Atractus trihedrurus Amaral 1926
Creators: name: Passos, Paulo
name: Fernandes, Ronaldo
name: Bérnils, Renato S.
name: De Moura-Leite, Julio C.
Publisher: name: Zenodo
Year: 2010
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Reptilia
Squamata
Dipsadidae
Atractus
Atractus trihedrurus

description: Atractus trihedrurus Amaral, 1926   
Figs. 15D, 16B,D, 18A  
 Atractus trihedrurus Amaral, 1926; Arch. Mus. Nac. 24:105.   
 Atractus trihedrurus – Peters & Orejas-Miranda; Bull. Nat. Mus. Nat. Hist. 297:327 (insertae sedis).   
 Atractus trihedrurus – Fernandes, 1996; Comun. Mus. Ciênc. Tecnol. PUCRS, Sér. Zool., 8:51.   
 Holotype: Adult male, IBSP 3098, from São Bento do Sul (26º15’S, 49º23’W, ca. 870 m), state of Santa Catarina, Brazil, collected by J. Naderer on 17 October 1924 (specimen examined).   
 Paratype: Adult female, IBSP 3067, from Piraquara (25º26’S, 49º04’, ca. 910 m), state of Paraná, Brazil, collected by G. Günst on January 27, 1923 (specimen examined).   
 Diagnosis: Atractus trihedrurus is distinguished from all congeners by the following combination of characters: (1) 17/17/17 smooth dorsal scale rows; (2) generally two postoculars; (3) loreal moderate to long; (4) temporals 1+2; (5) generally seven supralabials, third and fourth contacting chinshields; (6) seven infralabials, first four contacting chinshields; (7) eight to ten maxillary teeth; (8) generally three gular scale rows; (9) generally three preventrals; (10) 146–159 ventrals in females, 136–150 in males; (11) 16–23 subcaudals in females, 23–29 in males; (12) dorsum uniformly beige, grayish brown, or black in adults and beige or creamish red with black bands in juveniles and sub-adults; (13) venter creamish brown to uniformly black; (14) large body size, with females reaching 1010 mm SVL and males 735 mm SVL; (15) tail short in females (7.3–10.7% SVL), moderate in males (9.6–15.5% SVL); (16) hemipenis moderately bilobed, semicapitate, and semicalyculate.   
 Comparisons: Among all congeners, A. trihedrurus shares 17 dorsal scale rows on midbody and large body size in both sexes only with A. gigas, A. major, A. obesus, A. titanicus, and A. torquatus. Atractus trihedrurus differs from all of them, except A. gigas, by having a grayish brown or black dorsum in adult specimens and maximum female SVL> 1,000 mm. Atractus trihedrurus differs from A. gigas by having generally four infralabials contacting chinshields, 16–23 subcaudals in females and 23–29 in males (vs. two or three infralabials contacting chinshields, 31–37 subcaudals in females and 42–46 in males).   
 Description: Head longer than wide, arched in lateral view, sub-triangular in dorsal view; snout truncate in lateral view, round in dorsal view; canthus rostralis well marked in lateral view; cervical constriction barely distinct; rostral broader than high, sub-triangular in frontal view, poorly visible in dorsal view; internasal as long as wide; internasal suture sinistral with respect to prefrontal suture; prefrontal broader than long; supraocular sub-rectangular, longer than wide; frontal sub-triangular, as long as wide; parietal twice longer than wide; nasal divided; nostril generally restricted to prenasal; prenasal and postnasal twice as high as long; moderate to long loreal, contacting second and third supralabials; pupil sub-elliptical; generally two postoculars; upper postocular slightly higher and longer than lower postocular; temporals 1+2; anterior temporal twice longer than high; upper posterior temporal elongate, three times longer than wide; generally seven supralabials, third and fourth contacting orbit; second supralabial higher than first and smaller than third; sixth higher and seventh longer than remaining supralabials; symphisial triangular, twice broader than long; seven infralabials, first four contacting chinshields; first pair of supralabials in contact behind symphisial, preventing symphisial/chinshields contact; chinshields twice longer than wide; generally three gular scale rows; generally three preventrals; 17/17/17 smooth dorsal scale rows; dorsals lacking apical pits, supra-anal tubercles, and keels; caudal spine long, robust, and rhomboid.   
 Maxillary arch: Slightly arched in dorsal view, with six to eight prediastemal and two or three postdiastemal teeth; prediastemal teeth large, moderately spaced, of similar size, curved posteriorly, angular in cross section, robust at base, narrower at apices; maxillary diastema short; postdiastemal teeth smaller than prediastemal tooth; lateral process poorly developed, lacking posterior projection.   
 Colour in preservative: Dorsum of head brown, beige, grayish brown or black; background of head brown or black to dorsal edges of supralabials; supralabials creamish white or pale brown; mental region beige, brown or black; mental region, if beige, with dark brown blotches concentrated on symphisial, first pair of infralabials, and anterior portion of chinshields; venter pale brown to uniformly black; venter occasionally with posterior margin of each ventral scales paler (beige or cream); tail brown to black, occasionally with posterior margins of each subcaudal beige; dorsal ground colour reticulate pale brown, dark brown, or black; dorsum if creamish or grayish brown, with darker edges of dorsal scales contrasting with pale centres; black bands clearly distinct in the dorsum of sub-adults and barely distinct in the adults (Fig. 15D, 16D).   
 Juvenile colouration in preservative: Juveniles and sub-adults with dorsum of head uniformly black or black with beige, red, or creamish red blotches along sutures between cephalic plates; dorsum of head occasionally beige, red, or creamish red with variegated black blotches above cephalic plates; ventral ground colour beige (juveniles) to dark brown (sub-adults); dorsal ground colour beige to reddish brown, with black bands on the flanks; dorsum frequently covered with complete bands (three to five scales long), alternated and connected to opposite ones along vertebral region; dorsum occasionally with irregular black blotches (two or three scales long) above paravertebral region and black dots (one or two scales long) fragmented on the flanks and paraventral region; small dots frequently connected dorsally to irregular blotches (Fig. 16B).   
 Colour in life: Adults with dorsal ground colour pale brown, grayish brown, or dark brown; sub-adults with dorsal ground colour beige to dark reddish covered with more or less evident black bands/blotches; juveniles with dorsal ground colour beige to red and clearly distinct black bands and/or blotches (Fig. 18A).   
 Hemipenis morphology (everted organs n = 5): Retracted organ bifurcates at eighth and extends to the level of 10 th subcaudal. Hemipenis moderately bilobed, semicapitate, semicalyculate; lobes distinct and restricted to distal portion of capitulum; lobes sub-cylindrical of similar size, with round apices; lobes considerably longer than remaining capitulum; lobes and capitulum covered with small spinulate calyces; horizontal walls of calyces forming well-defined calyculate flounces on lateral portion of the sulcate side of hemipenis; spinules replaced by papillae toward lobe apices; asulcate side of capitulum with irregular calyces, forming conspiculous medial and lobular crets; capitular groove slightly distinct on the sulcate side and well defined on the asulcate side of hemipenis; capitulum located just above sulcus spermaticus bifurcation and slightly smaller than hemipenial body; sulcus spermaticus bifurcates at the middle of organ; sulcus spermaticus branches centrifugally oriented, running to tip of lobes; margins of sulcus spermaticus stout and laterally expanded, bordered with spinules from the base to the apices of lobes; hemipenial body subcylindrical covered with moderate hooked spines; large spines concentrated on lateral portion of the sulcate side of hemipenis; basal naked pocket restricted to basal portion of hemipenial body; basal region of hemipenis with longitudinal plicae and diffuse spinules (Fig. 14E).   
 Variation: Largest male 735 mm SVL, 83 mm CL, largest female 1010 mm, SVL, 75 mm CL; tail 9.6– 15.5% (x¯ = 12.2; SD= 1.3; n = 29) SVL in males, 7.3–10.7% (x¯ = 8.8; SD= 1.1; n = 20) SVL in females; 136– 150 (x¯ = 143,5; SD= 3.9; n = 29) ventrals in males, 146–159 (x¯ = 151; SD = 3.1; n = 20) in females; 23–29 (x¯ = 25.2; SD = 1.4; n = 29) subcaudals in males, 16–23 (x¯ = 19; SD = 1.8; n = 20) in females; 6 (n = 4 sides), 7 (n = 89 sides), or 8 (n = 5 sides) supralabials; 3 (n = 6 sides) or 4 (n = 92 sides) first infralabials contacting chinshields; 2 (n = 1 side), 3 (n = 84 sides), or 4 (n = 24 sides) gular scale rows; 2 (n = 4), 3 (n = 31), or 4 (n = 19) preventrals; 0 (n = 1 side), 1 (n = 3 sides), or 2 (n = 94 sides) postoculars; 1+2 (n = 96 sides), or 2+2 (n = 2 sides); 8–12 (x¯ = 8.9; SD = 0.6; n = 98 sides) dorsal scale rows on the level of second subcaudal; 8 (n = 7 sides), 9 (n = 68 sides), or 10 (n = 9 sides) maxillary teeth; 5.3–39.4 mm body diameter; retracted hemipenis bifurcates on sixth to 14 th and extends from eighth to 16 th subcaudal (n = 8).   
 Distribution: A narrow and steep mountain region near the coast in southeast and south Brazil, from Ribeirão Pires (23º43’S, 46º25’W) in the state of São Paulo southward to Rio dos Cedros (26º40’S, 49º16’W) in the state of Santa Catarina. Atractus trihedrurus inhabits Submontane to Upper Montane Rainforest between 500–1400 m (Fig. 7).   
 Remarks: Amaral (1926) described A. trihedrurus based on two specimens from the southern part of Serra do Mar, Brazil. Amaral (1930d) proposed A. serranus on the basis of one individual from Serra de Paranapiacaba, a mountain range near São Paulo City, southeastern Brazil. Savage (1960) doubted the generic allocation of A. trihedrurus based on the original description of the species, in which Amaral (1926) mentioned two pairs of chinshields. Peters and Orejas-Miranda (1970) followed Savage’s suspiscion, placing A. trihedrurus as incertae sedis. Fernandes (1996) included A. trihedrurus in his key for Atractus species from southern portions of South America. Recently, Lema (2005) reported A. trihedrurus, without a voucher specimen, from the state of Rio Grande do Sul, but we suspect the specimen could be instead a melanic individual of A. paraguayensis because there is no further record of the A. trihedrurus for this area.
description: Published as part of Passos, Paulo, Fernandes, Ronaldo, Bérnils, Renato S. & De Moura-Leite, Julio C., 2010, Taxonomic revision of the Brazilian Atlantic Forest Atractus (Reptilia: Serpentes: Dipsadidae) 2364, pp. 1-63 in Zootaxa 2364 (1) on pages 47-49, DOI: 10.11646/zootaxa.2364.1.1, http://zenodo.org/record/5315506