<Tr> <Td> <Ul> <Li> Cyclostomata </Li> <Li> † Conodonta </Li> <Li> † Pteraspidomorphi </Li> <Li> † Myllokunmingiidae </Li> <Li> † Haikouellidae </Li> <Li> † Cephalaspidomorphi </Li> </Ul> </Td> </Tr> <Ul> <Li> Cyclostomata </Li> <Li> † Conodonta </Li> <Li> † Pteraspidomorphi </Li> <Li> † Myllokunmingiidae </Li> <Li> † Haikouellidae </Li> <Li> † Cephalaspidomorphi </Li> </Ul> <P> Agnatha (Greek, "no jaws") is a superclass of jawless fish in the phylum Chordata, subphylum Vertebrata, consisting of both present (cyclostomes) and extinct (conodonts and ostracoderms) species . The group is sister to all vertebrates with jaws, known as gnathostomes . </P> <P> Recent molecular data, both from rRNA and from mtDNA as well as embryological data strongly supports the hypothesis that living agnathans, the cyclostomes, are monophyletic . </P>

What distinguishes the super classes agnatha and gnathostomata
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