Bathornis

Though most material is highly incomplete, Bathornis is nonetheless known from a variety of skeletal elements: hindlimbs (most commonly tarso-metatarsals), forelimb elements (especially humeri), pelvises and skulls. Bathornis grallator is known from a mostly complete skeleton, including the skull, bearing a proportionally large, hooked beak. The bathornithid second toe is currently unknown, but the first toe is highly reduced, as with most Cariamiformes, and like phorusrhacids it possesses a robust jugal and reduced processus acrocoracoideus of coracoid, two features possibly having evolved in convergence due to their similar lifestyle. Overall, Bathornis is a long-legged, short-winged, large-skulled bird, similar in shape to phorusrhacids. Its numerous species span a large diversity of body sizes, ranging from forms about as large as modern seriemas to animals. ==Classification==

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) 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. 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. and several authorities consider Neocathartes and several other taxa to be nested with it (see below). However, at least one phylogenetic study recovers Bathornis (and its synonyms) as more closely related to phorusrhacids than to Paracrax, ==Discovery and naming==

The type species is B. veredus, its type specimen being Denver Mus. Nat. Hist. No. 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. First described by Alexander Wetmore, the bird was referred as a "cedicnemidid" (a wastebasket taxon for "thick-knee" birds) related to modern seriemas, erecting the subfamily Bathornithinae. Two birds described alongside it, the putative rallid Palaeocrex and the putative cathartid Palaeogyps, would later turn out to be bathornithid material, the latter in particular synonymous with B. veredus. The species name, "veredus", is not given an explanation, though it is a Latin word relating to speed. ==Species==

Bathornis is noted for its high number of species, and is the most speciose of all Cariamiformes, extinct or extant. Bathornis veredus The type species, whose discovery and etymology is mentioned above. It is known from Eocene and Oligocene deposits of the Chadron Formation in Colorado and Nebraska. 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." Skull material from this species is also known.), further examination has shown it to belong to Bathornis. There is some doubt about whereas it represents a different species or a younger morph of B. veredus.; known from a similar tibiotarsus that differs in several respects from its contemporary. Bathornis grallator B. grallator is known from the late Eocene Washakie Formation of Wyoming; similar fossils have been described from the Willwood Formation, but their status as Cariamiformes, let alone bathornithids, are unclear. Originally interpreted as a terrestrial cathartid, Storrs Olson reassigned it to Bathornis in 1985: The reconstruction published with the original description of Neocathartes has often been reprinted and has now made the "terrestrial vulture" an integral part of the lore of avian paleontology. Well, forget it. Neocathartes is just our old friend Bathornis in another guise. Since then, posterior researchers have flip-flopped in their evaluation of Neocathartes as a junior synonym of Bathornis, but most recent studies consistently refer to it within this genus. Other forms Several undescribed remains from the late Eocene and Oligocene have been putatively assigned to Bathornis. ==Palaeobiology==

Bathornis as a whole were large, terrestrial birds with long and powerful legs. Most if not all species are thought to having been flightless (B. grallator is traditionally considered as having been volant, but has since been found to be flightless), perhaps more specialised to this regard than even Paracrax, having proportionally short wings and keel, as well as a reduced processus acrocoracoideus in the coracoid. Bathornis was a carnivorous bird. Bathornis grallator and Bathornis veredus showcase that it had a strong beak akin to that of phorusrhacids, even sharing an identical reinforcement of the jugal, implicating a similar biting stresses. As Bathornis species reached large sizes, it is likely that they were apex predators within their environment, much as their South American phorusrhacid cousins; alongside the closely related Paracrax, they are examples of large predatory birds managing to compete successfully with mammals, having co-existed with large carnivorous mammals for over 17 million years. ==Palaeoecology==

Due to its longevity and high number of species, Bathornis spanned across several different types of environment. 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: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. In either case, Bathornis is found among rich mammalian faunas. B. cursor is found in close association with Megacerops, and B. geographicus with Merycoidodon, == Notes ==