Character investigation and homology, with a brief discussion on the phylogenetic relationships of Annelida and Polychaeta within Metazoa

The intense production of information demands coherent treatment of available bodies of theoretical knowledge. A critical revision of methods in use within research programs is essential to maintain an adequate ontology and to guarantee the particular epistemological position required by each research area. The theory of Phylogenetic Systematics was developed in multiple forms, resulting in hypotheses that may be widely incongruent. This reflects the crisis of present paradigm, and illustrates failures in present phylogenetic thinking. The aim of the study is to discuss characters and homology hypotheses based on Hennigian principles. We present samples from the most unresolved groups within the evolutionary history of the Metazoa: Annelida and Polychaeta. The main phylogenetic proposals appearing in the history of the Annelida, from morphological (living and fossilized organisms) to molecular approaches are discussed. We do not consider annelids and polychaetes to be monophyletic entities. Both taxa need more detailed comparisons with others groups, such as deuterostomes. According to our published opinions, Annelida and Polychaeta are placed at the base of the deuterostomes, and these worm-like organisms are ultimately the ancestors of the Enterocoela. Thus, in order to systematize the Metameria, we have regarded Annelida, Pleistoannelida, Lophotrochozoa and Protostomia as being paraphyletic taxa.