Jawless fish

Agnatha (; from Ancient Greek ἀ- (a-)  'without' and γνάθος (gnáthos)  'jaws') or jawless fish is a paraphyleticinfraphylum of animals in the subphylumVertebrata of the phylumChordata, characterized by the lack of jaws. The group consists of both living (cyclostomes such as hagfishes and lampreys) and extinctclades (e.g. conodonts and cephalaspidomorphs, among others). They are sister to vertebrates with jaws known as gnathostomes, who evolved from jawless ancestors during the early Silurian by developing folding articulations in the first pairs of gill arches.