Atractus iridescens Peracca, 1896

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 : 11-15

Atractus iridescens Peracca, 1896

Figs. 7 , 8

Atractus iridescens Peracca, 1896 ; Boll. Mus. Zool. Anat. Comp. Torino 252:2. Atractus iridescens — Boulenger, 1913; Proc. Zool. Soc. London 4:1035.

Holotype: Adult male, from “ América Meridionali” (= South America) originally deposited at Museo di Zoologia dell’ Università degli Studi di Torino, Turin MZUT R1830, now housed at Museo Regionali di Scienze Naturali, Turin ( Andreone & Gavetti 2007), (photographs examined).

Diagnosis: Atractus iridescens is distinguished from all congeners by combination of the following characters: (1) 17/17/17 smooth 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 three or four contacting chinshields; (7) six or seven maxillary teeth; (8) generally four gular scale rows; (9) three preventrals; (10) 135–144 ventrals in females, 135–150 in males; (11) 25–37 subcaudals in females, 33–38 in males; (12) dorsum reddish brown scattered with small and irregular dark blotches; (13) venter beige with a median line comprised of small black dots; (14) moderate body size, single subadult female with 170 mm SVL, males reaching 353 mm SVL; (15) long tail in females (16.4–17.6% SVL) and males (14.2–18.9% SVL); (16) hemipenis moderately bilobed, slightly semicapitate, and non-calyculate.

Comparisons: Atractus iridescens is distinguished from all congeners, except A. typhon by having a lateral projection on the base of the hemipenis. Atractus iridescens differs from A. typhon by having 17 dorsal scale rows at midbody, 135–150 ventrals in males, dorsum with irregular dark blotches, venter with median black stripe (vs. 15 dorsals, 156–163 ventrals, banded dorsum, venter with quadriculate dark bars).

Additionally, A. iridescens shares only with A. echidna (hemipenis unknown) 36 subcaudals in males, three preventrals, six to eight maxillary teeth, dorsum brown with irregular dark blotches. Atractus iridescens is distinguished from A. echidna by having 17 dorsal scale rows, 135–150 ventrals in males, venter with a median black stripe anteriorly and entirely black posteriorly (vs. 15 dorsals, 127 ventrals in the single male, venter cream with irregular brown spots posteriorly); from A. boulengerii , A. clarki , and A. multicinctus by having venter heavily marked with black dots, sometimes concentrated on the center of each ventral scale forming a conspicuous midline (vs. venter immaculate creamish white, occasionally with a few disperse black dots posteriorly in A. clarki ).

Description: Head about twice as long as wide, flattened 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, poorly visible in dorsal view; internasal as long as wide; internasal suture linear or sinistral with respect to prefrontal suture; prefrontal as long as wide; supraocular sub-trapezoidal, about twice as long as wide; frontal sub-triangular, as long as wide; parietal about twice as long as wide; nasal divided; nostril restricted to prenasal; prenasal twice as high as long; postnasal as high as long; loreal long, contacting second and third supralabials; pupil round; two postoculars; upper postocular slightly higher and longer than lower; temporals 1+2; first temporal twice as long as high; upper posterior temporal elongate, three times longer than wide; seven supralabials, third and fourth contacting orbit; first two supralabials of similar size and smaller than third; sixth higher and seventh longer than remaining supralabials; symphisial semicircular, about three times broader than long; seven infralabials, first three or four contacting chinshields; first pair of infralabials in contact behind symphisial, preventing symphisial/chinshields contact; chinshields about three times longer than wide; four gular scales rows; three or four preventrals; generally 17/17/17 smooth dorsal scale rows; dorsals lacking apical pits, supra-anal tubercles, and keels; caudal spine moderate, conical, and acuminated.

Maxillary arch: Arched in dorsal view, with four or five prediastemal and two postdiastemal teeth; prediastemal teeth large, moderately spaced, of similar size, curved posteriorly, angular in cross section, robust at base, narower at apices; maxillary diastema moderately long; postdiastemal teeth half size of the last prediastemal tooth; lateral process absent.

Colour in preservative: Dorsum of head reddish brown, occasionally with small beige spots at the orbital region; head background reddish brown to dorsal margin of supralabials, except for black postorbital and creamy temporal stripes; temporal region and posterior portion of seventh supralabial creamish white, forming lower portion of temporal stripe; supralabials mostly cream, with invasion of brown pigment on posterior suture of supralabials; fifth and sixth supralabials predominantly dark brown, constituting the descending portion of postocular stripe; infralabials, chinshields, gulars, and preventrals creamish white with diffuse dark brown dots; ventral ground colour beige with three series of dark brown spots disposed linearly, forming ventral lines; two small paraventral stripes restricted to lateral or latero-medial region of ventrals; large median stripe increasing in size posteriorly; ventral lines collapsed on posterior regions of belly, covering ventral scales entirely; tail uniformly black; dorsal ground colour reddish brown with about 30 irregular black blotches; dark blotches with creamy borders and disposed linearly, extending from third to sixth dorsal scale rows; blotches (two or three scales long and wide) generally clearly distinct from dorsal ground colour and paired on paravertebral region; blotches occasionally collapsed at vertebral region on the first third of body; posterior blotches decreasing in size (one or two scales long and wide) and not connected to opposite one above vertebral region; blotches occasionally weakly distinct from dorsal ground colour, forming almost reticulate pattern.

Hemipenis morphology (everted organs n = 4): Organ moderately bilobed, slightly semicapitate, and non-calyculate; lobes attenuate, centrifugally oriented, covered with disperse spinules, and slightly smaller than hemipenial body; apices of lobes curved and oriented medially, forming well defined distal clasps; tips of lobes covered with disperse papillae; hemipenial body with intrasulcar region thick (capitular area) on both sides of organ; weakly defined capitular groove with inverted “V” shape, delimiting capitate area on the sulcate side, and with median retraction on the asulcate side of hemipenis; capitular region delimited on the sulcate side by large hooked spines arranged in diagonal series; intrasulcar region with six moderate hooked spines; median spines decreasing in size toward proximal portion of asulcate side of organ; sulcus spermaticus bifurcates on basal portion of hemipenis; sulcus spermaticus branches centrifugally oriented, running to the tips of lobes; margins of sulcus spermaticus stout and narrow; hemipenial body mostly smooth, with a series of moderate spines on asulcate side of organ immediately below large spines, which delimit the capitular region of hemipenis; basal portion of hemipenis body with a large lobular projection; proximal region of hemipenis with longitudinal plicae and disperse spinules ( Fig. 9 a, b).

Variation: Largest male 353 mm SVL, 50 mm CL, largest female 170 mm SVL, 38 mm CL; tail 14.2– 18.9% (x¯ = 17.7; SD = 2.5; n = 4) SVL in males, 16.4–17.6% (n = 2) SVL in females; 135–150 (x¯ = 137.8; SD = 3.3; n = 5) ventrals in males, 134–144 (x¯ = 139; SD = 4.6; n = 3) in females; 33–43 (x¯ = 37.7; SD = 1.6; n = 5) subcaudals in males, 25–37 (n = 2) in females; 3 (n = 1 side) or 4 (n = 15 sides) first infralabials contacting chinshields; 3 (n = 3 side) or 4 (n = 10 sides) gular scale rows; 3 (n = 5) or 4 (n = 2) preventrals; 8–11 (x¯ = 8.8; SD = 0.7; n = 12 sides) dorsal scale rows at the level of second subcaudal; 4.4–6.6 mm (x¯ = 5.4; SD = 1.2; n = 6) body diameter; 6 (n = 4 sides) or 7 (n = 4 sides) maxillary teeth; 5 (n = 2 sides) palatine teeth; 10 (n = 1) or 11 (n =1) pterigoyd teeth; 8 (n = 1) dentary teeth.

Distribution: Pacific lowlands of Colombia from Nuqui (05º43’N, 77º16’W) west of Condoto (05º08’N, 76º39’W) in the department of Chocó south to Barbacoas (01º39’N, 78º10’W) in the department of Nariño. Atractus iridescens inhabits rainforest at elevations of 50–150 m ( Fig. 6 ).

Remarks: Peracca (1896) described A. iridescens based on a specimen from “ America Meridionali” (= South America) without precise collection data. Boulenger (1913) associated the name with three specimens collected at Peña Lisa, Condoto in the department of Chocó, Colombia. Analyses of data and photographs of the holotype of A. iridescens corroborate Boulenger’s identification. We report herein three additional specimens extending the species’ distribution about 500 km south. We found another specimen (CSJ 563) that may be referable to A. iridescens , but it is labelled as coming from “ San Pedro ”, a municipality on the other side of the Andes. There are at least five localities named San Pedro in the department of Antioquia, Colombia, and it is very likely that the specimen came from San Pedro de Urabá (08º17’N, 76º23’W, ca. 200 m), on the northern portion of the Pacific lowlands of Colombia. If this record would be considered, the species range would extend 300 km north from Nuqui. However, the colour pattern of this specimen is poorly preserved and its identity cannot be properly established, thus we prefer not to include this doubtful record of A. iridescens until further specimens become available.

Figures

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

FIGURE 7. Dorsal (A) and ventral (B) views of Atractus iridescens (ICN 10902). SVL 353 mm, CL 50 mm.

FIGURE 8. Dorsal (A) and lateral (B) views of the head of Atractus iridescens (ICN 10902). Scale = 5 mm.

FIGURE 9. Sulcate and asulcate sides of the hemipenis of (A) Atractus iridescens (ICN 10902), (B) detailed view of lateral expansion of the hemipenis of Atractus iridesnces, (C) sulcate and asulcate sides of the hemipenis of Atractus typhon sp. nov. (ICN 10901). Scale = 5 mm.