Abstract
Including the results reported in this paper, there are 41 species of Oxypetalum (Apocynaceae, Asclepiadoideae) that occur in Argentina, eight of them endemic: O. arenicola, O. fontellae, O. gracile, O. lynchianum, O. longipedunculatum, O. pubescens, O. tucumanense and O. teyucuarense. The last is a new species from the Paraje Teyú Cuaré, San Ignacio, Misiones Province, Argentina, which is described and illustrated here. It shares some morphological features with O. jorgensenii, but, overall, it does not closely resemble any other species of the genus morphologically in its unique assemblage of characteristics. In addition to this new species, we here report two additional species for the first time in Argentina.