Cyclostomi

Cyclostomes; Temporal range: Lochkovian - Recent
	Sea lamprey from Sweden
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Infraphylum:	Agnatha
Superclass:	Cyclostomi; Duméril, 1806
Classes
	Myxini (hagfishes); Petromyzontida (lampreys);

Cyclostomi, often referred to as Cyclostomata /sɪkloʊˈstɒmətə/, from Ancient Greek κύκλος (kúklos), meaning "circle", and στόμα (stóma), meaning "mouth",^[1]^[2]^[3] is a superclass of vertebrates that comprises the living jawless fishes: the lampreys and hagfishes. Both groups have jawless mouths with horny epidermal structures that function as teeth called ceratodontes, and branchial arches that are internally positioned instead of external as in the related jawed fishes.^[4] The class was named by Joan Crockford-Beattie.^[5]

^ Kuraku, Shigehiro, S. Blair; Ota, Kinya G. & Kuratani, Shigeru (2009b). "Jawless fishes (Cyclostomata)". In S.B. Hedges & S. Kumar (eds.). Timetree of Life. Oxford University Press. pp. 317–319. ISBN 978-0-19-953503-3.
^ Haeckel (1895). Systematische Phylogenie der Wirbelthiere (Vertebrata). Entwurf einer systematischen Stammesgeschichte (in German). Vol. 3 (1 ed.). Berlin: Georg Reimer. pp. 142–143.
^ Duméril, A.M. Constant (1806). Zoologie analytique, ou me´thode naturelle de classification des animaux, Rendue plus facile a l'Aide de Tableaux Synoptiques (in French). Paris: Allais.
^ The oldest fish in the world lived 500 million years ago | SBS News
^ Turner, Susan; Beattie, Joan (2008). "Joan Crockford-Beattie D.Sc." (PDF). Annals of Bryozoology 2: Aspects of the History of Research on Bryozoans. 2: viii, 442.