Summary: | Abstract A general study of morphology (internal anatomy mainly) of Plecoptera from all of the 15 families has been used to elaborate their phylogenetic system (in the sense of HENNIG) (fig. 1). New suborders (Arctoperlaria: Northern Hemisphere, some members secondarily in the South; Antarctoperlaria: amphinotic, several subgroups showing transantarctic distribution; 9% of all species) replace the formerly recognized ones (Setipalpia: a superfamily of Arctoperlaria; Filipalpia: a polyphyletic assemblage). The latter two dated from formal, predarwinistic classifications, but had later been treated like phylogenetic units. Presumed relations between a number of families proved incorrect, while the families themselves were found to be demonstrably monophyletic groups, in most cases.
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