Acer stewarti

[1][2] Both the Allenby and Klondike Mountain Formations preserve upland temperate floras which were first interpreted as being microthermal,[1] however further study has shown them 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.

[1] The specimens were studied by paleobotanists Jack A. Wolfe of the United States Geological Survey, Denver office and Toshimasa Tanai of Hokkaido University.

[1] The etymology of the chosen specific name stewarti is in recognition paleobotanist Wilson Stewart, finder of the holotype specimen, for his work teaching paleobotany.

The paired samaras of the species have a 40° attachment angle and the distal region of the nutlet and wing forming a broad sulcus.