Abstract
The genus Cnidoscolus is a New World assemblage here considered to contain 97 species, seven of which include nine subspecies and one variety. In the current study, we compile all previously published names of Cnidoscolus and provide information about their taxonomy, distribution, and nomenclature. 34 lectotypes are designated and three new synonyms are proposed. With 41 species, Brazil is the most diverse country, followed by Mexico with 25 species. Other countries with noteworthy diversity include Paraguay and Peru, with 14 and ten species respectively. Argentina and Bolivia each have seven and six species respectively. The level of endemism in the genus is relatively high in each country where it occurs, and 80 species are endemic to a single country. There are few studies that assess the category of risk for Cnidoscolus species, and only three taxa are included in the IUCN Redlist. However, many other species are thought to be rare and endangered, and as such worthy of conservation efforts.