Platanus neptuni (Ettingshausen) Buzek, Holy & Kvacek, a conspicuous element of late Eocene to Miocene floras in central and southern Europe, has recently been recognized from the Oligocene Yaquina flora of western Oregon. We investigated the associated reproductive and vegetative organs including globose inflorescences, in situ pollen, fruits, twigs and foliage based on compression and impression specimens. The concept that these dispersed organs represent a single species, already proposed by Buzek et al (1976), is now well supported by shared epidermal anatomy, as well as by co-occurrence at multiple localities in Europe and North America. We support an expanded concept of P. neptuni including both simple and compound leaves. Individual leaflets of trifoliolate and occasional quinquefoliolate leaves are indistinguishable in venation, marginal dentation, and epidermal anatomy from the co-occurring simple leaves. The elliptical laminae resemble the leaves of the extant evergreen species, P. kerrii of southeast Asia. However, vegetative twigs with intact P. neptuni foliage confirm a deciduous habit, with the base of each petiole enveloping an axillary bud--a feature shared with extant Platanus subg. Platanus , but not with extant Platanus kerrii . The infructescences of P. neptuni consist of numerous florets, each with short tepals and three or more achenes. Staminate inflorescences have little or no perianth; stamens with short filaments, anthers with domed connectives, and contain containing tricolpate, microreticulate pollen. Platanus neptuni is distinguished from all extant species of the genus by the presence of a prominent circumsissile collar on the peduncle immediately below each staminate and pistillate inflorescence. Platanus neptuni thus presents an intriguing combination of characters that justify its position within an extinct subgenus. The occurrences both in Oregon and central Europe indicate a common origin, possibly deriving from the circumboreal Paleocene compound foliage species P. bella (Heer) Kvacek & Manchester.

Key words: compound leaves, fossil, morphology, Oligocene, Platanus