Vegetative and Reproductive Morphology of an Extinct Plane Tree (Platanaceae) from the Eocene of Western North America

Abstract

An extinct type of plane tree, common in the Middle to Late Eocene of Oregon, is reconstructed as a whole plant on the basis of repeated co-occurrence of isolated platanaceous organs at numerous localities. It is described in detail on the basis of leaf architecture, petiole and stem anatomy, pistillate inflorescence morphology, fruit anatomy, staminate inflorescence morphology, and in situ pollen morphology, rendering it the most completely documented fossil angiosperm species. The leaves, Macginitiea angustiloba (Lesq.) comb. nov., are relatively large, with five to seven palmately arranged lobes and palinactinodromous venation. They resemble those of some modern Platanus species except in features associated with a narrower angle between adjacent primary veins. The petioles are basally expanded and hollow and appear to have enclosed the axillary buds, as in most extant Platanus species. Inflorescences are borne as globose heads along separate staminate and pistillate axes. The pistillate inflorescenc...