Woody vines, sometimes shrubby, rarely small trees. Stamens 10, all fertile (or the posterior 3 occasionally sterile in Callaeum); pollen globally symmetrical, with colpi not perpendicular to the equatorial plane and pores variously distributed; receptacle glabrous on both sides of stamens; gynoecium comprising 3 carpels, all fertile; styles 3. Fruit dry, breaking apart into samaras (or perhaps indehiscent in Flabellaria); samara with lateral wings dominant, cleft to nut at apex, confluent or ± deeply cleft at base; dorsal wing mostly small (almost as large as lateral wings in Callaeum macropterum); wings lost or reduced to ruffles or coriaceous or corky outgrowths in some species of Callaeum, Jubelina, and Malpighiodes; carpophore absent.
Distribution: Western Texas and Mexico to southern South America (six genera) and Africa (Flabellaria).
The Christianella clade as a whole is very strongly supported by molecular evidence—see the phylogenetic tree above, with bootstrap values above the branches, which is from Davis & Anderson (2010 [pdf]). In cases where more than one species of a genus was sampled the genera also enjoy strong support, as does the sister relationship of Flabellaria and Malpighiodes. On the other hand, support for structure within the tree is mostly lacking. The group is morphologically coherent in its samaras, all of which are "mascagnioid," i.e., with the lateral wings dominant and the dorsal wing mostly small; that similarity is somewhat obscured by the loss or modification of those wings in several species, presumably as an adaptation for dispersal by water.
The presence of the African genus Flabellaria in this clade is no surprise in the sense that in most of its morphological characters it fits nicely with the other six genera here; its samara is identical to that found in several of these genera. Lowrie (1982, p. 95) noted that the pollen of Flabellaria "is totally anomalous in the Old World" and added, "Its fruit is most similar to New World genera with lateral fruit-wings and its pollen does not disallow a relationship with any of those genera." Flabellaria is an example of the repeated migration of lineages of Malpighiaceae from the Neotropics to the Old World (Davis et al., 2001; pdf). Having arrived in the Old World, the ancestor of Flabellaria lost the calyx glands found in the neotropical genera of the clade, and the symmetry of its corolla shifted from bilateral to radial.