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.

[4][5] Four additional species are known exclusively from fossils of the Klondike Mountain Formation exposed at Republic in Ferry County, northeast Central Washington.

Four years later a list of insects from Republic was published by Wesley Wehr and Lisa Barksdale in a 1996 Washington Geology article.

[1] The odonate fossil material was studied subsequently by S. Bruce Archibald and Robert Cannings with a series of papers being published between 2019 and 2021 on the dragonflies[10] and damselflies of the Okanagan Highlands.

[1] Based on shared characters of the wings, such as a missing crossvein O and the CuA–A space being expanded, Archibald and Cannings placed the new genus into the extinct family Dysagrionidae.

Until 2021 the family had been treated as likely belonging to the living odonate suborder Zygoptera (damselflys), however the known head morphology of the included species has led to occasional placement questions.

Archibald, Cannings, and Robert Erickson evaluated the known head morphology of the fossils and concluded that they did not belong to any of the three defined odonate suborders, but instead were part of a new subfamily they named Cephalozygoptera.

[7] The erection of Cephalozygoptera was criticized by Andre Nel and Darren Zheng (2021) who argued that the noted differences were due in part to deformation of the head and eye areas during deposition and fossilization combined with characters that are present in a larger group of odonates than Archibald, Cannings, and Erickson reported.

Based on their review and critique of the justifications for cephalozygoptera, Nel and Zhang considered the name and grouping unwarranted and proposed it to be treated as a synonym of Zygoptera.

The genus is missing the oblique brace vein, which is present or unreported for the majority of dysagrionine species and there are no accessory crossveins immediately basal or apical to the CuP.

Archibald and Cannings coined the specific epithet from the Latin angustum meaning "narrow" in reference to the overall wing shape estimate.

Archibald and Cannings chose the species name "beardi" in recognition of Beard for his long dedication and energy towards British Columbian paleontology.

The specimen was collected and donated by Laurie Dorrell on October 31, 1992, and as such Archibald and Cannings chose to name the species dorrellae in recognition.

The species is the only one to be found in both Washington and British Columbia formations, with the majority of specimens being disarticulated wings, while the only semi-complete body fossil is from McAbee.

The remaining eleven specimens are all housed in the Stonerose Interpretive center collections and donated over a period from 1994 to 2017 from both the "Corner lot" and "Boot Hill" sites.

This was based on the frequency of sexually dimorphic color patterning in zygopteran species, and thus, having one male present in the group, they opted to take a conservative position on gender of the fossils.

[1] Okanagrion lochmum is known from only the holotype specimen, "RBCM 11799.001" of the Royal British Columbia Museum which was collected from the Hoodoo face beds of McAbee by John Leahy.

Archibald and Cannings created the species name "lochmum" from the Greek "Λόχμη", anglicized to lóchmi which means thicket as a reference to the amount of dense crossveins found on the wing.

[1] Found at the "Corner Lot" site A0307 on 8 April 1998, the holotype of Okanagrion threadgillae was Stonerose Interpretive Center specimen "SR 98-12-10".

The other wing has a more curved rear margin and straighter nodus to pterostigma features that are deemed distinct to Okanagrion hindwings by Archibald and Cannings.

[1] O. threadgillae wings are distinguished from O. beardi and O. dorrellae by the positioning of the MP and CuA veins when they terminate on the apical margin region.

[1] The species is most distinct in that the wing membrane is lightly but uniformly darkened, though Archibald and Cannings note the specimens might appear as hyaline in some fossils.

The Royal British Columbia Museum specimen "RBCM P1550" was collected by John Leahy from Hoodoo Face beds at McAbee.

[1] Species of Okanagrion and the related Okanopteryx were noted by Archibald et al to be the dominant odonates of the Eocene Okanagan highlands forests.

[1] The genus is noted by Archibald and Cannings for being the most speciose dysagrionid odonate of the highlands, a situation attributed to factors driving both alpha and beta diversity in the Ypresian Okanagan region.

The highlands, including the Early Eocene formations between Driftwood Canyon at the north and Republic at the south, have been described as one of the "Great Canadian Lagerstätten"[18] based on the diversity, quality and unique nature of the paleofloral and paleofaunal biotas that are preserved.

The highlands temperate biome preserved across a large transect of lakes recorded many of the earliest appearances of modern genera, while also documenting the last stands of ancient lines.

[18] The warm temperate highland floras in association with downfaulted lacustrine basins and active volcanism are noted to have no exact modern equivalents.

[18] 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.

The CLAMP results after multiple linear regressions for Republic gave a mean annual temperature of approximately 8.0 °C (46.4 °F), with the LMA giving 9.2 ± 2.0 °C (48.6 ± 3.6 °F).