Zoológica Scripta, Vol. 26, No. 2, pp. 139-204, 1997 Pergamon Elsevier Science Ltd © 1997 The Norwegian Academy of Science and Letters All rights reserved. Printed in Great Britain PII: S0300-3256(97)00010-X 0300-3256/97 $17.00 + 0.00 Cladistics and polychaetes G. W. ROUSE and K. FAUCHALD Accepted2A April X')')! Rouse, G. W. & Fauchald, K. 1997. Cladistics and polychaetes.•Zoo/. Scr. 26: 139-204. A series of cladistic analyses assesses the status and membership of the taxon Polychaeta. The available literature, and a review by Fauchald & Rouse (1997), on the 80 accepted families of the Polychaeta are used to develop characters and data matrices. As well as the polychaete families, non- polychaete taxa, such as the Echiura, Euarthropoda, Onychophora, Pogonophora (as Frenulata and Vestimentifera), Clitellata, Aeolosomatidae and Potamodrilidae, are included in the analyses. All trees are rooted using the Sipuncula as outgroup. Characters are based on features (where present) such as the prostomium, peristomium, antennae, palps, nuchal organs, parapodia, stomodaeum, segmental organ structure and distribution, circulation and chaetae. A number of analyses are performed, involving different ways of coding and weighting the characters, as well as the number of taxa included. Transformation series are provided for several of these analyses. One of the analyses is chosen to provide a new classification. The Annelida is found to be monophyletic, though weakly supported, and comprises the Clitellata and Polychaeta. The Polychaeta is monophyletic only if laxa such as the Pogonophora, Aeolosomatidae and Potamodrilidae are included and is also weakly supported. The Pogonophora is reduced to the rank of family within the Polychaeta and reverts to the name Siboglinidae Caullery, 1914. The new classification does not use Linnaean categories, and the Polychaeta comprises two clades, the Scolecida and Palpata. The Palpata has the clades Aciculata and Canalipalpata. The Aciculata contains the Phyllodocida and Eunicida. The Canalipalpata has three clades; the Sabellida (including the Siboglinidae) Spionida and Terebellida. The position of a number of families requires further investigation. © 1997 The Norwegian Academy of Science and Letters. Greg W. Rouse, School of Biological Sciences A08, University of Sydney. N.S.iV. 2006, Sydney, Alts t ralia Krislian Fauchald, Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington. DC 20560, U.S.A. Contents Abstract 139 Position of other problematic taxa 161 Introduction 139 New classification 161 Methods 140 Transformations 164 Taxa considered 140 Palps 164 Taxa excluded from restricted analysis 140 Stomodaeum 164 (A) Symbiotic ( = Commensal/Parasitic) taxa 140 Nephridia, segmental organs and circulatory systems 164 (B) Pelagic taxa 140 Assessment of Goodrich's (1945) hypotheses 165 (C) Interstitial (or small) taxa 141 Evolution of nephridia and segmental organs 166 (D) Poorly known taxa 141 Nephridia and circulation 167 Taxa excluded completely 141 Conclusions 168 Scoring of taxa 141 Acknowledgements 168 Characters 141 References 169 Coding issues 142 Appendix I 176 Analysis 145 la. Characters: Absence/Presence coding 176 Abbreviations used in figures 146 lb. Characters: Multistate coding 176 Results 148 Appendix 11 178 Restricted analyses 148 lia. Matrix of A/P coding 178 Complete analyses 150 lib. Matrix of Multistate coding 180 Descriptions of trees and transformations 151 Appendix III: /I priori weights applied to the initial analysis for Restricted analyses 151 A/Pe and A¡Pw 182 Complete analyses 154 Appendix IV: Justification of scores in both A/P and Multistate Discussion 155 matrices 182 Status of the Pogonophora 155 Appendix V: Classification of polychaete familites 204 Introduction tifera) and Polychaeta. A major assumption in that analysis was the monophyly of the Polychaeta, a taxon Rouse & Fauchald (1995) cast doubt on the monophyly of that has never been identified by apomorphy. This was not the traditionally formulated Annelida. They applied the particularly problematic in the context ofthat paper and in name Articulata to the clades Clitellata, Euarthropoda, fact allowed Rouse & Fauchald (1995: 294) to conclude Onychophora, Pogonophora ( = Frenulata and Vestimen- that "the Clitellata, 'arthropods', and Pogonophora may 139 Zoológica Scripta 26 140 G. W. Rouse and K. Fauchald Eibye-Jacobsen & Kristensen (1994) for the Dorvilleidae, which is well prove to fall inside the Polychaeta; use of these taxa as paraphyletic if the Dinophilidae (interstitial/minute) and Iphitimidae outgroups for an analysis of polychaete relationships is not (commensals with crustaceans) are recognised. This paper has a series of justifiable at this time". analyses where all polychaete families that can be classified as being symbiotic (sensu lato), pelagic or interstitial were excluded. It is likely that The history of the taxon Polychaeta was reviewed in many of the families excluded from the restricted analyses will prove to detail by Fauchald & Rouse (1997), along with a summary make other taxa paraphyletic. This is not to suggest that all the families of the various taxa at the family level and of morphological included in the restricted analyses are monophyletic; this is probably very far from the truth. The use of paraphyletic taxa is not problematic in features that have been used to classify the group. cladistic analyses and is a common occurrence (Rouse 1996). In general, Fauchald & Rouse (1997) found that 80 families currently paraphyletic taxa will appear as the sister group to their excluded (or usually) placed in the Polychaeta should be considered members. However, the mode of existence of most of the 29 excluded taxa is such that many of the features that they have probably lost, such as in any phylogenetic analysis at that taxonomic level. chaetae, would have to be coded as absent and would appear as such in the Additionally, based on discussion and results of Rouse & resulting trees. This could possibly, though not necessarily, complicate the Fauchald (1995) and Fauchald & Rouse (1997), the status analyses and give misleading results. Four families were also excluded because they are insuflSciently known. All taxa are, however, scored and of current non-polychaete groups, such as the Aeolosoma- documented in the Appendices. Analyses including all 80 accepted tidae, Clitellata, Euarthropoda, Frenulata, Onychophora, polychaete families (and the Aeolosomatidae and Potamodrilidae) are Potamodrilidae and Vestimentifera, should be considered also shown for the various forms of character coding. The excluded taxa are grouped into several categories: in any analysis of the Polychaeta. (A) Symbiotic ( = commensal/parasitic) taxa. The assumption here is The aims of this paper are several: that any symbiotic group of polychaetes is derived from a free-living group. Parasitic organisms are known for their apomorphic features often 1. To assess the monophyly of the Polychaeta and combined with apparent morphological simplicity (Brooks & McLennan relationships among the taxa usually included in the 1993). Depending on the level of analysis chosen, this latter condition can appear as an absence rather than a loss and hence can seriously affect tree group and those traditionally excluded. topologies. All parasitic or commensal polychaete families are excluded 2. To provide a new classification. owing to this possibility. Cladistic placement has been hypothesised for 3. To discuss the possible transformation of characters most of them and should be assessed in more restricted analyses where more relevant characters can be used to assess relationships. In the used in the study. context of this study, the inclusion of most of the symbiotic groups is trivial. The excluded families in this category are: Proposing a new classification is somewhat problematic (1) HistriohdelUdae. Parasitic/commensal on crustaceans. Probable sister since this study is a first heuristic step in terms of bringing group among taxa with a hypertrophied ventral proboscis (see Jamieson polychaete systematics to an acceptable level of rigour. etal. 1985). Any classification proposed is unlikely to have any long- (2) Ichthyotomidae. Parasitic on anguilliform teleosts. Probable sister group among taxa either with a hypertrophied axial proboscis or evity because of the inadequate knowledge of many taxa. hypertrophied ventral proboscis (Fauchald 1977; Pettibone 1982). However, the current situation is untenable, so what is (3) Myzostomidae. Parasitic/commensal on echinoderms. Recent studies presented must be considered an improvement. Various on the myzostomids have all indicated that they should be regarded as a group of polychaetes (see review in Rouse & Fauchald 1995). Rouse & issues of character coding and weighting are explored since Fauchald ( 1995) proposed that myzostomids probably have a sister group these are fundamental to any cladistic analysis. among taxa having a hypertrophied axial proboscis. (4) Nautillienellidae. Parasitic/commensal of bivalves. Found to be either the sister group to the Pilargidae or Syllidae (Glasby 1993). (5) Oenonidae. In most cases, there is a parasitic phase of life cycle in other Methods polychaetes. Sister group among taxa with a hypertrophied ventral proboscis. (6) Spintheridae. 'Parasitic' on sponges, probable sister group in the Taxa considered amphinomid/euphrosinid clade. Rouse & Fauchald (1995) identified the Echiura as the sister group to the