Atractus serranus Amaral, 1930
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publication ID |
https://doi.org/ 10.11646/zootaxa.2364.1.1 |
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persistent identifier |
https://treatment.plazi.org/id/0390751B-3D4B-FFE0-FF61-FF3AFF13B84E |
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treatment provided by |
Felipe |
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scientific name |
Atractus serranus Amaral, 1930 |
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Atractus serranus Amaral, 1930
Figs. 15B View FIGURE 15 , 16A,C
Atractus serranus Amaral, 1930 ; Bull. Antivenin Inst. Amer. 4:65.
Holotype: Adult female, IBSP 7238 View Materials (not 5315, as reported in the original description), from an uncertain point at the northermost section of the Serra de Paranapiacaba (between the municipalities of São Paulo and São Vicente), state of São Paulo, Brazil, collected on 17 August 1930 by "men working in the construction of the railway between Mayrink and Santos " (sensu Amaral 1930d) (specimen examined).
Diagnosis: Atractus serranus 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) 150–163 ventrals in females, 141–147 in males; (11) 18–23 subcaudals in females, 26–29 in males; (12) dorsum uniformly black in adults and reddish brown to black scattered with irregular dorsal blotches in juveniles; (13) venter uniformly black in adults and usually paler in juveniles; (14) large body size in females (790 mm SVL) and males (515 mm SVL); (15) tail short in females (7.9–10.2% SVL), moderate in males (9.2–14.6% SVL); (16) hemipenis moderately bilobed, semicapitate, and semicalyculate.
Comparisons: Among all congeners, A. serranus shares 17 dorsal scale rows at midbody, large body (> 500 mm in mature females), and black colour on the belly only with A. gigas and A. trihedrurus . Atractus serranus differs from A. gigas by having four infralabials contacting chinshields, 18–23 subcaudals in females and 26–29 in males (vs. two or three infralabials contacting chinshields, 31–37 subcaudals in females and 42– 46 in males); from A. trihedrurus by having juvenile colouration red or reddish dark brown uniformly scattered with black irregular blotches or fragmented dots, belly uniformly black after 15 th ventral, 141–147 ventrals in males and 150–163 in females, maximum SLV 370 mm in males and 790 mm in females (vs. juveniles red or reddish brown with wide transverse bands reaching the paraventral region, 136–150 ventrals in males and 146–159 in females, maximum SVL 735 mm in males and 1010 mm in females).
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 on the apices; diastema short; postdiastemal teeth smaller than prediastemal tooth; lateral process poorly developed, lacking posterior projection.
Colour in preservative: Dorsum of head black; background of head black to dorsal edges of supralabials; supralabials creamish white, pale brown, or beige; 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 in the first 15 th scales and uniformly black after; venter occasionally with posterior margin of each ventral scales paler (beige); tail black, occasionally with posterior margins of each subcaudal beige; dorsal ground colour generally uniformly black; occasionally adults maintain poorly distinct black dots along body ( Fig. 14B View FIGURE 14 , 16C).
Juvenile colouration in preservative: Juveniles and sub-adults with dorsum of head reddish brown to dark brown; dorsum of head frequently with black dots along sutures or centre of cephalic plates; ventral ground colour brown (juveniles) or dark brown to black (sub-adults); dorsal ground colour of body reddish brown, with irregular black blotches (two or three scales long) above paravertebral region; blotches frequently fragmented as irregular dots (one or two scales long) on the flanks and paraventral region; small dots frequently connected dorsally to irregular blotches ( Fig. 16A).
Hemipenis morphology (everted organs n = 3): Retracted organ bifurcates on 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 generally of similar size and 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 conspicuous medial and lobular crests; capitular groove slightly distinct on the sulcate side and well defined (except above median crest) on the asulcate side of hemipenis; capitulum located just above sulcus spermaticus bifurcation and slightly smaller than hemipenial body; sulcus spermaticus bifurcates on 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 along length; 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. 14C View FIGURE 14 ).
Variation: Largest male 515 mm SVL, 68 mm CL, largest female 790 mm, SVL, 65 mm CL; tail 9.2– 14.6% (x¯ = 12.6; SD= 1.8; n = 6) SVL in males, 7.9–10.2% (x¯ = 8.8; SD= 0.6; n = 20) SVL in females; 141– 147 (x¯ = 145,7; SD= 2.3; n = 6) ventrals in males, 150–163 (x¯ = 157,7; SD = 3.1; n = 20) in females; 26–29 (x¯ = 27.6; SD = 1.3; n = 6) subcaudals in males, 18–23 (x¯ = 20.3; SD = 1.3; n = 20) in females; 6 (n = 1 side), 7 (n = 50 sides), or 8 (n = 1 side) supralabials; 6 (n = 1 side), or 7 (n = 51 sides) infralabials; 3 (n = 4 sides) or 4 (n = 48 sides) first infralabials contacting chinshields; 3 (n = 51 sides), or 4 (n = 1 side) gular scale rows; 1 (n = 1), 2 (n = 4), or 3 (n = 21) preventrals; 1 (n = 1 side), or 2 (n = 49 sides) postoculars; 1+1 (n = 2 sides), 1+2 (n = 48 sides), or 2+2 (n = 2 sides); 8–10 (x¯ = 8.9; SD = 0.5 n = 26) dorsal scale rows on the level of second subcaudal; 8 (n = 4 sides), 9 (n = 35 sides), or 10 (n = 2 sides) maxillary teeth; 4.1–25.2 mm body diameter; retracted hemipenis bifurcates on seventh to eighth and extends from ninth to 10 th subcaudal (n = 3) .
Distribution: Serra de Paranapiacaba and Tietê Valley, from Salesópolis (22º16’S, 42º32’W) westward to Campinas (22º54’S, 47º05’) and southward to Cubatão (24º56’S, 47º58’W) in the state of São Paulo, Brazil. Atractus serranus inhabits Lower Montane Rainforest between 700–1000 m elevation ( Fig. 7 View FIGURE 7 ). The Cubatão record is based probably on the label from the municipality's headquarters, without other data sources, and we suppose it was collected from high elevations in the foothills of the Serra do Mar.
Remarks: Amaral (1930d) described A. serranus on the basis of one individual from Serra de Paranapiacaba, a mountain range near São Paulo city, southeastern Brazil. Subsequently, several Brazilian herpetologists (including ourselves) in the last two decades have placed the taxonomic status of A. serranus in doubt with respect to A. trihedrurus (see Marques et al. 2001: 171). In order to test the morphometric discrimination of these two species and the similar A. francoi , we performed a DFA with all available samples of these nominal taxa. We labeled individuals according to similarity of colour pattern to the type series of A. serranus and A. trihedrurus , as well as considering the geographical proximity among subpopulations of each taxon. Thus the juveniles with wide dorsal bands and adults with dorsum pale to grayish brown and venter pale brown were labeled as A. trihedrurus ; juveniles having irregular blotches and adults with dark brown to black dorsum and venter were labeled as A. serranus ; juveniles and adults with a nearly uniform black dorsum and venter were labeled as A. francoi . Although the first two axes from DFA were insufficient to entirely discriminate A. serranus and A. trihedrurus , the female population of A. francoi was distinguished ( Fig. 17 View FIGURE 17 ). The first principal orthogonal axis corresponds to about 78.6% of intergroup variance and is strongly correlated with the number of ventral scales and CL/SVL ratio, whereas the second DFA function corresponds to about 21.4% of variance and was stronlgly correlated with the number of subcaudals ( Table 1). Nevertheless, qualitative (juvenile colour patterns) character analyses distinguish the populations previously labeled as A. serranus from the populations attributed to A. trihedrurus . Furthermore, the classificatory matrix from the DFA (based only on quantitative characters) resulted in more than 90% correct allocations of individuals into A. serranus and A. trihedrurus based on colour patterns ( Table 2).
rus, showing individuals correctly allocated based on the classification by Jackknife.
Additionally, we found that colour patterns of adult A. serranus and A. trihedrurus do not have a latidudinal or altitudinal cline in variation such as occurs in some other species of Atractus (Passos 2008) . In fact, the colour pattern of adult A. serranus is most similar to darker individuals from the extreme south of the distribution of A. trihedrurus (Brazilian states of Paraná and Santa Catatrina). This pattern is consistent with character displacement in which geographically closer populations of the two species (sympatric populations from vicinities of São Paulo city) have very different colour patterns ( Fig. 16), while subpopulations from nonoverlapping extremes of their distribution are, in general, most similar in colour. Therefore, despite difficulties in distinguishing adult specimens from some localities, we interpreted this as crypsis between A. serranus and A. trihedrurus rather than evidence for disparate intrapopulational variation in juveniles and adults of a single species.
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