Thryallis is sometimes confused with Galphimia, a genus that occurs mostly in Mexico (one species extending into Texas) and Central America; four species are found in South America, south of the Amazon Basin. At one time some species now assigned to Galphimia were referred to Thryallis, but the generic name Thryallis is now a conserved name according to the rules of the International Code of Botanical Nomenclature. The genus Thryallis is distinctive in the stellate hairs and scales found on the vegetative parts, and in that the limb of the petals is much wider than long, traits not found in Galphimia.
No species of Thryallis is cultivated. References in horticultural publications, in the nursery trade, and on websites to Thryallis glauca, Thryallis gracilis, and (often in South America) Thryallis brasiliensis are errors for Galphimia gracilis, a species widely cultivated in warm regions throughout the world, often under the common names gold shower or shower-of-gold or sometimes thryallis.