Genus: Iaceornis CLARKE, 2004
Etymology: Latin, iaceo, figurative for "to be neglected" and Greek, ornis, "bird": To be neglected bird.

Species: marshi CLARKE, 2004
Etymology: In honor of O.C. Marsh, who originally described the holotype specimen (MARSH, 1880)
= Aptornis celer (referred material).

Holotype: YPM 1734

Locality: Butte Creek, near Smoky Hill River, Logan County, Kansas.

Horizon: “yellow chalk of the Pteranodon beds”, Smoky Hill Member, Niobrara Formation.


Age: Coniacian Stage, Senonian Subepoch, Gulf Epoch, Late Cretaceous.

Material: Pelvis, both coracoids, both scapulae, proximal end of left clavicle, proximal end of left radius, left ulnare and radalae, right carpometacarpus, right phalanges 1 and 2 of manual digit II, proximal and distal fragments of left femur, distal right tibiotarsus, a rib, and miscellaneous unidentifiable fragments..