Late Palaeozoic lycopsid macrofossils from the Paraná Basin, South America – an overview of current knowledge

Lycopsids evolved arborescent and sub-arborescent growth habits and played a major paleoecological role during the late Palaeozoic. Here we provide an overview of lycopsid macrofossils documented so far in the late Palaeozoic deposits of the South American Parana Basin. Most of these lycopsid remains were reported from the Brazilian part of the basin, whereas only a few records have been documented from the Uruguayan and Paraguayan parts. The oldest well-documented macrofossil record of these plants in late Palaeozoic strata of this basin comes from Pennsylvanian interglacial deposits of the Itarare Group. As the late Palaeozoic ice retreated, arborescent and sub-arborescent lycopsids successfully colonized the Brazilian Cisuralian post-glacial palaeoenvironments represented by the Rio Bonito Formation, becoming important elements of the iconic Glossopteris flora. The late Palaeozoic transgression during the Artinskian coincided with the termination of the fluvio-deltaic and peat-forming systems of this formation in most areas of the basin, and this might have affected the lycopsids that grew in these peat-forming palaeoenvironments. Lycopsids again became significant components of the flora in the Brazilian part of the basin during the deposition of the Teresina and Corumbatai formations in the Guadalupian. After the increase of aridity in South America during the upper Permian, the group seems to have disappeared from the late Palaeozoic fossil record of the basin. The late Palaeozoic lycopsid macrofossil record of the Parana Basin consists mainly of fragmented and incompletely preserved specimens, which lack crucial parts for systematics, such as reproductive structures. Therefore many aspects of these plants are still poorly known. The discovery of more completely preserved specimens and reproductive structures is required to provide a robust taxonomical and systematical classification, and reliable palaeobiogeographical and evolutionary hypotheses for the distribution and evolution of these particular lycopsids.