Neognathae (; ) is a

infraclass In biological classification, class ( la, classis) is a taxonomic rank, as well as a taxonomic unit, a taxon, in that rank. It is a group of related taxonomic orders. Other well-known ranks in descending order of size are life, domain, kingdo ...

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

s, called neognaths, within the class

Aves Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...

of the

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

Archosauria. Neognathae includes the majority of living birds; the exceptions being the

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" come ...

s and the flightless ratites, which belong instead to the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

Palaeognathae. There are nearly 10,000 living

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of neognaths. The earliest

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s are known from the very end of the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

but molecular clocks suggest that neognaths originated sometime in the first half of the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

, about 90 million years ago. Since then, they have undergone adaptive radiation, producing the diversity of form, function, and behavior that exists today. Neognathae includes the order

Passeriformes A passerine () is any bird of the order Passeriformes (; from Latin 'sparrow' and '-shaped'), which includes more than half of all bird species. Sometimes known as perching birds, passerines are distinguished from other orders of birds by th ...

(perching birds), one of the largest orders of land vertebrates, containing some 60% of living birds. Passeriformes is twice as species-rich as

Rodentia Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are nat ...

and about five times as species-rich as

Chiroptera Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most bir ...

(bats), which are the two largest orders of mammals. Neognathae also contains some very small orders, often birds of unclear relationships like the

hoatzin The hoatzin ( ) or hoactzin ( ), (''Opisthocomus hoazin''), is the only species in the order Opisthocomiformes. It is a species of tropical bird found in swamps, riparian forests, and mangroves of the Amazon and the Orinoco basins in South Ameri ...

. The neognaths have fused

metacarpal In human anatomy, the metacarpal bones or metacarpus form the intermediate part of the skeletal hand located between the phalanges of the fingers and the carpal bones of the wrist, which forms the connection to the forearm. The metacarpal bones ar ...

s, an elongate third finger, and 13 or fewer

vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristi ...

e. They differ from the Palaeognathae in features like the structure of their jawbones. ''Neognathae'' means "new jaws", but it seems that the supposedly "more ancient" paleognath jaws are among the few

apomorph In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have ...

ic (more derived) features of the palaeognaths, meaning that the respective jaw structure of these groups is not informative in terms of comparative evolution. A neognath-like palate is however seen in modern basal birds like ''

Ichthyornis ''Ichthyornis'' (meaning "fish bird", after its fish-like vertebrae) is an extinct genus of toothy seabird-like ornithuran from the late Cretaceous period of North America. Its fossil remains are known from the chalks of Alberta, Alabama, ...

''.

Taxonomy and systematics

Neognathae was long

ranked A ranking is a relationship between a set of items such that, for any two items, the first is either "ranked higher than", "ranked lower than" or "ranked equal to" the second. In mathematics, this is known as a weak order or total preorder of ...

as a superorder subdivided into orders. Attempts to organise this group further, as in the ''Conspectus'' of Charles Lucien Bonaparte, were never accepted by a significant majority of ornithologists. Until the 1980s, there was little subdivision of the Aves in general, and even less of

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

merit. Since then, the availability of massive amounts of new data from

s (especially Enantiornithes and other

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretace ...

birds) and molecular ( DNA and

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

) sequences allowed scientists to refine the classification. With new groups of neognath orders being verified, the taxonomic rank of the group needed to shift. Most researchers have now employed the unranked

taxa In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

of phylogenetic nomenclature.Mindell & Brown (2005) Neognathae is now universally accepted to subdivide into two lineages, the "fowl" clade

Galloanseres Fowl are birds belonging to one of two biological orders, namely the gamefowl or landfowl (Galliformes) and the waterfowl ( Anseriformes). Anatomical and molecular similarities suggest these two groups are close evolutionary relatives; togethe ...

and the

Neoaves Neoaves is a clade that consists of all modern birds (Neornithes or Aves) with the exception of Paleognathae (ratites and kin) and Galloanserae (ducks, chickens and kin). Almost 95% of the roughly 10,000 known species of extant birds belong to ...

(sometimes called "higher neognaths"). The subdivisions of the latter are still not well resolved, but several

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

lineages have been proposed, such as the

Mirandornithes Mirandornithes () is a clade that consists of flamingos and grebes. Many scholars use the term Phoenicopterimorphae for the superorder containing flamingoes and grebes. Determining the relationships of both groups has been problematic. Flamingos ...

, Cypselomorphae,

Metaves Metaves ("other birds") is a controversial group proposed by Fain & Houde (2004) and later rescued on the studies of Ericson ''et al.'' (2006)Ericson, P.G.P. ''et al.'' (2006Diversification of Neoaves: integration of molecular sequence data and f ...

, and Coronaves. Although groups such as the former two (uniting a few closely related orders) are robustly supported, this cannot be said for the groups Metaves and Coronaves for which there is no material evidence at present, while the

record of Neognathae is at present utterly devoid of birds that should have been present if these proposed clades were real.

Systematics

The orders are arranged in a sequence that attempts to follow the modern view on neognath

phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spe ...

. It differs from the widely used

Clements taxonomy ''The Clements Checklist of Birds of the World'' is a book by Jim Clements which presents a list of the bird species of the world. The most recent printed version is the sixth edition (2007), but has been updated yearly, the last version in 202 ...

as well as from the Sibley-Ahlquist taxonomy, combining those elements from each that more modern research agrees with while updating those that are refuted. Most of the changes affect those "higher landbirds" that are sometimes united as

near passerine Near passerines and higher land-bird assemblage are terms of traditional, pre-cladistic taxonomy that have often been given to tree-dwelling birds or those most often believed to be related to the true passerines (order Passeriformes) owing to mor ...

s.Mindell ''et al.'' (2005)

Neognathia

Feduccia defined the clade Neognathia as birds whose

palatal The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly separ ...

mobility increased due to the following modifications (Feduccia 1980, 1996): * Loss of the Basipterygoid articulation with the

cranium The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...

. * Development of a

pterygoid Pterygoid, from the Greek for 'winglike', may refer to: * Pterygoid bone, a bone of the palate of many vertebrates * Pterygoid processes of the sphenoid bone ** Lateral pterygoid plate ** Medial pterygoid plate * Lateral pterygoid muscle * Medi ...

palatine A palatine or palatinus (in Latin; plural ''palatini''; cf. derivative spellings below) is a high-level official attached to imperial or royal courts in Europe since Roman times.

joint. * Reduction of the

vomer The vomer (; lat, vomer, lit=ploughshare) is one of the unpaired facial bones of the skull. It is located in the midsagittal line, and articulates with the sphenoid, the ethmoid, the left and right palatine bones, and the left and right max ...

, such that it does not reach caudally to the

, or is lost entirely.

Relationships

Neognathae

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...

of modern bird relationships based on Braun & Kimball (2021)Braun, E.L. & Kimball, R.T. (2021) Data types and the phylogeny of Neoaves. ''Birds'', 2(1), 1-22; https://doi.org/10.3390/birds2010001

Footnotes

References

* *Mindell, David P. & Brown, Joseph W. (2005): The Tree of Life Web Project
Neornithes
Version of 2005-DEC-14. Retrieved 2008-JAN-08. *Mindell, David P.; Brown, Joseph W. & Harshman, John (2005): The Tree of Life Web Project
Neoaves
Version of 2005-DEC-14. Retrieved 2008-JAN-08.

External links

Tree of Life: Neoaves Tree of Life: Galloanserae
{{Taxonbar, from=Q19168 Extant Maastrichtian first appearances Taxa named by William Plane Pycraft