Dark Ground Snake

description

Description: Head twice as long as wide, flattened in lateral view, rounded in dorsal view; snout slightly acuminate in lateral view, rounded in dorsal view; cervical constriction barely distinct; rostral subtriangular in frontal view, slightly broader than high, clearly visible in dorsal view; internasal longer than wide; internasal suture sinistral with respect to prefrontal suture; prefrontal longer than wide; supraocular sub-rectangular, about twice as long as wide; frontal subtriangular, as long as wide; parietal twice as long as wide; nasal divided; nostril restricted to prenasal; prenasal twice as high as long; postnasal as high as prenasal, slightly higher than long; loreal long, contacting second and third supralabials; pupil round; two postoculars of similar size; temporals 1 + 2; anterior temporal twice as long as high; upper posterior temporal occasionally elongate, six times longer than wide; seven supralabials, third and fourth contacting orbit; second supralabial higher than first and as high as third; sixth higher and seventh longer than remaining supralabials; symphisial semicircular, twice as broad as long, contacting chinshields posteriorly; six or seven infralab

Pacific lowland snakes of the genus Atractus (Serpentes: Dipsadidae), with description of three new species

diagnosis

Diagnosis: Atractus melas is distinguished from all congeners by the following combination of characters: (1) 17 / 17 / 17 smoooth dorsal scale rows; (2) two postoculars; (3) loreal long; (4) temporals 1 + 2; (5) seven supralabials, third and fourth contacting orbit; (6) seven infralabials, first four contacting chinshields; (7) six or seven maxillary teeth; (8) four gular scale rows; (9) four or five preventrals; (10) 144 ventrals in the single known female, 134 – 140 in males; (11) 25 subcaudals in female, 33 – 34 in males; (12) dorsum uniformly black; (13) venter uniformly black; (14) small body size, female with 205 mm SVL, males reaching 194 mm SVL; (15) long tail in female (17.1 % of SVL) and males (18.5 – 19.1 % of SVL); (16) hemipenis moderately bilobed. Comparisons: Atractus melas differs from all currently recognized Atractus in having a uniformly black dorsum and venter, without any invasion of light pigment.

Pacific lowland snakes of the genus Atractus (Serpentes: Dipsadidae), with description of three new species

discussion

Remarks: Boulenger (1908) described A. melas on the basis of a single specimen. Prado (1940) cited another individual of A. melas from the MLS collection but did not provide a collection number or voucher specimen data (it is likely that one of our specimens represent Prado’s individual from MLS, but the original catalogue number at MLS has been changed). No additional records for this species have been reported. This species is herein reported from two new specimens obtained in different localities in the Pacific coast of Colombia, extending the species range 300 km north of Juntas (Fig. 6). Additinally, another specimen of A. melas (not collected) from Buenaventura, department of Chocó, Colombia was examined indirectly via photographs taken in life. Despite A. melas having a very particular colour pattern, it is similar in several respects to A. iridescens. The two species share several features: 130 – 140 ventrals in males, 135 – 145 in females; 30 – 40 subcaudals in males, 25 in females; generally seven supralabials; first four infralabials contacting chinshields; six or seven large and well spaced maxillary teeth; long tail in males and females. Nonetheless, A. melas has a sym

Pacific lowland snakes of the genus Atractus (Serpentes: Dipsadidae), with description of three new species

distribution

Distribution: Pacific region of Colombia from corregimiento de Guayabal (05 º 44 ’ N, 76 º 38 ’ W) in the department of Chocó to Municipality of Juntas (03 º 46 ’ N, 76 º 45 ’ W) in the department of Valle del Cauca. Atractus melas inhabits rainforest at elevations of 80 – 300 m (Fig. 6).

Pacific lowland snakes of the genus Atractus (Serpentes: Dipsadidae), with description of three new species