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 (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, Bathornithidae, Idiornithidae 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, 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, i.e. Accipitriformes and owls) is also predatory, it is inferred that the common ancestor of 'core landbirds' ( Telluraves) 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 feel that this assessment is biased towards the more well known, predatory representatives of the clade, and indeed at least one form, '' Strigogyps'', 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,

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 seriemas, 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. 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''. 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