Abstract
Our understanding of the early evolution of animals will be greatly improved if a final solution can be found to the evolutionary relationships between Porifera, Placozoa, Ctenophora, Cnidaria and Bilateria. There have been many recent attempts to solve this key issue at the base of the metazoan tree of life, and these have sparked heated discussions and highlighted fundamental analytical problems. We argue that solving this problem will necessitate analysis of disparate data types, including phylogenomic data, larger scale genomic characters, developmental data and morphological characters. At the least, morphological and developmental data must be used to cross-validate phylogenomic conclusions, but ideally solutions should be sought to the problems of combining disparate data sources with appropriate character weighting and algorithm choice.
Highlights
The base of the metazoan tree of life is one of those phylogenetic enigmas that has charm, appeal, and elusiveness
“Unringing” the Urmetazoon Bell and we hope by placing this problem under the microscope that researchers facing similar phylogenetic/systematic problems will benefit from our discussion
If we want a solution to the problem of resolving the phylogeny and evolution of non-bilaterian metazoans and their relationships to Bilateria we will need to play by the “rules” of modern phylogenetics to get to the hypothesis best supported by the data
Summary
The base of the metazoan tree of life is one of those phylogenetic enigmas that has charm, appeal, and elusiveness. We need to discuss if there ever will be either (a) an unquestioned dataset and analysis, or (b) a middle ground where researchers will settle Addressing these questions requires that we examine multiple sources of data for two reasons. Such an examination might tell us why the controversy here is so pointed and sensitive to data input, and secondly to understand why the outcome of major studies addressing this problem are so prone to data handling and analytical approaches. Other parts of the tree of life are contentious “Unringing” the Urmetazoon Bell and we hope by placing this problem under the microscope that researchers facing similar phylogenetic/systematic problems will benefit from our discussion
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