Pelecaniformes
Encyclopedia
The Pelecaniformes is a (possibly invalid) order
of medium-sized and large waterbirds found worldwide. As traditionally—but erroneously—defined, they encompass all bird
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 nostril
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 altricial
, hatching from the egg helpless and naked in most. They lack a brood patch
.
In the all-encompassing "steganopode" circumscription, the Pelecaniformes had some 50–60 living species
. However, modern opinion considers the apparent similarities the result of convergent evolution
, and based on a wealth of evidence splits the classically defined "Pelecaniformes" into several groups. Most lineages—frigatebird
s, gannet
s, cormorant
s and anhinga
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 their own order. The pelican
s (Pelecanidae), meanwhile, are linked to the stork
s (Ciconiidae) by two bizarre monotypic families
, the Hammerkop
(Scopidae) and the Shoebill
(Balaenicipitidae). Indeed, they may be more closely related to storks than these are to heron
s. To overcome this confusion, it has been proposed to merge the "core" Pelecaniformes into the Ciconiiformes
.
and Ahlquist's landmark DNA-DNA hybridisation
studies (see Sibley-Ahlquist taxonomy
) led to them placing the families traditionally contained within the Pelecaniformes together with the grebe
s, cormorant
s, ibises and spoonbills
, New World vulture
s, stork
s, penguin
s, albatross
es, petrel
s, and loon
s together as a sub-group within a greatly expanded order Ciconiiformes
, 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 evolution
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 Neogene
. 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 Oligocene
rocks at Ronzon (France
), which was initially believed to be a sea-duck
and possibly is an ancestral pelecaniform.
The "pelecaniform" lineages appear to have originated around the end of the Cretaceous
. Monophyletic or not, they appear to belong to a close-knit group of "higher waterbirds" which also includes groups such as penguin
s and Procellariiformes
. It is interesting to note that there are quite a lot of fossil bones from around the K–T 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:
The proposed Elopterygidae—supposedly a family of Cretaceous Pelecaniformes—are neither monophyletic nor does Elopteryx appear to be a modern bird.
The following four families can be united as suborder Sulae (Sulides in older sources), and would make up the core of the Phalacrocoraciformes:
The tropicbird
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 marine lifestyle similar to frigatebirds. They are also noted for their aerobatic capabilities, appearing somewhat like large, slow, white hummingbird
s in courtship
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 clade
that is likely not monophyletic however; most evidence points towards a fairly close relationship with Procellariiformes
and/or Charadriiformes
.
Order (biology)
In 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 bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
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 nostril
Nostril
A 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 altricial
Altricial
Altricial, 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 patch
Brood patch
thumb|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 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
. However, modern opinion considers the apparent similarities the result of convergent evolution
Convergent evolution
Convergent 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, both birds and bats do, and are capable of powered flight. The wings are...
, and based on a wealth of evidence splits the classically defined "Pelecaniformes" into several groups. Most lineages—frigatebird
Frigatebird
The 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, gannet
Gannet
Gannets are seabirds comprising the genus Morus, in the family Sulidae, closely related to the boobies.The gannets are large black and white birds with yellow heads. They have long pointed wings and long bills. Northern gannets are the largest seabirds in the North Atlantic, with a wingspan of up...
s, cormorant
Cormorant
The 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 anhinga
Anhinga
The Anhinga , sometimes called Snakebird, Darter, American Darter, or Water Turkey, is a water bird of the warmer parts of the Americas. The word "anhinga" comes from the Brazilian Tupi language and means devil bird or snake bird.It is a cormorant-like bird with an average body length of , a...
s—constitute indeed a natural group, for which the name Phalacrocoraciformes
Suliformes
The Order Suliformes is a proposed order by the International Ornithologist's Union...
has been proposed. Tropicbirds are of unclear relationships, but appear to be a quite distinct lineage; they are typically placed in their own order. The pelican
Pelican
A pelican, derived from the Greek word πελεκυς pelekys is a large water bird with a large throat pouch, belonging to the bird family Pelecanidae....
s (Pelecanidae), meanwhile, are linked to the stork
Stork
Storks are large, long-legged, long-necked wading birds with long, stout bills. They belong 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 (Ciconiidae) by two bizarre monotypic families
Family (biology)
In 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. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
, the Hammerkop
Hammerkop
The 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 Shoebill
Shoebill
The Shoebill also known as Whalehead or Shoe-billed Stork, is a very large stork-like bird. It derives its name from its massive shoe-shaped bill. The adult bird is tall, long, across the wingspan and weighs . Their beaks have an average length of length of . The adult is mainly grey while the...
(Balaenicipitidae). Indeed, they may be more closely related to storks than these are to heron
Heron
The herons are long-legged freshwater and coastal birds in the family Ardeidae. There are 64 recognised species in this family. Some are called "egrets" or "bitterns" instead of "heron"....
s. To overcome this confusion, it has been proposed to merge the "core" Pelecaniformes into the Ciconiiformes
Ciconiiformes
Traditionally, 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...
.
Systematics and evolution
SibleyCharles Sibley
Charles 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 hybridisation
DNA-DNA hybridisation
DNA-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 taxonomy
Sibley-Ahlquist taxonomy
The Sibley-Ahlquist taxonomy is a 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 grebe
Grebe
A 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, cormorant
Cormorant
The 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 spoonbills
Threskiornithidae
The 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 vulture
New World vulture
The New World Vulture or Condor family Cathartidae contains seven species in fivegenera, all but one of which are monotypic. It includes five vultures and two condors found in warm and temperate areas of the Americas....
s, stork
Stork
Storks are large, long-legged, long-necked wading birds with long, stout bills. They belong 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, penguin
Penguin
Penguins 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, albatross
Albatross
Albatrosses, 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, petrel
Petrel
Petrels 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 loon
Loon
The 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 Ciconiiformes
Ciconiiformes
Traditionally, 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 evolution
Convergent evolution
Convergent 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, both birds and bats do, and are capable of powered flight. The wings are...
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 Neogene
Neogene
The Neogene is a geologic period and system in the International Commission on Stratigraphy Geologic Timescale starting 23.03 ± 0.05 million years ago and ending 2.588 million years ago...
. 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 Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 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 (France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
), which was initially believed to be a sea-duck
Mergus
Mergus 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 Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , 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 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 penguin
Penguin
Penguins 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 Procellariiformes
Procellariiformes
Procellariiformes is an order of seabirds that comprises four families: the albatrosses, petrels and shearwaters, storm petrels, and diving petrels...
. It is interesting to note that there are quite a lot of fossil bones from around the K–T boundary
K–T boundary
The K–T boundary is a geological signature, usually a thin band, dated to 65.5 ± 0.3 Ma ago. K is the traditional abbreviation for the Cretaceous period, and T is the abbreviation for the Tertiary period...
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:
- LonchodytesLonchodytesLonchodytes 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) - TorotixTorotixTorotix 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) - TytthostonyxTytthostonyxTytthostonyx is a genus of prehistoric seabird. Found in the much-debated Hornerstown Formation which straddles the Cretaceous-Paleogene 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 dubiumNomen dubiumIn zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
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.
- PelagornithidaePelagornithidaeThe 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 albatrossAlbatrossAlbatrosses, 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 squidSquidSquid are 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 arranged in pairs and two, usually longer, tentacles...
s more easily. They may actually be Galloanserae closely related to waterfowlWaterfowlWaterfowl are certain wildfowl of the order Anseriformes, especially members of the family Anatidae, which includes ducks, geese, and swans....
, not Neoaves like the other "pelecaniform" families. - PlotopteridaePlotopteridaePlotopteridae 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 monotypicMonotypicIn biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...
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 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:
- SulidaeSulidaeThe 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 ten 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 poorly known.
The tropicbird
Tropicbird
Tropicbirds 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 marine lifestyle similar to frigatebirds. They are also noted for their aerobatic capabilities, appearing somewhat like large, slow, white hummingbird
Hummingbird
Hummingbirds are birds that comprise the family Trochilidae. They are among the smallest of birds, most species measuring in the 7.5–13 cm range. Indeed, the smallest extant bird species is a hummingbird, the 5-cm Bee Hummingbird. They can hover in mid-air by rapidly flapping their wings...
s in courtship
Courtship
Courtship is the period in a couple's relationship which precedes their engagement and marriage, or establishment of an agreed relationship of a more enduring kind. In courtship, a couple get to know each other and decide if there will be an engagement or other such agreement...
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 clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
that is likely not monophyletic however; most evidence points towards a fairly close relationship with Procellariiformes
Procellariiformes
Procellariiformes is an order of seabirds that comprises four families: the albatrosses, petrels and shearwaters, storm petrels, and diving petrels...
and/or Charadriiformes
Charadriiformes
Charadriiformes 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...
.