Agnatha (from Ancient Greek ἀ- (a-) 'without' and γνάθος (gnáthos) 'jaws') is a paraphyletic infraphylum of non-gnathostome vertebrates, or jawless fish, in the phylum Chordata, subphylum Vertebrata, consisting of both living (cyclostomes) and extinct (conodonts, anaspids, and ostracoderms, among others). Among recent animals, cyclostomes are sister to all vertebrates with jaws, known as gnathostomes.
