NEW PHYLOGENY-BASED AND LINNAEAN CLASSIFICATIONS OF THE CRINOIDEA (ECHINODERMATA)

Biological classification provides a system to convey phylogenetic relationships and to promote communication among researchers and the public at large. Phylogenetic taxonomy is a useful framework for defining clades and delineating their taxonomic content based on well-supported phylogenetic hypotheses. The Crinoidea (Echinodermata) is one of the five clades of living echinoderms and have a rich fossil record spanning nearly a half billion years. Based on recent phylogenetic analyses, the first phylogeny-based classification is presented for the Crinoidea and its constituent subclades. Although differing opinions exist on certain aspects of early crinoid evolution, there is overwhelming agreement regarding the existence of particular crinoid clades, e.g., Camerata and Disparida.

A series of stem- and node-based definitions are proposed to recognize these clades. In addition, recent phylogenetic analyses support the resurrection of two names previously abandoned in the crinoid taxonomic literature: the Pentacrinoidea Jaekel, 1918 and Inadunata Wachsmuth and Springer, 1885. A rank-based classification is also proposed that reflects the clades recognized in recent computational analyses. The traditional taxonomic system is preserved where possible. However, numerous changes were necessary to achieve monophyly, especially above the order level. These phylogeny-based revisions provide a useful template for crinoid paleontologists, biologists, and non-experts alike to better explore evolutionary patterns and processes with fossil and living crinoids.