Habit and leaf form. Microphyllous shrubs (with long- and short-shoots). 0.3–1.2 m high. Leptocaul. Xerophytic. Leaves small (7–21 mm long); alternate; spiral (on the long-shoots, clustered on the short-shoots); flat; leathery to fleshy (‘subcoriaceous, rather thick, fleshy’); shortly petiolate to subsessile; non-sheathing; simple; epulvinate. Lamina entire; lanceolate, or oblong, or ovate (ovate to broadly oblong-lanceolate); (when cleared) pinnately veined to palmately veined; rounded at the base (and abruptly contracted into the peglike petiole). Leaves exstipulate. Lamina margins entire; flat.
Leaf anatomy. Stomata on both surfaces; anomocytic. Hairs present (the leaves canescent-strigose pubescent, the hairs T-shaped, ‘Malpighian’ type); eglandular; unicellular (though embedded in multicellular ‘bases’). Complex hairs absent.
Lamina dorsiventral to isobilateral (with adaxial and abaxial palisades).
Stem anatomy. Cork cambium present; initially superficial. Nodes unilacunar. Primary vascular tissue in a cylinder, without separate bundles. Secondary thickening developing from a conventional cambial ring. Xylem with fibre tracheids; with libriform fibres; with vessels (these mostly solitary). Vessel end-walls simple. Vessels without vestured pits. Primary medullary rays narrow (all uniseriate). Wood semi-ring porous to diffuse porous; not storied; parenchyma apotracheal and paratracheal (mainly paratracheal).
Reproductive type, pollination. Plants hermaphrodite. Floral nectaries absent (?).
Inflorescence, floral, fruit and seed morphology. Flowers solitary; axillary (near the ends of the branchlets, on 3–5 mm pedicels); ebracteate?; ebracteolate? — neither bracts nor bracteoles mentioned by Iltis et al; medium-sized to large (4–5 cm in diameter, showy); calyptrate (via the calyx); regular; 5–7 merous. Floral receptacle developing an androphore and developing a gynophore (androphore short, gynophore well developed). Free hypanthium absent. Hypogynous disk absent.
Perianth with distinct calyx and corolla; 10, or 12, or 14; 2 whorled; isomerous. Calyx 5, or 6, or 7; 1 whorled; gamosepalous (calyptrate); entire; regular; persistent to not persistent; non-accrescent; calyptrate (ultimately splitting basipetally into one or two reflexed, semi-persistent flaps); valvate (or thus interpretable). Corolla 5, or 6, or 7; 1 whorled; polypetalous; imbricate; regular; bright blue (to lilac or violet); deciduous; non-accrescent. Petals clawed (ovate-spathulate); entire.
Androecium (40–)60–76. Androecial members unbranched (in obscure fascicles); maturing centrifugally; free of the perianth; markedly unequal; obscurely coherent, or free of one another (ostensibly only); 5 adelphous, or 6 adelphous, or 7 adelphous (the stamens ostensibly randomly arranged, but on close examination resolvable into 5, 6 or 7 ‘fascicles’, each comprising a radially-arranged row of pairs of stamens). The androecial bundles alternating with the corolla members. Androecium exclusively of fertile stamens. Stamens (40–)60–76; polystemonous; filantherous. Anthers basifixed; non-versatile; dehiscing via longitudinal slits; introrse; bilocular; tetrasporangiate. Pollen shed as single grains. Pollen grains aperturate; 3 aperturate; colpate.
Gynoecium 3 carpelled. Carpels reduced in number relative to the perianth. The pistil 3 celled. Gynoecium syncarpous; synovarious to synstylovarious; superior. Ovary 3 locular; stipitate. Gynoecium stylate. Styles 1, or 3 (the style trifurcating above); if considered three, partially joined; attenuate from the ovary; apical. Stigmas 3. Placentation axile. Ovules 10–14 per locule; funicled; biseriate; anatropous; bitegmic.
Fruit non-fleshy; dehiscent; deeply trisulcate, a capsule, or a siliqua (i.e., on a short gynophore, with three valves dehiscing from a thin placental column, cf. two cruciferous valves separating from a replum?). Capsules valvular. Dispersal unit the seed. Fruit 6–30 seeded. Seeds non-endospermic (the endosperm one-layered, ‘obsolete’); small to medium sized (7–11 mm long); winged (at the cotyledonar end, and straight, by contrast with the reniform seeds characteristic of the order). Cotyledons 2. Embryo straight (large, flat, spathulate).
Seedling. Germination phanerocotylar.
Physiology, biochemistry. Mustard-oils present.
Geography, cytology. Neotropical. Mexico.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Violiflorae; Capparales. Cronquist’s Subclass Dilleniidae; Capparales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; malvid; Order Brassicales.
Species 1. Genera 1; the monotypic genus, Setchellanthus.
Long uncomfortably referred to Capparidaceae; promoted to family rank on seemingly good morphological grounds, and with the support of data from nucleic acid sequencing, by Iltis et al. (1999).