TRIFOLIOLATE LEAVES OF PLATANUS BELLA (HEER) COMB. N. FROM THE PALEOCENE OF NORTH AMERICA, GREENLAND, AND ASIA AND THEIR RELATIONSHIPS AMONG EXTINCT AND EXTANT PLATANACEAE

Trifoliolate leaves of Platanus bella (Heer) comb. n., a species previously known only from the Paleocene of western Greenland, are newly recognized from the Paleocene of northern Wyoming, U.S.A., and Altai of Xinjiang Province, northwestern China, indicating that the species was circumboreal in the early Tertiary. Epidermal anatomy preserved in specimens from all three areas confirms that these compound leaves belong to the Platanaceae. Platanus bella (Heer) comb. n. differs from modern species of Platanus but resembles the European Tertiary species Platanus fraxinifolia (Johnson & Gilmore) Walther and Platanus neptuni (Ettingshausen) Bůžek, Holý & Z. Kvacek, in the presence of large peltate glandular trichomes. We erect a new subgenus, Glandulosa, to accommodate P. bella, P. fraxinifolia, and P. neptuni. Each of these species possesses similar leaf epidermal structure, with the characteristic platanaceous stomatal apparatus and compound hair bases. In addition, the fossils bear peltate glandular trichom...