Dinicthys, an extinct Placoderm

Skull of Dinichthys, a Devonian Placoderm. The distinguishing synapomorphy the Class Placoderma is a hinged craniovertebral joint, which allow the maxilla to roll back and enhance the jaw gape. Dinicthys was a 9-meter predator with toothe plates permanently attached to the jaws; other placoderms were benthic planktivores.