Late Paleocene Lagerstätten: What Can They Tell Us about Systematics?

Studies of Late Paleocene paleobotany of the past two decades, particularly in western North America, have emphasized paleoecological and paleoclimatological reconstructions. Consequently, the systematic affinities of Paleocene plants have tended to take a backseat to leaf physiognomic approaches using morphotypes. Most of the systematic studies that have been done for this time period have clarified details for well known families (e.g., Cornaceae, Platanaceae, Ulmaceae), however an understanding of the breadth of diversity of families present in the Late Paleocene has been wanting. In our studies of the Almont-Beicegel Creek Lagerstätten of North Dakota we note several angiosperm families that have been poorly known for the Paleocene, including Ranunculaceae, Polygalaceae, Icacinaceae and Ochnaceae. Also of interest are families such as the Bignoniaceae and legumes that appear in the Late Paleocene and radiate during the PETM to eventually occupy their present broad distributions. Additionally we recognize genera of well known families that have a mosaic of characters not seen in extant genera (e.g., Betulaceae, Hamamelidaceae), as well as aquatic plants (Nymphaeaceae). The Almont-Beicegel Creek Lagerstätten provide us with critical taxonomic details that allow a new focus on Late Paleocene systematics, and a way to better relate the fossil taxa represented by morphotypes used in paleoclimate studies to their extant descendants. Tracking the response of Late Paleocene taxa into the Eocene has the potential of providing insight regarding how modern members of these families could respond to future climate change. This will only be possible as we decipher the systematic affinities of recognized leaf morphotypes.