Summary

ABSTRACTSnakes of the pseudoboine genera Clelia, which is probably polyphyletic, and Boiruna are distributedfrom southern Argentina, southern Brazil, and Uruguay northwards into central México. Six membersoccur in Paraguay and Argentina: B. maculata, Clelia bicolor, C. clelia, C. plumbea, C. quimi,and C. rustica. Historically, there has been taxonomic confusion among the larger species(B. maculata, C. clelia, C. plumbea, and C. rustica) and between the small species (C. bicolorand C. quimi). All of the species except C. rustica have distinct ontogenetic color changes. Speciescan be distinguished on the bases of size, color, hemipenial spines, and loreal, supralabial, andventral scale counts. Much of the morphological evolutionary differentiation in Boiruna and Cleliaseems to have taken place in the snout region, as evidenced by the differing proportions of the scales ofthe loreal region. Boiruna maculata has the widest ecological amplitude. It is broadly distributed inmost vegetation types north of the 38th parallel in central Argentina, being absent only from thedeltaic sediments of Buenos Aires Province, Argentina and the broad valleys and rolling hills ofeastern Paraguay. Clelia bicolor is most common in the Paraguay and Paraná river valleys, with afew records from the Andean foothills in northern Argentina. Clelia clelia is distributed along theRío Paraguay and the lower Paraná, and is also found throughout much of eastern Paraguay. Cleliaplumbea is apparently parapatric with C. clelia along the Río Paraná in southeastern Paraguayand Misiones Province, Argentina. The ranges of C. quimi to the east and C. bicolor in the westabout in this same region without apparent overlap. There are no vouchered records of Clelia rusticafrom Paraguay. In Argentina, it is a species of temperate climates; north of the 30th parallel, it occursin the Andean foothills and the wet forests of Misiones Province. Southwards, it is widely distributedto beyond the 40th parallel.KEYWORDS: Clelia, Boiruna, Argentina, Paraguay, pseudoboines, colubrids.