Fluorescence Properties of Exceptionally Preserved Colored Leaves from the Pliocene of the Willershausen Lagerstätte, Germany

Abstract

The Willershausen Fossil-Lagerstätte in Germany is well-known for the exceptional preservation of plant and animal fossils and represents one of the taxonomically richest Pliocene assemblages in Europe. Vertebrate fossils found in the laminated carbonates from Willershausen often show preservation of soft parts, and leaves are famous for their color preservation. Here, we report the discovery of distinct UV-light induced fluorescence in different fossil angiosperm leaf taxa from Willershausen. An astonishing observation was the presence of different fluorescence colors that ranged from yellow to red. Moreover, fluorescence properties were found to be related to genera. Using confocal laser scanning microscopy, fluorescence emission spectra were measured from fossil and present-day leaves. On the basis of their emission maxima, it was possible to distinguish broad groups of fluorophores. Our results suggest that fluorescence properties of the Willershausen leaves are mainly caused by taxon-dependent degeneration of organic compounds during senescence. Therefore, fluorescence properties might be used for supplementary taxonomic information. Because the investigated leaf fossils from Willershausen were found in a single horizon, it can be excluded that observed differences in fluorescence properties are the result from differences in diagenesis.