In addition, there are archaic elements, such as the antiarch and arthrodire placoderms as well as acanthodians. |
Such giant cephalopods play or played a similar ecological role of top predator to that of Devonian arthrodire placoderms, Mesozoic pliosaurs and Cenozoic toothed whales. |
The basicranial circulation of Ptomacanthus resembles that in arthrodire placoderms. |