Atractus caxiuana, Prudente, Ana Lúcia Da Costa & Santos-Costa, Maria Cristina Dos, 2006

Prudente, Ana Lúcia Da Costa & Santos-Costa, Maria Cristina Dos, 2006, A new species of Atractus Wagler, 1828 (Serpentes: Colubridae) from Eastern Amazonia, Brazil, Zootaxa 1285, pp. 21-29 : 22-27

Atractus caxiuana n. sp.

( Figures 1–4 )

Atractus sp. Hoogmoed & Prudente, 2003

Atractus sp. Prudente & Santos­Costa, 2005

Type Material All specimens are from the same locality: “Estação Científica Ferreira Penna”, Flona de Caxiuanã , Pará State, Brazil (1 42’33” S 51 31’ 45” W), 0 m. Holotype: Museu Paraense Emílio Goeldi—MPEG 19964, date and collector unknown. Paratypes: MPEG 19657, September, 1999, collected by J. A. R. Bernardi; MPEG 20128 (specimen injured), 27 January, 2002, collected by M.C. Santos­Costa.

Diagnosis The new species is diagnosed by the following set of characters: 17­17­17 smooth dorsal scales without pits; 162 ventrals in the male and 171 in the female; 30 pairs of subcaudals in the male and 24 in the female; nasal contacting loreal, internasals, rostral, and the two first pairs of supralabials; loreal contacting internasal, and second and third supralabials; no preocular; two postoculars; two light spots on the back of the head, wideblack median ventral band of varying width on a white background; subcaudals totally black.

Description Holotype ( Figure 1 ), MPEG 19964; adult male; TL 249 mm; SVL 220 mm; TAL 29 mm (11% of TL); and HL 7.6 mm (3 % of TL). Head slightly wider than neck. Body cylindrical, belly flattened, ventrolateral area rounded. Snout rounded. Tail short and conical. Dorsal scales smooth, lacking apical pits, in 17­17­17 rows; 162 ventrals; anal plate undivided; 30 pairs of subcaudals. Rostral wider than high, visible from above. Internasals small and pentagonal. Prefrontals much larger than internasals, in contact with eye, internasals, loreal, frontal, and supraoculars. Prefrontal median suture right orientation to internasal suture. Frontal wider than long, its width being 68% of interorbital distance. Supraocular small, irregularly pentagonal. Parietals large, with median suture as long as prefrontal median suture. Nasal divided, contacting loreal, internasals, rostral, and the two first pairs of supralabials. Loreal contacting internasal, eyes, second and third supralabials. Loreal long, 1.75 times longer than greatest height, and contacting the eye. Eyes small, pupil round. Interorbital distance 40 % of head length. Diameter of eyes about 73 % of loreal length. Preocular absent. Two postoculars, one in contact with 4th and 5th supralabials. Temporal 1+2; single anterior temporal, in contact with parietal, 5th and 6th supralabials, and postoculars; upper posterior temporal elongate, lower short. Seven supralabials, 3th and 4th in contact with the eyes. Seven infralabials, first pair contacting the median, and the first three pairs in contact with the chinshields.

Color pattern in preservative body and head brown, with two lighter rows on each flank (on the region of where the dorsal row is in contact with ventral scales). Scales on anterior and lateral part of head (rostral, internasals, nasals, prefrontals and loreal) with small, central lighter areas. One small light spot covering part of first, second and third supralabials. One small light spot covering part of 5th and 6th supralabials. Head with two light spots on each side, covering a small posterior part of the parietals, the posterior zone of temporals, and the posterior zone of the 7th supralabial. Anterior zone of the chinshields, mental, and infralabials black. Gular region white, with irregular small black spots. Venter with a central black band of irregular width. Sides of ventral scales black, rest white. Anal and underside of tail black ( Figures 2 and 3 ).

Variation The two paratypes show differences in size, and in some scale counts as follows: Paratype MPEG 19657 (the left part of head is anomalous)—adult female, TL 289 mm; SVL 265 mm; TAL 24 mm (8.30% of TL); HL 7.9 mm (2,7 % of TL, and 2,9 % of SVL); 171 ventrals; 24 pairs of subcaudals; prefrontals much larger than the internasals, contacting eyes, and their median suture left orientation, almost continuous, to internasal suture, distinct of holotype; frontal wider than long, its width 67.3% of the interorbital distance; loreal long, 2.2 times longer than greatest height, and in broad contact with the eye; interorbital distance 36.8 % of head length; diameter eye about 66 % of loreal length; seven infralabials, first pair not in contact in the median. Paratype MPEG 20128 (the posterior part of body and tail is injured)—HL 7.86 mm; prefrontals much larger than the internasals, contacting eyes, and their median suture sinistral (it is almost continuous) to the internasal suture; frontal wider than long with its width being 68% of the interorbital distance; loreal 1.4 times longer than greatest height, and in broad contact with the eye; interorbital distance 28.6 % of head length; diameter of the eye about 69.4 % of loreal length; postoculars contacting both the 4th and 5th supralabials.

Two paratypes (MPEG 19657 and MPEG 20128) with the same color pattern as the holotype. The paratype MPEG 19657 has sides of ventral scales wider than the paratype MPEG 20128.

Hemipenis. hemipenis reaching to the 6th or 7th subcaudal. Moderately bifurcate, noncapitate, with lobes comprising about one­fourth of total length. Sulcus spermaticus dividing at the middle of organ, branches diverging, ending at the top of lobes. Small spines covering basal area, becoming enlarged and hooked at the upper half of hemipenial body. Spinulate calyces appearing at intrasulcar region and extending to tip of lobes ( Figure 3 ).

Etymology The specific epithet “ caxiuana ” is a proper noun from the type­locality. It comes from the Tupi language and means “the place with plenty of snakes”.

Geographic range Known only from type locality ( Figure 4 ).

Remarks Savage (1960), mainly using hemipenial morphology, scutellation, dentition, and coloration defined three putatively monophyletic groups to accommodate species of Atractus occurring in Ecuador: the elaps , badius , and trilineatus groups. A. caxiuana has an undifferentiated hemipenis as presented in elaps group, but lacks some of the scutellation characters that define this group (large rostral and internasals, broad prefrontal, and short loreal). A. caxiuana can be distinguished from A. albuquerquei , A. elaps , A. insipidus , A. poeppigi , and A. trilineatus by presenting 17 dorsal scale rows (vs. 15). It shares 17 dorsal scales (putatively plesiomorphic state) with ten Amazonian species ( A. badius , A. flammigerus , A. latifrons , A. major , A. snethlageae , A. torquatus , A. zidoki , A. natans , A. schach , and A. alphonsehogei ). However, the adults of A. caxiuana are much smaller than those of A. badius , A. flammigerus , A. latifrons , A. major , A. snethlageae , and A. torquatus . The new species is distinguished from Atractus zidoki by the underside of tail being black (vs. black with white spots on many subcaudals), and from A. alphonsehogei by the presence of two light spots in the posterior part of head (vs. the absence of light band in the head). Finally, it is distinguished from A. natans , by the contact between loreals and prenasals (vs. contact between loreals and nasals).

Figures

FIGURE 1. Head of Atractus caxiuana (holotype—MPEG 19964). Dorsal (a), ventral (b), and lateral (c) views. Scale bar 5 mm.

FIGURE 2. Atractus caxiuana (holotype—MPEG 19964 — TL 249 mm). Dorsal (a) and ventral (b) views.

FIGURE 3. Hemipenis of Atractus caxiuana (holotype—MPEG 19964). Sulcate (a) and asulcate (b) sides. Scale bar 5 mm.

FIGURE 4. Map of the Amazon basin showing type­locality (square) of Atractus caxiuana.