From Mori et al. (in review)

Couroupita clade (Prance, 1990a)—the growth form of the three species of this genus (Prance, 1990a) is intermediate between the pachycaul and leptocaul types. The stems are stout (ca. 5 mm diam.) and the leaves are tightly congested as in pachycauls but the trees have many orders of branching and the leaves are medium-sized as in leptocauls. The trunk is cylindrical to the ground. The flowers possess six petals, the androecia are zygomorphic (Fig. 4A), and the stamens arise from a staminal ring (Figs, 4D, 4L), a character common to all zygomorphic species except those of Cariniana (see below). Several characters are found in all species of Couroupita but infrequently in other neotropical Lecythidaceae: the strictly cauline or ramiflorous inflorescences (Fig. 4E) are not found in other species of large trees although they do occur in the smaller trees of Grias, Gustavia, and some species of Eschweilera; the 6-locular ovary (Fig. 4C) of species of Couroupita consistently occurs only in species of Gustavia related to G. hexapetala; the presence of staminodes (Fig. 4D) is also found in all species of Corythophora and some species of the Lecythis pisonis and L. corrugata clades; oxidation of fruits to bluish-green occurs in the L. pisonis clade and a few species of Eschweilera (e.g., E. decolorans); and foliaceous, opposite cotyledons also occur in Cariniana and Couratari. In contrast, bilamellar placentae attached throughout the middle of the locules (Fig. 4B); spherical, indehiscent fruits (Fig. 4F) that fall to the ground at maturity; seeds embedded in fruit pulp (Figs. 4G, 4H); and pubescent seed coats (Tsou & Mori, 2002) are unique to Couroupita.