''Bathornis'' ("tall bird") is an extinct lineage of birds related to modern day

seriemas The seriemas are the sole living members of the small bird family Cariamidae, which is also the only surviving lineage of the order Cariamiformes. Once believed to be related to cranes, they have been placed near the falcons, parrots and passer ...

, that lived in

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

about 37–20 million years ago. Like the closely related and also extinct

phorusrhacids Phorusrhacids, colloquially known as terror birds, are an extinct clade of large carnivorous flightless birds that were one of the largest species of apex predators in South America during the Cenozoic era; their conventionally accepted temporal ...

, 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 The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

to the

Burdigalian The Burdigalian is, in the geologic timescale, an age (geology), age or stage (stratigraphy), stage in the early Miocene. It spans the time between 20.43 ± 0.05 annum, Ma and 15.97 ± 0.05 Ma (million years ago). Preceded by the Aquitanian (sta ...

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

epochs.

Description

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 The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a round ...

), pelvises and skulls.Federico L. Agnolin (2009)
"Sistemática y Filogenia de las Aves Fororracoideas (Gruiformes, Cariamae)"
(PDF). Fundación de Historia Natural Felix de Azara: 1–79. ''Bathornis grallator'' is known from a mostly complete skeleton, including the skull, bearing a proportionally large, hooked beak.Gerald Mayr (2009). Paleogene Fossil Birds The bathornithid second toe is currently unknown, but the first toe is highly reduced, as with most Cariamiformes, and like

it possesses a robust

jugal The jugal is a skull bone found in most reptiles, amphibians and birds. In mammals, the jugal is often called the malar or zygomatic. It is connected to the quadratojugal and maxilla, as well as other bones, which may vary by species. Anatomy ...

and reduced processus acrocoracoideus of

coracoid A coracoid (from Greek κόραξ, ''koraks'', raven) is a paired bone which is part of the shoulder assembly in all vertebrates except therian mammals (marsupials and placentals). In therian mammals (including humans), a coracoid process is prese ...

, two features possibly having evolved in convergence due to their similar lifestyle.Gerald Mayr (2016). "Osteology and phylogenetic affinities of the middle Eocene North American Bathornis grallator—one of the best represented, albeit least known Paleogene cariamiform birds (seriemas and allies)". Journal of Paleontology 90 (2): 357–374. doi:10.1017/jpa.2016.45. 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

to 2 meter tall animals.

Classification

''Bathornis'' is the type genus of

Bathornithidae Bathornithidae is an extinct family of birds from the Eocene to Miocene of North America. Part of Cariamiformes, they are related to the still extant seriemas and the also extinct Phorusrhacidae. They were likely similar in habits, being terrest ...

, a family of Cariamiformes, related to the modern

(this relationship has been recognised ever since its first description) and also a variety of extinct forms like

, ''

Strigogyps ''Strigogyps'' is an extinct genus of prehistoric bird from the Middle Eocene to Early Oligocene of France and Germany. It was probably around the size of a large chicken or a guan, weighing not quite . Apparently, as indicated by the ratio of le ...

'' and idiornithids, in turn part of the Australaves assemblage that also includes

falcons Falcons () are birds of prey in the genus ''Falco'', which includes about 40 species. Falcons are widely distributed on all continents of the world except Antarctica, though closely related raptors did occur there in the Eocene. Adult falcons ...

passerines A passerine () is any bird of the order Passeriformes (; from Latin 'sparrow' and '-shaped'), which includes more than half of all bird species. Sometimes known as perching birds, passerines are distinguished from other orders of birds by th ...

and

parrots Parrots, also known as psittacines (), are birds of the roughly 398 species in 92 genus (biology), genera comprising the order (biology), order Psittaciformes (), found mostly in tropics, tropical and subtropics, subtropical regions. The order ...

. 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 A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of converg ...

group. It is usually considered the sister clade to ''

Paracrax ''Paracrax'' ("near curassow") is a genus of extinct North American flightless birds, possibly related to modern seriemas and the extinct terror birds. Part of Bathornithidae (though some analysis recover it as closer to the living seriemas inst ...

'', 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

than to ''Paracrax'', though this is considered premature and based on far too few synapomorphies. The most recent phylogenetic studies find ''Bathornis'' to be the sole representative of Bathornithidae, within Cariamiformes but outside of the clade composing

seriema The seriemas are the sole living members of the small bird family Cariamidae, which is also the only surviving lineage of the order Cariamiformes. Once believed to be related to cranes, they have been placed near the falcons, parrots and passeri ...

s and

phorusrhacid Phorusrhacids, colloquially known as terror birds, are an extinct clade of large carnivorous flightless birds that were one of the largest species of apex predators in South America during the Cenozoic era; their conventionally accepted temporal ...

s. ''

'' is found to be outside of Bathornithidae, with its status as a Cariamiformes uncertain.

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 The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

deposits of

Weld County Weld County is a county located in the U.S. state of Colorado. As of the 2020 United States Census, 2020 census, the population was 328,981. The county seat is Greeley, Colorado, Greeley. Weld County comprises the Greeley, CO Metropolitan Stati ...

Colorado Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of t ...

, which also heralded the cathartid '' Phasmagyps''. First described by

Alexander Wetmore Frank Alexander Wetmore (June 18, 1886 – December 7, 1978) was an American ornithologist and avian paleontologist. He was the sixth Secretary of the Smithsonian Institution. Early life and education The son of a Country Physician, Frank Al ...

, the bird was referred as a "cedicnemidid" (a

wastebasket taxon Wastebasket taxon (also called a wastebin taxon, dustbin taxon or catch-all taxon) is a term used by some taxonomists to refer to a taxon that has the sole purpose of classifying organisms that do not fit anywhere else. They are typically defined ...

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 bird was noted as being massive in comparison to its modern seriema relatives, presumably the reason as to receive its genus name, "tall bird". The species name, "veredus", is not given an explanation, though it is a Latin word relating to speed. wikt:veredus

Species

''Bathornis'' is noted for its high number of species, and is the most speciose of all Cariamiformes, extinct or extant. A minimum of five species are consistently recognised, with several otherwise monotypic taxa often either aligned with this genus or rendered outright synonyms of established species. 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.

''Bathornis veredus''

The type species, whose discovery and etymology is mentioned above. It is known from

and

deposits of the

Chadron Formation Chadron Formation is a rock formation in North Dakota, South Dakota, northwestern Nebraska, and eastern Wyoming. It is named after the town of Chadron, Nebraska. It was mapped out by Carl Vondra Carl may refer to: *Carl, Georgia, city in USA *Car ...

and

Nebraska Nebraska () is a state in the Midwestern region of the United States. It is bordered by South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Kansas to the south; Colorado to the southwe ...

. It is known from multiple tibiotarsal material, depicting an animal roughly the size of a modern

emu The emu () (''Dromaius novaehollandiae'') is the second-tallest living bird after its ratite relative the ostrich. It is endemic to Australia where it is the largest native bird and the only extant member of the genus ''Dromaius''. The 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.

''Bathornis cursor''

A species first described by

in 1933. 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. Wetmore referred to the bird as "a large edition of ''Bathornis celeripes'' from the same deposits", but posterior analysis showcases strong distinction from that taxon as well, and it occurs in considerably earlier deposits.

''Bathornis geographicus''

A species first described by

in 1942. An upper Oligocene species from deposits in

South Dakota South Dakota (; Sioux language, Sioux: , ) is a U.S. state in the West North Central states, North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Lakota people, Lakota and Dakota peo ...

and

Wyoming Wyoming () is a U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the south ...

, 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 ''

gigantea'' in the

Brule Formation The Brule Formation was deposited between 33 and 30 million years ago, roughly the Rupelian age (Oligocene). It occurs as a subunit of the White River Formation in Nebraska, Colorado, North Dakota, South Dakota, and Wyoming. It is a sequence of ...

, where it shared a macropredatory role with it and mammals like ''

Hyaenodon ''Hyaenodon'' (" hyena-tooth") is an extinct genus of carnivorous hyaenodont mammals from tribe Hyaenodontini, within subfamily Hyaenodontinae in family Hyaenodontidae,Malcolm C. McKenna, Susan K. Bell (1997."Classification of Mammals: Above t ...

''.

''Bathornis fax''

Originally referred to the rallid genus ''Palaeocrex'' (in the same paper originally describing ''B. veredus'', no less), 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''.; if it is its own independent species, it is among the smallest forms at about the size of a modern

''Bathornis celeripes''

A species described by Wetmore in 1958, dating to the upper Oligocene deposits of

. It is relatively well studied at about 16 specimens, mostly of hindlimbs but also forelimb and shoulder girdle material. Though it was described as a smaller variant of ''B. cursor'' by Wetmore, it was actually similar to it in size, though it was still dwarfed by the larger ''B. geographicus'' and the larger ''Paracrax'' species, which would have co-existed with it.

''Bathornis fricki''

One of the youngest of all bathornithid species, recovered form

Early Miocene The Early Miocene (also known as Lower Miocene) is a sub-epoch of the Miocene Epoch made up of two stages: the Aquitanian and Burdigalian stages. The sub-epoch lasted from 23.03 ± 0.05 Ma to 15.97 ± 0.05 Ma (million years ago). It was prece ...

Arikareean The Arikareean North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 30,600,000 to 20,800,000 years BP, a period of . It is usuall ...

deposits in Willow Creek. There is a strong similarity to ''B. celeripes'', and some researchers consider it to be the direct ancestor of ''B. fricki''.

''Bathornis minor''

A species conspecific with ''B. fricki'', known from a similar tibiotarsus that differs in several respects from its contemporary.

''Bathornis grallator''

''B. grallator'' is known from the late

Washakie Formation The Washakie Formation is a geologic formation in northern Colorado and southern Wyoming. It preserves many mammal, bird, reptile and other fossils dating back to the Lutetian stage of the Eocene within the Paleogene period. The sediments fall i ...

; similar fossils have been described from the

Willwood Formation The Willwood Formation is a sedimentary sequence deposited during the late Paleocene to early Eocene, or Clarkforkian, Wasatchian and Bridgerian in the North American land mammal age, NALMA classification.cathartid,

Storrs Olson Storrs Lovejoy Olson (April 3, 1944 – January 20, 2021) was an American biologist and ornithologist who spent his career at the Smithsonian Institution, retiring in 2008. One of the world's foremost avian paleontologists, he was best known ...

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 The Botanical and Zoological Codes of nomenclature treat the concept of synonymy differently. * In botanical nomenclature, a synonym is a scientific name that applies to a taxon that (now) goes by a different scientific name. For example, Linna ...

of ''Bathornis'', but most recent studies consistently refer to it within this genus.

Other forms

Several undescribed remains from the late

and

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 ''

'', 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 ''

'', 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 The Great Plains (french: Grandes Plaines), sometimes simply "the Plains", is a broad expanse of flatland in North America. It is located west of the Mississippi River and east of the Rocky Mountains, much of it covered in prairie, steppe, an ...

; 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 A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The ...

biomes. In either case, ''Bathornis'' is found among rich mammalian faunas. ''B. cursor'' is found in close association with ''

Megacerops ''Megacerops'' ("large-horned face", from '' méga-'' "large" + '' kéras'' "horn" + '' ōps'' "face") is an extinct genus of the prehistoric odd-toed ungulate (hoofed mammal) family Brontotheriidae, an extinct group of rhinoceros-like browsers ...

'', and ''B. geographicus'' with ''

Merycoidodon ''Merycoidodon'' ("ruminating teeth") is an extinct genus of herbivorous artiodactyl of the family Merycoidodontidae, more popularly known by the name ''Oreodon'' ("hillock teeth"). It was endemic to North America during the Middle Eocene to Mid ...

'', which might imply predation on these mammals. It shared its environment with several carnivorous mammals like hyaenodontids,

entelodonts Entelodontidae, the entelodonts, are an extinct family of pig-like artiodactyls (even-toed ungulates) which inhabited the Northern Hemisphere (Asia, Europe, and North America) from the late Eocene to the Middle Miocene epochs, about 38-19 million ...

and

nimravids Nimravidae is an extinct family of carnivorans, sometimes known as false saber-toothed cats, whose fossils are found in North America and Eurasia. Not considered to belong to the true cats (family Felidae), the nimravids are generally considered ...

, as well as the fellow cariamiform ''Paracrax'', with which it would have competed. In particular, there may be evidence of niche partitioning with the latter, as it occurs in drier environments.

Notes

References

{{Taxonbar, from=Q24259260 Bathornitidae Eocene birds Miocene birds Oligocene birds Bird genera Paleogene birds of North America Extinct flightless birds Miocene birds of North America White River Fauna Taxa named by Alexander Wetmore