According to most recent studies, only one specimen can be definitively assigned to this species, a fossil catalogued as number IVPP V9769 and currently housed in the collections of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing.

[1] Cathayornis can be told apart from similar Enantiornithes (especially Sinornis, Eocathayornis, and Houornis) by its larger size, a shorter and straighter first finger with a slightly longer claw, and other anatomical details.

[4] Similarly, C. caudatus was so named for its supposedly bony tail lacking a pygostyle, and was further differentiated by its small size.

[1] Other species of similar birds from the Jiufotang Formation have been regarded as synonymous with C. yandica by some researchers, including Largirostrornis sexdentoris and Cuspirostrisornis houi,[8] though this has yet to be supported by rigorous study.

[4] O'Connor and colleagues noted that Longchengornis sanyanensis, also synonymized with C. yandica by some authors, seems to show distinct anatomy not shared with at least that species of Cathayornis.