The controversial nomenclature of the fossil plant names Cheirolepis , Cheirolepidium and Hirmeriella (Cheirolepidaceae/Cheirolepidiaceae/Hirmeriellaceae)

A comprehensive nomenclatural analysis of the generic and suprageneric names used for an extinct conifer group, treated as a distinct family under the names Cheirolepidaceae, Cheirolepidiaceae or Hirmeriellaceae or a distinct order, Cheirolepidiales or Hirmeriellales, is presented. The fossil generic name Cheirolepis Schimp. (1870) is an illegitimate later homonym of the name of the extant genus Cheirolepis Boiss. (1849; Asteraceae). It has been superfluously substituted with a new generic name, Cheirolepidium Takht. (1957). The authorship and place of valid publication of Cheirolepidium is corrected based on newly discovered information. The correct generic name for these fossils is Hirmeriella Hörhammer (1933), established originally for a cone consisting of persistent bract scales lacking seed scales, because it has priority over the generic name Cheirolepidium Takht. All three fossil generic names were employed for the same fossil cone taxon, which represented different stages of maturity of the same seed cone. The inclusion of both Cheirolepis and Cheirolepidium under Hirmeriella was proposed by Jung (1968) in his formal lectotypification of the type of the genus name, Cheirolepis muensteri ( ≡ Brachyphyllum muensteri ), with a cone specimen that was cited in the protologues of the types of both genera, Cheirolepis muensteri and Hirmeriella rhaetoliassica . The lectotypification of Cheirolepis muensteri and Hirmeriella rhaetoliassica using the same elements results in the three generic names being homotypic synonyms. As a consequence, the correct family name for the fossil conifer group is Hirmeriellaceae, to be proposed for conservation against Cheirolepidiaceae. Cheirolepidaceae is inadmissible being based on the illegitimate later homonym Cheirolepis Schimp. and thus itself illegitimate.