The neotropical genus Averrhoidium Baillon (Sapindaceae) belongs to the tribe Doratoxyleae and comprises four species with disjunct areas of distribution. Recently a new species, Averrhoidium dalyi Acevedo & Ferrucci, was described from Peru and Brazil, based on vegetative material and undehisced fruits. The other three species are known from a few herbarium specimens only. Here we present for the first time observations on live material and detailed morphological and anatomical data of flowers and dehisced fruits. This information contributes to a more complete circumscription of the genus Averrhoidium. The fruits of Averrhoidium dalyi are one-seeded capsules. They dehisce on one side, allowing the placenta and parts of the septa to turn outwards like a tongue. The single seed, with a conspicuous white sarcotesta, is still fixed to the placenta but is dangling between neighboring undehisced red capsules, and presumably attracts birds for seed dispersal. Seeds displayed by their own placenta have not been reported for Sapindaceae as yet. A morphological cladistic analysis including these new morphological characters was conducted in order to infer the phylogenetic relationships of Averrhoidium within the family. Its inclusion within the Doratoxyleae clade was confirmed based on the presence of an uninflated fruit with a single pendulous seed. It occupies a basal position in this clade and is distinguishable from the other members by the possession of dehiscent fruits.

Key words: Averrhoidium, Doratoxyleae, flower morphology, fruit morphology, Sapindaceae