Hyperoartia

Hyperoartia or Petromyzontida is a group of jawless fish that includes the modern lampreys and their fossil relatives, the jawless fish of the class Anaspida. Examples of hyperoartians from early in their fossil record are Endeiolepis and Euphanerops, fishes with hypocercal tails that lived during the Late Devonian Period. Some paleontologists still classify these forms among the jawless armored fishes.

The only hyperoartians surviving today are lampreys, classified in the Petromyzontiformes. The discovery of the fossil Priscomyzon, pushed back the oldest known occurrence of true lampreys to the Late Devonian. The evidence of phylogeny, however, suggests that the lamprey lineage diverged much earlier from other vertebrates, rather than arising from ostracoderm fishes. The origin of Hyperoartia may therefore extend back to the early Paleozoic, if not earlier.