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Palaeognathae
Palaeognathae
Palaeognathae
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Paleognaths
Temporal range: Paleocene – Holocene, 60–0 Ma
Palaeognathae biodiversity.[a]
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Infraclass: Palaeognathae
Pycraft, 1900
Orders

Palaeognathae (/ˌpæliˈɒɡnəθi/; from Ancient Greek παλαιός (palaiós) 'old' and γνάθος (gnáthos) 'jaw') is an infraclass[1] of birds, called paleognaths or palaeognaths, within the class Aves of the clade Archosauria. It is one of the two infraclasses of birds, the other being Neognathae, both of which form Neornithes. Palaeognathae contains five extant orders consisting of four flightless lineages (plus two that are extinct), termed ratites, and one flying lineage, the Neotropic tinamous.[2][3] There are 47 species of tinamous, five of kiwis (Apteryx), three of cassowaries (Casuarius), one of emus (Dromaius) (another became extinct in historic times), two of rheas (Rhea) and two of ostriches (Struthio).[4] Recent research has indicated that paleognaths are monophyletic but the traditional taxonomic split between flightless and flighted forms is incorrect; tinamous are within the ratite radiation, meaning flightlessness arose independently multiple times via parallel evolution.[5]

There are three extinct groups that are undisputed members of Palaeognathae: the Lithornithiformes, the Dinornithiformes (moas) and the Aepyornithiformes (elephant birds), the latter two of which became extinct in the last 1250 years. There are other extinct birds which have been allied with the Palaeognathae by at least one author, but their affinities are a matter of dispute.[citation needed]

The word paleognath is derived from the Ancient Greek for 'old jaws' in reference to the skeletal anatomy of the palate, which is described as more primitive and reptilian than that in other birds.[6] Paleognathous birds retain some basal morphological characters but are by no means living fossils as their genomes continued to evolve at the DNA level under selective pressure at rates comparable to the Neognathae branch of living birds, though there is some controversy about the precise relationship between them and the other birds. There are also several other scientific controversies about their evolution (see below).[7]

Origin and evolution

[edit]
See also: List of paleognaths

No unambiguously paleognathous fossil birds are known until the Cenozoic (though birds occasionally interpreted as lithornithids occur in Albian appalachian sites[8][9]), but there have been many reports of putative paleognaths, and it has long been inferred that they may have evolved in the Cretaceous. Given the Northern Hemisphere location of the morphologically most basal fossil forms (such as Lithornis, Pseudocrypturus, Paracathartes and Palaeotis), a Laurasian origin for the group can be inferred. The present almost entirely Gondwanan distribution would then have resulted from multiple colonisations of the southern landmasses by flying forms that subsequently evolved flightlessness, and in many cases, gigantism.[10]

Pseudocrypturus cercanaxius fossil cast, Copenhagen Zoological Museum

One study of molecular and paleontological data found that modern bird orders, including the paleognathous ones, began diverging from one another in the Early Cretaceous.[11] Benton (2005) summarized this and other molecular studies as implying that paleognaths should have arisen 110 to 120 million years ago in the Early Cretaceous. He points out, however, that there is no fossil record until 70 million years ago, leaving a 45 million year gap. He asks whether the paleognath fossils will be found one day, or whether the estimated rates of molecular evolution are too slow, and that bird evolution actually accelerated during an adaptive radiation after the Cretaceous–Paleogene boundary (K–Pg boundary).[12]

Other authors questioned the monophyly of the Palaeognathae on various grounds, suggesting that they could be a hodgepodge of unrelated birds that have come to be grouped together because they are coincidentally flightless. Unrelated birds might have developed ratite-like anatomies multiple times around the world through convergent evolution. McDowell (1948) asserted that the similarities in the palate anatomy of paleognaths might actually be neoteny, or retained embryonic features. He noted that there were other features of the skull, such as the retention of sutures into adulthood, that were like those of juvenile birds. Thus, perhaps the characteristic palate was actually a frozen stage that many carinate bird embryos passed through during development. The retention of early developmental stages, then, may have been a mechanism by which various birds became flightless and came to look similar to one another.[13]

Life restoration of Lithornis.

Hope (2002) reviewed all known bird fossils from the Mesozoic looking for evidence of the origin of the evolutionary radiation of the Neornithes. That radiation would also signal that the paleognaths had already diverged. She notes five Early Cretaceous taxa that have been assigned to the Palaeognathae. She finds that none of them can be clearly assigned as such. However, she does find evidence that the Neognathae and, therefore, also the Palaeognathae had diverged no later than the Early Campanian age of the Cretaceous period.[14]

Vegavis is a fossil bird from the Maastrichtian stage of Late Cretaceous Antarctica. Vegavis is most closely related to true ducks. Because virtually all phylogenetic analyses predict that ducks diverged after paleognaths, this is evidence that paleognaths had already arisen well before that time.[15]

An exceptionally preserved specimen of the extinct flying paleognathe Lithornis was published by Leonard et al. in 2005. It is an articulated and nearly complete fossil from the early Eocene of Denmark, and thought to have the best preserved lithornithiform skull ever found. The authors concluded that Lithornis was a close sister taxon to tinamous, rather than ostriches, and that the lithornithiforms + tinamous were the most basal paleognaths. They concluded that all ratites, therefore, were monophyletic, descending from one common ancestor that became flightless. They also interpret the paleognath-like Limenavis, from late Cretaceous Patagonia, as possible evidence of a Cretaceous and monophyletic origin for paleognaths.[7]

Mysterious large eggs from the Pliocene of Lanzarote in the Canary Islands have been attributed to ratites.[16]

An ambitious genomic analysis of the living birds was performed in 2007, and it contradicted Leonard et al. (2005). It found that tinamous are not primitive within the paleognaths, but among the most advanced. This requires multiple events of flightlessness within the paleognaths and partially refutes the Gondwana vicariance hypothesis (see below). The study looked at DNA sequences from 19 loci in 169 species. It recovered evidence that the paleognaths are one natural group (monophyletic), and that their divergence from other birds is the oldest divergence of any extant bird groups. It also placed the tinamous within the ratites, more derived than ostriches, or rheas and as a sister group to emus and kiwis, and this makes ratites paraphyletic.[17]

A related study addressed the issue of paleognath phylogeny exclusively. It used molecular analysis and looked at twenty unlinked nuclear genes. This study concluded that there were at least three events of flightlessness that produced the different ratite orders, that the similarities between the ratite orders are partly due to convergent evolution, and that the Palaeognathae are monophyletic, but the ratites are not.[18]

Beginning in 2010, DNA analysis studies have shown that tinamous are the sister group to extinct moa of New Zealand.[3][5][19][20]

A 2020 molecular study of all bird orders found paleognaths and neognaths to have diverged in the Late Cretaceous or earlier, before 70 million years ago. However, all modern paleognath orders only originated in the latest Paleocene and afterwards, with ostriches diverging in the latest Paleocene, rheas in the early Eocene, kiwis (and presumably elephant birds) very shortly after in the early Eocene, and finally Casuariiformes and tinamous (and presumably moas) diverging from one another in the mid-Eocene.[21]

History of classifications

[edit]

In the history of biology there have been many competing taxonomies of the birds now included in the Palaeognathae. The topic has been studied by Dubois (1891), Sharpe (1891), Shufeldt (1904), Sibley and Ahlquist (1972, 1981) and Cracraft (1981).

Merrem (1813) is often credited with classifying the paleognaths together, and he coined the taxon "Ratitae" (see above). However, Linnaeus (1758) placed cassowaries, emus, ostriches, and rheas together in Struthio. Lesson (1831) added the kiwis to the Ratitae. Parker (1864) reported the similarities of the palates of the tinamous and ratites, but Huxley (1867) is more widely credited with this insight. Huxley still placed the tinamous with the Carinatae of Merrem because of their keeled sterna, and thought that they were most closely related to the Galliformes.

Pycraft (1900) presented a major advance when he coined the term Palaeognathae. He rejected the Ratitae-Carinatae classification that separated tinamous and ratites. He reasoned that a keelless, or "ratite", sternum could easily evolve in unrelated birds that independently became flightless. He also recognized that the ratites were secondarily flightless. His subdivisions were based on the characters of the palatal skeleton and other organ systems. He established seven roughly modern orders of living and fossil paleognaths (Casuarii, Struthiones, Rheae, Dinornithes, Aepyornithes, Apteryges, and Crypturi – the latter his term for tinamous, after the Tinamou genus Crypturellus).

The Palaeognathae are usually considered a superorder, but authors have treated them as a taxon as high as subclass (Stresemann 1927–1934) or as low as an order (Cracraft 1981 and the IUCN, which includes all paleognaths in an expanded Struthioniformes[22]). Palaeognathae was defined in the PhyloCode by George Sangster and colleagues in 2022 as "the least inclusive crown clade containing Tinamus major and Struthio camelus".[23]

Cladistics

[edit]
Palaeognathae

Cladogram based on Mitchell (2014)[5] with some clade names after Yuri et al. (2013)[24] Yuri et al. (2013) named the clades Notopalaeognathae and Novaeratitae, the former defined in the PhyloCode by Sangster et al. (2022) as "the least inclusive crown clade containing Rhea americana, Tinamus major, and Apteryx australis", while the latter also defined in the PhyloCode by Sangster et al. (2022) as "the least inclusive crown clade containing Apteryx australis and Casuarius casuarius".[23] Notopalaeognathae represents the grouping containing the majority of ratites with the exception of ostriches, and the clade Novaeratitae was named to support the relationship between kiwis, cassowaries, emus, and the extinct elephant birds.[25][23]

Cloutier, A. et al. (2019) in their molecular study places ostriches as the basal lineage with the rhea as the next most basal.[26]

An alternative phylogeny was found by Kuhl, H. et al. (2020). In this treatment, all members of Palaeognathae are classified in Struthioniformes, but they are still shown as distinct orders here.[21]

Palaeognathae

Other studies have suggested that the relationships between the four main groups of non-ostrich palaeognaths (Casuariiformes, Rheiformes, Apteryformes+Aepyornithformes and Tinamiformes+Dinornithformes) are an effective polytomy, with only slightly more support for Novaeratitae over the alternative hypotheses of Apterygiformes+Aepyornithformes being more closely related to Rheiformes or to Tinamiformes+Dinornithformes.[27] This lineage containing the sister relationship between tinamous and moas was given the clade name Dinocrypturi, being named and defined in the PhyloCode by Sangster et al. (2022) as "the smallest clade containing Tinamus major and Dinornis novaezealandiae".[23]

Description

[edit]

Paleognaths are named for a characteristic, complex architecture of the bones in the bony palate. Cracraft (1974) defined it with five characters.

  1. The vomer is large and articulates with the premaxillae and maxillopalatines anteriorly. Posteriorly the vomer fuses to the ventral surface of the pterygoid, and the palatines fuse to the ventral surface of this pterygovomer articulation.
  2. The pterygoid prevents the palatine from articulating medially with the basisphenoid.
  3. The palatine and pterygoid fuse into a rigid joint.
  4. The articulation on the pterygoid for the basipterygoid process of the basicranium is located near the articulation between the pterygoid and quadrate.
  5. The pterygoid–quadrate articulation is complex and includes the orbital process of the quadrate.[28]

Paleognaths share similar pelvis anatomy. There is a large, open ilio–ischiatic fenestra in the pelvis. The pubis and ischium are likely to be longer than the ilium, protruding out beneath the tail. The postacetabular portion of the pelvis is longer than the preacetabular portion.

Paleognaths share a pattern of grooves in the horny covering of the bill. This covering is called the rhamphotheca. The paleognath pattern has one central strip of horn, with long, triangular, strips to either side.

In paleognaths, the male incubates the eggs. The male may include in his nest the eggs of one female or more than one. He may also have eggs deposited in his nest by females that did not breed with him, in cases of nest parasitism. Only in ostriches and the great spotted kiwi does the female also assist in incubating the eggs.[29]

The tinamous of Central and South America are primarily terrestrial, though they fly weakly. Tinamous have very short tail feathers, giving them an almost tailless aspect. In general, they resemble galliform birds like quails and grouse.

Tinamous have a very long, keeled, breastbone with an unusual three-pronged shape. This bone, the sternum, has a central blade (the Carina sterni), with two long, slender lateral trabeculae, which curve to either side and nearly touch the keel posteriorly. These trabeculae may also be thought of as the rims of two large foramina that incise the posterior edge of the sternum, and extend almost its whole length. Tinamous have a proper semicircular furcula, with no trace of a hypocleidium.[30] There is an acute angle between the scapula and coracoid, as in all flying birds. The pelvis has an open ilio–ischiatic fenestra that incises the posterior edge between the ilium and ischium, as in all paleognaths. Tinamous have no true pygostyle, their caudal vertebrae remain unfused, as in ratites.[31]

Tinamou feathers look like those of volant birds in that they have a rachis and two vanes. The structure of tinamou feathers is unique, however, in that they have barbs that remain joined at their tips. Thus the parallel barbs are separated only by slits between them.[32] Tinamous have uropygial glands.

Comparison of a kiwi, ostrich, and Dinornis, each with its egg

Ratite birds are strictly flightless and their anatomy reflects specializations for terrestrial life. The term "ratite" is from the Latin word for raft, ratis, because they possess a flat breastbone, or sternum, shaped like a raft. This characteristic sternum differs from that in flighted birds, where the pectoral musculature is disproportionately large to provide the power for wingbeats and the sternum develops a prominent keel, or carina sterni to anchor these muscles. The clavicles do not fuse into a furcula. Instead, if present at all, each is splint-like and lies along the medial border of the coracoid, attached there by a coraco–clavicular ligament. There is an obtuse angle between the scapula and coracoid, and the two bones fuse together to form a scapulocoracoid.[31] Ratites have reduced and simplified wing structures and strong legs. Except in some rhea wing feathers, the barb filaments that make up the vanes of the feathers do not lock tightly together, giving the plumage a shaggier look and making it unnecessary to oil their feathers. Adult ratites have no preen gland (uropygial gland) that contains preening oil.

Paleognaths as a whole tend to have proportionally small brains, and are among the living birds with the most limited cognitive abilities. Kiwis are exceptional, however, and have large brains comparable to those of parrots and songbirds, though evidence for similar levels of behaviour complexity is currently lacking.[33]

Sizes

[edit]

Living members of Palaeognathae range from 6 inches (15 cm) to 9 feet (2.7 m) and weight can be from .09 to 345 pounds (0.0–156.5 kg).[29] Ostriches are the largest struthioniforms (members of the order Struthioniformes), with long legs and neck. They range in height from 5.7 to 9 feet (1.7–2.7 m) and weigh from 139 to 345 pounds (63–156 kg).[29] They have loose-feathered wings. Males have black and white feathers while the female has grayish brown feathers. They are unique among birds in that they retain only the third and fourth toe on each foot. Ostrich wings have claws, or unguals, on the first and second fingers (and, in some individuals, also on the third). Ostriches differ from other paleognaths in that they have a reduced vomer bone of the skull.[citation needed]

Emus are 6 to 7.5 feet (1.8–2.3 m) in height and weigh 75 to 110 pounds (34–50 kg).[29] They have short wings and the adults have brown feathers.

Rheas are 3 to 4.6 feet (91–140 cm) and weigh 33 to 88 pounds (15–40 kg).[29] Their feathers are gray or spotted brown and white. They have large wings but no tail feathers. They have no clavicles.

Cassowaries are 3.5 to 5.6 feet (1.1–1.7 m) in height and weigh 30 to 130 pounds (14–59 kg).[29] They have rudimentary wings with black feathers and six stiff, porcupine-like, quills in the place of their primary and secondary feathers.

Kiwis are the smallest of ratites, ranging in height from 14 to 22 inches (36–56 cm) and weight 2.6 to 8.6 pounds (1.2–3.9 kg).[29] They have shaggy brown feathers.

Tinamous range in size from 8 to 21 inches (20–53 cm) and weigh 1.4 to 5 pounds (640–2,270 g).[29]

Locomotion

[edit]

Many of the larger ratite birds have extremely long legs and the largest living bird, the ostrich, can run at speeds over 35 mph (60 km/h). Emus have long, strong legs and can run up to 30 mph (48 km/h). Cassowaries and rheas show a similar likeness in agility and some extinct forms may have reached speeds of 45 mph (75 km/h).[citation needed]

Biogeography

[edit]

Today, the ratites are largely restricted to the Southern Hemisphere, though across the Cenozoic they were also present in Europe, North America and Asia. In the Cretaceous, these southern continents were connected, forming a single continent called Gondwana. Gondwana is the crucial territory in a major scientific question about the evolution of Palaeognathae, and thus about the evolution of all of the Neornithes.

There are two theories regarding the evolution of paleognaths. According to the Gondwana vicariance hypothesis, the paleognaths evolved once, from one ancestor, on Gondwana during the Cretaceous, and then rode on the daughter landmasses that became today's southern continents. This hypothesis is supported most strongly by molecular clock studies, but it is weakened by the lack of any Cretaceous or southern fossil paleognaths, as well as the early radiation of paleognaths in Laurasian landmasses. According to the Tertiary radiation hypothesis,[b] they evolved after the Cretaceous–Paleogene extinction event from multiple flying ancestors on multiple continents around the world. This hypothesis is supported by molecular phylogeny studies and matches the fossil record, but it is weakened by morphological phylogenetic studies. Both hypotheses have been supported and challenged by many studies by many authors.[6]

A 2016 study of both genetic and morphological divergence concludes that the group had a Laurasian origin.[10]

Gondwana vicariance hypothesis

[edit]

Cracraft (2001) gave a comprehensive review to the data and strongly supported the Gondwana vicariance hypothesis with phylogenetic evidence and historical biogeography. He cites molecular clock studies that show a basal divergence date for neornithes being around 100 Mya. He credits the authors of the molecular clock studies with the observation that the lack of southern paleognath fossils may correspond to the relatively scarce southern Cretaceous deposits, and the relative lack of paleontological field work in the Southern Hemisphere. Moreover, Cracraft synthesizes the morphological and molecular studies, noting conflicts between the two, and finds that the bulk of the evidence favors paleognath monophyly. He also notes that not only the ratites, but other basal groups of neognathous birds, show trans-Antarctic distribution, as would be expected if the paleognaths and neognaths had diverged in Gondwana.[35]

Geological analyses have suggested that New Zealand may have been entirely under water as recently as 28 Mya, making it impossible for flightless birds to have survived.[citation needed] However, the discovery of a Sphenodon fossil dating to the Early Miocene 19–16 Mya raises question as to whether the island mass was completely submerged. This finding offers further evidence that ancient Sphenodon species lived on some portion of the land mass since it separated from Gondwana approximately 82 Mya. Evidence of a sea level rise submerging much of New Zealand is generally accepted, but there is a debate about how much of New Zealand was submerged. A Sphenodon species surviving on a remnant part of the island suggests that larger species may have survived as well.[36]

Ultimately, the earliest recorded paleognaths are flying, presumably plesiomorphic lithornithids, found quite possibly as early as the Late Cretaceous in North America,[8][9] while some of the earliest flightless ratites occur in Europe.[37] The vicariance hypothesis relies on the assumption southern landmasses were more relevant to ratite evolution than the northern ones.[37][38]

Tertiary radiation hypothesis[b]

[edit]

Feduccia (1995) emphasized the extinction event at the Cretaceous-Paleogene boundary as the probable engine of diversification in the Neornithes, picturing only one or very few lineages of birds surviving the end of the Cretaceous. He also noted that birds around the world had developed ratite-like anatomies when they became flightless, and saw the affinities of modern ratites, especially kiwis, as ambiguous.[39] In this emphasis on the Cenozoic, rather than Cretaceous period, as the time of basal divergences between neornithines, he follows Olson.[40]

Houde demonstrated that the Lithornithiformes, a group of flying birds that were common in the Cenozoic of the Northern Hemisphere, were also paleognaths. He argues that the lithornithiform bird Paleotis, known from fossils in Denmark (Northern Hemisphere), shared unique anatomical features of the skull that make it a member of the same order as the ostriches. He also argued that the kiwis should not have reached New Zealand, which moved away from the mainland in the Early Cretaceous, if their ancestor was flightless; this claim at least has been vindicated by the discovery of the possibly volant Proapteryx. He therefore deduced that lithornithiform ancestors could have reached the southern continents some 30 to 40 million years ago, and evolved flightless forms which are today's ratites.[41] This hypothesis is contradicted by some later molecular studies,[42] but supported by others.[18]

Relationship to humans

[edit]

The human lineage evolved in Africa in sympatry with ostriches. After Homo appeared and left Africa for other continents, they continued to encounter ostriches in Arabia and much of southern and central Asia. No contact was made with other palaeognath genera until the Papuan and Aboriginal Australian peoples populated New Guinea and Australia. Subsequently, Paleo-Indians encountered tinamous and rheas in Central and South America, Austronesian settlers encountered and exterminated the elephant birds of Madagascar, and the Maori did likewise to the moa of New Zealand. The giant ratites of Madagascar and New Zealand had evolved with little or no exposure to mammalian predators, and were unable to cope with predation by humans; many other oceanic species met the same fate (as apparently had the Australian dromornithids earlier). Worldwide, most giant birds became extinct by the end of the 18th century and most surviving species are now endangered and/or are decreasing in population. However, the co-existence between elephant birds and human beings appears to have been longer than previously thought.[43]

Today, ratites such as the ostrich are farmed and sometimes even kept as pets. Ratites play a large role in human culture; they are farmed, eaten, raced, protected, and kept in zoos.

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Palaeognathae

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Palaeognathae is a monophyletic of birds within the subclass Neornithes, serving as the to the more diverse and representing one of the two primary lineages of modern birds. This group encompasses approximately 60 extant species distributed across five orders: (ostriches), (rheas), (cassowaries and emus), Apterygiformes (kiwis), and Tinamiformes (tinamous). Characterized by a distinctive primitive featuring enlarged basipterygoid processes, fused pterygoids and , a grooved rhamphotheca, a single quadrate articular facet, and open ilioischiadic foramina, palaeognaths include both flightless forms known as ratites and the volant tinamous. Phylogenetically, palaeognaths originated likely before the extinction event around 66 million years ago, with their diversification tied to the breakup of the Gondwanan supercontinent and subsequent ecological opportunities in the . Molecular and morphological analyses confirm the of Palaeognathae, though traditional ratites are paraphyletic, with tinamous nested within them; ostriches often appear as the basalmost lineage, followed by a including rheas, tinamous, kiwis, and extinct groups like moas and . Flightlessness has evolved independently at least six times within the , resulting in reduced wings, strong legs, and a flat or reduced sternal in ratites, while tinamous retain the ability to fly short distances despite their terrestrial habits. The fossil record of palaeognaths extends from the , with early taxa like the from and representing small, volant ancestors, and later forms showing gigantism and regional endemism, such as the extinct Dinornithiformes (moas) in and Aepyornithiformes () in . Extant palaeognaths exhibit diverse ecologies, from the large, fast-running ostriches of African savannas to the nocturnal, insectivorous kiwis of forests, and the quail-like tinamous of South American grasslands. Many species face conservation challenges due to loss and introduced predators, with kiwis and some tinamous classified as vulnerable or endangered.

Taxonomy and classification

Historical classifications

In the early 19th century, ratites were classified in separate taxonomic groups rather than as a unified assemblage. Johann Karl Illiger, in his 1811 Prodromus systematis mammalium et avium, established the order Struthiones specifically for ostriches (Struthio), while rheas were placed in the distinct order Cursores and other flightless forms like cassowaries in Proceri, reflecting a focus on geographic distribution and superficial morphology over shared traits. By the late , more detailed anatomical studies began to highlight potential affinities among . Max Fürbringer's comprehensive work, Untersuchungen zur Morphologie und Systematik der Vögel, emphasized skeletal and muscular characters, noting the diverse morphology of the palaeognathous across ratite groups and suggesting it as a primitive trait potentially linking them, though he leaned toward polyphyletic origins due to variations in palate structure and limb adaptations. The early 20th century saw the formal proposal of Palaeognathae as a higher encompassing both ratites and tinamous, based on shared primitive features like the complex, groove-patterned bony . Percy R. Lowe, in his 1920s publications such as the 1928 Ibis paper on ostrich phylogeny, advocated for Palaeognathae as a subclass, arguing that the 's configuration—featuring fused pterygoids and enlarged basipterygoid processes—indicated a common ancestral stock diverging early from other birds. Wetmore, in his 1930 systematic classification, endorsed this by placing ratites and tinamous within the superorder Palaeognathae but as separate orders (Ratitae and Tinamiformes), citing palatal and cranial similarities despite differences in sternum keeling and flight ability; however, critics like Joel Asaph Allen rejected full inclusion of tinamous, emphasizing the 's subtler variations and the flighted nature of tinamous as evidence against close ratite affinity. Pre-molecular era debates persisted into the mid-20th century, particularly regarding internal relationships, such as whether kiwis (Apteryx) and emus () formed a distinct . Studies in the 1960s on microstructure, including those by W.J. Schmidt, revealed shared features like a thick mammillary layer and columnar crystals in kiwi and emu shells, supporting a potential sister-group relationship between them and contrasting with and rhea eggshells, though these interpretations fueled ongoing controversies over convergence versus homology in flightless adaptations. These morphological frameworks laid the groundwork for later cladistic analyses.

Modern phylogeny

Genomic studies have firmly established the monophyly of Palaeognathae as the sister group to Neognathae within the clade Neornithes, representing one of the two basal lineages of modern birds. This positioning is supported by whole-genome analyses of 48 avian species, which resolved early branches in the avian tree of life using over 400 million base pairs of aligned sequence data. Recent time-calibrated phylogenies, incorporating updated fossil calibrations and expanded taxon sampling, continue to affirm this topology, with crown Palaeognathae diverging around 68–62 million years ago in the Late Cretaceous to Early Paleogene. Within Palaeognathae, the phylogeny shows ostriches () as the basalmost lineage, followed by rheas (), with tinamous (Tinamiformes, comprising approximately 47 species across two subfamilies) sister to the of kiwis (Apterygiformes), emus (), and cassowaries (). This nesting of tinamous within the otherwise flightless ratites renders the traditional Ratitae paraphyletic. Ratites include the extant orders (ostrich, Struthio spp.), (rheas, Rhea spp.), (cassowaries, Casuarius spp., and emu, Dromaius novaehollandiae), and Apterygiformes (kiwis, Apteryx spp.), as well as extinct groups such as Aepyornithiformes () and Dinornithiformes (moas). Molecular phylogenies recover a resolved topology where the ostrich is sister to all other palaeognaths, followed by the rhea as the next successive outgroup, with tinamous sister to the comprising kiwis sister to emus and cassowaries. This structure is congruent across concatenated and coalescent species-tree methods using nuclear and mitochondrial markers. Debates persist regarding the exact branching order within ratites, particularly the position of kiwis relative to emus and cassowaries, stemming from earlier Bayesian analyses that suggested alternative affinities based on incomplete sampling or conflicting morphological data. However, comprehensive phylogenomic datasets have largely resolved these uncertainties, supporting the kiwi-(emu + cassowary) clade through whole-genome alignments that account for incomplete lineage sorting, with tinamous as their sister group. A recent molecular phylogeny of tinamous, incorporating all 47 recognized species, confirms the division into the forest-dwelling Tinaminae (e.g., Crypturellus, Tinamus, Nothocercus) and open-habitat Nothurinae (e.g., Nothoprocta, Nothura, Rhynchotus), with Neotropical diversification dated to 31–40 million years ago in the late Eocene to early . Key synapomorphies uniting Palaeognathae include a reduced or absent sternal in ratites, adapted for flightlessness, contrasted with the retained, well-developed in tinamous that supports limited flight capability; molecular evidence further demonstrates that ratites form a paraphyletic group with tinamous nested within them.

Morphology and physiology

Size and body form

Palaeognathae display remarkable variation in body size and form among extant , spanning from the largest living birds to some of the smallest flight-capable forms. The (Struthio camelus), the tallest and heaviest, stands up to 2.75 m high and can weigh 156 kg, primarily in males which are larger than females. At the opposite extreme, kiwis (Apteryx spp.) are among the smallest, with the reaching a maximum length of 55 cm and weight of 3.3 kg in females, while the measures about 40 cm and weighs up to 1.9 kg. Tinamous, the only flying palaeognaths, are generally small ground-dwellers averaging 20–50 cm in length and 40 g–1,250 g in mass, exemplified by the dwarf tinamou at 14.5 cm and 43 g or the at 46 cm and up to 1.25 kg. This size gradient highlights adaptations in flightless ratites toward larger bodies for terrestrial life, contrasting with the compact, agile builds of flying tinamous. Body plans in palaeognathae reflect ecological niches, with flightless forms like es and rheas featuring elongated necks—up to 1 m in es—for foraging and vigilance, paired with robust, upright postures. In contrast, kiwis and tinamous possess more compact, rounded bodies suited to dense undergrowth navigation, with short legs and minimal tails. Sexual size dimorphism is prevalent, with females exceeding males in mass for most ratites including emus (females ~37 kg vs. males ~32 kg), cassowaries (females ~46 kg vs. males ~32 kg), and kiwis (e.g., females ~2.7 kg vs. males ~2.3 kg in A. australis), as well as in tinamous; however, males are larger in es (~115 kg vs. ~100 kg) and rheas (~28 kg vs. ~22 kg). Distinct proportions further differentiate palaeognathae, such as the relatively large in kiwis compared to body mass, supporting advanced olfaction and despite their small eyes—the smallest relative to body size among birds. Flightless ratites exhibit reduced proportions, with vestigial limbs often hidden beneath dense feathers and measuring mere centimeters, emphasizing terrestrial specialization over aerial capabilities. Fossil evidence from stem-palaeognaths like lithornithids reveals ancestral medium-sized flying forms, with body masses estimated at 1.5–2.8 kg based on skeletal and phylogenetic analyses.

Skeletal and flight adaptations

The palaeognathous , a defining feature of the group, is characterized by a broad, flat and robust pterygoids that articulate with the , retaining primitive avian traits such as an unossified or reduced vomer and fused elements that differ from the more ossified, narrower palates in neognathous birds. This structure, historically viewed as plesiomorphic for crown-group birds (Neornithes), may instead represent a synapomorphy unique to Palaeognathae, as supported by comparative analyses of cranial fossils. The in ratites exhibits a flat or greatly reduced (), an correlated with the loss of flight capability, as the normally anchors the large required for wing-powered locomotion in flying birds. In contrast, tinamous retain a keeled , albeit smaller and less pronounced than in most neognaths, enabling short bursts of flight for escape or navigation. Adaptations in the and pectoral further distinguish ratites from tinamous. In ratites, the is reduced in size and robusticity, while the and are fused into a single element, minimizing the flight apparatus and redirecting skeletal support toward . Tinamous, however, possess a functional yet asymmetric pectoral with a more developed, albeit simplified, and , supporting limited aerial capabilities despite overall reduction compared to neognaths. Recent paleoneurological studies of stem palaeognaths, such as the from Lithornis vulturinus, reveal braincase morphology with relatively large olfactory bulbs and regions, a plesiomorphic condition that exceeds the reduced olfactory proportions typical in , indicating retention of ancestral sensory priorities in early palaeognath evolution. adaptations in Palaeognathae emphasize terrestrial prowess, with elongated femora and tibiotarsi providing leverage for rapid running, as seen in ostriches that achieve speeds over 70 km/h. Emus reach speeds up to 50 km/h. In species such as cassowaries, the feet feature three stout toes equipped with powerful claws, enhancing stability and defensive capabilities on forested floors.

Locomotion

Palaeognathae exhibit a range of locomotion strategies adapted to their environments, from the flightless, running of s to the short-distance flight of tinamous. Ratites, including ostriches, emus, rheas, cassowaries, and kiwis, are primarily bipedal runners, relying on powerful hindlimbs for terrestrial movement. Ostriches (Struthio camelus), the largest ratites, achieve sustained running speeds of 50-60 km/h and short bursts up to 70 km/h, enabled by their elongated legs and efficient stride . These birds also employ powerful kicks for defense, delivering forward slashes with their strong legs that can injure predators. In contrast, kiwis (Apteryx spp.) are nocturnal walkers, moving slowly and deliberately through undergrowth at night using their short legs for foraging and navigation. Tinamous, the only flying palaeognaths, are predominantly ground-dwelling but capable of short, explosive flights when disturbed. Their takeoffs involve rapid, noisy wing beats producing a characteristic whirring sound, low and direct, seldom exceeding 10-20 meters in height, reflecting their small wings and high . Recent phylogenetic analyses of stem-palaeognaths indicate that ancestral members possessed flight capabilities akin to those of modern tinamous, with flightlessness in ratites evolving convergently across multiple lineages due to insular or terrestrial adaptations. This supports the hypothesis of multiple independent losses of flight within the group, rather than a single ancestral event. Energy efficiency in locomotion is enhanced by high stride lengths, particularly in rheas and , where long legs allow strides of 3.5-7 meters, minimizing the cost of transport during sustained running. Ratites use their vestigial wings minimally, primarily for balance and stability during high-speed maneuvers rather than propulsion. These adaptations, supported by robust pelvic limb skeletons, optimize bipedal for endurance over long distances.

Evolutionary history

Fossil record

The fossil record of Palaeognathae begins in the Late Cretaceous with early neornithine forms that exhibit traits toward flightlessness. Patagopteryx deferrariisi, discovered in the Anacleto Formation of , , dates to approximately 80 million years ago (Ma) and represents an early . This small , measuring about 50 cm in height, exhibits skeletal features such as reduced wings and robust legs, indicating secondary flightlessness derived from flying ancestors within the broader avian radiation. In the Paleogene, the record expands with volant forms of the , small flying palaeognaths that bridge stem and crown groups. Lithornis species, such as L. vulturinus from the early Eocene Fur Formation in (around 55 Ma), preserve nearly complete skeletons showing well-developed flight adaptations, including strong keeled sterna and long wings. Similar fossils from the Green River Formation in further document this group's distribution across during the early Eocene, suggesting early palaeognaths were ecologically diverse and capable of powered flight before the evolution of modern ratites. Ostrich relatives first appear in the Eocene, with stem-struthionids like Palaeotis from Middle Eocene deposits in (around 45 Ma); later diversification includes fossils from Miocene deposits in , such as and northwest . Later fossils reveal the evolution of gigantic extinct ratites, underscoring the group's capacity for extreme body size increases. , an from Pleistocene to deposits in , reached weights of up to 450 kg and heights exceeding 3 m, with eggshell fragments and skeletal remains providing evidence of its herbivorous lifestyle in island ecosystems. Similarly, moas of the genus from , known from subfossil bones in caves and swamps, attained masses up to 250 kg, representing the largest terrestrial birds until their rapid around 600 years ago due to human hunting. These giants exemplify late adaptive peaks in isolated Gondwanan settings. Recent analyses incorporating internal fossil constraints, including tip-dating methods on phylogenomic datasets, have refined divergence estimates for crown Palaeognathae to approximately 66–80 Ma, placing the group's origin near or before the Cretaceous-Paleogene (K-Pg) extinction and emphasizing the role of fossils in calibrating avian timelines. However, the overall record remains fragmentary, particularly in the , where preservation biases limit insights into n evolution; notable exceptions include tarsometatarsi from the La Meseta Formation on , , which suggest early southern presence and vicariant origins tied to continental breakup. These Antarctic discoveries, though rare, imply a broader prehistoric distribution for palaeognaths across polar .

Origin and diversification

The origin of Palaeognathae traces back to the divergence from approximately 110 million years ago (Mya) during the , likely within the ancient supercontinent of , where ancestral lineages of modern birds began to differentiate. These early palaeognaths are inferred to have been small, volant birds adapted to forested environments, which facilitated their survival across the Cretaceous-Paleogene (K-Pg) boundary mass around 66 Mya. Post-extinction, the absence of large predatory dinosaurs and enantiornithine birds created ecological opportunities for these surviving lineages to persist and begin radiating in the . Recent phylogenomic studies confirm ostriches as the basal extant lineage, with tinamous nested within ratites, supporting a primarily Gondwanan origin but with debates on Laurasian contributions for northern forms like lithornithids. Diversification within Palaeognathae accelerated in the , with flightlessness evolving independently at least four to six times within the between approximately 40 and 60 Mya, driven by reduced predation pressure and the availability of open habitats following the K-Pg event. The tinamous, the sole volant palaeognath order, underwent a radiation in around 40 Mya, adapting to diverse Neotropical ecosystems while retaining flight capabilities. Time-calibrated phylogenies from recent genomic analyses place the (Struthio) as the basal extant lineage, diverging around 50-60 Mya, followed by splits such as that between kiwis and emus/cassowaries approximately 30-40 Mya. These timelines highlight how vicariance from Gondwanan fragmentation and subsequent dispersals shaped distributions, with later events—such as the human-driven loss of moas in about 600 years ago—further sculpting modern diversity. Key evolutionary drivers included the post-K-Pg decline in aerial and terrestrial predators, enabling terrestrial adaptations like flight reduction and, in isolated island settings, convergent gigantism as seen in moas and extinct . Recent phylogenetic reconstructions incorporating evidence support a pan-palaeognath that includes volant Paleogene forms like lithornithids, confirming that flightlessness represents a derived trait rather than a primitive condition for the group.

Biogeography

Current distribution

The extant species of Palaeognathae exhibit a highly disjunct distribution across the and Neotropics, reflecting their ancient Gondwanan origins but with no overlap between major lineages. Ratites, the flightless members, are confined to specific southern landmasses: the (Struthio camelus) is native to , spanning countries including , , , , , , , and , among others. The (Rhea americana) and lesser rhea (Rhea pennata) are endemic to , with the ranging from northeast through eastern , , , and northern , while the lesser rhea occupies southern and western regions including in , , , and . The (Dromaius novaehollandiae) is widespread across , from coastal areas to inland regions. Cassowaries (Casuarius spp.), comprising three species, are native to (in and ) and northeastern (), particularly in lowland rainforests. Kiwis (Apteryx spp.), with five species, are strictly endemic to , primarily on the North and South Islands and adjacent offshore islands. Tinamous, the volant palaeognaths, are exclusively Neotropical and represent the most diverse group with 47 species distributed from southern through to southern , reaching in species like the Darwin's nothura (Nothura darwinii). In 2025, the dwarf tinamou (Taoniscus nanus) was newly recorded in , extending its known range approximately 1,500 km westward from central . They occupy a broad latitudinal range, from to high elevations up to 4,500 m, in varied open and forested habitats. Unlike ratites, tinamous show no current presence in , despite fossil evidence of stem-palaeognath relatives like lithornithids from the and Eocene of that continent. Introduced populations of ratites occur outside their native ranges, primarily due to farming and escapes. Ostriches have established feral groups in and are commercially farmed worldwide for meat, feathers, and hides, with significant operations in the United States, , and . Emus are raised on farms globally, including in the United States and , and have introduced wild populations on () and (). Rheas have feral populations in from escaped farm birds, with occasional escapes reported in parts of and . Cassowaries and kiwis have no established introduced populations outside their native ranges, though kiwis have been translocated within for conservation. Tinamous lack any documented introduced populations. Range fragmentation is pronounced in several lineages, particularly kiwis, whose populations are isolated across fragmented forest remnants on New Zealand's islands, with each of the five occupying discrete, often small areas due to habitat loss and predation. exhibit some disjunct distributions, such as the black (Tinamus osgoodi) in isolated Andean pockets, but overall maintain more continuous ranges compared to ratites. As of November 2025, while no widespread range expansions have been recorded for palaeognath , isolated extensions such as that of the dwarf in highlight potential undocumented distributions. poses emerging threats to southern distributions, including intensified dry seasons in Neotropical habitats and shifting suitable areas for Australian and South American ratites.

Origin hypotheses

The Gondwana vicariance hypothesis posits that the ancestors of modern palaeognaths diverged as the supercontinent fragmented between approximately 80 and 100 million years ago, leading to the isolation of lineages on separate landmasses such as ostriches in , rheas in , emus and cassowaries in , and kiwis in . This model is supported by morphological phylogenetic analyses that align divergence patterns with known geological events of . However, it has been challenged by molecular dating evidence indicating more recent divergences that postdate the full breakup of . In contrast, the Tertiary radiation and dispersal hypothesis proposes that palaeognaths underwent multiple overland or trans-oceanic dispersals after the Cretaceous-Paleogene boundary, around 30 to 50 million years ago, rather than being strictly confined by vicariance. For instance, ostriches are thought to have dispersed from to via land bridges during the . Recent phylogenomic and biomechanical studies from 2025 emphasize the flight capabilities of stem-palaeognaths, supporting multiple independent losses of flight and facilitating dispersals across southern continents and islands. Hybrid models integrate elements of both vicariance and dispersal, with tinamous as ancient Neotropical relicts nested within the , while kiwis arrived in through overwater rafting of a volant during the . These scenarios account for the non-monophyletic distribution of ratites by positing initial Gondwanan splits followed by subsequent colonizations. Key evidence includes molecular clock estimates showing crown-group divergences as young as 40 million years ago for some lineages, such as basal splits between 31 and 40 million years ago, which conflict with the older minima of around 80 million years ago implied by vicariance. Critiques of pure vicariance highlight the presence of s, such as the Eocene Lithornis from and , which suggest an early northern origin or dispersal pathway incompatible with a strictly southern Gondwanan radiation. This disjunct modern distribution across , , and underscores the ongoing debate between these mechanisms.

Ecology and behavior

Habitat and diet

Palaeognathae exhibit diverse habitat preferences shaped by their phylogenetic branches, with ratites generally occupying open or forested environments across southern continents. Ostriches (Struthio camelus) thrive in arid savannas, grasslands, and scrub forests of , favoring drier sandy areas where they form territorial flocks during breeding seasons. Rheas (Rhea spp.) inhabit open , grasslands, and sparse woodlands in , adapting to both temperate and arid conditions. Emus (Dromaius novaehollandiae) range across a broad spectrum of Australian habitats, from arid shrublands to coastal woodlands, showing high environmental tolerance. In contrast, cassowaries (Casuarius spp.) and kiwis (Apteryx spp.) prefer dense understories and temperate forests in , , and , respectively, where vegetation cover supports their ground-dwelling lifestyles. Tinamous, the volant members of Palaeognathae, predominantly occupy the understory of Neotropical tropical woodlands, rainforests, scrublands, and grasslands from to southern , spanning elevations up to 5,000 meters. They favor dense cover for concealment, spending most time on the ground but occasionally roosting in low trees, and adapt to varied conditions including arid steppes and edges. Diets among ratites are largely herbivorous or frugivorous, centered on , leaves, fruits, and grasses, though many incorporate seasonally for protein. Ostriches primarily graze on forbs, new grasses, and , with occasional like locusts. Emus consume green plants, fruits, and , avoiding dry herbage. Cassowaries are frugivores, relying on fallen fruits from over 100 plant species while dispersing intact. Kiwis, uniquely among ratites, maintain an insectivorous diet dominated by earthworms (40-45%) and other (40-45%), supplemented by 10-15% plant matter. Tinamous are omnivorous ground-foragers, feeding on fruits, , , arthropods (including and spiders), and small vertebrates like and frogs. Foraging strategies reflect locomotor adaptations, with most palaeognaths pecking or probing the ground. Ostriches use their long necks to selectively peck seed heads and flowers in open areas, often in groups that enhance detection of resources. Kiwis forage nocturnally by probing soil with their bills, aided by vibrissae-like feathers around the gape that form a sensory "net" to detect prey in leaf litter. Tinamous dig shallowly with their bills for buried items, exploiting vegetation for opportunistic meals. Key dietary adaptations include the use of (gastroliths) across ratites to grind tough material in their stomachs, compensating for weak bills and facilitating digestion of fibrous foods; ostriches, for instance, retain digesta for 21-76 hours with stone assistance. Seasonal shifts occur, as in greater rheas (Rhea americana), where females increase protein intake (e.g., via ) during breeding to support egg production, with captive studies showing improved on high-protein diets. Recent studies highlight climate change impacts on ecology in the Neotropics, where altered rainfall seasonality and warming may reduce fruit availability, potentially favoring adaptable species like the elegant crested (Eudromia elegans) in semiarid regions while stressing forest-dependent frugivores. Projections indicate high vulnerability for specialized Neotropical frugivores, including tinamous, due to niche constraints and shifting plant phenology.

Reproduction

Palaeognathae exhibit diverse systems adapted to their ecological niches. Among ratites, ostriches and rheas display , with a single male with multiple females that contribute eggs to a communal nest; emus show a flexible system combining , , and ; cassowaries exhibit , with females with multiple males; while kiwis maintain monogamous pairs that remain together for life, with both partners contributing to defense but the male taking primary reproductive roles. In contrast, tinamous display , with females laying eggs in the nests of several males, while males form sequential pair bonds with multiple females during the breeding season. These systems reflect evolutionary pressures for maximizing reproductive output in flightless or semi-flightless species, often involving seasonal breeding triggered by photoperiod or rainfall. Eggs in Palaeognathae are notably large relative to body size, featuring thick, pigmented shells that provide protection and ; for instance, eggs weigh up to 1.5 kg and measure about 15 cm in length. Ratites typically lay in simple ground scrapes or shallow depressions that may be covered with for concealment, while tinamous use unlined scrapes often hidden under leaf litter. Clutch sizes vary widely, from 5–45 eggs in emus to 8–56 in rheas, with communal laying allowing multiple females to contribute to a single nest in polygynous species. A distinctive trait in tinamous is egg , where the glossy, iridescent shells in , , or resemble surrounding foliage to deter predators. Incubation is predominantly male-only in ratites and tinamous, lasting 30–56 days depending on the ; ostriches require 42 days, primarily by the male but with some female assistance, while emus and rheas rely exclusively on males who do not eat or drink during this period. In tinamous, males incubate clutches of 4–12 eggs for about 16–22 days, often remaining on the nest for extended bouts up to 47 hours. Kiwis have the longest among birds, 70–90 days, mostly performed by the male in a nest, with females occasionally relieving briefly. This extended duration in kiwis supports the development of their large, nutrient-rich eggs, which are laid singly or occasionally as pairs annually. Chicks in Palaeognathae are precocial, hatching covered in downy plumage and capable of following parents shortly after emerging from the , typically within hours to two days. post-hatching involves leading and protecting the young, with males providing most guidance in ratites and tinamous; however, chick mortality is high in like emus and cassowaries due to predation and environmental stressors. A unique aspect of kiwi reproduction is their strategy of producing only one large per each year, which enhances offspring survival in nutrient-poor habitats despite the low reproductive rate.

Human interactions

Conservation status

The conservation status of Palaeognathae varies widely across its taxa, with many species facing significant threats from human activities, while others remain relatively secure. Kiwis (Apteryx spp.) are classified as Endangered or Vulnerable on the IUCN Red List, with a total population estimated at approximately 70,000 individuals as of 2023, primarily due to predation by introduced mammals; recent conservation efforts have increased numbers in managed areas by around 7,000 since 2020. Cassowaries (Casuarius spp.) are listed as Least Concern overall, though populations are decreasing due to ongoing habitat loss from deforestation and fragmentation in their tropical rainforest ranges. Ostriches (Struthio spp.), including the common ostrich, are categorized as Least Concern overall, though the Somali ostrich is Vulnerable; the common ostrich population is estimated at 300,000–900,000 mature individuals (as of 2016, decreasing trend), with the Somali ostrich smaller and declining, facing localized poaching pressures. Emus (Dromaius novaehollandiae) are also Least Concern, with an estimated population of around 700,000 in Australia, where they contend with invasive predators and habitat degradation. Rheas (Rhea spp.) are Near Threatened, particularly the greater rhea, owing to hunting and agricultural expansion in South America. Tinamous (Tinamidae), comprising over 40 species, are mostly Least Concern but include several Vulnerable or Endangered forms like the dwarf tinamou; their populations are generally stable yet understudied, with recent assessments indicating declines in some due to deforestation. Major threats to Palaeognathae include , which severely impacts kiwis in New Zealand's forests by isolating populations and exacerbating predation risks. Hunting poses a direct peril to rheas across and grasslands in , where they are targeted for meat and feathers, contributing to population fragmentation. Invasive predators, such as cats, stoats, and rats, threaten emus and other ground-nesting species in by preying on eggs and chicks, though emus' large size offers some resilience. For tinamous, ongoing in Neotropical regions has led to habitat loss, with 2025 monitoring efforts revealing accelerated declines in several amid expanding . Conservation efforts have yielded notable successes, particularly for kiwis through programs like Operation Nest Egg, which involves collecting eggs from wild nests, hatching them in controlled environments, and releasing juveniles into predator-free areas to boost survival rates to over 65%. This initiative, led by the Department of Conservation and partners, has contributed to population increases in subspecies like the rowi kiwi, with recent 2025 reports showing stabilized numbers in key sites such as Ōkārito Forest. Reintroduction programs for rheas in and have restored populations in protected grasslands, using captive-bred individuals to counter hunting losses and habitat recovery. Tinamou conservation focuses on monitoring and habitat protection in the Amazon and Andean regions, with 2025 IUCN updates emphasizing the need for expanded surveys to address understudied declines from . Historical extinctions underscore the vulnerability of Palaeognathae to human impacts, as seen with the moas (Dinornithiformes), which were driven to in around the 1400s AD primarily through overhunting by Polynesian settlers. Similarly, the (Aepyornithidae) of became extinct around 1,000 years ago (circa 1000 CE) due to overhunting and habitat alteration following , serving as a cautionary analogy for current threats to surviving ratites like kiwis and cassowaries. These cases highlight the importance of proactive measures to prevent further losses in this ancient avian clade.

Cultural significance

Palaeognathae species hold diverse roles in human societies, particularly among indigenous communities where they feature in myths, rituals, and traditional practices. In of , the kiwi is revered as a (treasured possession) under the protection of , the forest god, with its feathers historically used in cloaks symbolizing status and heritage. The extinct also appears in Māori whakataukī (proverbs) and oral traditions, reflecting its former ecological dominance and cultural memory as a significant source and emblem of the pre-human landscape. Among , the embodies creator spirits in Dreamtime stories, often depicted as a flying ancestor that shaped the land, and plays a central role in male initiation ceremonies tied to spiritual and kinship networks. In various African indigenous groups, feathers symbolize purity, bravery, and spiritual connection; for instance, the Maasai incorporate them into headdresses during rituals to denote social standing and courage, while in Yoruba traditions, they facilitate and divine communion. Economically, ostrich farming represents a key human interaction with Palaeognathae, centered in where it supplies meat, leather, and feathers to global markets, with the industry valued for its sustainable protein and durable products. farming, prominent in and expanding internationally, focuses on oil extraction from back fat, which is utilized in and pharmaceuticals for its and moisturizing properties, drawing from traditional Aboriginal uses for joint treatments. As scientific and cultural icons, tinamous serve as valued game birds in Neotropical indigenous communities, integral to and subsistence hunting, with species like the featuring in stories of forest spirits and providing feathers for ceremonial adornments. The extinct moas inspire reconstructions and bolster , where museum displays of their skeletons and habitats draw visitors to sites like , fostering public appreciation of prehistoric biodiversity. In modern contexts, ostriches and other ratites appear in zoos worldwide, educating visitors on avian diversity, as seen in exhibits highlighting their dinosaurian traits. Recent 2025 museum displays, such as the Louisville Zoo's addition of a southern cassowary to its Wallaroo Walkabout, emphasize ratite evolution and conservation through immersive setups. Human interactions also involve conflicts, including illegal trade in eggs across , where tens of thousands are harvested annually from wild nests, threatening local populations despite cultural taboos against . Ethical debates surround racing events, criticized by animal welfare advocates for causing stress, spinal injuries, and unnatural handling of ostriches, leading some venues to phase out rides in favor of observational .

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