title: Evidence from 12S ribosomal RNA sequences that onychophorans are modified arthropods.
abstract: The evolutionary relationships of the onychophorans (velvet worms) and the monophyly of the arthropods have generated considerable debate. Cladistic analyses of 12S ribosomal RNA sequences indicate that arthropods are monophyletic and include the onychophorans. Maximum parsimony analyses and monophyly testing within arthropods indicate that myriapods (millipedes and centipedes) form a sister group to all other assemblages, whereas crustaceans (shrimps and lobsters) plus hexapods (insects and allied groups) form a well-supported monophyletic group. Parsimony analysis further suggests that onychophorans form a sister group to chelicerates (spiders and scorpions) and crustaceans plus hexapods, but this relationship is not well supported by monophyly testing. These relationships conflict with current hypotheses of evolutionary pathways within arthropods.
authors.affiliation: Division of Entomology, CSIRO, Canberra, Australia.
authors.forename: J W
authors.initials: JW
authors.lastname: Ballard
authors.forename: G J
authors.initials: GJ
authors.lastname: Olsen
authors.forename: D P
authors.initials: DP
authors.lastname: Faith
authors.forename: W A
authors.initials: WA
authors.lastname: Odgers
authors.forename: D M
authors.initials: DM
authors.lastname: Rowell
authors.forename: P W
authors.initials: PW
authors.lastname: Atkinson
mesh_terms: D000818:Animals; D001483:Base Sequence; D004272:DNA, Mitochondrial / Q000235:genetics*; D006801:Humans; D007448:Invertebrates / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D012335:RNA, Ribosomal / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid
chemical_list: D004272:DNA, Mitochondrial; D012335:RNA, Ribosomal