Various aspects of the taxonomy, systematic positions, and nomenclature of South American Amaranthaceae are discussed, including members of the following genera: Alternanthera, Celosia, Gomphrena, Iresine, Pfaffia, Quaternella, and Trommsdorffia. Eleven new species are described, as well as two new subspecies, five new varieties, and one new form. Twelve new combinations are made, one new name and one change of status proposed, and several species are re-assigned to genera, where they have not been placed recently. Keys are provided for several groups of closely related taxa, including the members of Pfaffia sect. Pfaffia.
Amaranthaceae, new taxa, taxonomy, systematic positions, nomenclature, South America