title: Evidence from 18S ribosomal RNA sequences that lampreys and hagfishes form a natural group.
abstract: Lampreys and hagfishes (cyclostomes) traditionally were considered to be a natural (monophyletic) group. Recently, the consensus of opinion, based largely on morphological analyses, has shifted to a view that lampreys are more closely related to jawed vertebrates (gnathostomes) than to hagfishes. Phylogenetic comparisons of 18S ribosomal RNA sequences from two hagfishes, two lampreys, a tunicate, a lancelet, and a number of gnathostomes support the monophyly of the cyclostomes. These data force a reassessment of several features of early vertebrate evolution.
authors.affiliation: Department of Ecology, Ethology, and Evolution, University of Illinois, Urbana 61801.
authors.forename: D W
authors.initials: DW
authors.lastname: Stock
authors.forename: G S
authors.initials: GS
authors.lastname: Whitt
mesh_terms: D000818:Animals; D001483:Base Sequence; D004275:DNA, Ribosomal / Q000235:genetics*; D014644:Genetic Variation; D006196:Hagfishes / Q000145:classification / Q000235:genetics*; D007798:Lampreys / Q000145:classification / Q000235:genetics*; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D010802:Phylogeny; D016133:Polymerase Chain Reaction / Q000379:methods; D012337:RNA, Ribosomal, 18S / Q000235:genetics*
chemical_list: D004275:DNA, Ribosomal; D009838:Oligodeoxyribonucleotides; D012337:RNA, Ribosomal, 18S