Historically, many rhizarians were considered animals, with their movement and heterotrophy as justification. However, when the five-kingdom system took prevalence over the animal-plant dichotomy, the rhizarians were put into the kingdom Protista. Then, after Carl Woese published his three-domain system, taxonomists turned their attention to the eukaryote domain. The protists are paraphyletic, so needed to be split into monophyletic clades. After much debate, which continues to this day, Rhizaria emerged as one of those monophyletic groups.