The
Pelecaniformes are a (possibly invalid)
orderIn scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
of medium-sized and large waterbirds found worldwide. As traditionally – but erroneously – defined, they encompass all
birdBirds are winged, bipedal, endothermic , vertebrate animals that lay eggs. There are around 10,000 living species, making them the most numerous tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Birds range in size from the Bee Hummingbird to the ...
s that have feet with all four toes webbed. Hence, they were formerly also known by such names as
totipalmates or
steganopodes. Most have a bare throat patch (gular patch), and the
nostrilA nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation...
s have evolved into dysfunctional slits, forcing them to breathe through their mouths.
The
Pelecaniformes are a (possibly invalid)
orderIn scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
of medium-sized and large waterbirds found worldwide. As traditionally – but erroneously – defined, they encompass all
birdBirds are winged, bipedal, endothermic , vertebrate animals that lay eggs. There are around 10,000 living species, making them the most numerous tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Birds range in size from the Bee Hummingbird to the ...
s that have feet with all four toes webbed. Hence, they were formerly also known by such names as
totipalmates or
steganopodes. Most have a bare throat patch (gular patch), and the
nostrilA nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation...
s have evolved into dysfunctional slits, forcing them to breathe through their mouths. They feed on fish, squid or similar marine life. Nesting is colonial, but individual birds are monogamous. The young are
altricialAltricial, meaning "requiring nourishment", refers to a pattern of growth and development in organisms which are incapable of moving around on their own soon after hatching or being born...
, hatching from the egg helpless and naked in most. They lack a
brood patchthumb|250px|Brood patch of [[Sand Martin]]A brood patch is a patch of featherless skin that is visible on the underside of birds during the nesting season. This patch of skin is well supplied with blood vessels at the surface making it possible for the birds to transfer heat to their eggs when...
.
In the all-encompassing "steganopode" circumscription, the Pelecaniformes had some 50-60 living
speciesIn biology, a species is:* a taxonomic rank or* a unit at that rank ....
. However, modern opionion considers the apparent similarities the result of
convergent evolutionConvergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, birds and bats do, and are capable of powered flight. The wings are similar in...
, and based on a wealth of evidence splits the classically defined "Pelecaniformes" into several groups. Most lineages –
frigatebirdThe frigatebirds are a family, Fregatidae, of seabirds. There are five species in the single genus Fregata. They are also sometimes called Man of War birds or Pirate birds. Since they are related to the pelicans, the term "frigate pelican" is also a name applied to them...
s,
gannetGannets are seabirds in the family Sulidae, closely related to the boobies.The gannets are large black and white birds, with long pointed wings and long bills. Northern gannets are the largest seabirds in the North Atlantic, with a wingspan of up to 2 metres...
s,
cormorantThe bird family Phalacrocoracidae is represented by some 40 species of cormorants and shags. Several different classifications of the family have been proposed recently, and the number of genera is disputed.- Names :...
s and
anhingaThe Anhinga , sometimes called Snakebird, Darter, American Darter, or Water Turkey, is a water bird of the warmer parts of the Americas...
s – constitute indeed a natural group, for which the name Phalacrocoraciformes has been proposed. Tropicbirds are of unclear relationships, but appear to be a quite distinct lineage; they are typically placed in an own order today. The pelicans, meanwhile, are linked to the
storkStorks are large, long-legged, long-necked wading birds with long stout bills, belonging to the family Ciconiidae. They are the only family in the biological order Ciconiiformes, which was once much larger and held a number of families....
s by two bizarre
monotypicIn biology, a monotypic taxon is a taxonomic group with only one type. The usage differs slightly between botany and zoology:In botany, a monotypic taxon is a taxon that has only one species: Ginkgo is a monotypic genus, while Ginkgoaceae is a monotypic family...
familiesIn biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus...
, the
HammerkopThe Hamerkop , also known as Hammerkop,Hammerkopf, Hammerhead, Hammerhead Stork, Umbrette, Umber Bird, Tufted Umber, or Anvilhead, is a medium-sized wading bird...
(Scopidae) and the
ShoebillThe Shoebill, Balaeniceps rex, also known as Whalehead, is a very large stork-like bird. It derives its name from its massive shoe-shaped bill....
(Balaenicipitidae). Indeed, they may be closer related to storks than these are to
heronThe herons are wading birds in the Ardeidae family. There are 64 recognised species in this family. Some are called egrets or bitterns instead of herons....
s. To overcome this confusion, it has been proposed to merge the "core" Pelecaniformes into the Ciconiiformes.
Systematics and evolution
SibleyCharles Gald Sibley was an American ornithologist and molecular biologist. He had an immense influence on the scientific classification of birds, and the work that Sibley initiated has substantially altered our understanding of the evolutionary history of modern birds.Sibley's taxonomy has been a...
and Ahlquist's landmark
DNA-DNA hybridisationDNA-DNA hybridization generally refers to a molecular biology technique that measures the degree of genetic similarity between pools of DNA sequences. It is usually used to determine the genetic distance between two species...
studies (see
Sibley-Ahlquist taxonomyThe Sibley-Ahlquist taxonomy is a radical bird taxonomy proposed by Charles Sibley and Jon Edward Ahlquist. It is based on DNA-DNA hybridization studies conducted in the late 1970s and throughout the 1980s....
) led to them placing the families traditionally contained within the Pelecaniformes together with the
grebeA grebe is a member of the Podicipediformes order, a widely distributed order of freshwater diving birds, some of which visit the sea when migrating and in winter...
s,
cormorantThe bird family Phalacrocoracidae is represented by some 40 species of cormorants and shags. Several different classifications of the family have been proposed recently, and the number of genera is disputed.- Names :...
s,
ibises and spoonbillsThe family Threskiornithidae includes 34 species of large terrestrial and wading birds, falling into two subfamilies, the ibises and the spoonbills. It was formerly known as Plataleidae. The spoonbills and ibises were once thought to be related to other groups of long-legged wading birds in the...
,
New World vultureThe New World vulture family Cathartidae contains seven species in five genera, all but one of which are monotypic. It includes five vultures and two condors found in warm and temperate areas of the Americas....
s,
storkStorks are large, long-legged, long-necked wading birds with long stout bills, belonging to the family Ciconiidae. They are the only family in the biological order Ciconiiformes, which was once much larger and held a number of families....
s,
penguinPenguins are a group of aquatic, flightless birds living almost exclusively in the southern hemisphere, especially in Antarctica. Highly adapted for life in the water, penguins have countershaded dark and white plumage, and their wings have become flippers...
s,
albatrossAlbatrosses, of the biological family Diomedeidae, are large seabirds allied to the procellariids, storm-petrels and diving-petrels in the order Procellariiformes . They range widely in the Southern Ocean and the North Pacific...
es,
petrelPetrels are tube-nosed seabirds in the bird order Procellariiformes. The common name does not indicate relationship beyond that point, as "petrels" occur in three of the four families within that group...
s, and
loonThe loons or divers are a group of aquatic birds found in many parts of North America and northern Eurasia...
s together as a sub-group within a greatly expanded order
CiconiiformesTraditionally, the order Ciconiiformes has included a variety of large, long-legged wading birds with large bills: storks, herons, egrets, ibises, spoonbills, and several others. Ciconiiformes are known from the Late Eocene...
, a radical move which by now has been all but rejected: their "Ciconiiformes" merely assembled all early advanced land- and seabirds for which their research technique delivered insufficient phylogenetic resolution.
Recent research strongly suggests that the similarities between the Pelecaniformes as traditionally defined are the result of
convergent evolutionConvergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, birds and bats do, and are capable of powered flight. The wings are similar in...
rather than common descent, and that the group is paraphyletic. All families in the traditional or revised Pelecaniformes except the Phalacrocoracidae have only a few handfuls of species at most, but many were more numerous in the early
NeogeneThe Neogene is a geologic period and system starting 23.03 ± 0.05 million years ago and lasting either until today or ending 2.588 million years ago with the beginning of the Quaternary. The Neogene Period follows the Paleogene Period of the Cenozoic Era...
. Fossil genera and species are discussed in the respective family or genus accounts; one little-known prehistoric pelecaniforms, however, cannot be classified accurately enough to assign them to a family. This is
"Sula" ronzoni from Early
OligoceneThe Oligocene is a geologic epoch of the Paleogene period and extends from about 33.9 million to 23 million years before the present. As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
rocks at Ronzon (
FranceFrance , officially the French Republic , is a country located in Western Europe, with several overseas islands and territories located on other continents. Metropolitan France extends from the Mediterranean Sea to the English Channel and the North Sea, and from the Rhine to the Atlantic Ocean...
), which was initially believed to be a
sea-duckMergus is the genus of the typical mergansers, fish-eating ducks in the seaduck subfamily . The Hooded Merganser, often termed Mergus cucullatus, is not of this genus but closely related...
and possibly is an ancestral pelecaniform.
The "pelecaniform" lineages appear to have originated around the end of the
CretaceousThe Cretaceous , Latin language for "chalky", usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago . In the geologic timescale, the Cretaceous follows on the Jurassic period and is followed by the Paleogene period of the...
. Monophyletic or not, they appear to belong to a close-knit group of "higher waterbirds" which also includes groups such as
penguinPenguins are a group of aquatic, flightless birds living almost exclusively in the southern hemisphere, especially in Antarctica. Highly adapted for life in the water, penguins have countershaded dark and white plumage, and their wings have become flippers...
s and
ProcellariiformesProcellariiformes is an order of seabirds that comprises four families: the albatrosses, procellariids, storm-petrels and diving petrels. Formerly called Tubinares and still called tubenoses in English, they are often referred to collectively as the petrels, a term that has been applied to all...
. It is interesting to note that there are quite a lot of fossil bones from around the K–Pg boundary which cannot be firmly placed with any of these orders and rather combine traits of several of them. This is of course only to be expected, if the theory that most if not all of these "higher waterbird" lineages originated around that time is correct. Of those apparently basal taxa, the following show some similarities to the traditional Pelecaniformes:
- Lonchodytes
Lonchodytes is a Late Cretaceous genus of aquatic bird, which lived along the shores of the Western Interior Seaway. It lived probably during the Maastrichtian, 70 million years ago , and was found in Lance Creek Formation rocks in Wyoming though it seems still somewhat unclear if it did fossilize...
(Lance Creek Late Cretaceous of Wyoming, USA)
- Torotix
Torotix is a Late Cretaceous genus of aquatic bird. It lived along the shores of the Western Interior Seaway, but it is not clear whether it was a seabird or a freshwater bird, as it is only known from a humerus. Consequently, the genus is monotypic, with the single species Torotix clemensi.It...
(Late Cretaceous)
- Tytthostonyx
Tytthostonyx is a genus of prehistoric seabird. Found in the much-debated Hornerstown Formation which straddles the Cretaceous-Paleocene boundary 65 million years ago, this animal was apparently closely related to the ancestor of some modern birds, such as Procellariiformes and/or "Pelecaniformes"...
(Late Cretaceous/Early Palaeocene)
- Cladornis (Deseado Early Oligocene of Patagonia, Argentina)
- "Liptornis" - a nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application. Note that in the ICBN and ICNB the phrase "nomen dubium" has no status In zoological nomenclature, a nomen dubium (Latin for "doubtful name", plural nomina dubia) is a scientific name that...
The proposed Elopterygidae - supposedly a family of Cretaceous Pelecaniformes - are neither monophyletic nor does
Elopteryx appear to be a modern bird.
List of "pelecaniform" families
- Pelecanidae: pelicans. Very large birds with throat pouches in which they catch and store fish while hunting.
- Pelagornithidae
The Pelagornithidae, commonly called pelagornithids, pseudodontorns, bony-toothed birds, false-toothed birds or pseudotooth birds, are a prehistoric family of large seabirds...
: pseudotooth birds. An extinct family of gigantic seabirds that looked similar to albatrossAlbatrosses, of the biological family Diomedeidae, are large seabirds allied to the procellariids, storm-petrels and diving-petrels in the order Procellariiformes . They range widely in the Southern Ocean and the North Pacific...
es, but had a large bill with tooth-like projections that enabled them to pick up slippery prey like fish or squidSquid are marine cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms and two longer tentacles arranged in pairs...
s more easily. They may actually be Galloanserae closely related to waterfowlWaterfowl are certain wildfowl of the order Anseriformes, especially members of the family Anatidae, which includes ducks, geese, and swans.They are strong swimmers with medium to large bodies. They have historically been an important food source, and continue to be hunted as game, or raised as...
, not Neoaves like the other "pelecaniform" families.
- Plotopteridae
Plotopteridae is the name of an extinct family of flightless seabirds from the order Pelecaniformes. Related to the gannets and boobies, they exhibited remarkable convergent evolution with the penguins, particularly with the now extinct giant penguins...
: plotopterids or diving-"boobies". An extinct group of penguin-like seabirds. Possibly link penguins and (some?) pelecaniforms. Depending on how the remaining Pelecaniformes would be split up, the plotopterids might have to be placed in a monotypicIn biology, a monotypic taxon is a taxonomic group with only one type. The usage differs slightly between botany and zoology:In botany, a monotypic taxon is a taxon that has only one species: Ginkgo is a monotypic genus, while Ginkgoaceae is a monotypic family...
order, as some similarities with penguins are possibly synapomorphies.
- Fregatidae: frigatebirds. A group of five closely related large birds with black and white plumage, very long wings, and parasitical hunting habits. Red throat patches are inflated in display. They are usuually placed in a monotypic suborder Fregatae, and this seems to be appropriate. If split off in the Phalacrocoraciformes, it may also be simply treated as a basal (evolution) lineage thereof.
The following four families can be united as suborder
Sulae (
Sulides in older sources), and would make up the core of the Phalacrocoraciformes:
- Sulidae
The bird family Sulidae comprises the gannets and boobies. Collectively called sulidas, they are medium-large coastal seabirds that plunge-dive for fish and similar prey. The species in this family are often considered congeneric in older sources, placing all in the genus Sula...
: gannets and boobies. Medium to large species which hunt by diving from the air into the sea (plunge diving). Long wings and bills, often coloured feet.
- Phalacrocoracidae: cormorants and shags. Medium to large with hooked bills and usually black or similar dark plumage. Plumage is not fully waterproof.
- Anhingidae: darters. Another small closely related group of four species, with long bills, snake-like necks and the ability to swim with their body submerged. Plumage is not fully waterproof.
- Protoplotidae: an extinct family which apparently is derived from the same ancestor as the darters, but is very badly known.
The
tropicbirdTropicbirds are a family, Phaethontidae, of tropical pelagic seabirds now classified in their own order Phaethontiformes. Their relationship to other living birds is unclear, and they appear to have no close relatives. There are three species in one genus Phaethon...
s (Phaethontidae) and their prehistoric relatives Prophaethontidae were traditionally placed in the Pelecaniformes, but molecular and morphological studies indicate they are not that close relatives. They have been placed in their own order Phaethontiformes. They are medium-sized birds, adapted to a matrine lifestyle similar to frigatebirds. They are also noted for their aerobatic capabilities, appearing somewhat like large, slow, white
hummingbirdHummingbirds are among the smallest of birds, and include the smallest extant bird species, the Bee Hummingbirds. They can hover in mid-air by rapidly flapping their wings 12-90 times per second . They can also fly backwards, and are the only group of birds able to do so. Their English name derives...
s in
courtshipCourtship is the traditional dating period before engagement and marriage. During a courtship, a couple dates to get to know each other and decide if there will be an engagement...
flight. Adults have two long central tail feathers, no gular patch and normal nostrils. Hatchlings are covered in down. They have been included in the "Metaves" a proposed
cladeA clade is a term used in modern alpha taxonomy, the scientific classification of living and fossil organisms, to describe a monophyletic group, defined as a group consisting of a single common ancestor and all its descendants.[The term "monophyletic group" is used in this article...]
that is likely not monophyletic however; most evidence points towards a fairly close relationship with
ProcellariiformesProcellariiformes is an order of seabirds that comprises four families: the albatrosses, procellariids, storm-petrels and diving petrels. Formerly called Tubinares and still called tubenoses in English, they are often referred to collectively as the petrels, a term that has been applied to all...
and/or
CharadriiformesCharadriiformes is a diverse order of small to medium-large birds. It includes about 350 species and has members in all parts of the world. Most Charadriiformes live near water and eat invertebrates or other small animals; however, some are pelagic , some occupy deserts and a few are found in thick...
.
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