Arthrodira is divided into three main groups: the
paraphyletic Actinolepida and
Phlyctaenii, and then the
monophyletic Brachythoraci. Brachythoraci is then further divided into the large derived
clade Eubrachythoraci and several
basal groups:
Buchanosteoidea,
Homosteidae, and
Holonematidae. (Although Holonematidae's membership in Brachythoraci is disputed.) Below is a
cladogram from the 2016 Zhu
et al. phylogenetic study: ==References==