Chapter

Invertebrate Problematica: kinds, causes, and solutions

Ronald A. Jenner, D. Timothy and J. Littlewood

in Animal Evolution

Published in print August 2009 | ISBN: 9780199549429
Published online September 2009 | e-ISBN: 9780191721601 | DOI: http://dx.doi.org/10.1093/acprof:oso/9780199549429.003.0011
 Invertebrate Problematica: kinds, causes, and solutions

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Problematica are taxa that defy robust phylogenetic placement. Traditionally the term was restricted to fossil forms, but it is clear that extant taxa may be just as difficult to place, whether using morphological or molecular (nucleotide, gene, or genomic) markers for phylogeny reconstruction. This chapter discusses the kinds and causes of Problematica within the Metazoa, but particularly focussing on the invertyebrate taxa, as well as suggesting criteria for their recognition and possible solutions. The inclusive set of Problematica changes depending upon the nature and quality of (homologous) data available, the methods of phylogeny reconstruction and the sister taxa inferred by their placement or displacement. Rather than excluding Problematica from phylogeny reconstruction, as has often been preferred, this chapter concludes that the study of Problematica is crucial both for the resolution of metazoan phylogeny, and the proper inference of body plan evolution. This chapter provides an annotated list of key extant problematic taxa.

Keywords: Problematica; Metazoa; Bilateria; phylogenomics; animal evolution; character loss

Chapter.  11307 words.  Illustrated.

Subjects: Evolutionary Biology

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