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Lampreys (A) and hagfish (B) are the only extant jawless vertebrates. (C) Phylogenetic tree showing relationships among vertebrates and invertebrate chordates. Hagfish and lamprey are on top forming the jawless cyclostome clade, with the jawed vertebrates below. The closest living relatives to the vertebrates are the tunicates, a lineage of invertebrate chordates (bottom). Images from panels (A) and (B) were used with permission from Wikipedia Commons.
