Fagus langevinii is an extinct species of beech in the family Fagaceae. The species is known from fossil fruits, nuts, pollen, and leaves found in the early Eocene deposits of South central British Columbia, and northern Washington state, United States.
Distribution
The described specimens are from the Eocene Okanagan Highlands British Columbian sites of McAbee and Falkland in the Tranquille Formation, the Allenby Formation around Princeton, and with additional fossils also known from the Klondike Mountain Formation in north eastern Washington. Tuffs of the Klondike Mountain Formation had been dated to , the youngest of the Okanagan Highlands sites, though a revised oldest age of was given based on isotopic data published in 2021. The lake sediments at McAbee were first radiometrically dated using the K-Ar method in the 1960s based on ash samples exposed in the lake bed. These samples yielded an age of ~; however, a data published in 2005 provided a 40Ar-39Ar radiometric date placing the McAbee site at . Dillhoff, Leopold, and Manchester (2005) identified leaves belonging to Fagus, but not placed to species, from the Eocene Okanagan highland sites of the Chu Chua Formation, British Columbia.
History and classification
Fossil leaves identified as Fagus species were first briefly mentioned by Gandolfo (1999) from Republic and the Allenby Formation in Princeton, while fossil nuts and cupules from Republic and McAbee were first mentioned briefly by Pigg and Wehr (2002). The fossil material was studied subsequently by Steven R. Manchester and Richard Dillhoff (2004) with the type description of the species being published in the Canadian Journal of Botany. They designated the holotype as cupule specimen UWBM 97583, which was in the paleobotanical collections of the Burke Museum in Seattle at that time. The cupule, from the McAbee site, was supplemented by a suit of paratype fossils encompassing additional cupules, nuts, leaves and a branchlet with attached leaves and axillary buds. The paratypes were specimens of the Burke museum, as well as the University College of the Cariboo in Kamloops, British Columbia and the Florida Museum of Natural History in Gainesville, Florida. Not included in the type series were pollen samples washed from a matrix specimen collected at McAbee. Manchester and Dillhoff coined the specific epithet langevinii as a patronym honoring David Langevin for his dedication to the collection and study of McAbee fossils.
F. langevinii cupules have a similar morphology to that seen in species of Fagus subgenus Engleriana, having antler like appendages present, and also having pollen morphology resembling those species. The leaves however are more similar to species of the paraphyletic Fagus subgenus Fagus. F. langevinii is considered the earliest unequivocal Fagus species described, and used as support for a northwestern North American origin of the genus.
Description
Fagus langevinii cupules range between long by wide giving an ovate outline. Each cupule is born on an up to long peduncle which thickens near its apical end. The peduncles can reach up to 2.5 times the cupule length. Across the outer surface of the cupules spiny ornamentations up to high and occasionally forking once near the tips. Each cupule has four valves which contain the two trigonal nuts. The long by wide nuts range from obovate through elliptical to ovate in outline, and occasionally sport a small flange or wing along each angle of the nut.