Abstract
Macropsychanthus magnus a new species from Costa Rica and Nicaragua is described, illustrated, and its morphological relationships with related species are discussed. Macropsychanthus magnus is characterized by its papyraceus leaflets, with 12–15 pairs of secondary nerves, terminal or axilar inflorescences, flowers 1.8–2.4 cm long, standard 1.7–1.9 × 2.1–2.4 cm, wings 1.9–2.4 × 1.4–1.6 cm, cuspidate keels 1.7–1.9 cm long, turgid fruits with fuscous indumentum and two to four overgrown seeds. This new species is related with Macropsychanthus malacocarpus, from which it differs by its pendule flowers, wider standard, wider wings and rugose seeds. Until the date, this species is restricted to Costa Rica and Nicaragua. For these two countries, I present a key to the genera of the Dioclea clade and a key to the species of Macropsychanthus.