A revision of paleotropical Plukenetia (Euphorbiaceae) including two new species from Madagascar

A revision of the seven paleotropical species of Plukenetia (Euphorbiaceae) is given. Three sections or species groups are recognized. Two genera, Tetracarpidium (synonym Angostylidium) and Pterococcus, are treated here as sections of Plukenetia. The monotypic P. sect. Angostylidium includes the African species P. conophora, while P. sect. Hedraiostylus (synonym P. sect. Pterococcus) comprises two African species (P. africana and P. procumbens) and one Asian species (P. corniculata). A third species group restricted to Madagascar is distinguished by an androecium of sessile anthers on an elongate receptacle, and comprises three species, two described here. Plukenetia decidua, from southeastern Madagascar, is close to P. madagascariensis and shares styles partly fused into a cylindrical column, but differs in its narrower ovate or triangular-ovate leaf blades, smaller eglandular bracts, racemes with flowers single per node, and fewer anthers on a shorter ellipsoid receptacle. Plukenetia ankaranensis from northern Madagasar is distinguished from the previous two species by its styles entirely fused into an enlarged obovate stylar column. A key to the seven paleotropical species is provided and their relationship to neotropical species is discussed.