The controversial nomenclature of the fossil plant names Cheirolepis, Cheirolepidiumand 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 CheirolepisSchimp. (1870) is an illegitimate later homonym of the name of the extant genus CheirolepisBoiss. (1849; Asteraceae). It has been superfluously substituted with a new generic name, CheirolepidiumTakht. (1957). The authorship and place of valid publication of Cheirolepidiumis corrected based on newly discovered information. The correct generic name for these fossils is HirmeriellaHörhammer (1933), established originally for a cone consisting of persistent bract scales lacking seed scales, because it has priority over the generic name CheirolepidiumTakht. 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 Cheirolepisand Cheirolepidiumunder Hirmeriellawas 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 muensteriand Hirmeriella rhaetoliassica. The lectotypification of Cheirolepis muensteriand Hirmeriella rhaetoliassicausing 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 CheirolepisSchimp. and thus itself illegitimate.