Water fern spores (Salviniales) from the Late Cretaceous of Patagonia, Argentina

Abstract

We describe a water fern spore assemblage from the Maastrichtian La Colonia Formation, Chubut Province, Patagonia, Argentina. The assemblage includes three species of Azolla (A. andreisii sp. nov., A. coloniensis, and A. sp. 1), two species of Azollopsis (A. intermedia and A. tomentosa), Crybelosporites pannuceus, Gabonisporis cristata, Ghoshispora sp., Grapnelispora loncochensis, two species of Molaspora (M. lobata and M. reticulata), and Paleoazolla patagonica. A. tomentosa, A. intermedia, G. cristata, and M. reticulata are recorded for the first time in the Southern Hemisphere. Ghoshispora sp. constitutes the southernmost record of the genus and its first mention for Argentina. In addition, the genus Azollopsis is emended to include megaspore apparatuses with more than one megaspore. This water fern spore assemblage is one of the most diverse so far known for South America and substantiates the significant radiation that aquatic ferns underwent worldwide at the end-Cretaceous. Furthermore, it also implies that the presence of widespread suitable paleoenvironments allowed the establishment and rapid evolution of these plant communities in Patagonia.