Neoephemera antiqua is known only from one fossil, the holotype, number "UWBM76324". It is a single, mostly complete naiad of undetermined sex, preserved as a compression fossil in fine grained shale. The fossil specimen is from the University of Washington site number UWBM A0307B which works sediments from the Tom thumb tuff member of the Klondike Mountain Formation. Outcrops of the formation are found in and around Republic. The type specimen is currently preserved in the paleoentomology collections housed in the Burke Museum of Natural History and Culture, part of the University of Washington in Seattle, Washington, USA. N. antiqua was first studied by Nina D. Sinitchenkova of the Paleontological Institute of the Russian Academy of Sciences, with her 1999 type description being published in the Russian text Palaeontological Journal. The specific epithet antiqua was coined from the Latin "antiquus", meaning old.
