Abstract
The new species Cissampelos arenicola M. Nee & R. Ortiz, from the Bolivian and Paraguayan Chaco is described, its affinities are discussed, and its preliminary conservation status is evaluated. The species is at present known from 13 collections from sand dunes or dry forests. Cissampelos arenicola is distinguished from all other American species in the genus by its ovate- to subreniform-trilobed leaves, 8-locular synandria, and relatively large, and scarcely ornamented endocarps. The most common perianth condition in the pistillate flowers of Cissampelos is one sepal and one antesepalous petal, and while these may vary in number, they are always found adaxial to the carpel, and although the southern African taxon called Cissampelos capensis, whose generic position is uncertain, superficially resembles Cissampelos arenicola, its sepals and petals are consistently lateral to the carpel and not adaxial.