The family Actinocrinitidae was a significant contributor to the global biodiversity peak of crinoids that occurred during the Mississippian and is referred to as the “Age of Crinoids.” Although the actinocrinitids are a major component of that high diversity, they are also a source of much taxonomic confusion. Previously, generic concepts were not applied equally between Europe and North America creating disparity in the definition of genera. In this contribution, all genera are defined objectively by discrete characters, and the generic assignments of all species are reevaluated. Twenty genera are described. A total of 206 species were evaluated of which 56 species and one taxon in open nomenclature are reassigned to different genera, 21 species are designated as nomina dubia, and three species and one genus are now incertae sedis.

A phylogenetic hypothesis is presented for the relationships of the genera of Actinocrinitidae genera based on a parsimony-based analysis and plotted against stratigraphic ranges. Although groupings were revealed in this analysis, the Actinocrinitidae cannot be readily subdivided into subfamilies. Rapid diversification occurred during the Tournaisian following the Hangenberg Extinction of probable fish predators. The late Devonian (Famennian) occurrence of the highly derived genera Abactinocrinus and Physetocrinus suggests there is a more extensive, but undocumented, evolutionary history for the Actinocrinitidae during the Devonian.

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