Oligocene ferns from the Rancahué Formation (Aluminé, Neuquén, Argentina): Cuyenopteris patagoniensis nov. gen., nov. sp. (Polypodiales: Blechnaceae/Dryopteridaceae) and Alsophilocaulis calveloi Menéndez emend. Vera (Cyatheales: Cyatheaceae)

The study of abundant permineralized fern remains collected in the Oligocene Rancahué Formation (Neuquén Province, Argentina) allowed the identification of two different taxa. The name Cuyenopteris patagoniensis nov. gen., nov. sp. is proposed for several stems and fronds characterized by the presence of caulinar dictyosteles with root gaps, producing C-shaped leaf traces composed by two hippocampiform bundles flanked by eight to ten small round bundles, half of them diverging from cauline meristeles and the rest from the hippocampiform bundles. The presence of these features, along with frond bases with adaxial grooves and a pair of pneumatophores, suggest affinities with the Blechnaceae or Dryopteridaceae. The second identified taxon is Alsophilocaulis calveloi Menéndez. Based on features observed in these new materials, including characteristics of the mantle of adventitious roots and anatomy of the petiole bases, an emended diagnosis for this latter species is proposed.