Orinoquia brasiliensis (Apocynaceae, Asclepiadoideae), a new endemic species and the first record of the genus in Brazil

A new species of Orinoquia (Gonolobinae, Apocynaceae) from the state of Mato Grosso, in the Central-West region of Brazil is described and illustrated, making this the first record of this genus in the country. Orinoquia brasiliensis is morphologically similar to O. yanomamica, which is known to occur only in Venezuela, but differs mainly by branches only with long simple trichomes, longer pedicels and sepals, and ovate corolla lobes; the follicles of the genus are here described for the first time. The new species is endemic to the Cerrado and known from only one population; therefore, its conservation status is suggested as Data Deficient (DD), according to IUCN criteria. A distribution map with the occurrence of the two known Orinoquia species is presented, as well as taxonomic comments, images, an illustration, a comparative table with the main features to distinguish the genus, and an identification key to the Gonolobinae of Mato Grosso.