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 have been placed near the falcons, parrots, and passerines, as well as the extinct Phorusrhacidae (terror birds). The seriemas are large, long-legged territorial birds that range from 70–90 cm (28–35 in) in length. They live in grasslands, savanna, dry woodland and open forests of Brazil, Bolivia, Argentina, Paraguay and Uruguay. There are two species of seriemas, the red-legged seriema (Cariama cristata) and the black-legged seriema (Chunga burmeisteri). Names for these birds in the Tupian languages are variously spelled as siriema, sariama, and çariama, and mean "crested".

Both species are around 90 cm (35 in) long (the red-legged seriema is slightly bigger than the black-legged, with 90 and 70–85 cm respectively). The seriemas forage on foot and run from danger rather than fly (though they can fly for short distances, and they roost in trees). They have long legs, necks, and tails, but only short wings, reflecting their way of life. Also, they are among the largest ground-dwelling birds endemic to the Neotropics (only behind rheas).

They are brownish birds with short bills and erectile crests, found in fairly dry open country, the red-legged seriema preferring grasslands and the black-legged seriema preferring scrub and open woodland. Also, they give loud, yelping calls and are often heard before they are seen. Furthermore, they have sharp claws, with an extensible and very curved second toe claw.

These birds are thought to be the closest living relatives of a group of gigantic (up to 10 ft or 3.0 m tall) carnivorous "terror birds", the phorusrhacids, which are known from fossils from South and North America. Several other related groups, such as the idiornithids and bathornithids were part of Palaeogene faunas in North America and Europe and possibly elsewhere too. However, the fossil record of the seriemas themselves is poor, with two prehistoric species, Chunga incerta and Miocariama patagonica (formerly Noriegavis santacrucensis), both from the Miocene of Argentina, having been described to date. Some of the fossils from the Eocene fauna of the Messel pit (i.e. Salimia and Idiornis) have also been suggested to be seriemas, as has the massive predatory Paracrax from the Oligocene of North America, though their status remains uncertain.

There are two living species of seriema.

Ecologically, the seriema is the South American counterpart of the African secretary bird. They feed on insects, snakes, lizards, frogs, young birds, and rodents, with small amounts of plant food (including maize and beans). They often associate with grazing livestock, probably to take insects the animals disturb. When seriemas catch small reptiles, they beat the prey on the ground (Redford and Peters 1986) or throw it at a hard surface to break resistance and also the bones. If the prey is too large to swallow whole, it will be ripped into smaller pieces with a sickle claw by holding the prey in the beak and tearing it apart with the claw.^{[citation needed]}

Because of these feeding behaviors, seriemas are important by eating detritivores and helping the soil get more nutrients from dead plant matter.^{[clarification needed]}

In contact with humans, seriemas are suspicious and if they feel threatened, usually spread their wings and face the threat. They walk in pairs or small groups. Although perfectly capable of flying, they prefer to spend most of their time on land. They take flight only when necessary, for example to escape a predator. Overnight they take shelter in the treetops, where they also build their nests.