Machaerium guidone (Leguminosae: Papilionoideae: Dalbergieae) — a remarkable new species from northeast Brazil, with a revised key to Machaerium species of the Caatinga

Summary Machaerium is a predominantly Neotropical genus comprising nearly 130 species of trees, shrubs, and lianas, ranging from southern Mexico to northern Argentina. In Brazil, approximately 74 species are recognised, 44 of which are endemic. This study is based on morphological observations on field and herbarium specimens, including detailed examination of 28 specimens and all Machaerium types. The relevant published literature was reviewed. A new species, Machaerium guidone , is described, it is predominantly found in the Brazilian Caatinga and detailed information on its habitat, distribution, conservation status, phenology and morphological, taxonomic affinities are provided. Additionally, we include field images, illustrations, a distribution map, IUCN Red List assessments and a revised identification key for all Machaerium species occurring in the Brazilian Caatinga. The newly described species increases the number of Machaerium species in the Brazilian Caatinga to 14 and the number of endemic species to 45 in the country. This discovery underlines the need for continued botanical inventories and protection of sensitive dry forests.