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Premise of research. The Río Genoa Formation of Argentine Patagonia hosts Early Permian fossil assemblages that document levels of plant diversity rare among coeval floras. Ongoing work to exhaustively characterize the diversity of these assemblages is key to understanding Permian vegetation and plant evolution. A new fern type identified in the Río Genoa Formation exhibits a novel combination of characters that required taxonomic assessment. Methodology. Observations and measurements of vegetative and reproductive morphology of compression fossils were used in a comparative framework to address the taxonomic placement of the fossils. Pivotal results. The new fern, Floratheca apokalyptika gen. et sp. nov., is characterized by small pinnules with a free base, weakly lobed margin, highly decurrent midvein, and rarely branched lateral veins, as well as radially symmetrical synangia with stellate dehiscence, consisting of six spindle-shaped sporangia. This unique combination of characters distinguishes Floratheca from the more than 25 Permo-Carboniferous marattialean genera known from compressions. Floratheca exhibits variable synangium morphology during development and variation in pinnule base morphology due to a combination of adaxial-abaxial asymmetry of ultimate rachises and taphonomic effects. Conclusions. Floratheca is one of only three late Paleozoic bona fide marattialean compression genera endemic to Gondwana and the second late Paleozoic endemic South American marattialean with preserved fertile structures. Floratheca adds to an increasing diversity of fossils that diminish the disparity between the Southern and Northern Hemispheres, in terms of the extent and intensity of exploration of the plant fossil record, currently skewed taxonomically toward Northern Hemisphere taxa. Variability of synangium and pinnule base morphology in Floratheca cautions against potential taxonomic inflation produced by establishment of new taxa based on small numbers of specimens and incomplete understanding of development and taphonomy. [ABSTRACT FROM AUTHOR]

Two new compression-impression species of the Osmundaceae described from reproductive and vegetative remains are erected for the first time from the Early Jurassic of Argentina. Todites cacereii sp. nov. and Osmundopsis rafaelii sp. nov. demonstrate that two main osmundaceous reproductive morphologies; i.e., differentiated reduced or unreduced fertile laminae were already present and widespread in Gondwana by this time. On the basis of a discussion of relevant morphological characters, the phylogenetic meaning of the fossils Todites and Osmundopsis is explored. Likewise, the systematics and taxonomy of fossil taxa and their relationships with modern ones are discussed in light of current hypotheses. In this regard, because clear synapomorphies or apomorphies are not yet fully understood, it is suggested that fossil representatives are better placed in morphotaxa (Todites, Osmundopsis) than in any current genus. Nonetheless, the clear record of characters of the leptopteroid clade by the early Jurassic proves to be older than previously assumed, which also points to an earlier time of origination for the osmundaceous ferns. [ABSTRACT FROM AUTHOR]