[2][1] The "Hi hole" site works strata was formerly thought to be part of the Museum Flow Package within the interbeds of the Sentinel Bluffs Unit of the central Columbia Plateau N2 Grande Ronde Basalt, Columbia River Basalt Group.

The Museum Flow Package interbeds are dated to the middle Miocene and are approximately 15.6 million years old.

[4] At the time of study, the holotype fruit, specimen UWBM 55134, and a series of paratype specimens were preserved in the Burke Museum of Natural History and Culture while additional paratypes, and examined fossils that were not part of the type series, were part of the paleobotanical collections at Arizona State University.

A total of over 24 specimens in or preserved by chert were studied by paleobotanists Kathleen Pigg and Melanie DeVore, with their 2005 type description being published in the American Journal of Botany.

[1] Based on similarities to the living genus Lagerstroemia, Pigg and DeVore placed Shirleya into Lythraceae, with no indication of a subfamily assignment.