Pachacamac Ground Snake

description

Atractus major Boulenger — Savage 1960: 47 (in part, see remarks); Duellman 1978: 229 (in part, see remarks); Pérez-Santos & Moreno 1991: 94 (in part, see remarks) Atractus sp. B — Dixon & Soini 1977: 37. Atractus flammigerus (F. Boie) — Hoogmoed 1980: 20 (in part, specimen from Peru); Dixon & Soini 1986: 93; Duellman & Salas 1991: 9; Duellman 2005: 366. Atractus flammigerus snethlageae Cunha & Nascimento 1983: 19. Atractus snethlageae — Vanzolini 1986: 25; Martins & Oliveira 1993: 34; Martins & Oliveira 1999: 97; Giraudo & Scrocchi 2000: 82.

A new giant Atractus (Serpentes: Dipsadidae) from Ecuador, with notes on some other large Amazonian congeners

description

Color pattern. Two different color pattern types occur in this species with considerable variation within them. The most common pattern (pattern II in statistical analyses) consists of a dark brown or dark grayish brown ground coloration with cream or buff yellow dorsal crossbands that extend down to the second or third dorsal scale row on the sides. The dorsal bands typically expand longitudinally into one or two dorsal scales and are edged by black, but in some specimens the bands are irregular and form blotches that may expand longitudinally more than two dorsal scales. Rarely the black edges are inconspicuous. The crossbands may be complete across the dorsum, interrupted in the vertebral region or alternating on the sides. The interspace between crossbands is longer than the crossbands themselves, encompassing two to seven dorsal scales but with variation within individuals. The first two dorsal scales have an irregular pattern of dark and pale mottling and solid cream spots might also be present at that level. A large white or cream nuchal band is present in juveniles and small adults but gradually darkens and disappears as individuals get larger. In adults the top of the head

A new giant Atractus (Serpentes: Dipsadidae) from Ecuador, with notes on some other large Amazonian congeners

diagnosis

Diagnosis. A species of Atractus with 17 dorsal scales rows, differing from all congeners by the following combination of characters: (1) large size, adults reaching about 700 mm in TL; (2) loreal long (about three times longer than high); (3) generally seven (rarely eight) supralabials with third and fourth (fourth and fifth whenever eight supralabials are present) in contact with eye; (4) generally eight (rarely seven) infralabials with first four in contact with chinshields; (5) six to seven maxillary teeth; (6) 151 – 180 ventral scales in females and 137 – 165 in males; (7) 19 – 28 subcaudal scales in females and 27 – 45 in females; (8) tail of moderate length: Tail / TL 6.9 – 17.6 %; (9) dorsal color pattern of dark gray / brown ground coloration with pale crossbands or blotches usually edged in black, or dorsal ground color pale brown with dark brown or black blotches. Comparisons. The comparisons and confusions in the literature involving A. snethlageae and A. major are discussed in the previous species account and will not be repeated here. With respect to Amazonian species with 17 dorsal scales, the frequent color morph of A. snethlageae is rather unique in having well-def

A new giant Atractus (Serpentes: Dipsadidae) from Ecuador, with notes on some other large Amazonian congeners

discussion

Remarks. As stated above, A. snethlageae has been repeatedly confused with A. major in Ecuador (e. g. Savage 1960; Duellman 1978; Pérez-Santos & Moreno 1991). We think that part of this confusion stems from the great amount of intraspecific color pattern variation in A. snethlageae, especially the fact that two distinct color morphs are found in this species, one of which (pattern III in this study) is similar in general aspects to the color pattern observed in A. major. Discrete polymorphism in color pattern as documented here for A. snethlageae, although rare in snakes, has been found in other species of Atractus (Fajardo 2000; Passos & Prudente 2012; Schargel, unpublished observations) and will likely become a more common observation as we obtain larger samples of poorly known species and a better understanding of the taxonomy of the genus. The name A. badius has also been used for specimens of A. snethlageae from Argentina, Bolivia, Brazil, Ecuador and Peru in the literature or on a significant number of museum specimens that we have examined. This has been the case in the literature (e. g. Carrillo & Icochea 1995; Doan & Arizábal 2000) even after Hoogmoed (1980) had redescribe

A new giant Atractus (Serpentes: Dipsadidae) from Ecuador, with notes on some other large Amazonian congeners