Atractus major Boulenger, 1894

Schargel, Walter E., Lamar, William W., Passos, Paulo, Valencia, Jorge H., Cisneros-Heredia, Diego F. & Campbell, Jonathan A., 2013, A new giant Atractus (Serpentes: Dipsadidae) from Ecuador, with notes on some other large Amazonian congeners, Zootaxa 3721 (5), pp. 455-474 : 462-464

Atractus major Boulenger, 1894

Figs. 1 , 3 and 4

Rhabdosoma maculatum— Günther, 1859: 411 (in part).

Rhabdosoma badium— Jan 1862: 13 (in part); Jan & Sordelli 1865: Plate 1, Fig. 1

Atractus major Boulenger 1894: 307 ; Amaral 1930b: 61; Savage 1960: 47 (in part, see remarks. Lectotype designated); Roze 1961: 114, 1966: 84; Duellman 1978: 229 (in part, see remarks); Dixon & Soini 1986: 95; Pérez-Santos & Moreno 1991: 94 (in part, see remarks); Martins & Oliveira 1993: 28, 1999: 96; Silva Haad 2004: 435; Duellman 2005: 367; Esqueda & La Marca 2005: 7; Passos et al. 2010b: 76.

Atractus arangoi Prado 1939: 1 . Holotype: female, “ Colombia ” (MLS 136). Daniel 1949: 314 (distribution restricted to Puerto Asís). [new synonymy, see remarks]

Atractus badius (F. Boie) — Peréz-Santos & Moreno 1988: 68 (in part, pictures 17 and 18 on plate 10).

Lectotype and type locality. Juvenile male, BMNH 1946.9.7.27 (formerly BMNH 80.12.8.129; Fig. 4), collected by Buckley at locality of Canelos (01°36’S, 77°48’W; ca. 520 m), Province of Pastaza, Ecuador. The lectotype was designated by Savage (1960), restricting the type locality from eastern Ecuador to “Canelos, Ecuador.”

Diagnosis. A species of Atractus with 17 midbody dorsal scales rows, differing from all congeners by the following combination of characters: (1) large size, adults reaching almost 800 mm in TL; (2) loreal long (about three times longer than high); (3) generally seven (rarely six) supralabials with third and fourth in contact with eye; (4) generally seven (rarely six) infralabials with first three in contact with chinshields; (5) five to seven maxillary teeth, usually with a single postdiastemal teeth; (6) 163–185 ventral scales in females and 150–173 in males; (7) 27–37 subcaudal scales in females and 29–53 in males; (8) tail of moderate length: Tail/TL 9.4–12.5% in females and 11.6–18.8% in males; (9) dorsal color pattern consisting of dark brown blotches or bands edged by yellow or cream on a pale to medium brown ground color.

Comparisons. Atractus major is widely sympatric with A. snethlageae and these two species have been repeatedly confused with each other. In terms of color pattern A. major has brown crossbands which are darker than the background coloration and are also edged by yellow or cream. In A. snethlageae the crossbands are typically paler than the background coloration and are edged by black; less frequently the background color is pale brown with dark crossbands/blotches, but these are never edged by a different color as in A. major . When confusion persists, the best way to distinguish between the two species is examining the number of infralabials on each side in contact with the chinshields and the number of postdiastemal teeth (three infralabials contacting chinshields and a single postdiastemal tooth in A. major vs. four infralabials and two postsiastemal teeth in A. snethlageae ). With respect to other Amazonian species of Atractus having 17 dorsal scale rows, A. major is similar in aspects of color pattern and size to A. schach , and A. torquatus . Atractus major differs from A. torquatus by having blotches/ crossbands edged by a pale color (no pale edges on the bloches/crossbands in A. torquatus ) and having two postoculars (as opposed to one postocular). Atractus schach is sympatric with A. major in northcentral Amazonia but this species lacks pale edges on the dark dorsal blotches/crossbands and it also has four infralabials in contact with the chinshields and two postdiastemal teeth. Atractus natans is sympatric with A. major in western Amazonia and specimens of this species oftentimes have pale-edged dark blotches; however, A. natans is a much smaller species with adults rarely exceeding 400 mm in TL, which, as opposed to A. major , has a mostly dark (dark grayish brown to black) venter (mostly cream in A. major ) and four infralabials in contact with the chinshields.

Color pattern. The dorsal ground color is pale to medium brown or grayish brown, with irregular or ellipsoidal dark brown, primary blotches or crossbands narrowly edged by pale coloration, which can be pale brown, cream or yellow. The first dorsal blotch is usually elongated forming a short middorsal stripe on the neck, with separate, irregular blotches on the sides. The size, shape, extent on the lateral regions, and distance between the blotches/crossbands is variable but they generally expand longitudinally on the middorsal region. Typically the blotches/crossbands occupy a smaller area than the interspace between them, but the two specimens examined from Bolívar State, Guayana region of Venezuela, are notable exceptions in which the bands are at least twice as large as the interspace between them. In some specimens the blotches are in series of two and do not contact each other either because they do not reach the vertebral scale row (typical condition in specimens from Táchira, Venezuela) or, if they do, they do not coincide with each other. Most individuals also have smaller, irregular secondary blotches on the lower half of the sides. These secondary blotches are the same color as the primary blotches and might alternate with them or they might appear as broken continuations of the primary blotches on the sides. The first two scales rows are typically paler than the dorsal background coloration but they are often also overlaid with small, irregular dark spots and mottling. The head is usually darker than the dorsal background color. The venter is also variable in color pattern, but generally the background color is cream with brown spots and/or blotches. In some specimens the blotches are located contiguously across scales forming broken ventral stripes, in which case the most common pattern is a single midventral stripe.

Distribution. Amazon Rainforests of Ecuador, Colombia, Peru, Venezuela, and Brazil.

Remarks. Savage (1960) redescribed A. major based on a significant number of specimens from Ecuador; however, he erroneously included many specimens of A. snethlageae as A. major in his work. Color pattern D, and most likely color pattern E, as well as some of the specimens allocated to color pattern B, described by Savage (1960) for A. major , represent specimens of A. snethlageae . Duellman (1978) & Pérez-Santos & Moreno (1991) committed the same mistake apparently following Savage (1960); that is, their accounts for A. major include specimens of A. snethlageae . Moreover, the pictures referred as A. major in Duellman (1978), figure 138, page 229, and in Pérez-Santos & Moreno (1991), Photo 59, page 484, are indeed A. snethlageae . Duellman (2005) later realized his mistake and indicated that he had included specimens of A. flammigerus (= A. snethlageae ) in his earlier account of A. major in Amazonian Ecuador (Duellman 1978).

Prado (1939) described A. arangoi from Colombia without specifying the type locality. Daniel (1949) mentioned that this species is known from Puerto Asís, Department of Putumayo, southeastern Colombia. Prado (1939) only compared A. arangoi with A. major , which he indicated was related, but in his view A. arangoi differed in color pattern, having a smaller size, and fewer ventrals and subcaudals. However, all the putative diagnostic characters for A. arangoi fall within the variation in A. major as herein defined. The examination of the holotype of A. arangoi ( Fig. 5 ) by one of us (PP) has confirmed an agreement with A. major in all other examined morphological features that were not reported in the original description of the species. The holotype of A. arangoi is a female (MLS 136), 373 mm in TL, tail is 15.5% of TL. The variation is standard meristic characters is: 161 ventrals, two preventrals, three gulars separating chinshields from first preventral, 32 subcaudals, 6/7 supralabials, seven infralabials (first three in contact with chinshields), 6/5 maxillary teeth. The dorsal color pattern consists of 36 dorsal, pale bordered, dark brown blotches on the body and 10 on the tail. Based on all the evidence at hand we consider A. arangoi to be a junior synonym of A. major .

Figures

FIGURE 1. Specimens of large banded / blotched Atractus from the Amazon Basin grouped into three color pattern types (I: top row, II: middle, III: bottom). Extremes of variation within each color pattern type are shown.

FIGURE 3. Photographs of individuals in life of A. major (top left: Amazonas, Venezuela; top right: Bolívar, Venezuela; bottom left: Ecuador) and A. snethlageae (bottom right: Ecuador).

FIGURE 5. Holotype (MLS 136) of A. arangoi.