Cephalaspidomorphi

Cephalaspidomorphi is a class of jawless fishes that is presently regarded as uniting the osteostracans, galeaspids and pituriaspids. Most biologists regard this taxon as extinct, but the name is still sometimes used in the classification of lampreys because they were once thought to be descended. If lampreys are included they would extend the known range of the group from the Silurian and Devonian periods, when they are traditionally assumed to have lived, to the present day. Modern works typically assume the cephalaspidimorphs to be the closest relatives of jawed fishes, who may have emerged from within them; if this is true, they would survive if the jawed fish are included. The cephalaspidomorphs possessed armored head-shields, a heterocercal tail fin, and in some groups paired pectoral fins.

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