A review of the species of Populus (Salicaceae) subgenus Tacamahaca, and new Platanus (Platanaceae) from the cretaceous

摘要

The study of herbarium specimens of the extant species of Populus provided diagnostic features of leaf morphology of the genus, its subgenera, sections and series. Reexamination of fossil remains from the territory of the FSU which were previously assigned to Populus showed that all of the Cretaceous remains and vast majority of the Danian fossils did not belong to this genus. The extinct species of Populus were treated by a team of paleobotanists and each species was presented on photographs, which demonstrate all the diagnostic characters used. For the subgenus Tacamahaca, 25 extinct species were recognized which mostly refer to the section Leucoides and series Laurifoliae of section Tacamahaca. The most ancient finding of the latter is dated the late Danion, while that of the section Leucoides is assigned an age to late Paleocene. A revision of geological history of the genus Populus does not support the hypothesis of its Arcto-Tertiary origin. Platanus hyrcanica and P.daralagensis from the lower Senomanian of Armenia, which are excluded from the genus Populus, are described and illustrated.