Allenbya holmesae has been recovered from a single location in the Eocene Okanagan Highlands, the type locality being on an exposure of the Allenby Formations Vermilion Bluffs shale unit 4 km (2.5 mi) south Princeton, British Columbia.

[1] In their initial description Archibald and Cannings noted that the incomplete nature of the fossil left room for classification changes if more complete specimens were recovered.

In the preserved section of the holotype, the MA, MP, and CuA veins were deemed to be of similar positions and progressions up the wing as seen in the Dysagrionidae genera Okanopteryx and Stenodiafanus described the year earlier from Republic and McAbee.

Due to the missing area of the wing being the basal region, they opted to maintain a conservative stance on the higher taxonomic affiliations and deemed Allenbya as cf.

Until 2021 the family had been treated as likely belonging to the living odonate suborder Zygoptera, 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.

[6] 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.

[1] The Okanagan Highland sites represent upland lake systems that were surrounded by a warm temperate ecosystem with nearby volcanism.

[13] 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.