Revalidation of the genera Bia and Zuckertia (Euphorbiaceae) with B. capivarensis sp. nov. from Serra da Capivara, Brazil

Bia Kl. and Zuckertia Baill. have long been considered sections of the genus Tragia L. Webster revalidated the generic status of Bia based on morphological and molecular analyses and proposed two sections, Bia sect. Bia restricted to South America comprising four species, and B. sect. Zuckertia as a monotypic section from Mexico. Also based on morphological and more recent phylogenetic analyses, we propose the revalidation of the generic status of Zuckertia, present a new circumscription and morphological data for the genus Bia, and describe B. capivarensis D. Medeiros, Senna‐Valle & Alves sp. nov., a new species from Serra da Capivara National Park, Piauí, Brazil. Based on the collected material, an illustration and a detailed description of the new species are provided, as well as a key to Zuckertia and Bia and their species.