The genus Sciadotenia Miers, of which eighteen species were recognized at the most recent revision (Bameby & Krukoff, 1971), has consisted hitherto of mesophytic trees and forest vines, the majority Amazonian extending weakly in the Guianas. One is native to extra-Amazonian Colombia and Panama, and two are endemic to moist for- est of the Brazilian Atlantic slope in Bahia and Espirito Santo. The discovery of an appropriately modified sciadotenia in the sea- sonally dry campo of the Brazilian Planalto is therefore most unexpected. In the terminology of Martius (Fl. bras. 1(1): tab. geograph. 1857) this new species is an oread among naiads.
In its staminate flowers S. campestris is an unexceptional member of Sciadotenia sect. Sychnosepalum (Eichler) Bameby & Krukoff, and in light of our key to the genus (Bameby & Krukoff, 1971: 18-20) it would appear most closely related to the two species endemic to Atlantic Brazil in approx- imately the same latitude. From these it dif- fers much in habit, being a stiffly erect shrub about a meter tall, not a vine of indefinite extension. In leaf outline it is most nearly comparable with S. pubistaminea (K. Schumann) Diels, but has relatively short peti- oles, stiff-textured leaf-blades, efoliate flowering branchlets, and glabrous androecium. The flower spikes of S. pubistaminea arise from the axil of developed leaves along lateral branchlets, whereas those of S. campestris terminate secondary branchlets and are preceded by several rudimentary brac- teiform leaves