Ateuchosaurus okinavensis (Thompson, 1912)

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 okinavensis (Thompson, 1912)

Figs 5 , 6 , 7 Suggested Japanese name: Okinawa-Hime-Tokage

Lygosaurus pellopleurus Hallowell, 1861: 496-497 (part); Stejneger 1907: 222-224 (part); 1927: 2; Van Denburgh 1912a: 7 (part); 1912b: 240-241 (part); Sclater 1950: 114.

Lygosoma pellopleurum : Boulenger 1887: 319; Okada 1891: 70.

Lygosoma (Homolepida) pellopleurus : Boettger 1895: 107.

Lygosoma okinavensis Thompson, 1912: 4.

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: 7 ("southern 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).

Holotype.

CAS 21537 collected from Nago, Okinawajima Island, Okinawa Group, Ryukyu Archipelago, Japan.

Material examined.

Japan • Okinawa Prefecture, Iheya Village, Iheyajima Island ; KUZ R55183 to 55185, 77521 to 77529, 77531 to 77533 • Okinawa Prefecture, Okinawajima Island ; KUZ R65611 , 66980 to 66982, 68039 to 68040, 69900, 70122 to 70123, 70125, 70130 to 70131, 70673 to 70674, 77442, 77445 to 77446, 77450 to 77454, 77458 to 77462, 77464, 77466 to 77467, 77470 to 77471, 77587, OMNH R745, 1143, 3061 to 3064 • Okinawa Prefecture, Motobu Town, Minnajima Island ; KUZ R77438 to 77440, 77574 to 77584 • Okinawa Prefecture, Uruma City, Miyagijima Island ; KUZ R70132 to 70133 • Okinawa Prefecture, Uruma City, Hamahigajima Island ; KUZ R70126 to 70128 • Okinawa Prefecture, Tokashiki Village, Tokashikijima Island ; KUZ R47122 to 47141, 47143, 70501 to 70503, 70505 to 70507, OMNH R1102, 1107 to 1108 • Okinawa Prefecture, Aguni Village, Agunijima Island ; KUZ R77623 to 77625, 77628 to 77632 • Okinawa Prefecture, Tonaki Village, Tonakijima Island ; KUZ R66983 • Okinawa Prefecture, Kumejima Town, Kumejima Island ; KUZ R70480 , 70483 to 70488, 70490 to 70491, 70496 to 70497, 70499 to 70500, OMNH R3065.

Emended diagnosis.

An Ateuchosaurus species characterized by the following: usually fused FrNa and frontal; 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 = 28, 25-28); 54-64 (mode = 59) and 55-67 DMSs (mode = 58) in male and female, respectively; 10-16 TIVs (mode = 13); 10 preanals not enlarged; usually no black stripe on dorsal scale row or one pair of DSRBS; a karyotype of 2 n = 28 ( Ota et al. 1998).

Comparison.

Ateuchosaurus okinavensis , together with A. pellopleurus , 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 also is distinguished from A. chinensis by the karyotype of 2 n = 28 (vs. 2 n = 26; no information about the karyotype of A. pellopleurus ; Ota et al. 1998). Ateuchosaurus okinavensis resembles A. pellopleurus in MSR and body size but differs in almost having a fused FrNa and frontal (vs. separated ones), 54-64 and 55-67 DMSs in male and female (vs. 53-70 and 56-69 DMSs in male and female), 10-16 TIVs (vs. 8-14 TIVs), usually 0-1 pair of DSRBS (vs. usually 2-3 pairs).

The mean K2P distance ± standard deviation (range in parenthesis) based on cytochrome b sequences between A. okinavensis and A. chinensis was 24.7% ± 0.3% (23.9%-25.5%); the value between A. okinavensis and A. pellopleurus , see Comparison of A. pellopleurus .

Description.

Mainly based on a specimen (KUZ R77462), an adult male collected from Ogimi Village in Okinawajima Island (26°41'44.88"N, 128°07'31.14"E, 111 m above sea level) (followed by ranges of several morphometric and meristic characters in parenthesis; N = 13 collected from Ogimi Village, KUZ R70673-70674, 77446, 77451-77454, 77458-77462, 77464); SVL 54.4 mm (55.0 ± 4.4, 49.8-64.8); HL 6.7 mm (6.3 ± 0.4, 5.7-7.0); HW 5.4 mm (5.5 ± 0.4, 5.1-6.1); HH 3.8 mm (3.8 ± 0.3, 3.3-4.4); SEyL 3.2 mm (3.1 ± 0.2, 2.8-3.4); EyL 2.3 mm (2.3 ± 0.2, 2.0-2.6); EyEaL 3.3 mm (3.0 ± 0.3, 2.6-3.3); EaD 1.0 mm (1.1 ± 0.1, 0.9-1.4); SAL 19.3 mm (19.2 ± 1.5, 16.7-21.8); AGL 31.1 mm (31.8 ± 2.8, 27.5-37.5); TaL 38.8 mm (the tip of tail lost; the remaining tail original; 61.4 ± 3.5, 57.6-64.5, N = 3 with undamaged original tail); FlL 8.5 mm (8.9 ± 0.9, 7.5-10.2, N = 12); HlL 14.3 mm (14.2 ± 1.0, 12.3-15.5); FIIIL 2.0 mm (1.9 ± 0.2, 1.6-2.3, N = 12); TIVL 4.4 mm (4.3 ± 0.4, 3.5-5.1).

Snout obtusely pointed; rostral visible from above, overlapping supranasal and nasal; nasal fused with first supralabial, with no groove on boundary between nasal and labial parts; nostril at center of nasal part of nasal; supranasal unpaired with posterior edge concaved, overlapped by nasal; supraloreal overlapped by supranasal and anterior and posterior loreals, overlapping frontonasal part and first supraciliary; frontonasal and frontal fused, frontonasal part overlapped by supranasal, overlapping first supraocular, frontal part overlapping frontoparietals and interparietal; no prefrontal; four supraoculars (no variation, N = 12), anterior ones overlapping posterior ones, first one overlapped by first, second and third supraciliaries, first and second ones overlapping frontal part, 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, a little longer and narrower than frontoparietal, overlapping parietals; ectoparietal pentagonal, shorter than and as wide as fourth supraocular, overlapped by fourth supraocular and upper pretemporal, overlapping parietal; parietals shorter and almost 1.2 times wider than interparietal, separated from each other by interparietal; no distinct nuchal.

Two loreals with a half length and similar height of second supralabial, anterior one overlapped by nasal, overlapping supranasal, posterior one and second supralabial, posterior one overlapped by second supralabial, overlapping first supraciliary and upper and lower preoculars; eight supraciliaries (mode = 8, 8-9), anterior ones overlapping posterior ones, first one overlapped by upper preocular, third and fourth ones overlapping second supraocular, fifth and sixth ones overlapping third supraocular, seventh one 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 larger than upper one, overlapped by second supralabial, overlapping third supralabial; two presuboculars, anterior one overlapped by lower preocular in left side (overlapped by third supralabial and lower preocular in right side), overlapping third supralabial and posterior one in left side (overlapping posterior one in right side), posterior one overlapped by third supralabial, 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 anterior and lower postoculars; three postoculars, anterior one overlapping upper and lower ones, upper one overlapping lower one; 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 scale; 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 and second one on left side (overlapped by primary temporal, overlapping second one on right side), 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 as wide as and lower than rostral, overlapping postmental and first infralabial; single postmental as long as and narrower than mental, overlapped by first infralabial, overlapping chinshields; six infralabials on left side (five on right side, mode = 6, 4-7), anterior ones overlapping posterior ones, first one overlapping chinshield, sixth one smallest; a pair of chinshields, separated from each other, smaller than postmental, overlapped by second infralabial, overlapping postgenial; a pair of postgenials, smaller than chinshields, overlapped by second and third infralabials.

Ear opening with oval shape, no ear lobule; forelimbs with five short but distinct fingers, third one longest; third finger with supradigital scales of single row at tip and two rows at base and eight subdigital scales (mode = 7, 7-8, N = 12); 25 scale rows around midbody (mode = 26, 25-28); 59 pairs of dorsal median scales from posterior side of parietal to position of posterior margin of preanal (mode = 56, 55-61); usually three keels on a dorsal scale; hindlimbs with five distinct toes, fourth one longest; fourth toe with three rows of supradigital scales at base and 14 subdigital scales (mode = 14, 13-16); 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, outermost ones small; subcaudal not enlarged; 18 scale rows around tail at 10th subcaudal position.

In alcohol, dorsal surface of head to tail light brown, first scale row from dorsal median line on midbody marginally darker with small blackish spots; no distinct blackish stripe on dorsal scale row (mode = 0, 0-1); 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 wider than dorsolateral scale at position above forelimb, 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 neck brownish white with many black spots; lateral surface of upper and lower jaws with several black spots; lateral surface around forelimb to tail dark brown; ventral surface pale yellow from head to tail, with many short stripes and spots irregularly scattered in head, black spots between hindlimb, and a pale black spot on each scale in tail; dorsal surface of forelimb dark brown with a rough blackish line on each scale row; ventral surface of forelimb pale yellow without blackish line; dorsal surface of hindlimb dark brown with a blackish line on each scale row; ventral surface of hindlimb pale yellow with a blackish dotted line on each scale row.

Variation.

For SuNa, this species usually shows a single scale with a concave posterior edge (84/104 specimens), and sometimes two laterally separated scales (1/104 specimens) or a single scale with an almost straight posterior edge (19/104 specimens).

This species usually has a long fused FrNa and frontal scale, but sometimes FrNa and frontal are distinct (Table 1 ; Ota et al. 1999).

In the Tokashikijima population, males have smaller DMSs (mode = 57, 54-61) than females (mode = 60, 56-62).

Mitochondrial DNA sequences differ among the four groups of Iheyajima and Izenajima Islands (site 14 and the adjacent island), the northern part of Okinawajima Island (site 15) and the adjacent islets (including site 16), the southern part of Okinawajima Island and the islands of the Kerama Group (site 19 and the adjacent islets), and Agunijima, Tonakijima, and Kumejima Islands (sites 20-22) ( Makino et al. 2020). The populations in the northern and southern parts of Okinawajima Island have different RAG1 allele compositions ( Makino et al. 2020).

Distribution.

Okinawa Group (sites 14-22 and surrounding islets in Fig. 1 ) of the Ryukyu Archipelago.

Natural history.

Ateuchosaurus okinavensis exhibits similar microhabitat use to A. pellopleurus . On Iheyajima, Okinawajima, Minnajima, Tokashikijima, Agunijima and Kumejima Islands (sites 14-16, 19, 20, and 22 in Fig. 1 ), A. okinavensis is usually seen in the daytime (6:53-17:54, 62/72 specimens) in spring to autumn (T.M., personal observation); however, it is sometimes also seen at night (18:06-23:18, 10/72 specimens). This species is found in warm microhabitats (28.6 ± 2.1 °C, 25.1-33.2 °C, 72 specimens), and is more frequently seen on sunny days (47/72 specimens) than on cloudy (15/72 specimens) or rainy days (10/72 specimens).

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 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.

Figure 5. Dorsal (a) and ventral (b) views of the holotype of Ateuchosaurus okinavensis (CAS 21537).

Figure 6. Dorsal, lateral, and ventral views of head scalation of Ateuchosaurus okinavensis (KUZ R 77462). See Fig. 4 legend for abbreviations of scale names.

Figure 7. Photograph of a live individual of Ateuchosaurus okinavensis collected at Urasoe Park in Urasoe City, Okinawajima Island (26 ° 15 ' 17.37 " N, 127 ° 43 ' 41.25 " E, 38 m above sea level).