Reinstatement of Thyrsacanthus Moric. (Acanthaceae) and taxonomic novelties in the genus

Phylogenetic studies based on molecular data indicated that the Neotropical genus Anisacanthus Nees (Acanthaceae), as traditionally circumscribed, is not monophyletic. Based on the priority of the description of Thyrsacanthus ramosissimus Moric. versus the description of Thyrsacanthus Nees, we are reinstating the name Thyrsacanthus (Art. 42.1 of the ICBN) to include the South American species traditionally assigned to Anisacanthus. Drejera Nees is included in the synonymy of Thyrsacanthus, a new species (T. microphyllus A. Côrtes & Rapini) is described, three new combinations are proposed, two new taxonomic synonyms at the species level indicated and three lectotypes designated. The positions of Anisacanthus trilobus Lindau and A. pohlii Lindau are uncertain, requiring further investigations.