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Achalinus formosanus BOULENGER, 1908

IUCN Red List - Achalinus formosanus - Least Concern, LC

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Higher TaxaXenodermidae, Colubroidea, Caenophidia, Alethinophidia, Serpentes, Squamata (snakes)
SubspeciesAchalinus formosanus chigirai OTA & TOYAMA 1989
Achalinus formosanus formosanus BOULENGER 1908 
Common NamesE: Formosa Odd-scaled Snake 
SynonymAchalinus formosanus BOULENGER 1908: 222
Achalinopsis sauteri STEINDACHNER 1913: 219
Achalinopsis sauteri — ZONG & MA 1983
Achalinus formosanus — SHIE 2005
Achalinus formosanus — WALLACH et al. 2014: 5

Achalinus formosanus chigirai OTA & TOYAMA 1989
Achalinus formosanus chigirai — GORIS & MAEDA 2004: 203
Achalinus formosanus chigirai — O’SHEA 2018 
Distributionformosanus: Taiwan, Type locality: “Punkiho, Kagi district, Central Formosa”

chigirai: Japan (S Ryukyu islands); type locality: Uehara (altitude ca 70 m), Iriomotejima Island, Yaeyama Group, Japan.  
TypesSyntypes: BMNH 1946.1.7.78, NMW
Holotype: OMNH (Osaka) R2673, an adult male, collected on a road at night on 18 May 1985, by K. Miyagi. Paratype: OPM H0488, an adult male [chigirai] 
DiagnosisOriginal description (Achalinus formosanus): “Head small, once and two-thirds as lo1 g as broad rostral small, broader than deep, not visible from above ; suture between the internasals a little shorter than that between the prefrontals frontal slightly broader than long, three times as broad as the supraocular, about half as long as the parietals ; boreal nearly three times as long as deep; temporals 2 + 2, the upper anterior in contact with the eye; three shields bordering the parietals on each side; six upper labials, first very small, tourth and fifth entering the eve, sixth much elongate; two pairs of large chin-shields, immediately followed by the ventrals. Scales unicarinate, In 27 rows. Ventrals 173; anal entire subcaudals 64. Blackish above, the outer scales pale in the centre labial, ventral, and caudal shields yellowish white, edged with blackish. Total length 560 mm. tail 140. A single female specimen, obtained at Punkiho, Kagi district, Central Formosa, by Dr. A. Moltrecht.” (Boulenger 1908)

Original description (Achalinopsis sauteri): “Kopf verlängert, schmal. Supralabialia 6, das vorderste sehr klein, das letzte sehr groß, auffallend lang, das 4. und 5. an das Auge stoßend. Frontale klein, breiter als lang und nur halb. so lang wie die Parietalia. 3 Infralabialia begrenzen das vordere Kinnschildpaar, welches etwas kürzer und schmäler als das hintere Kinnschildpaar ist, auf welches unmittelbar wie bei Achalinus ein breites Ventrale folgt. Seiten des Rumpfes olivengrün bis grauviolett (bei Wein geistexemplaren), in der Mitte der Schuppen der 3 bis 4 untersten Längsreihen ein helleres, verschwommenes Fleckchen. V. 176 bis 184. Subc. 62 bis 70. Schuppen in 27 Längs reihen, gewölbt und gekielt.” (Steindachner 1913)

Diagnosis (formosanus). Loreal usually fused with, but rarely separated from prefrontal; dorsal scales of body and tail with outermost row strongly keeled; midbody scale rows 27; subcaudals 61-83. (Ota & Toyama 1989)

Description of holotype (formosanus). Head only slightly broader than neck; rostral triangular, one and a half times as broad as high, not exposed to upper side; snout short, but projecting beyond lower jaw; internasal small, rectangular, one and a half times as long as broad; suture between prefrontals as long as that between internasals, and about one and a half times as long as suture between prefrontal and internasal; a suture from anterior margin of supraocular to posterior margin of nasal separating loreal and prefrontal on right side (Fig. 2A); left side, such suture lacking and an aberrant wrinkle-like suture originating from anterior margin of eye extending forward, but reaching only halfway (Fig. 2B); frontal pentagonal, slightly broader than long; parietal nearly twice as long as broad, contacted posterolaterally by an enlarged paraparietal; suture between parietals as long as distance between eyes, and much longer than frontal; supraocular small, one and a half times longer than broad; temporal 2 + 2 on both sides, upper one of anterior row intervening between lower one and parietal; supralabials six, fourth and fifth in contact with eye, sixth largest; maxillary teeth 17; infralabials seven on left and six on right sides, first one intervening between mental and first postmental; postmentals paired, in two rows; ventrals 173; anal entire; subcaudals 65, entire; dorsal scales on body and tail including outermost row strongly keeled; alteration pattern of dorsal scales on body: 29[(5+6 = 5(4)]/[5+6=5(4)]27[5+6=(155)]/[5+6=5(168)]25 scales of an outermost row not much enlarged when compared with adjacent scales in postcloacal region. (Ota & Toyama 1989)

Measurements (formosanus, in mm).-SVL 717; tail length 136; snout to anterior margin of eye 6.3; diameter of eye 1.9; sutures between internasals 3.5, prefrontals 3.4, parietals 6.7; frontal length 4.0, breadth 4.5; parietal length 9.6, breadth 5.0. (Ota & Toyama 1989)

Color in ethanol (formosanus). Dorsal ground color grayish tan, with a dark longitudinal line on middorsal row of scales on body and tail; ventral ground color light yellowish gray, slightly darker on tail than on body. (Ota & Toyama 1989)

Variation (formosanus). Range of variation in each character is presented in Table 1. The other examined specimen of this subspecies (NSMT H02566) was collected from Alishan, Cha-I Prefecture (Fig. 1b) and exhibits alteration of dorsal scale rows to be formulated as: [see formula in paper] The other known specimens (n = 8), identified as Achalinopsis sauteri by Steindachner (1913) and Maki (1931), lack sutures separating loreals from prefrontals. (Ota & Toyama 1989)

Diagnosis (chigirai). Loreal fused to prefrontal; dorsal scales of body and tail with outermost row strongly keeled; 25-27 scale rows at midbody; subcaudal count greater than that in the nominal subspecies, 96-97 for the types. (Ota & Toyama 1989)

Description of holotype (chigirai). The holotype of A. f. chigirai shows several character states similar to those in the type of the nominal subspecies, from which it differs in the following characteristics; rostral twice as broad as high; loreal wholly fused to prefrontal on both sides; suture between prefrontals same length as that between prefrontal and internasal, and slightly shorter than suture between internasals; frontal pentagonal, as long as broad; parietal more than twice as long as broad; suture between parietals slightly longer than frontal; supraocular small, twice as long as broad; lower temporal of anterior row in contact with parietal behind upper one; maxillary teeth 14; infralabials six on left, five on right side; ventrals 167; subcaudals 96; alteration pattern of dorsals on body: [see formula in paper] (Ota & Toyama 1989)

Measurements (chigirai, in mm). -SVL 252; tail 117; snouteye 3.0; eye 0.9; sutures between internasals 1.7; prefrontals 1.4; parietals 3.2; frontal length and breadth 3.0; parietal length 5.2, breadth 2.3. (Ota & Toyama 1989)

Color in ethanol (chigirai). Dorsal ground color dark gray, with a darker longitudinal line on middorsal row of scales on body and tail; ventral coloration similar to that in the type of A. f. formosanus. (Ota & Toyama 1989)

Variation (chigirai). Range of variation for each character is presented in Table 1. The paratype exhibited alteration in dorsal scale rows as: [see formula in paper] whereas NSMT H04011 showed invariably 25 rows throughout the body. (Ota & Toyama 1989) 
CommentConservation: A. f. chigirai is classified as “near threatened” in Japan (Ota 2000). 
EtymologyNamed after its distribution in Taiwan (= Formosa). 
  • Boulenger, GEORGE A. 1908. Description of a new frog and a new snake from Formosa. Ann. Mag. Nat. Hist. (8) 2: 221-222 - get paper here
  • Chen, Y. 2009. Conservation biogeography of the snake family Colubridae of China. North-Western Journal of Zoology 5 (2): 251-262 - get paper here
  • FUKUYAMA, RYOBU & IBUKI FUKUYAMA. 2021. ACHALINUS FORMOSANUS CHIGIRAI (Yaeyama Odd-scaled Snake). DEFENSIVE BEHAVIOR and DIET. Herpetological Review 52 (1): 144–145. - get paper here
  • Gemel, R.; G. Gassner & S. Schweiger 2019. Katalog der Typen der Herpetologischen Sammlung des Naturhistorischen Museums Wien – 2018. Ann. Naturhist. Mus. Wien, B 121: 33–248
  • Goris, R.C. & Maeda, N. 2004. Guide to the Amphibians and Reptiles of Japan. Krieger, Malabar, 285 pp.
  • LI, K., WU, Y. Y., XU, R. Y., ZHU, F., REN, J. L., GUO, P., & DONG, B. J. 2021. A new species of the Achalinus rufescens complex (Xenodermidae: Achalinus) from Fujian Province, China. Zootaxa 5026 (2): 239-254 - get paper here
  • Ota, H. 2000. Current status of the threatened amphibians and reptiles of Japan. Popul. Ecol. 42: 5-9 - get paper here
  • Ota, H. and Toyama, M. 1989. Two additional specimens of Achalinus formosanus chigirai (Colubridae: Ophidia) from the Yaeyama Group, Ryukyu Archipelago. Japanese Journal of Herpetology 13 (2): 40-43 - get paper here
  • Ota, H. and Toyama, M. 1989. Taxonomic re-definition of Achalinus formosanus Boulenger (Xenoderminae: Colubridae: Ophidia), with description of a new subspecies. Copeia 1989 (3): 597-602 - get paper here
  • O’Shea, M. 2018. The Book of Snakes. Ivy Press / Quarto Publishing, London, - get paper here
  • Shie, Jia-Rung 2005. Phylogeography of Odd-scaled Snake Achalinus in Taiwan. Masters thesis, National Sun Yat-sen University, 53 pp.
  • Steindachner, F. 1913. Über zwei neue Schlangenarten aus Formosa. Anz. Kaiserl. Akad. Wiss. Wien, Math.-Nat. Ser. 50: 218-220
  • Stejneger, L. 1910. The batrachians and reptiles of Formosa. Proc. US Natl. Mus. 38: 91-114 - get paper here
  • Wallach, Van; Kenneth L. Williams , Jeff Boundy 2014. Snakes of the World: A Catalogue of Living and Extinct Species. [type catalogue] Taylor and Francis, CRC Press, 1237 pp.
  • Zhao, E.M. 2006. The snakes of China [in Chinese]. Hefei, China, Anhui Sience & Technology Publ. House, Vol. I, 372 pp., Vol. II (color plates), 280 pp.
  • ZIEGLER, THOMAS; TRUONG QUANG NGUYEN, CUONG THE PHAM, TAO THIEN NGUYEN, ANH VAN PHAM, MONA VAN SCHINGEN, THAM THI NGUYEN, MINH DUC LE 2019. Three new species of the snake genus Achalinus from Vietnam (Squamata: Xenodermatidae). Zootaxa 4590 (2): 249-269 - get paper here
  • Zong Y; Ma J 1983. A new species of the genus Achalinopsis from Jiangxi and the restoration of this genus [in Chinese]. Acta Herpetologica Sinica 2 (2): 61-63 - get paper here
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