Anisopteris, M.Hirmer, 1940

Genus Anisopteris ( OB.- BRINK) HIRMER in Hirmer and Guthörl 1940

T y p e. Cyclopteris inaequilatera GÖPP., 1859 ≡ Anisopteris inaequilatera ( GÖPP.) HIRMER in Hirmer and Guthörl (1940: 50) designated by Boureau and Doubinger (1975).

R e m a r k s. Oberste-Brink (1914) originally established the name Anisopteris as a Section of the genus Rhacopteris SCHIMP., 1869 . Oberste-Brink (1914) noted that Anisopteris was only known from the “Culm” (Mississippian), whilst the other Section, Eurhacopteris, was only known from the Pennsylvanian (although following Turland et al. (2018) the Section name Eurhacopteris is not valid as it included the type of the genus Rhacopteris and its epithet does not repeat the generic name unaltered). Due to the stratigraphic grouping, Walton (1926) believed that the division was biased and that it should not be adopted. However, Hirmer (1940) emended the diagnosis and elevated the name Anisopteris to full generic rank, asserting that the division was not merely stratigraphic, with the Lower Carboniferous species Rhacopteris transitionis excluded from Anisopteris . It was also reported that fertile fronds are unknown in Rhacopteris , while Anisopteris includes fertile material ( Oberste-Brink 1914, Hirmer 1940). A type species for Anisopteris was only designated later when Boureau and Doubinger (1975) selected Anisopteris inaequilatera ( GÖPP.) HIRMER, 1940 . Anisopteris is not a nomenclatural synonym of Rhacopteris SCHIMP., 1869 as these two generic names are heterotypic (with Rhacopteris elegans ( ETTINGSH.) SCHIMP., 1869 given as the type species of Rhacopteris ; Kidston 1890). The taxa are considered morphologically distinct, with Anisopteris pinnules defined as strikingly asymmetrical, with no trace of a central vein ( Oberste-Brink 1914, Boureau and Doubinger 1975).