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 f rom the Paleocene of northern Wyoming, U.S.A., and Altai of Xinjiang Provin ce, northwestern China, indicating that the species was circumboreal in the early Tertiary. Epidermal anatomy preserved in specimens from all three ar eas confirms that these compound leaves belong to the Platanaceae. Platanus bella (Heer) comb. n. differs from modern species of Platanus but resemble s the European Tertiary species Platanus fraxinifolia (Johnson & Gilmore) W alther and Platanus neptuni (Ettingshausen) Buzek, Holy & Z. Kvacek, in the presence of large peltate glandular trichomes. We erect a new subgenus, Gl andulosa, to accommodate P. bella, P. fraxinifolia, and P. neptuni. Each of these species possesses similar leaf epidermal structure, with the charact eristic platanaceous stomatal apparatus and compound hair bases. In additio n, the fossils bear peltate glandular trichomes on the epidermal surfaces t hat are not known among extant Platanus species. Reproductive structures li nked to P. neptuni indicate that subgenus Glandulosa is properly placed in the Platanaceae but that it is a distinct clade from those of the extant su bgenera Platanus and Castaneophyllum Leroy. We also review the status of th e fossil genera Debeya and Dewalquea, to which some Cretaceous and Tertiary leaves of similar morphology have been placed, and reject the use of eithe r of these names to accommodate leaves of subgenus Glandulosa.