A ratite () is any of a diverse group of
flightless, large, long-necked, and long-legged birds of the infraclass
Palaeognathae
Palaeognathae (; ) is a infraclass of birds, called paleognaths, within the class Aves of the clade Archosauria. It is one of the two extant infraclasses of birds, the other being Neognathae, both of which form Neornithes. Palaeognathae conta ...
.
Kiwi, the exception, are much smaller and shorter-legged and are the only
nocturnal
Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite.
Nocturnal creatures generally have highly developed sens ...
extant ratites.
The systematics of and relationships within the paleognath clade have been in flux. Previously, all the flightless members had been assigned to the order
Struthioniformes, which is more recently regarded as containing only the
ostrich
Ostriches are large flightless birds of the genus ''Struthio'' in the order Struthioniformes, part of the infra-class Palaeognathae, a diverse group of flightless birds also known as ratites that includes the emus, rheas, and kiwis. There ...
.
The modern bird superorder Palaeognathae consists of ratites and the
flighted Neotropic
The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropical terrestrial ecoregions of the Americas and the entire South American temperate zone.
Definition
In ...
tinamou
Tinamous () form an order of birds called Tinamiformes (), comprising a single family called Tinamidae (), divided into two distinct subfamilies, containing 46 species found in Mexico, Central America, and South America. The word "tinamou" co ...
s (compare to
Neognathae
Neognathae (; ) is a infraclass of birds, called neognaths, within the class Aves of the clade Archosauria. Neognathae includes the majority of living birds; the exceptions being the tinamous and the flightless ratites, which belong instead to ...
).
Unlike other flightless birds, the ratites have no
keel
The keel is the bottom-most longitudinal structural element on a vessel. On some sailboats, it may have a hydrodynamic and counterbalancing purpose, as well. As the laying down of the keel is the initial step in the construction of a ship, in Br ...
on their
sternum — hence the name, from the Latin ''ratis'' (
raft, a vessel which has no keel - in contradistinction to extant flighted birds with a keel).
Without this to anchor their wing muscles, they could not have flown even if they developed suitable wings. Ratites are a
paraphyletic
In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and most of its descendants, excluding a few monophyletic subgroups. The group is said to be paraphyletic ''with respect to'' the excluded subgroups. In ...
group; tinamous fall within them, and are the
sister group of the extinct
moa.
This implies that flightlessness is a trait that evolved independently multiple times in different ratite lineages.
Most parts of the former
supercontinent Gondwana
Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final sta ...
have ratites, or did have until the fairly recent past.
So did Europe in the
Paleocene
The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek ''pala ...
and
Eocene
The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', ...
, from where the first flightless paleognaths are known.
Ostriches were present in Asia as recently as the
Holocene
The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...
, although the genus is thought to have originated in Africa.
However, the ostrich order may have evolved in Eurasia.
A recent study posits a
Laurasia
Laurasia () was the more northern of two large landmasses that formed part of the Pangaea supercontinent from around ( Mya), the other being Gondwana. It separated from Gondwana (beginning in the late Triassic period) during the breakup of Pa ...
n origin for the clade.
Geranoidids, which may have been ratites, existed in North America.
Species
Living forms
The African
ostrich
Ostriches are large flightless birds of the genus ''Struthio'' in the order Struthioniformes, part of the infra-class Palaeognathae, a diverse group of flightless birds also known as ratites that includes the emus, rheas, and kiwis. There ...
is the largest living ratite. A large member of this species can be nearly tall, weigh as much as ,
and can outrun a horse.
Of the living species, the Australian
emu is next in height, reaching up to tall and about .
Like the ostrich, it is a fast-running, powerful bird of the open plains and
woodland
A woodland () is, in the broad sense, land covered with trees, or in a narrow sense, synonymous with wood (or in the U.S., the '' plurale tantum'' woods), a low-density forest forming open habitats with plenty of sunlight and limited shade (see ...
s.
Also native to Australia and the islands to the north are the three species of
cassowary
Cassowaries ( tpi, muruk, id, kasuari) are flightless birds of the genus ''Casuarius'' in the order Casuariiformes. They are classified as ratites (flightless birds without a keel on their sternum bones) and are native to the tropical ...
. Shorter than an emu, but heavier and solidly built, cassowaries prefer thickly vegetated
tropical
The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in
the Southern Hemisphere at S. The tropics are also referred to ...
forest. They can be dangerous when surprised or cornered because of their razor-sharp
talons. In
New Guinea
New Guinea (; Hiri Motu: ''Niu Gini''; id, Papua, or , historically ) is the world's second-largest island with an area of . Located in Oceania in the southwestern Pacific Ocean, the island is separated from Australia by the wide Torres ...
, cassowary eggs are brought back to villages and the chicks raised for eating as a much-prized delicacy, despite (or perhaps because of) the risk they pose to life and limb. They reach up to tall and weigh as much as
South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sou ...
has two species of
rhea, large fast-running birds of the
Pampas. The larger
American rhea grows to about tall and usually weighs .
The smallest ratites are the five species of
kiwi from New Zealand. Kiwi are
chicken
The chicken (''Gallus gallus domesticus'') is a domesticated junglefowl species, with attributes of wild species such as the grey and the Ceylon junglefowl that are originally from Southeastern Asia. Rooster or cock is a term for an adu ...
-sized, shy, and
nocturnal
Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite.
Nocturnal creatures generally have highly developed sens ...
. They nest in deep
burrow
An Eastern chipmunk at the entrance of its burrow
A burrow is a hole or tunnel excavated into the ground by an animal to construct a space suitable for habitation or temporary refuge, or as a byproduct of locomotion. Burrows provide a form of s ...
s and use a highly developed sense of smell to find small insects and grubs in the soil. Kiwi are notable for laying eggs that are very large in relation to their body size. A kiwi egg may equal 15 to 20 percent of the body mass of a female kiwi. The smallest species of kiwi is the
little spotted kiwi, at and .
Holocene extinct forms
At least nine species of
moa lived in New Zealand before the arrival of humans, ranging from turkey-sized to the
giant moa ''
Dinornis robustus
The South Island giant moa (''Dinornis robustus'') is an extinct moa from the genus ''Dinornis.''
Context
The moa were ratites, flightless birds with a sternum without a keel. They also had a distinctive palate. The origin of these birds is b ...
'' with a height of and weighing about .
They became extinct by A.D. 1400 due to hunting by
Māori
Māori or Maori can refer to:
Relating to the Māori people
* Māori people of New Zealand, or members of that group
* Māori language, the language of the Māori people of New Zealand
* Māori culture
* Cook Islanders, the Māori people of the Co ...
settlers, who arrived around A.D. 1280.
''
Aepyornis maximus
''Aepyornis'' is a genus of aepyornithid, one of three genera of ratite birds endemic to Madagascar until their extinction sometime around 1000 CE. The species ''A. maximus'' weighed up to , and until recently was regarded as the largest known ...
'', the "elephant bird" of
Madagascar
Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Afric ...
, was the heaviest bird ever known. Although shorter than the tallest moa, a large ''A. maximus'' could weigh over and stand up to tall.
Accompanying it were three other species of ''
Aepyornis'' as well as three species of the smaller genus ''
Mullerornis''. All these species went into decline following the arrival of humans on Madagascar around 2,000 years ago, and were gone by the 17th or 18th century if not earlier.
Classification
There are two
taxonomic approaches to ratite classification: one combines the groups as
families in the
order
Order, ORDER or Orders may refer to:
* Categorization, the process in which ideas and objects are recognized, differentiated, and understood
* Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...
Struthioniformes, while the other supposes that the lineages evolved mostly independently and thus elevates the families to order rank (Rheiformes, Casuariformes etc.).
Evolution
The longstanding story of ratite evolution was that they share a common flightless ancestor that lived in
Gondwana
Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final sta ...
, whose descendants were isolated from each other by
continental drift, which carried them to their present locations. Supporting this idea, some studies based on morphology, immunology and DNA sequencing reported that ratites are
monophyletic.
Cracraft's 1974 biogeographic vicariance hypothesis suggested that ancestral flightless paleognaths, the ancestors of ratites, were present and widespread in Gondwana during the Late Cretaceous. As the supercontinent fragmented due to
plate tectonics
Plate tectonics (from the la, label= Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of larg ...
, they were carried by plate movements to their current positions and evolved into the species present today.
The earliest known ratite fossils date to the
Paleocene
The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek ''pala ...
epoch about 56 million years ago (e.g., ''
Diogenornis
''Diogenornis'' is an extinct genus of ratites, that lived during the Early Eocene (Itaboraian to Casamayoran in the SALMA classification).[paleognaths
Palaeognathae (; ) is a infraclass of birds, called paleognaths, within the class Aves of the clade Archosauria. It is one of the two extant infraclasses of birds, the other being Neognathae, both of which form Neornithes. Palaeognathae conta ...]
are known from several million years earlier,
and the classification and membership of the Ratitae itself is uncertain. Some of the earliest ratites occur in Europe.
Recent analyses of genetic variation between the ratites do not support this simple picture. The ratites may have diverged from one another too recently to share a common Gondwanan ancestor. Also, the Middle Eocene ratites such as ''
Palaeotis
''Palaeotis'' is a genus of paleognath birds from the middle Eocene epoch of central Europe. One species is known, ''Palaeotis weigelti''. The holotype specimen is a fossil tarsometatarsus and phalanx. Lambrect (1928) described it as an extinct ...
'' and ''
Remiornis'' from Central Europe may imply that the "out-of-Gondwana" hypothesis is oversimplified.
Molecular phylogenies of the ratites have generally placed ostriches in the
basal position and among extant ratites, placed rheas in the second most basal position, with Australo-Pacific ratites splitting up last; they have also shown that both the latter groups are monophyletic.
Early mitochondrial genetic studies that failed to make ostriches basal
were apparently compromised by the combination of rapid early radiation of the group and long terminal branches.
A morphological analysis that created a basal New Zealand clade
has not been corroborated by molecular studies. A 2008 study of nuclear genes shows ostriches branching first, followed by rheas and tinamous, then kiwi splitting from emus and cassowaries.
In more recent studies, moas and tinamous were shown to be
sister groups,
and elephant birds were shown to be most closely related to the New Zealand kiwi.
Additional support for the latter relationship was obtained from morphological analysis.
The finding that tinamous nest within this group, originally based on twenty nuclear genes
and corroborated by a study using forty novel nuclear loci
makes 'ratites'
polyphyletic rather than monophyletic.
Since tinamous are weak fliers, this raises interesting questions about the evolution of flightlessness in this group. The branching of the tinamous within the ratite radiation suggests flightlessness
evolved independently
Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last co ...
among ratites at least three times.
More recent evidence suggests this happened at least six times, or once in each major ratite lineage.
Re-evolution of flight in the tinamous would be an alternative explanation, but such a development is without precedent in avian history, while loss of flight is commonplace.
By 2014, a mitochondrial DNA phylogeny including fossil members placed ostriches on the
basal branch, followed by rheas, then a clade consisting of moas and tinamous, followed by the final two branches: a clade of emus plus cassowaries and one of elephant birds plus kiwis.
Vicariant speciation based on the
plate tectonic
Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large te ...
split-up of Gondwana followed by continental drift would predict that the deepest phylogenetic split would be between African and all other ratites, followed by a split between South American and Australo-Pacific ratites, roughly as observed. However, the elephant bird–kiwi relation appears to require dispersal across oceans by flight,
as apparently does the colonization of New Zealand by the moa and possibly the back-dispersal of tinamous to South America, if the latter occurred.
The phylogeny as a whole suggests not only multiple independent origins of flightlessness, but also of gigantism (at least five times).
Gigantism
Gigantism ( el, γίγας, ''gígas'', " giant", plural γίγαντες, ''gígantes''), also known as giantism, is a condition characterized by excessive growth and height significantly above average. In humans, this condition is caused by ov ...
in birds tends to be
insular; however, a ten-million-year-long window of opportunity for evolution of avian gigantism on continents may have existed following the
extinction of the non-avian dinosaurs, in which ratites were able to fill vacant herbivorous niches before mammals attained large size.
Some authorities, though, have been skeptical of the new findings and conclusions.
Kiwi and tinamous are the only palaeognath lineages not to evolve gigantism, perhaps because of competitive exclusion by giant ratites already present on New Zealand and South America when they arrived or arose.
The fact that New Zealand has been the only land mass to recently support two major lineages of flightless ratites may reflect the absence of native mammals, which allowed kiwi to occupy a mammal-like nocturnal
niche
Niche may refer to:
Science
*Developmental niche, a concept for understanding the cultural context of child development
* Ecological niche, a term describing the relational position of an organism's species
*Niche differentiation, in ecology, the ...
.
However, various other landmasses such as South America and Europe have supported multiple lineages of flightless ratites that evolved independently, undermining this competitive exclusion hypothesis.
Most recently, studies on genetic and morphological divergence and fossil distribution show that paleognaths as a whole probably had an origin in the northern hemisphere. Early Cenozoic northern hemisphere paleognaths such as ''
Lithornis
''Lithornis'' is a genus of extinct paleognathous birds. Although ''Lithornis'' was able to fly well, their closest relatives are the extant tinamous (which are poor flyers) and ratites (which are flightless birds).
Fossils of ''Lithornis'' ar ...
'', ''
Pseudocrypturus
''Pseudocrypturus'' is a genus of extinct paleognathous bird. One species is known, ''Pseudocrypturus cercanaxius''. It is a relative of such modern birds as ostriches. It lived in the early Eocene.
The holotype fossil is in the collection of th ...
'', ''
Paracathartes
''Paracathartes'' is a genus of extinct bird from the Wasachtian horizon of lower Eocene Wyoming. One species, ''Paracathartes howardae'' has been described.
It is a paleognathous bird, turkey-like in stature and size, that probably resembled ...
'' and ''
Palaeotis
''Palaeotis'' is a genus of paleognath birds from the middle Eocene epoch of central Europe. One species is known, ''Palaeotis weigelti''. The holotype specimen is a fossil tarsometatarsus and phalanx. Lambrect (1928) described it as an extinct ...
'' appear to be the most basal members of the clade.
The various ratite lineages were probably descended from flying ancestors that independently colonised South America and Africa from the north, probably initially in South America. From South America they could have traveled overland to Australia via Antarctica,
(by the same route marsupials are thought to have used to reach Australia
) and then reached New Zealand and Madagascar via "sweepstakes" dispersals across the oceans. Gigantism would have evolved subsequent to trans-oceanic dispersals.
Loss of flight
Loss of flight allows birds to eliminate the costs of maintaining various flight-enabling adaptations like high
pectoral muscle
Pectoral muscles (colloquially referred to as "pecs") are the muscles that connect the front of the human chest with the bones of the upper arm and shoulder. This region contains four muscles that provide movements to the upper limbs or ribs.
Pe ...
mass, hollow bones and a light build, et cetera.
The basal metabolic rate of flighted species is much higher than that of flightless terrestrial birds.
But energetic efficiency can only help explain the loss of flight when the benefits of flying are not critical to survival.
Research on flightless rails indicates the flightless condition evolved in the absence of predators.
This shows flight to be generally necessary for survival and dispersal in birds.
In apparent contradiction to this, many landmasses occupied by ratites are also inhabited by predatory mammals.
However, the
K–Pg extinction event created a window of time with large predators absent that may have allowed the ancestors of ratites to evolve flightlessness.
They subsequently underwent selection for large size.
One hypothesis suggests that as predation pressure decreases on islands with low raptor species richness and no mammalian predators, the need for large, powerful flight muscles that make for a quick escape decreases.
Moreover, raptor species tend to become generalist predators on islands with low species richness, as opposed to specializing in the predation of birds. An increase in leg size compensates for a reduction in wing length in insular birds that have not lost flight by providing a longer lever to increase force generated during the thrust that initiates takeoff.
Description
Ratites in general have many physical characteristics in common, which are often not shared by the family
Tinamidae, or tinamous. First, the
breast muscles are underdeveloped. They do not have keeled
sterna. Their wishbones (
furculae) are almost absent. They have a simplified wing skeletons and musculature. Their legs are stronger and do not have air chambers, except the
femur
The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates ...
s. Their tail and flight feathers have retrogressed or have become decorative plumes. They have no feather vanes, which means they do not need to oil their feathers, hence they have no
preen gland
The uropygial gland, informally known as the preen gland or the oil gland, is a bilobed sebaceous gland possessed by the majority of birds used to distribute the gland's oil through the plumage by means of preening. It is located dorsally at the ...
s. They have no separation of pterylae (feathered areas) and apteria (non-feathered areas), and finally, they have
palaeognathous
palates.
Ostriches have the greatest
dimorphism, rheas show some
dichromatism
Dichromatism (or polychromatism) is a phenomenon where a material or solution's hue is dependent on both the concentration of the absorbing substance and the depth or thickness of the medium traversed. In most substances which are not dichromatic, ...
during the breeding season. Emus, cassowaries, and kiwis show some dimorphism, predominantly in size.
While the ratites share a lot of similarities, they also have major differences. Ostriches have only two toes, with one being much larger than the other. Cassowaries have developed long inner toenails, used defensively. Ostriches and rheas have prominent wings; although they don't use them to fly, they do use them in courtship and predator distraction.
Without exception, ratite chicks are capable of swimming and even diving.
On an
allometric basis,
paleognaths have generally smaller brains than
neognaths. Kiwis are exceptions to this trend, and possess proportionally larger brains comparable to those of
parrots and
songbirds, though evidence for similar advanced cognitive skills is currently lacking.
Gallery of living species
Image:Autruche Thoiry 19801.jpg, Ostrich
Ostriches are large flightless birds of the genus ''Struthio'' in the order Struthioniformes, part of the infra-class Palaeognathae, a diverse group of flightless birds also known as ratites that includes the emus, rheas, and kiwis. There ...
Image:Masai Ostriches Benh.jpg, Ostrich herd (''S. camelus massaicus'')
Image:Rhea side profile.jpg, American rhea
Image:Darwin-Nandus.jpg, Darwin's rhea
Darwin's rhea or the lesser rhea (''Rhea pennata'') is a large flightless bird, the smaller of the two extant species of rheas. It is found in the Altiplano and Patagonia in South America.
Description
The lesser rhea stands at tall. Leng ...
Image:Double-wattled Cassowary.jpg, Southern cassowary
The southern cassowary (''Casuarius casuarius''), also known as double-wattled cassowary, Australian cassowary or two-wattled cassowary, is a large flightless black bird. It is one of the three living species of cassowary, alongside the dwarf c ...
File:Casuarius unappendiculatus -Northern Cassowary -head to toe.jpg, Northern cassowary
Image:Mooruk-Wolf.jpg, Dwarf cassowary
File:Dromaius novaehollandiae qtl1.jpg, Emu
Image:Apteryx haastii.jpg, Great spotted kiwi
Image:Apteryx owenii 0.jpg, Little spotted kiwi
Image:Kiwifugl.jpg, North Island brown kiwi
Behavior and ecology
Feeding and diet
Ratite chicks tend to be more
omnivorous or
insectivorous; similarities in adults end with feeding, as they all vary in diet and length of digestive tract, which is indicative of diet. Ostriches, with the longest tracts at , are primarily
herbivorous. Rheas' tracts are next longest at , and they also have
caeca. They are also mainly
herbivores, concentrating on broad-leafed plants. However, they will eat insects if the opportunity arises. Emus have tracts of length, and have a more omnivorous diet, including insects and other small animals. Cassowaries have next to the shortest tracts at . Finally, kiwi have the shortest tracts and eat earthworms, insects, and other similar creatures.
Moas
Moa are extinct giant flightless birds native to New Zealand.
The term has also come to be used for chicken in many Polynesian cultures and is found in the names of many chicken recipes, such as
Kale moa and Moa Samoa.
Moa or MOA may also refe ...
and
elephant birds were the largest native herbivores in their faunas, far larger than contemporary herbivorous mammals in the latter's case.
Some extinct ratites might have had odder lifestyles, such as the narrow-billed ''
Diogenornis
''Diogenornis'' is an extinct genus of ratites, that lived during the Early Eocene (Itaboraian to Casamayoran in the SALMA classification).[Palaeotis
''Palaeotis'' is a genus of paleognath birds from the middle Eocene epoch of central Europe. One species is known, ''Palaeotis weigelti''. The holotype specimen is a fossil tarsometatarsus and phalanx. Lambrect (1928) described it as an extinct ...]
'', compared to the shorebird-like
lithornithids, and could imply similar animalivorous diets.
Reproduction
Ratites are different from the flying birds in that they needed to adapt or evolve certain features to protect their young. First and foremost is the thickness of the shells of their eggs. Their young are hatched more developed than most and they can run or walk soon thereafter. Also, most ratites have communal nests, where they share the incubating duties with others. Ostriches, and great spotted kiwis, are the only ratites where the female incubates; they share the duties, with the males incubating at night. Cassowaries and emu are polyandrous, with males incubating eggs and rearing chicks with no obvious contribution from females. Ostriches and rheas are polygynous with each male courting several females. Male rheas are responsible for building nests and incubating while ostrich males incubate only at night. Kiwis stand out as the exception with extended monogamous reproductive strategies where either the male alone or both sexes incubate a single egg.
Ratites and humans
Ratites and humans have had a long relationship starting with the use of the egg for water containers, jewelry, or other art medium. Male ostrich feathers were popular for hats during the 18th century, which led to hunting and sharp declines in populations. Ostrich farming grew out of this need, and humans harvested feathers, hides, eggs, and meat from the ostrich. Emu farming also became popular for similar reasons and for their
emu oil. Rhea feathers are popular for dusters, and eggs and meat are used for chicken and pet feed in South America. Ratite hides are popular for leather products like shoes.
United States regulation
The USDA's
Food Safety and Inspection Service (FSIS) began a voluntary, fee-for-service ratite inspection program in 1995 to help the fledgling industry improve the marketability of the meat. A provision in the FY2001 USDA appropriations act (P.L. 106–387) amended the
Poultry Products Inspection Act to make federal inspection of ratite meat mandatory as of April 2001 (21 U.S.C. 451 et seq.).
See also
*
List of Struthioniformes by population
References
External links
Websites With Information On Ratites
{{Taxonbar, from=Q19170
Flightless birds
Extant Thanetian first appearances
Taxa named by William Plane Pycraft
Paraphyletic groups