A Lineage Phylogeny for the Paleogene Planktonic Foraminifera

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Abstract
A stratophenetic lineage phylogeny (''phylogram'') is proposed for the Paleogene planktonic foraminifera, based on an extensive taxonomic review and fundamental reassessment of their geohistoric record. In this phylogeny, an attempt is made to delineate lines of genetic descent through lineages, rather than relationships among typologically defined morphospecies. The phylogenetics of 20 subgroups of the Paleogene planktonic foraminifera are summarized in a series of ''plexigrams,'' which are graphical representations of previous taxonomic opinions. The phylogeny is constructed with additional consideration of stratigraphic ranges and known examples of intergradation between taxa. As a result, approximately 800 morphospecies are grouped into six principal clades and 134 lineages, of which 70 are terminal (ending in extinction or surviving into the Neogene) and 64 are nonterminal (ending in branching). The phylogeny is in no way intended to replace the existing taxonomic methodology but rather is intended to help elucidate patterns of evolution in the group by allowing cladogenetic and anagenetic modes of evolution to be identified.