6879, 6881 to 6883, 6885, 6891 to 6892 • Kagoshima Prefecture, Tokunoshima Island ; KUZ R70680 , 77672, 77674, OMNH R3039 to 3042, 3044 to 3060, 6877, 6888 • Kagoshima Prefecture, Okinoerabujima Island ; KUZ R34987 to 34996, 66740, 66780, 70675 to 70679, 70681 to 70682, 77637 to 77640, 77642 to 77644, 77647, 77649 to 77650, 77652 to 77661, 77664 to 77665, 77667 to 77671, OMNH R262 to 266, 3037 .

Emended diagnosis.

An Ateuchosaurus species characterized by the following characters: FrNa and frontal usually distinct; a pair of frontoparietals that do not contact each other; eight SuCis; anteroposteriorly reduced parietals separated from SuO and pretemporal by EcP; no distinct nuchals; usually six InLas; body size medium (SVL ca. 42-70 mm); widely separated forelimb and hindlimb when appressed; usually 26 or 28 MSRs (mode = 26, 24-30); 53-70 (mode = 62) and 56-69 DMSs (mode = 63) in male and female, respectively; 8-14 TIVs (mode = 11); 10 preanals not enlarged; usually 2-3 pairs of DSRBS.

Comparison.

Ateuchosaurus pellopleurus , together with A. okinavensis (see below), is distinguished from A. chinensis by having the following characters ( Nguyen et al. 2008): usually six InLas (vs. seven InLas); smaller body size (SVL ca. 42-70 mm vs. 70.0-83.8 mm; see also Okamoto and Kurita 2021); usually 26 or 28 MSRs (vs. 30 scale rows); usually 10-14 TIVs (vs. usually 16-18 TIVs); 10 preanals (vs. usually six preanals); blackish line on dorsolateral surface from snout to midbody (vs. no such line). This species resembles A. okinavensis in MSR and body size but differs in usually having the separated state of FrNa and frontal (vs. the fused state), 53-70 and 56-69 DMSs in male and female (vs. 54-64 and 55-67 DMSs in male and female), 8-14 TIVs (vs. 10-16 TIVs), and usually 2-3 pairs of DSRBS (vs. usually 0-1 pair).

The mean K2P genetic distance ± standard deviation (range in parenthesis) based on cytochrome b sequences between A. pellopleurus and A. chinensis was 24.6% ± 0.3% (24.2%-25.5%); the distance between A. pellopleurus and A. okinavensis was 13.1% ± 0.9% (11.3%-16.0%).

Description.

Mainly based on a topotype (KUZ R77703), an adult male collected from Amami City in Amamioshima Island (28°23'44.29"N, 129°28'04.32"E, 2 m above sea level) (followed by ranges of several morphometric and meristic characters in parenthesis; N = 23, topotypes, KUZ R66188, 72543, 77679-77682, 77686, 77689-77690, 77692, 77694-77698, 77700, 77702-77708); SVL 53.5 mm (53.5 ± 2.3, 49.0-57.0); HL 6.7 mm (6.5 ± 0.3, 6.0-7.0); HW 5.0 mm (5.4 ± 0.3, 4.8-6.0); HH 4.2 mm (4.2 ± 0.3, 3.7-5.0); SEyL 3.3 mm (3.2 ± 0.2, 2.8-3.6); EyL 2.1 mm (2.3 ± 0.1, 2.1-2.5); EyEaL 3.1 mm (3.2 ± 0.2, 2.9-3.5); EaD 1.1 mm (1.0 ± 0.1, 0.8-1.2); SAL 18.1 mm (17.2 ± 0.9, 15.5-18.6); AGL 31.4 mm (32.2 ± 1.7, 28.9-34.5); TaL 56.3 mm (original tail 32.6 mm; regenerated tail 23.7 mm; 66.1 ± 0.9, 65.5-66.8, N = 2 with undamaged original tail); FlL 9.0 mm (8.8 ± 0.6, 7.8-9.8); HlL 15.9 mm (14.8 ± 1.0, 12.5-16.5); FIIIL 1.8 mm (1.6 ± 0.2, 1.3-2.0); TIVL 4.3 mm (4.0 ± 0.3, 3.5-4.6).

Snout obtusely pointed; rostral visible from above, overlapping supranasal, nasal and first supralabial; nasal fused with first supralabial, with shallow groove on boundary between nasal and labial parts; nostril at center of nasal; supranasal unpaired with posterior edge concaved, overlapped by nasal; supraloreal overlapped by supranasal and anterior and posterior loreals, overlapping frontonasal and first supraciliary; frontonasal not fused with frontal, as large as supranasal, with flat posterior edge, overlapped by supranasal, overlapping first supraocular and frontal; no prefrontal; frontal large, shorter than distance from it to snout, longer than frontonasal, a part between first supraoculars narrower anteriorly, overlapping frontoparietals and interparietal; four supraoculars (no variation), anterior ones overlapping posterior ones, first one overlapped by first, second and third supraciliaries, first and second ones overlapping frontal, third and fourth ones overlapping frontoparietal; a pair of frontoparietals as long as width, separated from each other by interparietal, overlapping interparietal, parietal and ectoparietal; interparietal with short arrowhead-like tetragonal shape, similar length and width of frontoparietal, overlapping parietals; ectoparietal pentagonal and similar size to fourth supraocular, overlapped by fourth supraocular and upper pretemporal, overlapping parietal; parietals shorter and 1.5 times wider than interparietal, left one overlapped by right one; no distinct nuchal.

Two loreals with a half length and similar height of second supralabial, anterior one overlapped by nasaland second supralabial, overlapping supranasal and posterior one, posterior one overlapped by second supralabial, overlapping first supraciliary and upper and lower preoculars; eight supraciliaries (mode = 8, 7-8), anterior ones overlapping posterior ones, first one overlapped by upper preocular, third and fourth ones overlapping second supraocular, fourth to sixth ones overlapping third supraocular, sixth and seventh ones overlapping fourth supraocular, eighth one overlapping upper pretemporal and upper postocular; two preoculars, upper one similar size to first supraciliary, overlapped by lower one, lower one three times larger than upper one, overlapping third supralabial and anterior presubocular; two presuboculars overlapped by third supralabial, anterior one overlapping posterior one, posterior one overlapping fourth supralabial; three postsuboculars, lower ones overlapping upper ones, lowermost one largest, overlapped by fourth supralabial, lowermost and middle ones overlapping fifth supralabial, middle and uppermost ones overlapping primary temporal, uppermost one overlapping lower postocular; two postoculars, upper one overlapping lower one (usually three postoculars, anterior one overlapped by uppermost postsubocular, overlapping upper and lower ones); two pretemporals, upper one overlapped by fourth supraocular and upper postocular, overlapping lower one and uppermost secondary temporal, lower one smaller than upper one, overlapped by upper and lower postoculars, overlapping first to third secondary temporals; temporals with similar shape and size of body scales; single primary temporal overlapped by lower postocular and fifth supralabial, overlapping sixth supralabial; four secondary temporals, uppermost one overlapped by ectoparietal, second one overlapped by uppermost one, third one overlapped by primary temporal, overlapping second one, lowermost one overlapped by primary temporal, third one and sixth supralabial, overlapping upper postlabial; six supralabials (no variation), anterior ones overlapping posterior ones, fourth and fifth ones largely interrupted by lower-anterior postsubocular, fifth one longest, third to fifth ones under eye; two postlabials overlapped by sixth supralabial, upper one overlapping lower one.

Mental wider than and as high as rostral, overlapping postmental and first infralabial; single postmental, right part enlarged relative to left part, overlapped by first infralabial, overlapping chinshields; six infralabials on left side (five on right side) (mode = 6, 5-6), anterior ones overlapping posterior ones, first one overlapping chinshield and postgenial, sixth one smallest; a pair of chinshields, separated from each other, left one enlarged toward right side, right one distorted and smaller than left one, overlapping postgenial; a postgenial only in left side, smaller than chinshields, overlapped by second infralabial, no right postgenial.

Ear opening with oval shape, no ear lobule; forelimbs with five short but distinct fingers, third one longest; third finger with two rows of supradigitals at base and seven subdigital scales (mode = 7, 5-7); 25 scale rows around midbody (mode = 26, 24-26); 61 pairs of dorsal median scales from posterior side of parietal to position of posterior margin of preanal (mode = 57, 53-62); usually three keels on a dorsal scale; hindlimbs with five short but distinct toes, fourth one longest; fourth toe with two rows of supradigitals at base and 13 subdigital scales (mode = 11, 10-14); 10 preanals, central ones with shorter length and similar width of midbody scales, overlapped by outer ones, right-central one overlapped by left-central one, outer ones small; subcaudal not enlarged; 15 scale rows around tail at 10th subcaudal position.

In alcohol, dorsal surface of head to tail light brown, first and second scale rows from dorsal median line with many blackish spots; no distinct blackish stripe on dorsal scale row (mode = 2, 0-3, N = 21); first scale row from dorsal median line on original tail with a pale blackish stripe; upper and lower eyelids whitish with blackish edge; blackish line on dorsolateral surface from snout to midbody interrupting dorsal and lateral sides, with narrower width of second supralabial on snout, interrupted by eye, with similar width of dorsolateral scale from eye to neck, 1.0-1.5 times as wide as dorsolateral scale at position above forelimb, gradually obscure from that position to midbody; upper margin of blackish line distinct from posterior corner of eye to midbody, located on middle position of scales on fourth scale row from dorsal median line; lateral surface of head to posterior position of forelimb whitish with small blackish spots; lateral surface of midbody to tail dark brown with small blackish spots; ventral surface of head to tail whitish, with a small number of blackish spots on head, small gray spots on midbody, rough blackish stripe on each trunk scale row around hindlimb including preanal scales, and a blackish spot on each subcaudal scale; forelimb and hindlimb light brown on dorsal surface and whitish on ventral surface with a blackish speckle on each scale row.

Variation.

Ateuchosaurus pellopleurus usually has a single SuNa with a concave posterior edge (248/299 specimens), but sometimes has a SuNa with a straight posterior margin (28/299 specimens) or two laterally separated SuNas (23/299 specimens).

This species usually has distinct FrNa and frontal, but sometimes these are fused (Table 1 ). The Takeshima and Iojima populations (sites 1 and 2) also show comparable frequencies for the separated and fused types.

This species has 8-14 TIVs (mode = 11) (Table 1 ). This character shows clinal geographic variation from northern to southern populations: 8-12 (mode = 10, sites 1-7), 10-12 (mode = 11, sites 8 and 9), 10-14 (mode = 11, sites 10 and 11), and 9-14 TIVs (mode = 12, sites 12 and 13).

The Amamioshima population has smaller MSRs, especially in males (mode = 24, 24-28 in males; mode = 26, 24-26 in females), than the other populations, which usually have 26 or 28 MSRs (mode = 26, 24-30 in males; mode = 26, 26-30 in females) with few sexual differences (Suppl. material 2).

Males have smaller DMSs (mode = 62, 53-70) than females (mode = 63, 56-69) (Suppl. material 3). This species usually has 2-3 pairs of DSRBS, but sometimes has no stripe on the dorsum or one pair of DSRBS.

The populations of the Osumi and Tokara Groups (sites 1-9), Kikaijima and Amamioshima Islands (sites 10 and 11), and Tokunoshima and Okinoerabujima Islands (sites 12 and 13) have different mitochondrial DNA (mtDNA) sequences ( Makino et al. 2020). The Osumi-Tokara populations have extremely low genetic diversity in the partial sequences of mtDNA and recombination activating gene 1 (RAG1) ( Makino et al. 2020).

Distribution.

Mishima (sites 1-3 in Fig. 1 ) of the Osumi Group, and the Tokara (sites 4-9 and surrounding islets) and Amami Groups (sites 10-13 and surrounding islets) of the Ryukyu Archipelago.

A skeletal remain, probably dating from the late 19th century, is known from Yoronjima Island (the island between sites 13 and 15) ( Nakamura et al. 2013), although it remains unknown whether the specimen represents this species or A. okinavensis .

Natural history.

This species occurs in leaf litter of grasslands and forest floors, including small vegetation around urban areas. Its reproductive season may range from May to August ( Okada et al. 1992).

This skink is more active on sunny days (56/75 specimens) than on cloudy (11/75 specimens) or rainy days (8/75 specimens). This species is usually seen in the daytime (10:03-17:52, 79/84 specimens) in spring to autumn, but is sometimes seen in the evening to nighttime (18:11-21:48, 5/84 specimens) on Takeshima, Iojima, Kodakarajima, Amamioshima, Tokunoshima and Okinoerabujima Islands (sites 1, 2, 8, and 11-13 in Fig. 1 ). It is found in warm microhabitats with temperatures of more than 20.0 °C (25.2 ± 2.5 °C, 20.8-30.2 °C, 84 specimens) (T.M., personal observation).

Conservation.

The island population of Iojima (site 2) is endangered by predation from the non-native Indian Peafowl Pavo cristatus Linnaeus, 1758, and the populations of Mishima (sites 1-3) are designated as Threatened Local Population (LP) in the Red Data Book of Japan ( Ota 2014).

Figures

Figure 1. Map of the geographic range of Ateuchosaurus pellopleurus and A. okinavensis in the Ryukyu Archipelago, and the sampling sites of the specimens examined in this study. A. The geographic location of the Ryukyu Archipelago; B. Sampling sites in the northern and central parts of the Ryukyu Archipelago. Each solid line indicates the geographic range of the Ateuchosaurus species revealed by Makino et al. (2020). Site numbers correspond to the locality numbers in Tables 1 - 2 and Suppl. materials 1 - 3.

Figure 3. Dorsal (A) and ventral (B) views of the lectotype of Ateuchosaurus pellopleurus (USNM 42110). These photographs were cited from the collection database of the Division of Amphibians and Reptiles in the National Museum of Natural History at the Smithsonian Institution (EZID of the dorsal view: http: // n 2 t. net / ark: / 65665 / m 3 c 86 ab 460 - 1 e 75 - 4 bb 1 - a 19 b- 89 e 8439 f 129 c, EZID of the ventral view: http: // n 2 t. net / ark: / 65665 / m 390991 fa 3 - b 108 - 4 c 49 - bdb 2 - a 4 e 443 ac 1 cfe).

Figure 4. Dorsal, lateral, and ventral views of head scalation of Ateuchosaurus pellopleurus (KUZ R 77703). CS, chinshield; EcP, ectoparietal; F, frontal; FrNa, frontonasal; FrP, frontoparietal; InLa, infralabial; IP, interparietal; Lo, loreal; M, mental; Na, nasal; P, parietal; PE, parietal eye; PoG, postgenial; PoLa, postlabial; PoM, postmental; PoO, postocular; PoSO, postsubocular; PrO, preocular; PrSO, presubocular; PrT, pretemporal; R, rostral; SuCi, supraciliary; SuLa, supralabial; SuLo, supraloreal; SuNa, supranasal; SuO, supraocular; T, temporal. The dashed line on the fused scale of Na and first SuLa in the lateral view indicates the line of a shallow groove on the scale.