Pierrebraunia Esteves is a controversial genus. In the latest literature it is included in Arrojadoa Britton & Rose by Anderson (2001, 117), considered as a separate genus in Hunt et al. (2006, text: 233) and in Anderson & Eggli (2011, 534), and again assimilated in Arrojadoa by Hunt (2013, xìì; 2016, 112) in the wake of anticipated molecular analysis (Machado et al. 2006). Based on the significant morphological distance between Pierrebraunia and Arrojadoa and pending the final results of the analysis, for the moment we prefer to keep the first taxon within the accepted genera in cactusinhabitat.org (Quoted from Anceschi & Magli 2021, 81)