[1] This geological formation has been dated to the late Cretaceous period, and more specifically to the Cenomanian To Turonian age, about 93.6 mya.

[2] A. antecedens is known only from a single fragmentary skeleton including shoulder, wing, and leg bones, but lacking a skull.

[5] In the past, Alexornis has been allied with the similarly sized Central Asian genus Kizylkumavis, based on characteristics which are known to unite them with other Cretaceous birds in the group Enantornithes.

[3] Evgeny Kurochkin argued in 1996 that Alexornis formed a natural group, the Alexornithidae, with Kizylkumavis and a second type of central Asian bird, Sazavis.

Among the enantiornithes, Alexornis shares many similarities of its skeletal anatomy with South American birds from about the same time period, including Martinavis and Elbretornis, and is united with them in the group Euenantiornithes.