Part of Bathornithidae (though some analysis recover it as closer to the living seriemas instead,[1] or possibly entirely out of Cariamiformes[2]), it is a specialised member of this group, being cursorial carnivores much like their South American cousins, some species attaining massive sizes.

[3] The type specimen, YPM 537, was collected in Weld County, Colorado, in 1871 by Othniel Charles Marsh, which identified it as a sort of turkey.

It has unique characteristics quite unlike the sternum of any other bird (though vaguely convergent to that of the modern hoatzin), making it easily identifiable.

[6] Both P. antiqua and P. gigantea were clearly flightless, being large birds with far too short forelimbs and keels, the former in particular having highly reduced metacarpals, though P. wetmorei might have still been capable of limited flight.

[7] Paracrax gigantea in particular is a very large bird, reaching estimated heights of over 2 m (6 ft 7 in), making it among the largest of bathornithids and among the tallest animals in its environment.