Atractus melas Boulenger, 1908

Passos, Paulo, Mueses-Cisneros, Jonh Jairo, Lynch, John D. & Fernandes, Ronaldo, 2009, Pacific lowland snakes of the genus Atractus (Serpentes: Dipsadidae), with description of three new species, Zootaxa 2293, pp. 1-34 : 18-19

Atractus melas Boulenger, 1908

Fig. 12

Atractus melas Boulenger, 1908 ; Ann. Mag. Nat. Hist. 8(1):114. Atractus melas Prado, 1940 ; Mem. Inst. Butantan 12:15.

Holotype: Adult female, NHM 1946.1.6.33 (formerly 1908.5.29.54), from Los Mangos (= Juntas, 03º46’N, 76º45’W, ca. 300 m), department of Valle del Cauca, Colombia, collected by Palmer (specimen examined).

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.

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 infralabials, first four contacting chinshields; chinshields four times longer than wide; four gular scale rows; three to five preventrals; 17/17/17 smooth dorsal scale rows; dorsals lacking apical pits, supra-anal tubercles, and keels; eight dorsal scale rows in the level of second subcaudal; caudal spine long, conical, and acuminated.

Maxillary arch: Arched in dorsal view, with five or six prediastemal and one or two postdiastemal teeth; prediastemal teeth large, similar in size, curved posteriorly, angular in cross section, robust at base, and narrower at apices; first four teeth moderately spaced, fifth tooth more widely spaced from these and postdiastemal teeth; maxillary diastema short; postdiastemal teeth half size of last prediastemal tooth; lateral process poorly developed, lacking posterior projection.

Colour in preservative: Dorsum and belly uniformly black; occasionaly there is a weakly indicated dark brown blotch in the nuchal region (evident only through alcohol immersion).

Variation: Largest male 184 mm SVL, 34 mm CL; largest female 205 mm SVL, 25 mm CL; tail 18.5– 19.1% (n = 2) SVL in males, 17.1% SVL in female; 134–140 ventrals in males (n = 2), 144 in female; subcaudals 33–34 (n = 2) in males, 25 in female; 6 (n = 2 sides) or 7 (n = 4 sides) infralabials; 3 (n = 1), 4 (n = 1) or 5 (n = 1) preventrals; 4.0– 4.2 mm body diameter; 6 (n = 1 side) or 7 (n = 3 sides) maxillary teeth; retracted hemipenis extends to 14th subcaudal (n = 1).

Distribution: Pacific region of Colombia from corregimiento de Guayabal (05º44’N, 76º38’W) in the department of Chocó to Municipality of Juntas (03º46’N, 76º45’W) in the department of Valle del Cauca. Atractus melas inhabits rainforest at elevations of 80–300 m ( Fig. 6 ).

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 symphisial scale in contact with chinshields (vs. first pair of infralabials preventing symphisial/chinshields contact in A. iridescens ). Elsewhere in the entire genus, the only species consistently having symphisial/chinshield contact is the Guianan A. favae (Passos 2008) .

Figures

FIGURE 6. Geographical distribution of the Atractus paucidens species group.

FIGURE 12. Dorsal (A) and ventral (B) views of Atractus melas (IV-C 8533). SVL 184 mm CL 34 mm.