A new species of Bonnetia Mart. (Bonnetiaceae) from the Pantepui of South America

<i>Bonnetia</i> is the most representative genus of the Pantepui woody flora and is among the groups with the greatest endemism in the local flora. The genus has 28 currently recognized species in tropical America, 26 of them endemic to the Pantepui. Here we describe <i>Bonnetiaayangannensis</i> from the summit of Mount Ayanganna tepui in Guyana, providing a morphological description, illustrations, distribution maps, characterization of micromorphology under scanning electron microscopy and leaf venation, comments comparing the new species with closely related species, and a key for the identification of the species of <i>Bonnetia</i> occurring in Guyana. With its restricted distribution threatened by climate change, <i>Bonnetiaayangannensis</i> is assessed in the conservation threat category of Critically Endangered. Its description raises the number of endemic species of <i>Bonnetia</i> in the Pantepui to 27.