 In a 2004 paper, Julia Clarke noted that the few unique characteristics preserved in the "A. celer" specimen, rather than suggesting a close relationship with "Ichthyornis" as originally thought, actually suggest it is more closely related to modern birds, a hypothesis also supported by Hope in 2002.Its exact relationships are unresolved, mainly due to the paucity of fossil remains.Though it has sometimes been considered to be closely related to modern waterfowl (Anseriformes), most researchers today consider it to be an early member of the clade Ornithurae.