A taxonomic revision of Thaumatocaryon (Boraginaceae) reveals hidden diversity in southern South America

Abstract

Thaumatocaryon is a small genus of South American Boraginaceae with only three accepted names. This genus, along with Moritzia, comprises a monophyletic lineage called Moritziinae. During a review of herbarium specimens, we found morphological divergences that led us to conclude that Thaumatocaryon is more complex than previously known. According to the morphologic analysis, we recognize nine species, resulting from the revalidation of T. hilarii and the description of five new species. The species are differentiated by characteristics such as phyllotaxy, indumentum, as well as the length and color of the corolla, the morphology of stems and basal leaves, and the arrangement of flowering stems. We present a detailed description of each species, updating the four previously described species, field photographs (when available), exsiccate plates, distribution maps, and a key for all species of the genus.