A class of archaic, jawed (gnathostome), and heavily armoured fish, which appeared in the Devonian Period and which were virtually extinct by its end. They were rather diverse in body form. They all possessed a head shield formed by bony plates. Pectoral and pelvic fins appear to have been present. Most of them were bottom-dwelling, with a depressed body terminating in a heterocercal tail.
Subjects: Earth Sciences and Geography — Zoology and Animal Sciences.