标题：Morphological extremes--two new snakes of the genus Atractus from northwestern South America (Colubridae, Dipsadinae) ; American Museum novitates, no. 3532
摘要："Two new Andean snakes exhibit extreme morphology in a genus of South American dipsadine colubrids. One, Atractus attenuatus, new species, is a slender, exceptionally attenuated snake 420 mm in total length (adult male holotype), with 17 scale rows, a high ventral + subcaudal count (226), and an extremely vague pattern of numerous, closely spaced, indistinct dark crossbars on a brown ground color. Atractus attenuatus comes from 1000 m elevation in the northern end of the Cordillera Central (Sabanalarga, Antioquia, Colombia). A geographic neighbor, Atractus sanguineus Prado, is of similar morphology but differs in having distinct, widely spaced crossbars on a red ground color. At another extreme, Atractus gigas, new species, is a very robust snake that exceeds a meter in length (adult female holotype 1040 mm in total length), with a hint of pale transverse dorsal bars on a brown ground color. It is the largest known Atractus, differing in color pattern and details of scutellation from t...
