[8][9] 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.

[12] 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.

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 is considered the earliest unequivocal Fagus species described,[13] and used as support for a northwestern North American origin of the genus.

The upper and lower margins are typically convex in outline with simple teeth spaced at regular intervals along the edges where the secondary veins terminate.

Together the fourth and fifth order veins form an orthogonal reticulum wit well developed polygonal areolar spaces that have 4-5 sides and singly forked freely ending veinlets.

[2] Fagus langevinii was likely found growing at distance from the highland lakes, based on the worn and abraded nature of preserved cupules with missing spines along the outer surfaces.

[2] The Okanagan Highland sites represent upland lake systems that were surrounded by a warm temperate ecosystem with nearby volcanism.

[15] The highlands likely had a mesic upper microthermal to lower mesothermal climate, in which winter temperatures rarely dropped low enough for snow, and which were seasonably equitable.

Princeton's multiple linear regression CLAMP results gave a slightly lower 5.1 °C (41.2 °F), and the LMA returned a mean annual temperature of 5.1 ± 2.2 °C (41.2 ± 4.0 °F).