Abstract The Pliocene flora of Frankfurt am Main described by Karl Mädler during the first half of the twentieth century is a key flora for the European Pliocene. In the present study, we revised the leaf fossil taxa described by Mädler and investigated plant material collected after Mädler’s publication. The revised and augmented floral list comprises seven new species and some new combinations of taxa described by Mädler. In total, 16 gymnosperm species in 15 genera and 73 angiosperm species (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, the diverse assemblage of exclusively deciduous Fagaceae, including six species of oaks, and the high diversity of Rosaceae. These features indicate cool temperate climatic conditions (comparable to Lugano in southern Switzerland). Angiosperm genera that are today confined to North America and/or East Asia ( Eucommia , Magnolia and Sassafras ) also are deciduous, whereas evergreen taxa are shrubs typical of the understorey ( Buxus , Ilex , Pachysandra , Prunus lusitanica type) and Viscum . Eighteen taxa recorded in the Pliocene of Frankfurt am Main are today absent from western Eurasia and eastern North America, and 25 taxa are absent from western North America. This shows ( i ) a strong biogeographic link of the Pliocene flora of Frankfurt am Main with East Asia, ( ii ) surprisingly high levels of speciation (Pliocene endemisms) and ( iii ) that the European flora was more diverse in woody species shortly before the onset of major Pleistocene glaciations than today.
An emended diagnosis of the extinct cupressoid genus Ditaxocladus S. X. GUO & Z. H. SUN (syn. Fokieniopsis MCIVER & BASINGER) and its three species is proposed based on new collections from the type locality in the Paleocene Wulonggu Formation of Altai in NW China, and other sites from China, SE Russia and western North America. Ditaxocladus planiphyllus S. X. GUO & Z. H. SUN (generitype) is now known from compound racemose fertile branches bearing several opposite pairs of globose to sub-globose seed cones composed of 6-12 decussate peltate scales, in addition to typically oppositely branched sprays. Besides D. planiphyllus, two more species are recognized based on differences in seed cone morphology. D. kivdensis KODRUL in KRASSILOV et al. from the Paleocene of Raichikha in Amur Province, Russia, is distinguished by similar but slender and pendulous cones, while D. catenulatus (W. A. BELL) S. X. GUO, KVACEK, MANCHESTER & Z. K. ZHOU comb. n. (syn. Fokieniopsis catenulata (W. A. BELL) MCIVER & BASINGER and Fokienia ravenscragensis MCIVER & BASINGER) typified by early Paleocene records in North America bears ovoid seed cones with a higher number of cone scales. All three species share the same type of bipinnately and oppositely ramified elongate sprays of cladode-like foliage and pinnately and oppositely arranged seed cones at successive nodes on compound racemose fertile branches. They differ from the living Fokienia, with which they were formerly compared, in oppositely (vs. alternately) branched leafy sprays and oppositely clustered (vs. solitary) seed cones consisting of much fewer cone scales (6-12 vs. 12-18 in Fokienia). Sterile foliage attributed to Ditaxocladus occurs in the Upper Cretaceous to Paleocene of North America, Russia and Paleocene of Spitsbergen. Tracing differentiation of Ditaxocladus populations (or species) over the Northern Hemisphere is hampered by incompleteness of most records based on quite uniform foliage without seed cones. Tetraclinis salicornioides (UNGER) KVACEK from the Eocene to Pliocene of Europe and the Oligocene to Miocene of North America, which shares very similar gross morphology of foliage, differs from Ditaxocladus in the quadrivalvate seed cones and papillate leaf epidermis with undulate anticlinal walls.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)
