Corylus, Carpinus, and Palaeocarpinus (Betulaceae) from the middle Eocene Klondike Mountain and allenby formations of northwestern North America

Coryloid reproductive remains (Betulaceae, subfamily Coryloideae) are documented from the middle Eocene Republic flora of northeastern Washington State and the Princeton flora of southern British Columbia. The oldest confirmed examples of two modern genera, Corylus johnsonii Pigg, Manchester & Wehr sp. nov., and Carpinus perryae Pigg, Manchester & Wehr sp. nov., are reported from the Republic flora, and three new species of the extinct genus Palaeocarpinus, Palaeocarpinus barksdaleae Pigg, Manchester & Wehr sp. nov., Palaeocarpinus stonebergae Pigg, Manchester & Wehr sp. nov., and Palaeocarpinus dentatus (Penhallow) Pigg, Manchester & Wehr comb, nov., are described from Republic, Washington; Princeton, British Columbia; and Stump Lake, British Columbia, respectively. Corylus johnsonii resembles three extant Asian species: Corylus wangii, Corylus ferox, and Corylus heterophylla. Involucres of this fossil species vary from being highly dissected and spiny like C. wangii and C. ferox to more laminar like C. heterophylla. This similarity is interesting because C. ferox and perhaps also C. wangii are members of section Acanthochlamys, thought to be basal within the genus. Carpinus perryae has asymmetric leaflike bracts that partly enclose an ovate nutlet and, thus, fits within the extant Carpinus subgenus Carpinus, a group with Asian, European, and North American affinities today. Palaeocarpinus, thought to be basal within the Coryloideae, is reported from several Eocene localities in the Okanogan Highlands. These occurrences demonstrate that this primarily Paleocene, extinct genus extended into the Eocene in western North America as it did in Asia. Associated staminate catkins containing coryloid pollen and Corylus-like leaves also occur at Republic along with P. barksdaleae. The presence in the Okanogan Highlands floras of a suite of coryloid plants including both extinct and extant genera demonstrates that, like the birch subfamily Betuloideae, the subfamily Coryloideae was also a significant and diverse group in western North America during the middle Eocene.