XVI International Botanical Congess

The Osmundaceae is consistently placed among the most basal of leptosporangiate ferns in phylogenetic analyses based on extant taxa, as it shares sporangial features with both the leptosporangiate and eusporangiate ferns. However, the modern Osmundaceae contains only three genera, which can potentially result in misleading hypotheses about relationships with other basal families, particularly as the closest relatives to other families may be extinct. Therefore, fossil morphological and anatomical data are essential to understanding the relationships among basal fern families. There is an abundance of fossil osmundaceous material available, as the group has had a long and diverse history traceable to the Permian. The group seems to have reached its maximum diversity and distribution during the Mesozoic, and is particularly interesting for information it has provided about character evolution and stasis in ferns. A preliminary analysis incorporating fossil osmundaceous specimens into a preexisting data set based on extant morphology is presented that provides additional insight regarding the relationships among the basal members of these groups.