Atractus paucidens Despax, 1910

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 : 24-26

Atractus paucidens Despax, 1910

Fig. 16

Atractus (Atractopsis) paucidens Despax, 1910 ; Bull. Mus. Hist. Nat. Paris 16:372. Atractus paucidens— Savage, 1960; Misc. Pub. Mus. Zool. U. Michigan 112:62.

Holotype: Adult female, housed at Musée National d’Histoire Naturelle ( MNHN 1906.245), from Santo Domingo de Los Colorados (00º15’S, 79º09’W, ca. 600 m), province of Pichincha, Ecuador (photographs examined).

Diagnosis: Atractus paucidens is distinguished from all congeners by the following combination of characters: (1) 17/17/17 smooth dorsals; (2) two postoculars; (3) loreal long; (4) temporals generally 1+2; (5) generally seven supralabials, third and fourth contacting orbit; (6) seven infralabials, first four contacting chinshields; (7) five or six maxillary teeth; (8) generally four gular scale rows; (9) four preventrals; (10) 169– 190 ventrals in females, 169–175 in males; (11) 31–38 subcaudals in females, 43–45 in males; (12) dorsal ground colour black with narrow cream bands on the flanks; (13) venter beige, heavily scattered with black dots to uniformly black; (14) moderate body size in females 419 mm SVL and small in males 263 mm SVL; (15) tail long in females (15.1–16.0% SVL) and males (18.6–21.3% SVL); (16) hemipenis moderately bilobed.

Comparisons: Among all congeners, Atractus paucidens shares the occasional occurrence of preoculars and long tail length in both sexes only with A. favae . Atractus paucidens differs from A. favae in having the first pair of infralabials preventing symphisial/chinshields contact, loreal long, 31–38 subcaudals in females and 43–45 in males, tail 15.1–16.0% SVL in females and 18.6–21.3% in males (vs. symphisial/chinshield contact, short loreal, 66 subcaudals in female and 57–67 in males, tail 33.5% SVL in females and 40.2% in male).

Description: Head twice as long as wide, arched in lateral view, rounded in dorsal view; snout truncate in lateral view, rounded in dorsal view; cervical constriction indistinct; rostral subtriangular in frontal view, broader than high, little visible in dorsal view; internasal as long as wide; internasal suture sinistral with respect to prefrontal suture; prefrontal as long as wide; supraocular sub-trapezoidal, slightly longer than wide; frontal sub-triangular, as long as wide; parietal twice as long as wide; nasal divided; nostril located between prenasal and postnasal; prenasal about three times as high as long; postnasal smaller than prenasal, about twice as high as long; loreal long, contacting second and third supralabials; small preocular (as long as high) ocasionally present, preventing orbit/loreal contact; pupil subelliptical; two postoculars; upper postocular slightly longer than lower and lower slightly higher than upper postocular; temporals 1+2; first temporal twice as long as high; upper posterior temporal elongate, four times as long as wide; generally seven supralabials, third and forth contacting orbit; second and third supralabials of similar size and slightly higher than first; sixth higher and seventh longer than remaining supralabials; symphisial semicircular, twice as broad as long; generally seven infralabials, first four contacting chinshields; first pair of infralabials in contact behind symphisial, preventing symphisial/chinshields contact; chinshields three or four times as long as wide; generally four gular scale rows; generally four preventrals; 17/17/17 smooth dorsal scale rows; dorsals lacking apical pits, supra-anal tubercles, and kells; caudal spine moderated, conical, and rhomboid.

Maxillary arch: Arched in dorsal view with three or four prediastemal and two postdiastemal teeth; prediastemal teeth large, of similar size, curved posteriorly, well spaced, angular in cross section, robust at base, and narrower at apices; long maxillary diastema; postdiastemal teeth half size of the last prediastemal tooth; lateral process of maxillar well developed, lacking posterior projection.

Colour in preservative: Dorsum of head uniformly dark brown; temporal region slightly lighter (brown); background of head dark brown to middle of supralabials; temporal region and posterior portion of seventh supralabial creamish yellow; ventral edge of supralabials and proximal margin of infralabials cream; proximal region of infralabials and anterior portion of chinshields dark brown; gular region and preventrals predominantly beige, occasionally with disperse dark brown spots; anterior region of belly with diffuse dark brown spots; mid region to posterior third of venter uniformly black; tail uniformly black; dorsal ground colour of body black, with five to seven rounded lateral beige blotches restricted to anterior region of body; blotches (two or three scales long and five or six scales wide) reaching paraventral region not in contact with opposite blotches on vertebral line; blotches gradually darker posteriorly; black interspaces between light blotches five or six scales long.

Variation: Largest male 263 mm SVL, 49 mm CL; largest female 412 mm SVL, tail amputated; tail 18.6– 21.3% (x¯ = 20.2; SD = 1.4; n = 3) SVL in males and 15.1–16.0% (x¯ = 15.5; SD = 0.4; n = 3) in females; 169– 175 (x¯ = 170.7; SD = 3.1; n = 3) ventrals in males, 169–190 (x¯ = 182.7; SD = 9.3; n = 4) in females; 43–45 (x¯ = 44.3; SD = 0.7; n = 4) subcaudals in males, 31–38 (x¯ = 35.3; SD = 3.8; n = 3) in females; 6 (n = 3 sides) or 7 (n = 11 sides) infralabials; 1+1 (n = 2 sides), 0+2 (n = 1 side) or 1+2 (n = 11 sides); 6 (n = 2 sides) or 7 (n = 10 sides) infralabials; 2 (n = 1 side), 3 (n = 3 sides) or 4 (n = 6 sides); 3 (n = 1) or 4 (n = 4) preventrals; preoculars absent (n = 11) or present (n = 5); 8 (n = 7 sides) or 9 (n = 3 sides) dorsal scale rows at the level of second subcaudal; 5 (n = 4 side) or 6 (n = 5 side) maxillary teeth; retracted hemipenis bifurcates from fifth to tenth and extends from 10th to 11th subcaudal (n = 2).

Distribution: Pacific coast of Ecuador from the mouth of the Pitzara River (02º00’N, 79º09’W) to Santo Domingo de Los Colorados (00º15’S, 79º09’W) in the province of Pichincha. Atractus paucidens inhabits rainforest at elevations of 200–600 m ( Fig. 6 ).

Remarks: Despax (1910) described Atractus (Atractopsis) paucidens , new subgenus and species distinguishing it from remaining Atractus by having a reduced maxillary bone with only four large teeth decreasing in size posteriorly. In a subsequent paper, Despaux (1911) figured the maxilla of Atractopsis paucidens . Savage (1960) did not recognize Atractopsis, pointing out that the maxilla illustrated by Despax (1911) was apparently broken and for that reason lacked posterior teeth. Savage (1960) advocated that this taxon was concordant with other Atractus species with regard to maxillary dentition and also agreed in other morphological features, and therefore allocated it tentatively to the A. trilineatus species group. Savage (1960) reported the second individual of A. paucidens from Pitzara River at province of Pichincha. We report herein seven (four males and three females) additional A. paucidens , all topotypes. Although the study of maxillary bones of these specimens does not corroborate Savage’s suspicion of a broken element (the species displays low number of maxillary teeth, see above), there is no reason to recognize the subgenus Atractopsis according to the actual Atractus concept (sensu Savage 1960). Furthermore, as suggested by Savage (1960), A. paucidens shows great morphological similarity to other Atractus from Pacific coast of Ecuador and Colombia (see discussion).

Figures

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

FIGURE 16. Dorsal (A) and ventral (B) views of Atractus paucidens (MZUSP 7703). SVL 263 mm, CL 49 mm.