Phylogenetic study of the cephalopoda based on anatomical, embryological and molecular data

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1) Comparative embryological studyOn the basis of well-preserved material from various localities throughout the world, Tanabe and Shigeta have investigated the embryonic shell features of the embryonic shells of various ammonoids using a scanning electron microsope, and the results were compared with data on other extant and fossil cephalopods. As a results, it was revealed that the embryonic shell features in ammonoids are quite different from those of nautilids but are quite similar to those of coleoids. Tanabe is now studying with Mr.Kimio Uchiyama of the Toba Aquarium on the embryonic shell development of living Nautilus in aquaria. Details of these studies will be published in a book chapter of "ammonoid Paleobiology" (Plenum Press) in 1996.2) Comparative anatomical studyTanabe and Mapes (1995) described the jaws and radula of a Carboniferous ammonoid Cravenoceras from Oklahoma and discussed its phylogenetic implications.3) Phylogenetic sutdyIn order to realize the phylogenetic position of the Ammonoidea within the Cephalopoda, Tanabe and Landman (American Museum of Natural History, New York) did a cladistic analysis of 14 embryonic and anatomical characters in five operational taxonomic units. As a result, it was realized the Cephalopoda consists of two monophyletic groups, the Nautiloidea and the Neocephalopoda, the latter includes the Sphaerorthocerida, Ammonoidea, and Coleoidea. This result will be published in Novitates in 1996.4) Molecular biological studyEndo is now doing research on the molecular systematic study on Nautilus, a well-known living fossil. He also is analyzing biomolecules preserved in cephalopod hard tissues to obtain data on molecular evolution.