Bonamia chontalensis, a new species of Convolvulaceae from Oaxaca and a key to the genus in Mexico1

Bonamia chontalensis Carranza sp. nov. is described and illustrated as a new species from the south of Oaxaca, Mexico. It is a rare plant, known only from a few collections in coastal areas. The species differs from other bonamias by evident unequal, suborbicular external and ovate to long-ovate internal sepals. Possible relations with other species and an identification key for the Mexican species are discussed and provided.