Article: Permian Leonardosia organic oospores from southern Brazil
Leonardosia Sommer is one of the scarce Permian charophyte genera and is part of the lineage that may include the ancestors of the post-Palaeozoic families. Oospores of the species Leonardosia langei Sommer have been found in strata of the Teresina Formation, Paraná Basin, Southern Brazil, where they are preserved as compressions. The charophyte organs found in this formation, including the original description of Leonardosia have been previously been interpreted as gyrogonites despite the presence of a carbonaceous film. We propose that these charophyte organs and the fructifications should be re-interpreted as organic oospores rather than gyrogonites. The coiling pattern, in most cases, proved to be reverse as a result of the compression of the oospore against the internal wall of the dissolved gyrogonite. In some cases, the coiling was ambiguously observed in both directions by an overlap of the opposite walls of the oospore and the dissolved gyrogonite. A simple basal plate for L. langei was registered, and its relation with the main ideas about the phylogeny and the evolution of Mesozoic charophytes is also discussed. The ‘Stellatocharoideae’ is polyphyletic including both the stem lineage of the Nitellaceae, represented by the multipartite basal plate genera, and a clade that belongs to the evolutionary line of the Monoplacata, represented by Leonardosia.