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A new species of Atractus, previously reported as a disjunct population of A. zidoki south of the Amazon River, differs from all congeners in having an undivided sulcus spermaticus. Herein, we restrict the concept of A. zidoki to populations north of the Amazon River, provide a detailed description of its everted hemipenis, and describe a new species to accommodate the population occurring to the south of the Amazon River. Additionally, we briefly discuss intraspecific variation and the systematic value of the hemipenis structure in snakes, mainly with respect to the genus Atractus. [ABSTRACT FROM AUTHOR]

ABSTRACT.-A new species of Atractus is described from Serra do Surucucu, a mountain slope at 1,000 m in the Guyana Shield, State of Roraima, Brazil. This species, only known by females, is diagnosed from all congeners by the following combination of characters: 17/17/17 smooth dorsal scale rows, without apical pits; 200-207 ventral scales; 25-26 subcaudal scales; moderate sized loreal, contacting second and third supralabials; seven supralabials, third and fourth contacting orbit; seven infralabials, first three contacting chinshields; moderate size, 222-388 mm SVL; short tail (7.7-8.8% snout-vent length); dorsal color pattern, in preservative, uniform chocolate to dark brown, with two conspicuous light paraventral lines, and a light incomplete occipital collar; venter immaculate creamish-white; tail uniform black; five maxillary teeth. We compared the new species with all currently recognized cis-Andean Atractus, and its affinities with Atractus alphonsehogei, Atractus caxiuana, Atractus collaris, Atractus gaigeae, Atractus limitaneus, and Atractus zidoki are discussed on the basis of putative morphological synapomorphies. [ABSTRACT FROM AUTHOR]

A new species of Atractus is described from Serra de Baturité, an Atlantic Forest enclave in the semiarid Caatinga of the state of Ceará, northeastern Brazil. The new species is distinguished from all congeners by the combination of 17 dorsal scale rows at midbody, long loreal, two postoculars, seven upper and lower labials, first four infralabials in contact with chinshields, seven maxillary teeth, moderate body and tall sizes, slightly bilobed and semicapitate hemipenis with lateral-tip projections, light dorsal color pattern uniformly scattered with small dark brown dots, and ventral color pattern uniformly creamish white. The new species shares most of the external morphology and hemipenis characters with A. pantoslictus, differing from this taxon by general color pattern and number of subcaudal scales. [ABSTRACT FROM AUTHOR]