Cariamiformes (or Cariamae) is an order of primarily flightless

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

s that has existed for over 50 million years. The group includes the family

Cariamidae The seriemas are the sole living members of the small bird family Cariamidae (the entire family is also referred to as "seriemas"), which is also the only surviving lineage of the order Cariamiformes. Once believed to be related to Crane (bird), ...

(seriemas) and the

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

families such as

Phorusrhacidae Phorusrhacids, colloquially known as terror birds, are an extinct family of large carnivorous, mostly flightless birds that were among the largest apex predators in South America during the Cenozoic era. Their definitive fossil records range from ...

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 extinct Phorusrhacidae. They were likely similar in habits, being terrestrial ...

Idiornithidae Idiornithidae is an extinct family of Cariamiformes Cariamiformes (or Cariamae) is an order of primarily flightless birds that has existed for over 50 million years. The group includes the family Cariamidae (seriemas) and the extinct families ...

and Ameghinornithidae. Extant members (seriemas) are only known from

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

, but fossils of many extinct taxa are also found in other continents including

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

and

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

. Though traditionally considered a suborder within

Gruiformes The Gruiformes ( ) are an order containing a considerable number of living and extinct bird families, with a widespread geographical diversity. Gruiform means "crane-like". Traditionally, a number of wading and terrestrial bird families that ...

, both morphological and genetic studies show that it belongs to a separate group of birds,

Australaves Australaves is a clade of birds, defined in 2012, consisting of the Eufalconimorphae (passerines, parrots and falcons) as well as the Cariamiformes (including seriemas and the extinct "terror birds"). They appear to be the sister group of Afroave ...

, whose other living members are

Falconidae The falcons and caracaras are around 65 species of Diurnality, diurnal birds of prey that make up the family Falconidae (representing all extant species in the order (biology), order Falconiformes). The family likely originated in South America d ...

, Psittaciformes and

Passeriformes 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 generally have an anisodactyl arrangement of their ...

. This proposal has been confirmed by a 2014 study of whole genomes of 48 representative bird species. This analysis shows that the Cariamiformes are basal among extant

, while falcons are next most basal; in combination with the fact that the most basal branch of

Afroaves Afroaves is a clade of birds, consisting of the kingfishers and kin (Coraciiformes), woodpeckers and kin (Piciformes), hornbills and kin (Bucerotiformes), trogons (Trogoniformes), cuckoo roller (Leptosomiformes), mousebirds (Coliiformes), owls (S ...

(

Hieraves Hieraves is a clade of telluravian birds named by Wu ''et al''. (2024) that includes the orders Strigiformes (owls) and Accipitriformes (hawks and their relatives). The Cathartidae (New World vultures) are usually included in Accipitriformes, b ...

, i.e.

Accipitriformes The Accipitriformes (; ) are an order of birds that includes most of the diurnal birds of prey, including hawks, eagles, vultures, and kites, but not falcons. For a long time, the majority view was to include them with the falcons in the Falc ...

and

owl Owls are birds from the order Strigiformes (), which includes over 200 species of mostly solitary and nocturnal birds of prey typified by an upright stance, a large, broad head, binocular vision, binaural hearing, sharp talons, and feathers a ...

s) is also predatory, it is inferred that the common ancestor of 'core landbirds' (

Telluraves Telluraves (also called land birds or core landbirds) is a recently defined clade of birds defined by their arboreality. Based on most recent genetic studies, the clade unites a variety of bird groups, including the australavians (passerines, ...

) was an

apex predator An apex predator, also known as a top predator or superpredator, is a predator at the top of a food chain, without natural predators of its own. Apex predators are usually defined in terms of trophic dynamics, meaning that they occupy the hig ...

. However, some researchers like

Darren Naish Darren William Naish (born 26 September 1975) is a British vertebrate palaeontologist, author and science communicator. As a researcher, he is best known for his work describing and reevaluating dinosaurs and other Mesozoic reptiles, including ...

feel that this assessment is biased towards the more well known, predatory representatives of the clade, and indeed at least one form, ''

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 l ...

'', appears to have been herbivorous. The earliest known unambiguous member of this group is the early

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

taxon '' Paleopsilopterus itaboraiensis''. An isolated

femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...

from the Cape Lamb Member of the Lopez de Bertodano Formation,

Vega Island Vega Island () is an island in Antarctica, long and wide, which is the northernmost of the James Ross Island group and lies in the west part of Erebus and Terror Gulf. It is separated from James Ross Island by Herbert Sound and from Trinit ...

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...

was briefly described as a cariamiform femur in 2006. This specimen, which dates to the late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

period 66 million years ago, was originally reported as indistinguishable from the femurs of modern

seriema The seriemas are the sole living members of the small bird family Cariamidae (the entire family is also referred to as "seriemas"), which is also the only surviving lineage of the order Cariamiformes. Once believed to be related to cranes, they ...

s, and belonging to a large bird about tall. Because of its age and geographic location, it was argued that this unnamed species may have been close to the ancestry of both cariamids and

phorusrhacids Phorusrhacids, colloquially known as terror birds, are an extinct family of large carnivorous, mostly flightless birds that were among the largest apex predators in South America during the Cenozoic era. Their definitive fossil records range from ...

. However, a subsequent study published by West ''et al.'' (2019) reinterpreted this specimen as a fossil of an unnamed large-bodied member of a non-cariamiform genus ''

Vegavis ''Vegavis'' is a genus of extinct bird that lived in Antarctica during the Maastrichtian stage of the Late Cretaceous. The type and only species is ''Vegavis iaai'', representing one of the earliest known crown group birds. Initially described ...

''. In 2024, two ungual phalanx specimens from the early

strata in Antarctica have been identified as those of a cariamiform, possibly of a phorusrhacid. Molecular

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

studies have shown that Cariamiformes is basal to the Falconiformes, Psittaciformes and Passeriformes:

References

Further reading