RESUMO
The Neotropical snake Siphlophis worontzowi was described based on a single specimen from Rio Amana, Amazonas state in the western portion of the Brazilian Amazon, but has subsequently become known from Bolivia and Peru as well. Here, we report a new morphological data set of S. worontzowi (meristic, morphometric, pholidosis, colour pattern, and hemipenial characters) and new geographic localities. Geographical variation and sexual polymorphism are analysed and described. Siphlophis worontzowi can be distinguished from its congeners by the combination of the following characters: dorsal scale rows 19-19-15, dorsals with two apical pits; undifferentiated vertebral scales; 3 postoculars; long loreal; 2+3 temporals; 8 supralabials, with the third, fourth and fifth contacting the orbit; 9 infralabials, first four pairs contacting chin shields; 14-17 prediastemal and 2 postdiastemal maxillary teeth; 21 mandibular teeth, with 4-5 larger than others; 2 or 3 preventrals; 221-243 ventrals; 93-119 subcaudals; body black with 12-22 conspicuous yellowish or reddish vertebral spots, and black head with one or two conspicuous reddish or orange nuchal spots when alive; hemipenis with Y-shaped and T-shaped conditions; intrasulcar surface with a row of three enlarged spines in the proximal region of each lobe. Additionally, we provide detailed descriptions of the hemipenis, and discuss its polymorphic condition in the genus Siphlophis.
