title: Details of the evolutionary history from invertebrates to vertebrates, as deduced from the sequences of 18S rDNA.
abstract: Almost the entire sequences of 18S rDNA were determined for two chaetognaths, five echinoderms, a hemichordate, and two urochordates (a larvacean and a salp). Phylogenetic comparisons of the sequences, together with those of other deuterostomes (an ascidian, a cephalochordate, and vertebrates) and protostomes (an arthropod and a mollusc), suggest the monophyly of the deuterostomes, with the exception of the chaetognaths. Chaetognaths may not be a group of deuterostomes. The deuterostome group closest to vertebrates was the group of cephalochordates. Ascidians, larvaceans, and salps seem to form a discrete group (urochordates), in which the early divergence of larvaceans is evident. These results support the hypothesis that chordates evolved from free-living ancestors.
authors.affiliation: Department of Zoology, Faculty of Science, Kyoto University, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Wada
authors.forename: N
authors.initials: N
authors.lastname: Satoh
mesh_terms: D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002816:Chordata, Nonvertebrate / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics*; D007448:Invertebrates / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D014714:Vertebrates / Q000235:genetics*
chemical_list: D017931:DNA Primers; D004275:DNA, Ribosomal