~ooIogrcalJourna1 zyxwvutsrqpo oj zyxwvutsrqponmlk the Lannean Socieg zyxwvutsrqpo (1997), 119: 83-265. With 5 figurer zyxwv Towards a phylogeny of gastropod molluscs: an analysis using morphological characters WINSTON F. PONDER Division of Invertebrate <oology, The Australian Museum, 6 College Street, Sydnq, NS. zy M;. 2000, Australia zyxwvu AND DAVID R. LINDBERG Department of Integrative Biology and Museum of Palaeontology, UniversiQ of Caltjimia, Berkeley, zyxwvut G4 94720-4780, U.S.A. ReceiL’ed Febmay I995, accepted zyxwvutsr for publication October I995 Morphological (including ultrastructural) and developmental characters utilized in recent literature are critically reviewed as the basis to reassess the phylogenetic relationships of gastropods. The purpose of this paper is to provide a framework of characters for future studies and a testable phylogenetic hypothesis. This is one of the fvst attempts to use such characters to assess the relationships of all major clades using parsimony methods. The analysis uses 1 17 characters and includes 40 taxa, predominantly ‘prosobranchs’. Five outgroup taxa are included, representing four conchiferan groups and Poly- placophora. Of the 1 17 characters reviewed and included in the analyses, nine are shell characters (four of these are shell structure), two opercular, two muscular, four ctenidial, 12 renopericardial and 24 reproductive (including 17 based on sperm and spermatogenesis), 27 of the digestive system, 32 of the nervous system and sense organs; the remainder are developmental (3) and of the foot and hypobranchial gland. In the initial analysis the data set included a mixture of binary and multistate characters with all characters unordered. These data were also analysed after scaling so that each character had equal weight. A third data set was constructed in which all characters were coded as binary characters. These analyses resulted in some implausible character transformations, mainly involving the regaining of lost pallial structures. Additional analyses were run on all three sets of data after removing five characters showing the most unlikely transformations. These analyses resulted in generally similar topologies. The robustness of the clades was tested using clade decay. The adaptive radiation of gastropods and their life history traits are briefly described and discussed and the terminology for simultaneous heririaphroditism refined. A scenario for the evolution of torsion equated with the fossil record is proposed and the effects of torsion and coiling on gastropods are discussed along with asymmetry imposed by limpet-shaped body forms. It is suggested that the first gastropods were ultradextral. The idea that heterochrony has played a major part in gastropod evolution is developed and discussed, particularly the paedomorphic stamp imposed on thc apogastropods. The veliger larvae of caenogastropods and heterobranchs are contrasted and found to differ in many respects. The evolution of planktotrophy within gastropods is discussed. Recent phylogenetic hypotheses for gastropods based on molecular data are generally in broad agreement with the present results. On the basis of our analyses we discuss the major monophyletic groups within gastropods. Gastropods appear to be a nionophyletic clade, and divide into two primary groups, the Eogastropoda (incorporating the patellogastropods and their (probably sinistrally coiled) ancestors and the Orthogastropoda ~ the Correspondence to W.F. Ponder. E-mail: witiston@amsg.austmus.oz.au 83 0024-4082/97/020083+ 183 $25.00/0/zj960066 01997 The Linnean Society of London Downloaded from https://academic.oup.com/zoolinnean/article-abstract/119/2/83/2684302 by guest on 11 June 2020