G-1

It is suggested alate Plioceneage (Reuverian) for this flora.Palynoflorasfrom drill cores in the surroundings ofFrankfurt am MainandHanaualso suggests a late Pliocene age. ThePlioceneflora ofFrankfurt am Maindescribed byKarl Mädlerduring the first half of the twentieth century is a key flora for the European Pliocene. In total 16gymnospermspecies in 15 genera and 73angiospermspecies (of which 15 could not be assigned to a genus) in 40 genera are recognised in the leaf record. Main characteristics of the flora are the high diversity of conifers, deciduousangiospermgenera such asEucommia,MagnoliaandSassafras, a diverse assemblage of exclusively deciduousFagaceae, including six species of oaks, the high diversity ofRosaceae, whereas evergreen taxa are shrubs typical of the understorey asBuxus,Ilex,Pachysandra,Prunus lusitanicaandViscum. These features indicate cool temperate climatic conditions comparable to present-dayLuganoin southern Switzerland. The flora shows a strong biogeographic link with East Asia, surprisingly high levels of Pliocene endemisms and that the European flora was more diverse in woody species shortly before the onset of the majorPleistoceneglaciations than today. The early part of the Pliocene (5.3–3.6 Ma) was characterised by warm conditions (ca. 3 °C higher global surface temperatures) and higher sea levels (10–20 m) and slightly higher CO2concentrations. During the second part of the Pliocene, gradual cooling culminated in a significant intensification of northern hemispheric glaciation at ca. 2.75 Ma. Despite this, many exotic taxa persisted as relicts from older epochs and modern diversity patterns of trees and shrubs across the Northern Hemisphere were established only during and after the major Pleistocene glaciations.