Like the closely related and also extinct phorusrhacids, it was a flightless predator, occupying predatory niches in environments classically considered to be dominated by mammals.
It was a highly diverse and successful genus, spanning a large number of species that occurred from the Priabonian Eocene to the Burdigalian Miocene epochs.
[5] Bathornis is the type genus of Bathornithidae, a family of Cariamiformes, related to the modern seriemas (this relationship has been recognised ever since its first description[4]) and also a variety of extinct forms like phorusrhacids, Strigogyps and idiornithids, in turn part of the Australaves assemblage that also includes falcons, passerines and parrots.
[note 1] Interspecific relations within the Cariamiformes are highly volatile and unresolved, bathornithids at times having been listed as sister taxa to seriemas, phorusrhacids and idiornithids, sometimes even as a polyphyletic group.
However, at least one phylogenetic study recovers Bathornis (and its synonyms) as more closely related to phorusrhacids than to Paracrax,[6] though this is considered premature and based on far too few synapomorphies.
[2] A recent phylogenetic study found Bathornis to be the sole representative of Bathornithidae, within Cariamiformes but outside of the clade composing seriemas and phorusrhacids.
805, a limb element (distal portion of a metatarsus), recovered by Philip Reinheinter from Oligocene deposits of Weld County, Colorado, which also heralded the cathartid Phasmagyps.
Some caution has been suggested, given the possibility that some sympatric species might actually represent different sexes or morphs, though the vast temporal spanning of the genus still offers a large diversity.
It is known from multiple tibiotarsal material, depicting an animal roughly the size of a modern emu, something that earned it the description of "one of the most remarkable of recent additions to our fossil avifauna."
Though occurring in the same deposits as B. veredus and similar to it in size, B. cursor is nonetheless considered distinct due to several features of the trochlea.
An upper Oligocene species from deposits in South Dakota, Nebraska and Wyoming, quite possibly a direct descendant of B. veredus itself.
It is a larger bird than B. veredus and B. cursor, quite possibly the largest described member of the genus, and it co-existed with the similar sized Paracrax gigantea in the Brule Formation, where it shared a macropredatory role with it and mammals like Hyaenodon.
One of the youngest of all bathornithid species[note 2], recovered form Early Miocene Arikareean deposits in Willow Creek.
As a rule of thumb, however, its known range occurred around what is now the Great Plains; this prompted Wetmore to imagine it as a strider in open plains environments:[4]Geologists, from available evidence, inform its that North America during the Oligocene was comparatively level with low relief, so that we may imagine the species here under discussion as coursing over extensive plains.However, more recent analyses conclude that it probably favoured wetland biomes.
It shared its environment with several carnivorous mammals like hyaenodontids, entelodonts and nimravids, as well as the fellow cariamiform Paracrax, with which it would have competed.