Trees or shrubs; petiole eglandular; lamina mostly bearing several–many glands on abaxial surface. Inflorescence terminal, unbranched or branched near base, each axis a raceme of short 1–7-flowered cincinni; lowest bracteole and alternate subsequent bracteoles bearing 1 large eccentric abaxial gland. Sepals all biglandular (except anterior sepal eglandular in M. sergipana) , leaving outermost petal exposed in bud; petals glabrous or bearing a tuft of hairs abaxially at base of claw; posterior petal strongly differentiated from the lateral 4, with a thick erect claw and large marginal glands on proximal half of limb or at apex of claw; receptacle glabrous on both sides of stamens; stamens all fertile or the posterior (1–) 3 bearing rudimentary anthers; pollen radially symmetrical, colporate; carpels completely connate in ovary; styles 3, slender and subulate with the stigmas very small, apical or slightly internal. Fruit dry, indehiscent, a nut without a bony endocarp, containing only 1 seed.
Distribution: South America.
The Mcvaughia clade is strongly supported by both molecular and morphological evidence. The phylogenetic tree shown above, from Davis & Anderson (2010 [pdf]), shows bootstrap values above the branches. Especially noteworthy among the morphological characteristics shared by these three genera are the shrubby or arborescent habit, the abaxial leaf glands, the flowers often in several-flowered cincinni, the large abaxial gland on alternate bracteoles, and the dry, indehiscent, one-seeded fruit.