The relationship of placoderms
BRIAN G. GARDINER · Journal of Vertebrate Paleontology · 1984
A review of the evidence suggests that placoderms are more closely related to osteichthyans than chondrichthyans. A new phylogeny of placoderms is proposed in which the ptyctodonts are considered the collateral descendants of all other placoderms. The short pectoral girdle with a single ring of bones is judged to be primitive and the sliding neck joint is presumed to be derived.