title: Phylogenetic position of Loricifera inferred from nearly complete 18S and 28S rRNA gene sequences.
abstract: BACKGROUND
  Loricifera is an enigmatic metazoan phylum; its morphology appeared to place it with Priapulida and Kinorhyncha in the group Scalidophora which, along with Nematoida (Nematoda and Nematomorpha), comprised the group Cycloneuralia. Scarce molecular data have suggested an alternative phylogenetic hypothesis, that the phylum Loricifera is a sister taxon to Nematomorpha, although the actual phylogenetic position of the phylum remains unclear.
  
  
  METHODS
  Ecdysozoan phylogeny was reconstructed through maximum-likelihood (ML) and Bayesian inference (BI) analyses of nuclear 18S and 28S rRNA gene sequences from 60 species representing all eight ecdysozoan phyla, and including a newly collected loriciferan species.
  
  
  RESULTS
  Ecdysozoa comprised two clades with high support values in both the ML and BI trees. One consisted of Priapulida and Kinorhyncha, and the other of Loricifera, Nematoida, and Panarthropoda (Tardigrada, Onychophora, and Arthropoda). The relationships between Loricifera, Nematoida, and Panarthropoda were not well resolved.
  
  
  CONCLUSIONS
  Loricifera appears to be closely related to Nematoida and Panarthropoda, rather than grouping with Priapulida and Kinorhyncha, as had been suggested by previous studies. Thus, both Scalidophora and Cycloneuralia are a polyphyletic or paraphyletic groups. In addition, Loricifera and Nematomorpha did not emerge as sister groups.
authors.affiliation: Department of Chemistry, Biology & Marine Science, Faculty of Science, University of the Ryukyus, Senbaru 1, Nishihara, Nakagami, Okinawa 903-0213 Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamasaki
authors.affiliation: Department of Zoology, Division of Biological Science, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502 Japan.
authors.forename: Shinta
authors.initials: S
authors.lastname: Fujimoto
authors.affiliation: Seto Marine Biological Laboratory, Field Science Education and Research Center, Kyoto University, Wakayama, 649-2211 Japan.
authors.forename: Katsumi
authors.initials: K
authors.lastname: Miyazaki
keywords: Cycloneuralia; Ecdysozoa; Molecular phylogeny; Nematoida; Panarthropoda; Scalidophora