Trees, shrubs, or subshrubs; stipules intra- and epipetiolar; leaves eglandular. Inflorescence terminal, unbranched or basally several-branched, each branch a pseudoraceme of 1-flowered cincinni or a raceme of several-flowered cincinni; bracts and bracteoles eglandular or bearing only small stipitate marginal glands. Sepals leaving outermost petal exposed in enlarging bud, all biglandular or all eglandular, the glands borne mostly below free part of sepals; corolla bilaterally symmetrical, the posterior petal differing in size, shape, stance, and/or color from the lateral 4; petals mostly glabrous or bearing only a few hairs at adaxial base of claw, abaxially sericeous in a few species; pollen radially symmetrical, tricolporate; receptacle bearing straight basifixed hairs between androecium and gynoecium; ovary with the 3 carpels completely connate (only 2 locules developing in some species); styles 3, slender and subulate with minute, apical or slightly internal stigmas. Fruit indehiscent, the seeds contained in a single, ovoid or spheroidal, bony, smooth or rugose stone, the exocarp dry or fleshy.
The Byrsonima clade is very strongly supported by both molecular and morphological evidence. The phylogenetic tree shown above is from Davis & Anderson (2010 [pdf]); the numbers above the branches are bootstrap values. Especially noteworthy among the morphological characters supporting the clade are the completely eglandular leaves, a condition found in few genera of Malpighiaceae, and the indehiscent stone of the fruit, which is unique in the family. Of the three genera in this wholly American clade, two are limited to northern South America, while the third, Byrsonima, is one of the largest and most widely distributed genera of the family.
For those who wish to recognize tribes within the Malpighiaceae, the Byrsonima clade has the name Byrsonimeae W. R. Anderson, Leandra 7: 7. 1978 ["1977"]; type genus, Byrsonima
H. B. K.—Byrsonima is also the type of subfamily Byrsonimoideae W. R. Anderson, Leandra 7: 6. 1978 ["1977"].