Pteraspidomorphi

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Pteraspidomorphi (superclass Agnatha) A class of jawless vertebrates that have an eel-like body, lack paired fins, have two semicircular canals, and a skeleton not consisting of true bone. The class includes the fossil order Pteraspidiformes, and the extant Myxiniformes (hagfish). Some authors place the Myxiniformes with the class Cephalaspidomorphi.