Definition that contains jawless fish
- suborder heterostraci extinct group of armored jawless fishes or fish-like vertebrate; taxonomy is not clear
- cephalaspid extinct jawless fish of the Devonian with armored head
- heterostraci extinct group of armored jawless fishes or fish-like vertebrate; taxonomy is not clear
- anaspid extinct small freshwater jawless fish usually having a heterocercal tail and an armored head; of the Silurian and Devonian
- osteostracan extinct jawless fish of the Devonian with armored head
- heterostracan extinct jawless fish with the anterior part of the body covered with bony plates; of the Silurian and Devonian