Agnatha (Greek, "no jaws") is a class or superclass of jawless fish in the phylum Chordata, subphylum Vertebrata. Many recent textbooks regard the group as paraphyletic but recent molecular data, both from rRNA and from mtDNA strongly supports living agnathans as monophyletic. It has existed since the Cambrian, and continues to live now. There are two extant groups of jawless fish (sometimes called cyclostomes), the lampreys and the hagfish, with about 100 species in total.