Hidden treasures in the cabinets: an overlooked new species of Solanum (Solanaceae) from northeastern Brazil described almost two centuries after its first collection

As part of an ongoing treatment of species of the Brevantherum clade of Solanum, a new species from the Atlantic Forest of Brazil was discovered and is described here. Solanum helix Giacomin & Stehmann sp. nov. is a species well represented in herbaria that has been overlooked for almost two centuries. It has a unique expanded non-inflated fruiting calyx that resembles a propeller and that is not found in any unarmed species of Solanum. This discovery highlights the importance of continued herbarium and field work in hyperdiverse ecosystems, such as the Atlantic Forest in South America. Taxonomic affinities are discussed and images, as well as mapped distribution, are given. A key to closely related species for NE Brazil is also provided.