Fossil record of the Icacinaceae and its paleogeographic implications

Abstract In the past decades, the concept of Icacinaceae has been refined greatly, as morphological and molecular data have led to a narrower circumscription of a monophyletic Icacinaceae family with only 23 genera (vs 58 sensu Sleumer, 1942 ). This family possesses an extensive fossil record, important to the biogeographic history of the Northern Hemisphere, but the reported fossils need to be carefully evaluated in the current phylogenetic framework. We evaluated 183 fossil reports of Icacinaceae from the literature but considered only 92 as reliably belonging to this family. Most of the accepted records are from endocarp remains. With this sampling, we show an increase of the species richness during the Paleocene. A great increase of diversity in terms of genera, species, and morphological range is shown through the Paleocene–Eocene interval and during the Early Eocene (Ypresian). Exchanges occurred between North America and Europe near the PETM in both directions. During the middle and late Eocene, several of the modern genera appear first in the fossil record such as Natsiatum, Phytocrene, and Pyrenacantha. Decreased diversity of post-Eocene records might be explained by cooling during and subsequent to the Oligocene, which was less favorable to climbers. We observe the same pattern in other megathermal families showing the global dynamic of megathermal groups of the North Hemisphere forest (boreotropical sensu. Wolfe, 1975 ) during the Paleogene.