Okanagrion

Okanagrion is an extinct odonate genus in the damselfly-like family Dysagrionidae. The genus was first described in 2021 with a series of eight species included from early Eocene Okanagan Highlands sites in western North America. The genus is known from the Late Ypresian sediments exposed in northeast central Washington at Republic where five species are present, and from the coeval McAbee Fossil Beds near Cache Creek in Central British Columbia, where four species are present. The species richness is attributed to high latitude high alpha diversity resulting from climatic equitability during the Early Eocene in combination with resultant beta diversity between sites due to impassible topographical barriers.

Distribution

Okanagrion fossils have been found at two sites belonging to the Eocene Okanagan Highlands of Washington and British Columbia. Of the eight described species, O. angustum, O. beardi, and O. lochmum are only found at the Tranquille Formation's McAbee Fossil Beds west of Cache Creek in central British Columbia. 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 ~51 million years ago; however, dating published in 2005 provided a 40Ar-39Ar radiometric date placing the McAbee site at 52.9 ± 0.83 million years ago.

Four additional species are known exclusively from fossils of the Klondike Mountain Formation exposed at Republic in Ferry County, northeast Central Washington. Two species, Okanagrion dorrellae and O. liquetoalatum are known only from the "Boot Hill" site UWBM B4131, while O. threadgillae is only known from the "Corner lot" site A0307 and one species, O. worleyae is reported from both the "Boot hill" and "Corner lot" sites.