A REVIEW OF SELECTED TRIASSIC TO EARLY CRETACEOUS FERNS

After becoming nearly extinct during the Permian, the ferns began a slow recovery during the Triassic as the climate of the earth moderated, As a result, a considerable number and variety were present and widely distributed during the Jurassic and Early Cretaceous. However, with the rapid expansion of the angiosperms during the Late Cretaceous, the ferns once again became reduced in variety and greatly restricted in distribution. Some of the Mesozoic ferns are rather primitive and obviously are closely related descendants of Paleozoic taxa. Such ferns are assigned mostly to the Marattiaceae, Guaireaceae, Osmundaceae, and Gleicheniaceae. The majority of the Mesozoic ferns, however, are distinctive and appear to have originated during that era. These fossil ferns generally fit into modern orders and families such as the Matoniaceae or the Dipteridaceae, In some cases, it is difficult to clearly distinguish some of the Mesozoic ferns from living genera.