Note 157 — Chapter XXXIII · ARTHRODIRES

"The name Arthrodira as given to Coccosteans, as distinguished from the Antiarcha, is not altogether a satisfactory one, since at least from the time of Pander the head of Pterichthys (Asterolepis) is known to be articulated with the armoring of the trunk in a way closely resembling that of Coccosteus. This term may, however, be retained as a convenient one for the order of Coccosteans, in which, together with other differentiating features, this structure is prominently evolved. A renewed examination of the subject has caused me to incline strongly to the belief, as above expressed, that Pterichthys and Coccosteans are not as widely separated in phylogeny as Smith Woodward, for example, has maintained. But, as far as present evidence goes, they appear to me certainly as distinct as fishes are from amphibia, or as reptiles are from birds or from mammals." (Dean.)

The name Placodermi used by McCoy in 1848 was applied to the Ostracophores as well as to the Arthrodires. Hay revives it as the name of a superorder to include the Antiarcha and the Arthrodira, the former being detached from the Ostracophores. This superorder is equivalent to the subclass Azygostei of Hay.