Rhus republicensis is known from specimens which are recovered from an outcrop of the early Eocene, Ypresian[1][2]Klondike Mountain Formation in Republic.[2] The Klondike Mountain Formation preserves an upland temperate flora which was first interpreted as being microthermal,[3][4] however further study has shown the flora to be more mesothermal in nature.[2] The plant community preserved in the Klondike Mountain formation is a mixed conifer–broadleaf forest with large pollen elements of birch and golden larch, but also having notable traces of fir, spruce, cypress, and palm.
Rhus republicensis leaves are pinnately compound on a 16.5 cm (6.5 in) long petiole, with a possible total length of 20 cm (7.9 in)for full leaves. The subopposite leaflets are sessile on the 10.5 cm (4.1 in) rachis between the flared wings that bracket the 1.1 mm (0.043 in) midvein. The 1.8–5.7 cm (0.71–2.24 in) leaflets are obovoid to ovoid in outline, tapering from the wide middle to both the base and apex. They have a width of 0.7–2.5 cm (0.28–0.98 in) and a length to width ratio of up to 3.1:1. The midveins of the leaflets are narrow and pass all the way to the leaflet apex, with smaller secondary veins branching off the midvein at acute angles. The narrow secondaries are spaced on the midvein unevenly and group closer together near the leaflet tip, while usually branching once near the leaflet margin. The branches of the secondaries enter a tooth or the sinus between two teeth. The teeth are rounded on their tips with convex basal and apical sides running towards variable sinuses. The teeth become more developed and closer spaced towards the tip of the leaflet. The leafy wings of the rachis have secondary veins that angle steeply towards the leaf tip and occasionally forking.[1]
^Wolfe, J.A.; Tanai, T. (1987). "Systematics, Phylogeny, and Distribution of Acer (maples) in the Cenozoic of Western North America". Journal of the Faculty of Science, Hokkaido University. Series 4, Geology and Mineralogy. 22 (1): 1–246. hdl:2115/36747.
