Strisores ( ) is a
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, ...
of
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 lightweigh ...
s that includes the living
families
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Ideall ...
and
orders
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 d ...
Caprimulgidae (nightjars, nighthawks and allies),
Nyctibiidae (potoos),
Steatornithidae
The oilbird (''Steatornis caripensis''), locally known as the , is a bird species found in the northern areas of South America including the Caribbean island of Trinidad. It is the only species in the genus ''Steatornis'', the family Steatornith ...
(
oilbird
The oilbird (''Steatornis caripensis''), locally known as the , is a bird species found in the northern areas of South America including the Caribbean island of Trinidad. It is the only species in the genus ''Steatornis'', the family Steatornith ...
s),
Podargidae (
frogmouths
The frogmouths are a group of nocturnal birds related to owlet-nightjars, swifts, and hummingbirds. Species in the group are distributed in the Indomalayan and Australasian realms.
Biology
They are named for their large flattened hooked bill and ...
),
Apodiformes
Traditionally, the bird order Apodiformes contained three living families: the swifts (Apodidae), the treeswifts (Hemiprocnidae), and the hummingbirds (Trochilidae). In the Sibley-Ahlquist taxonomy, this order is raised to a superorder Apodi ...
(swifts and hummingbirds), as well as the
Aegotheliformes (owlet-nightjars) whose distinctness was only recently realized. The Apodiformes (which include the "
Trochiliformes
Hummingbirds are birds native to the Americas and comprise the Family (biology), biological family Trochilidae. With about 361 species and 113 genus, genera, they occur from Alaska to Tierra del Fuego, but the vast majority of the species are ...
" of the
Sibley-Ahlquist taxonomy) and the Aegotheliformes form the
Daedalornithes
Apodimorphae is a clade of strisorean birds that include the extant families Trochilidae (hummingbirds), Hemiprocnidae (treeswifts), Apodidae (swifts), and Aegothelidae (owlet-nightjars), as well as many fossil families. This grouping of bir ...
.
Description
The material evidence for this group is very equivocal; the most ancient Strisores are quite nondescript tree-dwellers but already tend towards peculiarly
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 feet, and no
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 ...
fossils are known.
Torpor
Torpor is a state of decreased physiological activity in an animal, usually marked by a reduced body temperature and metabolic rate. Torpor enables animals to survive periods of reduced food availability. The term "torpor" can refer to the time ...
and other
metabolic
Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...
peculiarities are very frequently found in this group, perhaps more often than in any other bird lineage. The
synapomorphies that define this clade are the ''
ossa maxillaria'' separated by a large cleft, a
mandible
In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...
with very short ''pars symphysialis'', and ''
rami mandibulae'' very slender in their
distal
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...
half.
Taxonomic history
The taxonomy of this group of birds has a long and complicated history.
Jean Cabanis
Jean Louis Cabanis (8 March 1816 – 20 February 1906) was a German ornithologist.
Cabanis was born in Berlin to an old Huguenot family who had moved from France. Little is known of his early life. He studied at the University of Berlin from 18 ...
originally coined the name Strisores in 1847 as an order encompassing a much broader group of birds subdivided into two 'tribes': The Macrochires (
hummingbirds
Hummingbirds are birds native to the Americas and comprise the biological family Trochilidae. With about 361 species and 113 genera, they occur from Alaska to Tierra del Fuego, but the vast majority of the species are found in the tropics arou ...
,
swift
Swift or SWIFT most commonly refers to:
* SWIFT, an international organization facilitating transactions between banks
** SWIFT code
* Swift (programming language)
* Swift (bird), a family of birds
It may also refer to:
Organizations
* SWIFT, ...
s, and
nightjar
Nightjars are medium-sized nocturnal or crepuscular birds in the family Caprimulgidae and order Caprimulgiformes, characterised by long wings, short legs, and very short bills. They are sometimes called goatsuckers, due to the ancient folk ta ...
s, including
oilbird
The oilbird (''Steatornis caripensis''), locally known as the , is a bird species found in the northern areas of South America including the Caribbean island of Trinidad. It is the only species in the genus ''Steatornis'', the family Steatornith ...
s and
potoo
Potoos (family Nyctibiidae) are a group of birds related to the nightjars and frogmouths. They are sometimes called poor-me-ones, after their haunting calls. The family Nyctibiidae was formerly included with the nightjars in the order Caprimulg ...
s, but notably excluding
frogmouths
The frogmouths are a group of nocturnal birds related to owlet-nightjars, swifts, and hummingbirds. Species in the group are distributed in the Indomalayan and Australasian realms.
Biology
They are named for their large flattened hooked bill and ...
) and the Amphibolae (
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 ...
,
mousebird
The mousebirds are birds in the order Coliiformes. They are the sister group to the clade Eucavitaves, which includes the Leptosomiformes (the cuckoo roller), Trogoniformes (trogons), Bucerotiformes (hornbills and hoopoes), Piciformes (woodpec ...
s, and
turaco
The turacos make up the bird family Musophagidae ( "banana-eaters"), which includes plantain-eaters and go-away-birds. In southern Africa both turacos and go-away-birds are commonly known as loeries. They are semi-zygodactylous: the fourth ( ...
s).
Hermann Burmeister
Karl Hermann Konrad Burmeister (also known as Carlos Germán Conrado Burmeister) (15 January 1807 – 2 May 1892) was a German Argentine zoologist, entomologist, herpetologist, botany, botanist, and coleopterologist. He served as a professor at ...
later excluded the taxa in Cabanis' Amphibolae from Strisores, but added
kingfisher
Kingfishers are a family, the Alcedinidae, of small to medium-sized, brightly colored birds in the order Coraciiformes. They have a cosmopolitan distribution, with most species found in the tropical regions of Africa, Asia, and Oceania, ...
s and
motmot
The motmots or Momotidae are a family of birds in the order coraciiformes, which also includes the kingfishers, bee-eaters and rollers. All extant motmots are restricted to woodland or forests in the Neotropics, and the largest are in Middle A ...
s.
Subsequent authors used either definition according to their own judgement, with
Baird following Cabanis',
and
Cooper
Cooper, Cooper's, Coopers and similar may refer to:
* Cooper (profession), a maker of wooden casks and other staved vessels
Arts and entertainment
* Cooper (producers), alias of Dutch producers Klubbheads
* Cooper (video game character), in ...
following Burmeister's usage.
In 1867,
Thomas Henry Huxley
Thomas Henry Huxley (4 May 1825 – 29 June 1895) was an English biologist and anthropologist specialising in comparative anatomy. He has become known as "Darwin's Bulldog" for his advocacy of Charles Darwin's theory of evolution.
The storie ...
proposed the name Cypselomorphae for hummingbirds, swifts, and nightjars (including owlet-nightjars and potoos), however, he considered frogmouths and oilbirds unrelated due to aspects of their skull morphology.
In the 1880s
Anton Reichenow
Anton Reichenow (1 August 1847 in Charlottenburg – 6 July 1941 in Hamburg) was a German ornithologist and herpetologist.
Reichenow was the son-in-law of Jean Cabanis, and worked at the Natural History Museum of Berlin from 1874 to 1921. He wa ...
continued to use Strisores in a similar sense as Huxley's Cypselomorphae (this time also excluding the
owlet-nightjar
Owlet-nightjars are small crepuscular birds related to the nightjars and frogmouths. Most are native to New Guinea, but some species extend to Australia, the Moluccas, and New Caledonia. A flightless species from New Zealand is extinct. There is ...
s),
but by the late 19th Century, Strisores had fallen into disuse,
and this remained the case through the 20th Century.
By the early 21st century, analyses of anatomical morphology and molecular phylogenomics demonstrated that the order Caprimulgiformes as had been used for much of the 20th century (oilbirds, potoos, nightjars, frogmouths, and owlet-nightjars) is actually
paraphyletic
In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...
respective to Apodiformes (hummingbirds, swifts, and
treeswift
Treeswifts or crested swifts are a family, the Hemiprocnidae, of aerial near passerine birds, closely related to the true swifts. The family contains a single genus, ''Hemiprocne'', with four species. They are distributed from India and Southeast ...
s), with apodiform birds nesting deeply within caprimulgiformes and a sister taxon to the owlet-nightjars.
The discovery has led to a challenge of reconciling a Linnean hierarchy with phylogenetic relationships while still maintaining nomenclatural stability, resulting in a complicated situation where some researchers currently use the resurrected name Strisores in a new sense,
others expand the order Caprimulgiformes to include the 'traditional' apodiform families,
whereas others
use the superordinal name Caprimulgimorphae Cracraft, 2013,
raising the 'traditional' caprimulgiform families to the rank of order.
Proposed phylogenetic definitions of Strisores and Caprimulgimorphae treat Strisores as the
crown group
In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...
and Caprimulgimorphae as the
total group
In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...
.
This allows both names to be valid, with similar but not identical meanings.
Evolution
Strisores has a well-represented fossil record, with fossils of most major strisorean lineages known from the
Paleogene
The Paleogene ( ; British English, also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period, geologic period and system that spans 43 million years from the end of the Cretaceous Period million yea ...
.
[ Chen ''et al.'' (2019)] included 14 fossil lineages in their analysis. Nonetheless, it supports the emerging consensus phylogeny well. The genus ''Paraprefica
''Paraprefica'' is an extinct genus of potoo (family Nyctibiidae) from the middle Eocene (c. 48 million years ago). Its fossil remains have been found in the Messel pit at Messel, Germany.
Taxonomy
It is the only known member of the extinct s ...
'', probably from the Early Eocene
In the geologic timescale the Ypresian is the oldest age or lowest stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by the Eocene Lutetian Age. The Ypresian i ...
(though this is somewhat uncertain), seems to be a basal form that at times has been allied with the oilbird and the potoos, but cannot be assigned to either with certainty. In the consensus scenario, it would represent a record of the initial divergence of the three lineages.
This agrees with fossils suggesting that the basal divergence of the owlet-nightjar and apodiform branch also occurred during that time. In addition, ''Eocypselus
''Eocypselus'' is an genus of prehistoric birds believed to be ancestral to modern hummingbirds and swift
Swift or SWIFT most commonly refers to:
* SWIFT, an international organization facilitating transactions between banks
** SWIFT code
* Swi ...
'', a Late Paleocene
The Thanetian is, in the International Commission on Stratigraphy, ICS Geologic timescale, the latest age (geology), age or uppermost stage (stratigraphy), stratigraphic stage of the Paleocene epoch (geology), Epoch or series (stratigraphy), Serie ...
or Early Eocene
The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...
genus of North America, cannot be assigned to any one strisore lineage with certainty but appears to be some ancestral form.[ Over some 20 million years, throughout the ]Eocene
The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...
, the present-day diversity (as well as some entirely extinct lineages) slowly unfolds. By mid-Oligocene
The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...
, some 30 million years ago, the crown
A crown is a traditional form of head adornment, or hat, worn by monarchs as a symbol of their power and dignity. A crown is often, by extension, a symbol of the monarch's government or items endorsed by it. The word itself is used, partic ...
lineages are present and adapting to their present-day ecological niche
In ecology, a niche is the match of a species to a specific environmental condition.
Three variants of ecological niche are described by
It describes how an organism or population responds to the distribution of resources and competitors (for ...
s.
These Paleogene
The Paleogene ( ; British English, also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period, geologic period and system that spans 43 million years from the end of the Cretaceous Period million yea ...
birds strongly suggest that the two main extant lineages of strisores separated about 60-55 mya (Selandian
The Selandian is a stage in the Paleocene. It spans the time between . It is preceded by the Danian and followed by the Thanetian. Sometimes the Paleocene is subdivided in subepochs, in which the Selandian forms the "middle Paleocene".
Stratigr ...
-Thanetian
The Thanetian is, in the International Commission on Stratigraphy, ICS Geologic timescale, the latest age (geology), age or uppermost stage (stratigraphy), stratigraphic stage of the Paleocene epoch (geology), Epoch or series (stratigraphy), Serie ...
), and that some time around the Lutetian
The Lutetian is, in the geologic timescale, a stage or age in the Eocene. It spans the time between . The Lutetian is preceded by the Ypresian and is followed by the Bartonian. Together with the Bartonian it is sometimes referred to as the Midd ...
-Bartonian
The Bartonian is, in the ICS's geologic time scale, a stage or age in the middle Eocene Epoch or Series. The Bartonian Age spans the time between . It is preceded by the Lutetian and is followed by the Priabonian Age.
Stratigraphic definitio ...
boundary, some 40 mya, the common ancestors of Nyctibiidae, Caprimulgidae and eared nightjars diverged from those of oilbird and frogmouths.
The relationships of the Early Eocene '' Parvicuculus'' and '' Procuculus'' from the southern North Sea
The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...
basin are unresolved, but they bear some similarities to strisores.
By the distribution of fossils, the Paleogene radiation seems to have originated in Asia
Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...
, which at that time became a highly fragmented landscape as the Himalayas
The Himalayas, or Himalaya (; ; ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the planet's highest peaks, including the very highest, Mount Everest. Over 100 ...
lifted up and the Turgai Strait started to disappear.
Several fossil 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 ...
are tentatively placed here as basal or ''incertae sedis
' () or ''problematica'' is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...
''
* ''Eocypselus
''Eocypselus'' is an genus of prehistoric birds believed to be ancestral to modern hummingbirds and swift
Swift or SWIFT most commonly refers to:
* SWIFT, an international organization facilitating transactions between banks
** SWIFT code
* Swi ...
'' (Late Paleocene
The Paleocene, ( ) or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), E ...
or Early Eocene)
* ''Paraprefica
''Paraprefica'' is an extinct genus of potoo (family Nyctibiidae) from the middle Eocene (c. 48 million years ago). Its fossil remains have been found in the Messel pit at Messel, Germany.
Taxonomy
It is the only known member of the extinct s ...
'' (Early Eocene
The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...
?)
* Archaeotrogonidae
Archaeotrogonidae is a prehistoric bird family known from the Eocene and Oligocene of Europe. They are members of Strisores, and are thought to be closely related to nightjars.
The remains of '' Archaeotrogon'' have been found in the Quercy Pho ...
(Early Eocene of England ?- Late Eocene/Early Oligocene
The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...
of France)
* '' Hassiavis'' (Middle Eocene of Messel, Germany) - Archaeotrogonidae?
* '' Protocypselomorphus'' (Middle Eocene of Messel, Germany)
Systematics
Strisores contains the extant orders Aegotheliformes, Apodiformes
Traditionally, the bird order Apodiformes contained three living families: the swifts (Apodidae), the treeswifts (Hemiprocnidae), and the hummingbirds (Trochilidae). In the Sibley-Ahlquist taxonomy, this order is raised to a superorder Apodi ...
(with families Apodidae
The swifts are a family, Apodidae, of highly aerial birds. They are superficially similar to swallows, but are not closely related to any passerine species. Swifts are placed in the order Apodiformes with hummingbirds. The treeswifts are closely r ...
, Hemiprocnidae, and Trochilidae
Hummingbirds are birds native to the Americas and comprise the biological family Trochilidae. With about 361 species and 113 genera, they occur from Alaska to Tierra del Fuego, but the vast majority of the species are found in the tropics arou ...
), Caprimulgiformes
Nightjars are medium-sized nocturnal or crepuscular birds in the family Caprimulgidae and order Caprimulgiformes, characterised by long wings, short legs, and very short bills. They are sometimes called goatsuckers, due to the ancient folk tal ...
, Nyctibiiformes, Podargiformes Vertebrates
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () (chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Cho ...
, Steatornithiformes. Apodidae and Hemiprocnidae are grouped together as Apodi, Apodi and Trochilidae are grouped together as Apodiformes
Traditionally, the bird order Apodiformes contained three living families: the swifts (Apodidae), the treeswifts (Hemiprocnidae), and the hummingbirds (Trochilidae). In the Sibley-Ahlquist taxonomy, this order is raised to a superorder Apodi ...
, and Apodiformes and Aegotheliformes are grouped together as Daedalornithes.
The classification of the various birds that make up the order has long been controversial and difficult, particularly in the case of the nightjars and the paraphyly of the traditional Caprimulgiformes in relation to "Apodiformes
Traditionally, the bird order Apodiformes contained three living families: the swifts (Apodidae), the treeswifts (Hemiprocnidae), and the hummingbirds (Trochilidae). In the Sibley-Ahlquist taxonomy, this order is raised to a superorder Apodi ...
", traditionally considered a separate order.
The IUCN
The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...
adopts the following classification of Order Caprimulgiformes, which follows recent phylogenetic studies:
* Family Trochilidae
Hummingbirds are birds native to the Americas and comprise the biological family Trochilidae. With about 361 species and 113 genera, they occur from Alaska to Tierra del Fuego, but the vast majority of the species are found in the tropics arou ...
(hummingbirds, 368 species)
* Family Apodidae
The swifts are a family, Apodidae, of highly aerial birds. They are superficially similar to swallows, but are not closely related to any passerine species. Swifts are placed in the order Apodiformes with hummingbirds. The treeswifts are closely r ...
(swifts, 96 species)
* Family Caprimulgidae (nightjars, 98 species)
* Family Podargidae (frogmouths, 14 species)
* Family Aegothelidae (owlet-nightjars, 10 species)
* Family Nyctibiidae (potoos, 7 species)
* Family Hemiprocnidae (treeswifts, 4 species)
* Family Steatornithidae
The oilbird (''Steatornis caripensis''), locally known as the , is a bird species found in the northern areas of South America including the Caribbean island of Trinidad. It is the only species in the genus ''Steatornis'', the family Steatornith ...
(oilbird, 1 species)
The IUCN definition renders the order Caprimulgiformes identical to the clade Strisores. Authorities that favor the use of Strisores for this group (e.g., Yuri et al. 2013 and Chen ''et al.'' 2019) adopt a ''sensu stricto'' definition of the order, limiting to the family Caprimulgidae. They also elevate many (or even all) of the families traditionally placed in Caprimulgiformes to ordinal rank. This requires recognizing at least three additional orders: Nyctibiiformes, Steatornithiformes, and Podargiformes Vertebrates
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () (chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Cho ...
. Owlet-nightjars can be placed in their own order ( Aegotheliformes) or viewed as a family within Apodiformes
Traditionally, the bird order Apodiformes contained three living families: the swifts (Apodidae), the treeswifts (Hemiprocnidae), and the hummingbirds (Trochilidae). In the Sibley-Ahlquist taxonomy, this order is raised to a superorder Apodi ...
.
Traditionally, Caprimulgiformes were regarded, on morphological grounds, as being midway between the owls
Owls are birds from the Order (biology), order Strigiformes (), which includes over 200 species of mostly Solitary animal, solitary and Nocturnal animal, nocturnal birds of prey typified by an upright stance, a large, broad head, binocular vi ...
(Strigiformes) and the swifts
Swift or SWIFT most commonly refers to:
* SWIFT, an international organization facilitating transactions between banks
** SWIFT code
* Swift (programming language)
* Swift (bird), a family of birds
It may also refer to:
Organizations
* SWIFT, ...
. Like the owls, they are nocturnal hunters with a highly developed sense of sight, and like the swifts they are excellent flyers with small, weak legs. At one time or another, they have been allied with owls, swifts, kingfishers
Kingfishers are a family, the Alcedinidae, of small to medium-sized, brightly colored birds in the order Coraciiformes. They have a cosmopolitan distribution, with most species found in the tropical regions of Africa, Asia, and Oceania, ...
, hoopoes
Hoopoes () are colourful birds found across Africa, Asia, and Europe, notable for their distinctive "crown" of feathers. Three living and one extinct species are recognized, though for many years all of the extant species were lumped as a single ...
, mousebirds, hornbills
Hornbills (Bucerotidae) are a family of bird found in tropical and subtropical Africa, Asia and Melanesia. They are characterized by a long, down-curved bill which is frequently brightly coloured and sometimes has a casque on the upper mandibl ...
, rollers, bee-eaters
The bee-eaters are a group of non-passerine birds in the family Meropidae, containing three genera and thirty species. Most species are found in Africa and Asia, with a few in southern Europe, Australia, and New Guinea. They are characterised by ...
, woodpeckers
Woodpeckers are part of the bird family Picidae, which also includes the piculets, wrynecks, and sapsuckers. Members of this family are found worldwide, except for Australia, New Guinea, New Zealand, Madagascar, and the extreme polar regions. M ...
, trogons
The trogons and quetzals are birds in the order Trogoniformes which contains only one family, the Trogonidae. The family Trogonidae contains 46 species in seven genera. The fossil record of the trogons dates back 49 million years to the Early ...
and hummingbirds
Hummingbirds are birds native to the Americas and comprise the biological family Trochilidae. With about 361 species and 113 genera, they occur from Alaska to Tierra del Fuego, but the vast majority of the species are found in the tropics arou ...
. A close relationship to owls can be rejected since there is strong molecular evidence that owls are members of a clade, called Telluraves
Telluraves (also called land birds or core landbirds) is a recently defined clade of birds defined by their arboreality. Based on most recent genetic studies, the clade unites a variety of bird groups, including the australavians (passerines, p ...
, that excludes Caprimulgiformes.
Based on analysis of DNA sequence
DNA sequencing is the process of determining the nucleic acid sequence – the order of nucleotides in DNA. It includes any method or technology that is used to determine the order of the four bases: adenine, guanine, cytosine, and thymine. Th ...
data – notably β-fibrinogen
Fibrinogen (factor I) is a glycoprotein complex, produced in the liver, that circulates in the blood of all vertebrates. During tissue and vascular injury, it is converted enzymatically by thrombin to fibrin and then to a fibrin-based blood clo ...
intron
An intron is any nucleotide sequence within a gene that is not expressed or operative in the final RNA product. The word ''intron'' is derived from the term ''intragenic region'', i.e. a region inside a gene."The notion of the cistron .e., gene. ...
7 – Fain and Houde considered the families of the Caprimulgiformes to be members of the proposed clade 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 ...
, which also includes 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 ...
, tropicbirds
Tropicbirds are a family, Phaethontidae, of tropical pelagic seabirds. They are the sole living representatives of the order Phaethontiformes. For many years they were considered part of the Pelecaniformes, but genetics indicates they are most cl ...
, sandgrouse
Sandgrouse is the common name for Pteroclidae , a family (biology), family of sixteen species of bird, members of the order Pterocliformes . They are traditionally placed in two Genus, genera. The two central Asian species are classified as ''Sy ...
, pigeons
Columbidae () is a bird family consisting of doves and pigeons. It is the only family in the order Columbiformes. These are stout-bodied birds with short necks and short slender bills that in some species feature fleshy ceres. They primarily ...
, kagu
The kagu or cagou (''Rhynochetos jubatus'') is a crested, long-legged, and bluish-grey bird endemic to the dense mountain forests of New Caledonia. It is the only surviving member of the genus ''Rhynochetos'' and the family Rhynochetidae, alt ...
, sunbittern
The sunbittern (''Eurypyga helias'') is a bittern-like bird of tropical regions of the Americas, and the sole member of the family Eurypygidae (sometimes spelled Eurypigidae) and genus ''Eurypyga''. It is found in Central and South America, and ...
, mesites, flamingos
Flamingos or flamingoes are a type of wading bird in the family Phoenicopteridae, which is the only extant family in the order Phoenicopteriformes. There are four flamingo species distributed throughout the Americas (including the Caribbean) ...
, grebes
Grebes () are aquatic diving birds in the order (biology), order Podicipediformes . Grebes are widely distributed freshwater birds, with some species also found in sea, marine habitats during Bird migration, migration and winter. Some flightless ...
and swifts
Swift or SWIFT most commonly refers to:
* SWIFT, an international organization facilitating transactions between banks
** SWIFT code
* Swift (programming language)
* Swift (bird), a family of birds
It may also refer to:
Organizations
* SWIFT, ...
and hummingbirds
Hummingbirds are birds native to the Americas and comprise the biological family Trochilidae. With about 361 species and 113 genera, they occur from Alaska to Tierra del Fuego, but the vast majority of the species are found in the tropics arou ...
. Metaves was also found by the expanded study of Ericson ''et al.'' (2006), but support for the clade was extremely weak.
While only the latter study recovered monophyly of the Cypselomorphae
Strisores ( ) is a clade of birds that includes the living families and orders Caprimulgidae (nightjars, nighthawks and allies), Nyctibiidae (potoos), Steatornithidae (oilbirds), Podargidae ( frogmouths), Apodiformes (swifts and hummingbird ...
(see below) within Metaves, the former was based on only a single locus and could not resolve their relationships according to standard criteria of statistical confidence. No morphological synapomorphies
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 ...
have been found that uniquely unite Metaves (or Caprimulgiformes for that matter), but numerous unlinked nuclear genes
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
independently support their monophyly either in majority or whole. Ericson ''et al.'' (2006) concluded that if valid, the "Metaves" must originate quite some time before the Paleogene
The Paleogene ( ; British English, also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period, geologic period and system that spans 43 million years from the end of the Cretaceous Period million yea ...
, and they reconciled this with the fossil record.
While the relationships of cypselomorphs are a subject of ongoing debate, the 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 spec ...
of the individual lineages is better resolved. Much of the remaining uncertainty regards minor details.
Initial mtDNA
Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial DNA ...
cytochrome ''b'' sequence
In mathematics, a sequence is an enumerated collection of objects in which repetitions are allowed and order matters. Like a set, it contains members (also called ''elements'', or ''terms''). The number of elements (possibly infinite) is calle ...
analysis agreed with earlier morphological and DNA-DNA hybridization studies insofar as that the oilbird and the frogmouths seemed rather distinct. The other lineages appeared to form a 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, ...
, but this is now known to have been caused by methodological limitations.
The Aegothelidae ( owlet-nightjars) with about a dozen living species in one genus are apparently closer to the Apodiformes
Traditionally, the bird order Apodiformes contained three living families: the swifts (Apodidae), the treeswifts (Hemiprocnidae), and the hummingbirds (Trochilidae). In the Sibley-Ahlquist taxonomy, this order is raised to a superorder Apodi ...
; these and the Caprimulgiformes are closely related, being grouped together as Cypselomorphae
Strisores ( ) is a clade of birds that includes the living families and orders Caprimulgidae (nightjars, nighthawks and allies), Nyctibiidae (potoos), Steatornithidae (oilbirds), Podargidae ( frogmouths), Apodiformes (swifts and hummingbird ...
. The oilbird and the frogmouths seem quite distinct among the remaining Caprimulgiformes, but their exact placement cannot be resolved based on osteological data alone.
Even the study of Ericson ''et al.'' could not properly resolve the oilbird's and frogmouths' relationships beyond the fact that they are quite certainly well distinct. It robustly supported, however, the idea that the owlet-nightjars should be considered closer to Caprimulgiformes, unlike the methodologically weaker studies of Mariaux & Braun (1996) and Fain and Houde (2004).
Alternatively, Mayr's phylogenetic taxon Cypselomorphae might be placed at order rank and substitute the two present orders Caprimulgiformes and Apodiformes. Such a group would be fairly uninformative as regards its evolutionary history, as it has to include some very plesiomorphic
In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral character shared by all members of a clade, which does not distinguish the clade from other clades.
Plesiomorphy, symplesiomorphy, apomorphy, and ...
and some extremely derived lineages (such as hummingbirds) to achieve monophyly. Reddy ''et al''. (2017) included hummingbirds and swifts in Caprimulgiformes, preserving the monophyly of the order.
The following 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 ...
follows the results of Mayr's (2002) phylogenetic study, which used a parsimony analysis of 25 morphological characters:
Subsequent molecular work has converged on two alternative topologies (topologies 1 and 2 below) that differ in the placement of the root. Although Braun et al. (2019) suggested that topology 1 was favored in large-scale analyses of non-coding data were analyzed and that topology 2 was favored in large-scale analyses of coding data (e.g., Prum ''et al''. (2015)) subsequent analyses of datasets with many non-coding loci have also recovered topology 2. Thus, topology 2 should be viewed as the best-corroborated hypothesis at this time.
Topology 1: phylogeny according to Reddy ''et al''. (2017), which analyzed 54 nuclear loci (mostly introns
An intron is any nucleotide sequence within a gene that is not expressed or operative in the final RNA product. The word ''intron'' is derived from the term ''intragenic region'', i.e. a region inside a gene."The notion of the cistron .e., gene. ...
):
Topology 2: phylogeny according to Prum ''et al''. (2015) (259 "anchored hybrid enrichment" loci, which are mostly coding exons), Chen ''et al.'' (2019) (combined analysis of 2289 ultra-conserved elements CEsand 117 morphological characters and including fossil taxa), and White and Braun (2019) (based on analyses of multiple UCE datasets, ranging in size from 2289 to 4243 loci):
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 ...
based on Prum et al., with phylogenetic definitions following Chen et al.:[
]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 ...
based on Reddy, S. ''et al''. (2017):
Chen ''et al.'' (2019) proposed the name Vanescaves for the clade comprising all Caprimulgiformes (=Strisores) except Caprimulgidae. White and Braun (2019) acknowledged that some uncertainty remains; specifically, monophyly of the clade comprising Steatornithidae and Nyctibiidae was limited and that three different resolutions of Steatornithidae, Nyctibiidae, and the clade comprising Podargidae and Daedalornithes remain plausible. However, they viewed topology 2 as the best-supported hypothesis.
Presently, the taxonomy favored by the IOC
The International Olympic Committee (IOC; french: link=no, Comité international olympique, ''CIO'') is a non-governmental sports organisation based in Lausanne, Switzerland. It is constituted in the form of an association under the Swiss ...
splits oilbirds, potoos, nightjars, and frogmouths into their own orders, along with the order Apodiformes as previously defined.
References
{{Taxonbar, from=Q5198624
*
Selandian first appearances
Extant Paleocene first appearances