Teratornithidae is an extinct

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

of very large

birds of prey Birds of prey or predatory birds, also known as (although not the same as) raptors, are hypercarnivorous bird species that actively predation, hunt and feed on other vertebrates (mainly mammals, reptiles and smaller birds). In addition to speed ...

that lived in North and South America from the

Late Oligocene The Chattian is, in the geologic timescale The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the pro ...

Late Pleistocene The Late Pleistocene is an unofficial Age (geology), age in the international geologic timescale in chronostratigraphy, also known as the Upper Pleistocene from a Stratigraphy, stratigraphic perspective. It is intended to be the fourth division ...

. They include some of the largest known flying birds. Its members are known as teratorns.

Taxonomy

Teratornithidae are related to

New World vulture Cathartidae, known commonly as New World vultures or condors, are a family (biology), family of birds of prey consisting of seven extant species in five genus, genera. It includes five extant vultures and two extant condors found in the Americas. ...

s (Cathartidae, syn. Vulturidae). The fact that both of the oldest taxa in the group, ''Taubatornis'' and ''Argentavis'', originate from South America suggests that the group as a whole also evolved here, only migrating to North America in the latter part of the

Cenozoic The Cenozoic Era ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterized by the dominance of mammals, insects, birds and angiosperms (flowering plants). It is the latest of three g ...

. So far, seven species in six genera have been identified: * ''

Teratornis ''Teratornis'' (Greek: "wonder" (teratos), "bird" (ornis)) is an extinct genus of huge North American birds of prey—the best-known of the teratorns—of which, two species are known to have existed: ''Teratornis merriami'' and ''Teratornis woo ...

'' ** ''Teratornis merriami''. This is by far the best-known species. Over a hundred specimens have been found, mostly from the

La Brea Tar Pits La Brea Tar Pits comprise an active Paleontological site, paleontological research site in urban Los Angeles. Hancock Park was formed around a group of tar pits where natural Bitumen, asphalt (also called asphaltum, bitumen, or pitch; ''brea'' ...

. It stood about tall with an estimated wingspan of , and weighed about ; making it about a third bigger than extant

condor Condor is the common name for two species of New World vultures, each in a monotypic genus. The name derives from the Quechua language, Quechua ''kuntur''. They are the largest flying land birds in the Western Hemisphere. One species, the And ...

s. It became extinct at the end of Pleistocene, some 10,000 years ago. ** ''Teratornis woodburnensis''. The first species to be found north of the La Brea Tar Pits, this partial specimen was discovered at Legion Park, Woodburn, Oregon. It is known from a humerus, parts of the cranium, beak, sternum, and vertebrae which indicate an estimated wingspan of over . The find dates to the Late Pleistocene, between 11,000 and 12,000 years ago, in a stratum which is filled with the bones of mastodons, sloths, and condors, and has evidence of human habitation. * '' Aiolornis incredibilis'', previously known as ''Teratornis incredibilis''. This species is fairly poorly known; finds from Nevada and California include several wing bones and part of the beak. They show remarkable similarity with ''merriami'' but are uniformly about 40% larger: this would translate to a mass of up to and a wingspan of about for ''incredibilis''. The finds are dated from the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Cathartornis gracilis''. This species is known only from a couple of leg bones found from La Brea Ranch. Compared to ''T. merriami'', remains are slightly shorter and clearly more slender, indicating a more gracile build. * ''

Argentavis magnificens ''Argentavis'' is an extinct genus of teratornithid known from three sites in the Epecuén and Andalhualá Formations in central and northwestern Argentina dating to the Late Miocene (Huayquerian). The type species, ''A. magnificens'', is some ...

''. A partial skeleton of this enormous teratorn was found from La Pampa, Argentina. It is one of the largest flying birds known to have existed, only likely exceeded by measurement of wingspan by ''

Pelagornis sandersi ''Pelagornis'' is an extinct genus of prehistoric pseudotooth birds, a group of extinct seabirds. Species span from the Oligocene to the Early Pleistocene. Members of ''Pelagornis'' represent among the largest pseudotooth birds, with one specie ...

'', discovered in 1983. Fossil remains of this species have been dated to the

Huayquerian The Huayquerian () age is a period of geologic time (9.0–6.8 Ma) within the Late Miocene epoch of the Neogene, used more specifically within the SALMA classification. It follows the Chasicoan and precedes the Montehermosan age. Etymology T ...

, about 9 to 6.8 million years ago, and it is one of the few teratorn finds in South America. The initial discovery included portions of the skull, an incomplete humerus and several other wing bones. Even conservative estimates put its wingspan at and up, and it may have been as much as . The weight of the bird was estimated to have been around . * '' Oscaravis olsoni'' was described from the Pleistocene of

Cuba Cuba, officially the Republic of Cuba, is an island country, comprising the island of Cuba (largest island), Isla de la Juventud, and List of islands of Cuba, 4,195 islands, islets and cays surrounding the main island. It is located where the ...

, but its affinities are not completely resolved; it might not be a teratorn at all. There are also undescribed fossils from southwestern

Ecuador Ecuador, officially the Republic of Ecuador, is a country in northwestern South America, bordered by Colombia on the north, Peru on the east and south, and the Pacific Ocean on the west. It also includes the Galápagos Province which contain ...

. * '' Taubatornis campbelli'' is the earliest known teratorn species, from the

Early Miocene The Early Miocene (also known as Lower Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages: the Aquitanian age, Aquitanian and Burdigalian stages. The sub-epoch lasted from 23.03 ± 0.05 annum, Ma to ...

of the

Tremembé Formation Tremembé is a municipality in the state of São Paulo in Brazil. It is part of the Metropolitan Region of Vale do Paraíba e Litoral Norte. The population is 47,714 (2020 est.) in an area of 191.09 km². The elevation is 560 m. A s ...

Taubaté Basin Taubaté is a medium-sized city in the state of São Paulo (state), São Paulo, in southeastern Brazil. History Taubaté was part of the ancient Tupinambá people, Tupinambá Territory, along the Paraíba do Sul, Paraíba do Sul River. The Tu ...

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

Classification

Teratornithidae has only been included in a single phylogenetic analysis, published by Steven Emslie in 1988. The analysis was conducted using cranial characters of various taxa within the order

Ciconiiformes Storks are large, long-legged, long-necked wading birds with long, stout bills. They belong to the family Ciconiidae, and make up the order Ciconiiformes . Ciconiiformes previously included a number of other families, such as herons and ibise ...

, with a specific focus on Vulturidae (

Cathartidae Cathartidae, known commonly as New World vultures or condors, are a family of birds of prey consisting of seven extant species in five genera. It includes five extant vultures and two extant condors found in the Americas. They are known as "New W ...

). This analysis included ''Teratornis merriami'' as a representative of Teratornithidae, and found the group to be just outside of Vulturidae.

Description and ecology

Despite their size, there is little doubt that even the largest teratorns could fly. Visible marks of the attachments of contour feathers can be seen on ''Argentavis'' wing bones. This defies some earlier theories that extant condors,

swan Swans are birds of the genus ''Cygnus'' within the family Anatidae. The swans' closest relatives include the goose, geese and ducks. Swans are grouped with the closely related geese in the subfamily Anserinae where they form the tribe (biology) ...

s, and

bustard Bustards, including floricans and korhaans, are large, terrestrial birds living mainly in dry grassland areas and in steppe regions. They range in length from . They make up the family Otididae (, formerly known as Otidae). Bustards are ...

s represent the size limit for flying birds. The

wing loading In aerodynamics, wing loading is the total weight of an aircraft or flying animal divided by the area of its wing. The stalling speed, takeoff speed and landing speed of an aircraft are partly determined by its wing loading. The faster an airc ...

of ''Argentavis'' was relatively low for its size, a bit more than a

turkey Turkey, officially the Republic of Türkiye, is a country mainly located in Anatolia in West Asia, with a relatively small part called East Thrace in Southeast Europe. It borders the Black Sea to the north; Georgia (country), Georgia, Armen ...

's, and if there were any significant wind present, the bird could probably get airborne merely by spreading its wings, just like modern

albatross Albatrosses, of the biological family Diomedeidae, are large seabirds related to the procellariids, storm petrels, and diving petrels in the order Procellariiformes (the tubenoses). They range widely in the Southern Ocean and the North Paci ...

es. South America during the Miocene probably featured strong and steady westerly winds, as the

Andes The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the List of longest mountain chains on Earth, longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range ...

were still forming and not yet very high. ''T. merriami'' was small enough (relatively speaking) to take off with a simple jump and a few flaps. The fingerbones are mostly fused as in all birds, but the former

index finger The index finger (also referred to as forefinger, first finger, second finger, pointer finger, trigger finger, digitus secundus, digitus II, and many other terms) is the second digit of a human hand. It is located between the thumb and the m ...

has partially evolved into a wide shelf at least in ''T. merriami'', and as condors have a similar adaptation, probably in other species, too. Wing length estimates vary considerably but more likely than not were at the upper end of the range, because this bone structure bears the load of the massive primaries. Studies on

flight suggest that even the largest teratorns were capable of flight in normal conditions, as modern large soaring birds rarely flap their wings regardless of terrain. Traditionally, teratorns have been described as large scavengers, very much like oversized condors, owing to considerable similarity with condors. However, the long beaks and wide gapes of teratorns are more like the beaks of

eagle Eagle is the common name for the golden eagle, bald eagle, and other birds of prey in the family of the Accipitridae. Eagles belong to several groups of Genus, genera, some of which are closely related. True eagles comprise the genus ''Aquila ( ...

s and other actively predatory birds than those of vultures. Most likely teratorns swallowed their prey whole; ''Argentavis'' could technically swallow up to

hare Hares and jackrabbits are mammals belonging to the genus ''Lepus''. They are herbivores and live Solitary animal, solitarily or in pairs. They nest in slight depressions called forms, and their young are precociality, able to fend for themselves ...

-sized animals in a single piece. Although they undoubtedly engaged in opportunistic

scavenging Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding be ...

, they seem to have been active

predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

s most of the time. Teratorns had relatively longer and stouter legs than Old World vultures; thus it seems possible that teratorns would stalk their prey on the ground (much like extant

caracaras Caracaras are birds of prey in the family Falconidae. They are traditionally placed in subfamily Polyborinae with the forest falcons, but are sometimes considered to constitute their own subfamily, Caracarinae, or classified as members of the ...

), and take off only to fly to another feeding ground or their nests; especially ''Cathartornis'' seems well-adapted for such a lifestyle. ''Argentavis'' may have been an exception, as its sheer bulk would have made it a less effective hunter, but better adapted to taking over other predators' kills. As teratorns were not habitual scavengers, they most likely had completely feathered heads, unlike

vulture A vulture is a bird of prey that scavenges on carrion. There are 23 extant species of vulture (including condors). Old World vultures include 16 living species native to Europe, Africa, and Asia; New World vultures are restricted to Nort ...

s. The skull features of teratorns still share a lot of crucial similarities with specialized scavenging raptors. Many

old world vulture Old World vultures are vultures that are found in the Old World, i.e. the continents of Europe, Asia and Africa, and which belong to the family Accipitridae, which also includes eagles, buzzards, kites, and hawks. Old World vultures are not ...

s possess large bills similar to teratorns, and a longer bill is in fact an anatomic feature that points toward a scavenging rather than a predatory life style, as this allow them to probe deeper into large carcases - larger than those fed upon by active-hunting raptors. Other anatomical features, such as the relatively small and sideward facing orbits and the lower skull, are also consistent with a scavenging live style. More sideward facing eyes allow scavenging raptors to have a wider field of vision, which is advantageous in spotting carcases. In contrast, predatory raptors usually have proportionally larger and more forward facing orbits, as depth perception is more important for a predatory lifestyle. As in other large birds, a

clutch A clutch is a mechanical device that allows an output shaft to be disconnected from a rotating input shaft. The clutch's input shaft is typically attached to a motor, while the clutch's output shaft is connected to the mechanism that does th ...

probably had only one or two eggs; the young would be cared for more than half a year, and take several years to reach maturity, probably up to 12 years in ''Argentavis''.

References

External links

Vulture Territory Facts and Characteristics: Teratorns
{{Taxonbar, from=Q135217 Prehistoric bird families

† A dagger, obelisk, or obelus is a typographical mark that usually indicates a footnote if an asterisk has already been used. The symbol is also used to indicate death (of people) or extinction (of species or languages). It is one of the mo ...

New World vultures Oligocene birds Miocene birds Pliocene birds Pleistocene birds Oligocene first appearances Pleistocene extinctions Neogene birds of North America Neogene birds of South America Pleistocene birds of North America Pleistocene animals of South America Taxa named by Loye H. Miller