It is likely that many of the families excluded from the restricted analyzes will try to make other taxa paraphyletic. In the context of this study, the involvement of most symbiotic groups is irrelevant. Although considered part of the suborder Phyllodociformia by Fauchald (1977), the presence of a proventriculus actually suggests that a relationship with the Syllidae should be investigated (see Day 1967: 167).
Exclusion of the Gnathostomuhda is based on the lack of evidence supporting Nielsen's (1995) placement of them in the Polychaeta. Nereididae (Fitzhugh 1987), Phyllodocidae (Pleijel 1991), Sabellidae (Fitzhugh 1989), then a plesiomorphic state can be assessed for many of the characters involved. Much of the detail regarding characters and polychaete morphology can be found in Fauchald & Rouse (1997) and is not repeated here.
The weighted support branch values {bwr) for the SW-derived trees are shown next to the nodes of the consensus tree in the figure. The main difference between the SW-derived trees and the original trees is the shift of the clade (Arenicolidae, Capitellidae, Maldanidae) to a more basal position. Weighted branch support values {bwr) for the SW-derived trees are shown next to the nodes of the consensus tree in Figure 1.
In all AjPer and AjPwr trees, the loss of the limited (or absent) circulatory system is the only unambiguous character state that supports the clade (Echiura Articulata) (e.g. In A/P trees (both forms), the Annelida is represented by the same support. three features found in multistate coding, as well as having the prostomium separated from the peristomium by a distinct groove (A/P 1), and the first segment appendages the same as those that follow (A/P 37) (Fig . 67).The monophyly of the Polychaeta (including the Pogonophora) is supported in Mr trees by the (homoplastic) presence of palps (m 5) and the presence of myxonephridia (m 37) (Fig. 72).
In Mr trees, the presence (also homoplastic) of an anterior pair of excretory nephridia (m 39) is the only unequivocal condition supporting ((Frenulata Vestimentifera) (Sabellariidae (Serpulidae SabeUidae))) (Fig. 71). In the AjPec analysis (Fig. 63), Psammodrilidae appears as sister group to a clade that includes (Arenicolidae Capi- tellidae Maldanidae). In the AjPwc analysis, these taxa form a grade immediately basal to the taxa with grooved palps (Fig. 65).
One of the most important polychaete clades found in all three trees derived from SW for the AjPwr analysis (Fig. 59). One of the most important polychaete clades found in all three trees derived from SW for the A/Pwr analysis (Fig. 59).
- The families Alciopidae, Ichthyotomidae, lospilidae, Lopadorhynchidae, Myzostomidae, Nautillienellidae,
- The Oenonidae and Hartmaniellidae are members of the Eunicida
- The Ctenodrilidae, Fauveliopsidae, Poeobiidae and Sternaspidae all form a clade with the Acrocirridae,
- The Uncispionidae falls within the Spionida
- in Fig. 67) with a subsequent loss in the
- The homology of structures termed metanephridia and protonephridia and the transformation series between
- The association of nephridial systems with circulation patterns as proposed in a model by Ruppert &
- Taxa with metanephridial systems and no (or limited) circulatory system: Sipuncula, Ichthyotomidae,
- Taxa with adult protonephridial systems and a well- developed circulatory system: the Siboglinidae (in part),
- The phylum Pogonophora should be incorporated into the Polychaeta and reduced in rank to that of family,
- The Articulata is supported by essentially the same apomorphies as identified by Rouse & Fauchald (1995)
- A traditionally formulated Annelida is monophyletic (though weakly supported) and, for the time being, is
- The Aeolosomatidae and Potamodrilidae, formerly either members of the Clitellata or Annelida outside both
The grouping of the Myzostomidae and Spintheridae as basal polychaetes in the AjPec analysis (Figures 62, 63) should probably be disregarded as both groups are symbiotic, and their basal position can largely be considered losses occurring as primary absences (see below). Since their first description, the systematic position of the Psammodrilidae has been somewhat isolated (Swedmark 1958). However, it appears that the unusual features of the group by Kristensen &.
Since the classification requires the use of a limited analysis, the question is which of the coding methods. The former term is a new name based on the synapomorphy of the presence of palps. The Aciculata is a strongly supported clade and the name refers to one of the synapomorphies for the group, the presence of aciculae.
Most of the 29 families excluded from the limited analyzes can easily be placed in the above classification. The results of the full analysis show that the inclusion of paraphyletic taxa in general is not particularly problematic (see Rouse 1997). Basic classification of the taxa in these analyzes based on the trees derived from SW for the AjPwr analysis (Fig 59) The 29 taxa excluded from this analysis are placed within clade names shown here based on the A/Pnr analysis and arguments in the text (see Appendix V for the classification of excluded taxa).
This result shows several similarities with the scheme presented by Dales (1977) for the evolution of the polychaete stomodaeum. There are several questions regarding the nephridia and circulation that can be discussed in light of the findings represented in this paper. Goodrich defined nephromixia as structures resulting from the fusion of the two types of tissue.
The most interesting aspects of the Ruppert & Smith (1988) model are, of course, the exceptions. Branch support for Articulata (and Annelida) is weak, and further investigation into the position of Echiura should be pursued using molecular sequence data. The status of the Myzostomidae must now be considered in relation to other taxa with a hypertrophied axial pharynx.
Conclusions
From the available evidence for the taxa considered in this analysis, data based on cladistic relationships do not support Ruppert and Smith's model. This is clearly not the case, and similar errors by other workers have resulted in calls for the Linnaean system to be abandoned (eg many more independent examples of the co-occurrence of protonephridia and the limitation or absence of a BVS are necessary before their model can be interpreted as having any heuristic value.
Taxa with metanephridial systems and no (or limited) circulatory system: Sipuncula, Ichthyotomidae, circulatory system: Sipuncula, Ichthyotomidae, Capitellidae, Psammodrilidae and Sphaerodoridae. Taxa with enlarged protonephridial systems and a well-developed circulatory system: Siboglinidae (partially), developed circulatory system: Siboglinidae (partially), Nephtyidae and Protodrilidae. For Sipuncula, Ruppert & Smith cited evidence for the existence of podocytes in compensation sacs that could serve the purpose of primary filtration.
Ruppert & Smith (1988) and Smith & Ruppert (1988) explain taxa with protonephridia and a well-developed BVS that, in the case of the Nephtyidae, this may be an adaptation to retain hemoglobin molecules present in the coelom. Instead of seeking an adaptive explanation for the combination of protonephridia and BVS in nephthyids, further study of the relationships among taxa with secondarily derived protonephridia may be more fruitful. The stem Pogonophora should be included in Polychaeta and demoted to the position of family, in Polychaeta and demoted to the position of family Siboglinidae in the clade Sabellida.
Chaetae either evolved twice, once in Echiura and once in Annelida, or the presence of such structures is plesiomorphic for Articulata and was lost in Arthropoda. The traditionally formed Annelida is monophyletic (albeit weakly supported) and is (albeit weakly supported) and is for the time being accepted as a valid taxon. It consists of two clades, Clitellata and Polychaeta, although the monophyly of the latter is not well supported.
The Aeolosomatidae and Potamodrilidae, previously members of the Clitellata or Annelida outside both members of the Clitellata or Annelida outside both the Polychaeta and the Clitellata, should now be considered polychaetes. The use of Linnaean categories is avoided and a hierarchical set of names is given to group the 83 families that should now be considered polychaetes. If this article succeeds in any way, it should be in demonstrating the minimum level of knowledge necessary before considering any drastic step, such as starting a new family.
Acknowledgements
Academy of Sciences of the USSR, Moscow (also translated by the Israel Program for Scientific Translations, Jerusalem, 1965).
176 Appendix I
Dorsal gills are present in some taxa (Petersen & George 1991) and these are assumed to be plesiomorphic based on outgroup considerations that place them near or within the Cirratulidae (see Mesnil & Caullery 1897).
