Primitive types of early fish, with no articulated jaw were first identified in the Cambrian Period. Some species still survive, but the most spectacular of these types were the armored fish of the Silurian Period. These fish typically can't bite in the same way as a jawed fish, but have specialized teeth which shred their prey. Others are parasites, using their teeth to grip their hosts. The jawless fish are classified as part of the Agnatha superclass of fish. The Agnathans are unusual organisms, extremely primitive in terms of their physiology. Their evolutionary path is believed to have diverged from the majority of fish even before the evolution of dentine.