Agnatha

Agnatha or jawless fish is a paraphyletic infraphylum of animals in the subphylum Vertebrata of the phylum Chordata, characterized by the lack of jaws. The group consists of both living and extinct clades. 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.

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