Palaeochenoides
Encyclopedia
Palaeochenoides is a genus
of the prehistoric pseudotooth birds of somewhat doubtful validity. These were probably rather close relatives of either pelican
s and stork
s, or of waterfowl
, and are here placed in the order
Odontopterygiformes to account for this uncertainty.
Only a single species
, Palaeochenoides mioceanus, is known to date. The first fossil
assigned to it – a distal right femur
piece – was found near the source of the Stono River
in Charleston County, South Carolina
(USA). At first it was believed to be from the Early Miocene
Hawthorne Formation – its specific name, referring to the "Miocene
ocean
" as presumed habitat
– alludes to this. But in fact no Hawthorne Formation rocks were known in the Charleston region when the fossil was found, and consequently modern authors consider a Chattian
(Late Oligocene) age more likely and suggest the fossil came from the Cooper or Chandler Bridge Formation. Specimen MCZ
2514, a distal left tarsometatarsus
fragment from the Ashley River
, was more tentatively assigned to P. mioceanus later on; it was also erroneously believed to be from the Hawthorne Formation.
femur's classification mirrors the recently-renewed uncertainties about the pseudotooth birds' placement. At the time of its description, when it was still much surrounded by matrix
, it was believed to be from a giant goose
or swan
. This is referred to in the genus name, which means "ancient goose-like [bird]". But only one year later, the bone had been prepared from the matrix and ws submitted to an improvised phenetic analysis of its details. It was compared to that of Anserinae
and Dendrocygninae
(other Anseriformes
were either similar to these or too unlike P. mioceanus), as well as with Pelecanidae, Phaetontidae and Phalacrocoraciformes of the "higher waterbird" radiation, and found to resemble the former in one, the latter in 4 out of 5 traits. Some minor details of the femur were also unlike in the Anseriformes. The study proposed the fossil bird to have been "a large steganopod [...] somewhat larger than Pelecanus erythrorhynchos or P. onocrotalus," and not securely assignable to a known family
. But as cladistic analysis had not yet been developed, it was of course not studied whether the similarities between P. mioceanus and the "higher waterbirds" are apomorphies. It has been noted, however, that adaptation
to oceanic habits, has induced in pseudotooth bird legs and feet features convergent
to other seabird
s. Still, the fossil is a rather good specimen, considering how little humerus material known from pseudotooth birds; a recent cladistic analysis (which did not include P. mioceanus) did not put much emphasis on humerus traits, for example, as so few good fossils are known.
When Witmer Stone
, then editor of The Auk
, commented on the taxonomic confusion that the bird caused during less than 25 months after its description, he noted:
Only the end of the tarsometatarsus
remains, but this is complete and even not very much abraded. Only on the edges of the outer trochlea
e does significant material seem to be lost. Altogether, the bone is very similar to that of the sympatric and probably contemporary Tympanonesiotes wetmorei, only appearing a bit less albatross
-like. The spread of the toes must have resembled that found in a fulmar
quite a lot, by contrast. The thin-walled bone has a second toe
trochlea that attaches notably kneewards from the others and is angled slightly outwards while the hallux
was vestigial or missing, as is typical for the pseudotooth birds. The fossil is about one-quarter larger than that of Tympanonesiotes, with a maximum end width of 34.7 mm (1.4 in) – probably a bit more in life, as the trochlea rims are eroded away. The shaft is 22.3 mm (0.877952755905512 in) wide at the point where it flares into the trochleae. It was thus more than twice as large as large as "Odontoptila inexpectata" from the Late Paleocene/Early Eocene of the Ouled Abdoul Basin (Morocco
), and – like Osteodontornis orri – thus belonged to the large pseudotooth birds, with a wingspan of more than 5, perhaps as much as 6 m (16-20 ft). Its bill was presumably long and massive as in its relatives, and in length the bird exceeded the largest pelican
s.
The early systematic
uncertainties have been noted again in recent times, in the scope of the debate whether the pseudotooth birds were Galloanseres closely related to waterfowl or Neoaves related to pelicans. Meanwhile, as a presumed pelican relative, P. mioceanus was allied with Cyphornis
(another pseudotooth bird, known only from a proximal left tarsometatarsus
) and placed in a family
Cyphornithidae. This was subsequently assigned to a "pelecaniform" suborder Cladornithes. But the enigmatic Late Oligocene Cladornis – the type genus
of that supposed suborder – from the Argentinian part of Patagonia
is known from a distal right tarsometatarsus only, and thus was not directly comparable to Palaeochenoides and Cyphornis. Tympanonesiotes wetmorei, yet another pseudotooth bird, known from a distal right tarsometatarsus fragment, was initially presumed to be similar to Cladornis however, and also to Cyphornis; consequently, the three genera were allied simply because of their size and some similarities to the corresponding bones of pelicans. Today however, Cladornis is more generally held to be a terrestrial
bird rather than a seabird
.
As regards the supposed Cyphornithidae, most if not all pseudotooth birds placed there are probably closely related to the better-known Pelagornis
, type genus
of the family Pelagornithidae. And even if Cyphornis is the senior synonym of Palaeochenoides and Tympanoneisiotes (which is not overly likely due to size differences), according to the rules of zoological nomenclature the family name Pelagornithidae would not be affected. Cyphornithidae would almost certainly be a junior synonym of Pelagornithidae even if the pseudotooth birds are (as some have proposed) divided into several families – rather than being all placed in the Pelagornithidae as is usual nowadays – as Cyphornis, Osteodontornis
, Palaeochenoides, Pelagornis and perhaps the smaller Tympanoneisiotes appear to be very closely related and are probably part of a monophyletic lineage of (usually) giant pseudotooth birds. As at the time of its description no adequarte comparaticve material was known, it was explicitly cautioned that P. mioceanus might include Pseudodontornis – which may actually be synonymous with Pelagornis.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of the prehistoric pseudotooth birds of somewhat doubtful validity. These were probably rather close relatives of either 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 and 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, or of waterfowl
Waterfowl
Waterfowl are certain wildfowl of the order Anseriformes, especially members of the family Anatidae, which includes ducks, geese, and swans....
, and are here placed in the order
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...
Odontopterygiformes to account for this uncertainty.
Only a single 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...
, Palaeochenoides mioceanus, is known to date. The first fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
assigned to it – a distal right femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
piece – was found near the source of the Stono River
Stono River
The Stono River is a tidal channel in southeast South Carolina, located southwest of Charleston. The channel runs southwest to northeast between the mainland and Wadmalaw Island and Johns Island, from north Edisto River between Johns and James Island. The Intracoastal Waterway runs through...
in Charleston County, South Carolina
Charleston County, South Carolina
Charleston County is a county located in the U.S. state of South Carolina. According to a 2005 U.S. Census Bureau estimate, its population was 330,368. Its county seat is Charleston. It is the third-most populous county in the state . Charleston County was created in 1901 by an act of the South...
(USA). At first it was believed to be from the Early Miocene
Early Miocene
The Early Miocene is a sub-epoch of the Miocene Epoch made up of two stages: the Aquitanian and Burdigalian stages....
Hawthorne Formation – its specific name, referring to the "Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
ocean
Ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...
" as presumed habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
– alludes to this. But in fact no Hawthorne Formation rocks were known in the Charleston region when the fossil was found, and consequently modern authors consider a Chattian
Chattian
The Chattian is, in the geologic timescale, the youngest of two ages or upper of two stages of the Oligocene epoch/series. It spans the time between and . The Chattian is preceded by the Rupelian and is followed by the Aquitanian .-Stratigraphic definition:The Chattian was introduced by Austrian...
(Late Oligocene) age more likely and suggest the fossil came from the Cooper or Chandler Bridge Formation. Specimen MCZ
Museum of Comparative Zoology
The Museum of Comparative Zoology, full name "The Louis Agassiz Museum of Comparative Zoology", often abbreviated simply to "MCZ", is a zoology museum located on the grounds of Harvard University in Cambridge, Massachusetts. It is one of three museums which collectively comprise the Harvard Museum...
2514, a distal left tarsometatarsus
Tarsometatarsus
The tarsometatarsus is a bone that is found in the lower leg of certain tetrapods, namely birds.It is formed from the fusion of several bones found in other types of animals, and homologous to the mammalian tarsal and metatarsal bones...
fragment from the Ashley River
Ashley River (South Carolina)
The Ashley River is a blackwater / tidal river in South Carolina, rising from the Wassamassaw and Great Cypress Swamps in western Berkeley County. It consolidates its main channel about five miles west of Summerville, widening into a tidal estuary just south of Fort Dorchester...
, was more tentatively assigned to P. mioceanus later on; it was also erroneously believed to be from the Hawthorne Formation.
Description and systematics
The holotypeHolotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
femur's classification mirrors the recently-renewed uncertainties about the pseudotooth birds' placement. At the time of its description, when it was still much surrounded by matrix
Matrix (geology)
The matrix or groundmass of rock is the finer grained mass of material in which larger grains, crystals or clasts are embedded.The matrix of an igneous rock consists of finer grained, often microscopic, crystals in which larger crystals are embedded. This porphyritic texture is indicative of...
, it was believed to be from a giant goose
Goose
The word goose is the English name for a group of waterfowl, belonging to the family Anatidae. This family also includes swans, most of which are larger than true geese, and ducks, which are smaller....
or swan
Swan
Swans, genus Cygnus, are birds of the family Anatidae, which also includes geese and ducks. Swans are grouped with the closely related geese in the subfamily Anserinae where they form the tribe Cygnini. Sometimes, they are considered a distinct subfamily, Cygninae...
. This is referred to in the genus name, which means "ancient goose-like [bird]". But only one year later, the bone had been prepared from the matrix and ws submitted to an improvised phenetic analysis of its details. It was compared to that of Anserinae
Anserinae
The Anserinae is a subfamily in the waterfowl family Anatidae. It includes the swans and true geese. Under alternative systematical concepts , it is split into two subfamilies, the Anserinae containing the geese , while the Cygninae contain the swans.A number of other waterbirds, mainly related to...
and Dendrocygninae
Dendrocygninae
The whistling ducks or tree ducks are a subfamily, Dendrocygninae of the duck, goose and swan family of birds, Anatidae. In other taxonomical approaches, they are either considered a separate family "Dendrocygnidae", or a tribe "Dendrocygnini" in the goose subfamily Anserinae The whistling ducks or...
(other Anseriformes
Anseriformes
The order Anseriformes contains about 150 living species of birds in three extant families: the Anhimidae , Anseranatidae , and the Anatidae, which includes over 140 species of waterfowl, among them the ducks, geese, and swans.All species in the order are highly adapted for an aquatic existence at...
were either similar to these or too unlike P. mioceanus), as well as with Pelecanidae, Phaetontidae and Phalacrocoraciformes of the "higher waterbird" radiation, and found to resemble the former in one, the latter in 4 out of 5 traits. Some minor details of the femur were also unlike in the Anseriformes. The study proposed the fossil bird to have been "a large steganopod [...] somewhat larger than Pelecanus erythrorhynchos or P. onocrotalus," and not securely assignable to a known family
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...
. But as cladistic analysis had not yet been developed, it was of course not studied whether the similarities between P. mioceanus and the "higher waterbirds" are apomorphies. It has been noted, however, that adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....
to oceanic habits, has induced in pseudotooth bird legs and feet features convergent
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...
to other seabird
Seabird
Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...
s. Still, the fossil is a rather good specimen, considering how little humerus material known from pseudotooth birds; a recent cladistic analysis (which did not include P. mioceanus) did not put much emphasis on humerus traits, for example, as so few good fossils are known.
When Witmer Stone
Witmer Stone
Witmer Stone was an American ornithologist, botanist, and mammalogist, and was considered one of the last of the “great naturalists.” Stone is remembered principally as an ornithologist. He was president of the American Ornithologists’ Union 1920–23, and was editor of the AOU’s periodical The...
, then editor of The Auk
The Auk
The Auk is a quarterly journal and the official publication of the American Ornithologists' Union, having been continuously published by that body since 1884. The journal contains articles relating scientific studies of the anatomy, behavior, and distribution of birds. The journal is named for the...
, commented on the taxonomic confusion that the bird caused during less than 25 months after its description, he noted:
"It would seem desirable that those who name fossil birds should not fashion their generic names on those of existing birds as it is embarrassing to find them shifted into other families or orders where the name becomes somewhat of a misnomer!"
Only the end of the tarsometatarsus
Tarsometatarsus
The tarsometatarsus is a bone that is found in the lower leg of certain tetrapods, namely birds.It is formed from the fusion of several bones found in other types of animals, and homologous to the mammalian tarsal and metatarsal bones...
remains, but this is complete and even not very much abraded. Only on the edges of the outer trochlea
Trochlea
Trochlea is a term in anatomy. It refers to a grooved structure reminiscent of a pulley's wheel.Most commonly, trochleae bear the articular surface of saddle and other joints:* Trochlea of humerus* Trochlear process of the Calcaneus...
e does significant material seem to be lost. Altogether, the bone is very similar to that of the sympatric and probably contemporary Tympanonesiotes wetmorei, only appearing a bit less 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...
-like. The spread of the toes must have resembled that found in a fulmar
Fulmar
Fulmars are seabirds of the family Procellariidae. The family consists of two extant species and two that are extinct.-Taxonomy:As members of Procellaridae and then the order Procellariiformes, they share certain traits. First, they have nasal passages that attach to the upper bill called...
quite a lot, by contrast. The thin-walled bone has a second toe
Toe
Toes are the digits of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being digitigrade. Humans, and other animals that walk on the soles of their feet, are described as being plantigrade; unguligrade animals are those that walk on hooves at the tips of...
trochlea that attaches notably kneewards from the others and is angled slightly outwards while the hallux
Hallux
In tetrapods, the hallux is the innermost toe of the foot. Despite its name it may not be the longest toe on the foot of some individuals...
was vestigial or missing, as is typical for the pseudotooth birds. The fossil is about one-quarter larger than that of Tympanonesiotes, with a maximum end width of 34.7 mm (1.4 in) – probably a bit more in life, as the trochlea rims are eroded away. The shaft is 22.3 mm (0.877952755905512 in) wide at the point where it flares into the trochleae. It was thus more than twice as large as large as "Odontoptila inexpectata" from the Late Paleocene/Early Eocene of the Ouled Abdoul Basin (Morocco
Morocco
Morocco , officially the Kingdom of Morocco , is a country located in North Africa. It has a population of more than 32 million and an area of 710,850 km², and also primarily administers the disputed region of the Western Sahara...
), and – like Osteodontornis orri – thus belonged to the large pseudotooth birds, with a wingspan of more than 5, perhaps as much as 6 m (16-20 ft). Its bill was presumably long and massive as in its relatives, and in length the bird exceeded the largest 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.
The early systematic
Systematics
Biological systematics is the study of the diversification of terrestrial life, both past and present, and the relationships among living things through time. Relationships are visualized as evolutionary trees...
uncertainties have been noted again in recent times, in the scope of the debate whether the pseudotooth birds were Galloanseres closely related to waterfowl or Neoaves related to pelicans. Meanwhile, as a presumed pelican relative, P. mioceanus was allied with Cyphornis
Cyphornis
Cyphornis is a genus of the prehistoric pseudotooth birds. These were probably rather close relatives of either pelicans and storks, or of waterfowl, and are here placed in the order Odontopterygiformes to account for this uncertainty.-Description:...
(another pseudotooth bird, known only from a proximal left tarsometatarsus
Tarsometatarsus
The tarsometatarsus is a bone that is found in the lower leg of certain tetrapods, namely birds.It is formed from the fusion of several bones found in other types of animals, and homologous to the mammalian tarsal and metatarsal bones...
) and placed in a family
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...
Cyphornithidae. This was subsequently assigned to a "pelecaniform" suborder Cladornithes. But the enigmatic Late Oligocene Cladornis – the type genus
Type genus
In biological classification, a type genus is a representative genus, as with regard to a biological family. The term and concept is used much more often and much more formally in zoology than it is in botany, and the definition is dependent on the nomenclatural Code that applies:* In zoological...
of that supposed suborder – from the Argentinian part of Patagonia
Patagonia
Patagonia is a region located in Argentina and Chile, integrating the southernmost section of the Andes mountains to the southwest towards the Pacific ocean and from the east of the cordillera to the valleys it follows south through Colorado River towards Carmen de Patagones in the Atlantic Ocean...
is known from a distal right tarsometatarsus only, and thus was not directly comparable to Palaeochenoides and Cyphornis. Tympanonesiotes wetmorei, yet another pseudotooth bird, known from a distal right tarsometatarsus fragment, was initially presumed to be similar to Cladornis however, and also to Cyphornis; consequently, the three genera were allied simply because of their size and some similarities to the corresponding bones of pelicans. Today however, Cladornis is more generally held to be a terrestrial
Terrestrial animal
Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...
bird rather than a seabird
Seabird
Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...
.
As regards the supposed Cyphornithidae, most if not all pseudotooth birds placed there are probably closely related to the better-known Pelagornis
Pelagornis
Pelagornis is a widely-known genus of the prehistoric pseudotooth birds. These were probably rather close relatives of either pelicans and storks, or of waterfowl, and are here placed in the order Odontopterygiformes to account for this uncertainty....
, type genus
Type genus
In biological classification, a type genus is a representative genus, as with regard to a biological family. The term and concept is used much more often and much more formally in zoology than it is in botany, and the definition is dependent on the nomenclatural Code that applies:* In zoological...
of the family Pelagornithidae. And even if Cyphornis is the senior synonym of Palaeochenoides and Tympanoneisiotes (which is not overly likely due to size differences), according to the rules of zoological nomenclature the family name Pelagornithidae would not be affected. Cyphornithidae would almost certainly be a junior synonym of Pelagornithidae even if the pseudotooth birds are (as some have proposed) divided into several families – rather than being all placed in the Pelagornithidae as is usual nowadays – as Cyphornis, Osteodontornis
Osteodontornis
Osteodontornis is an extinct seabird genus. It contains a single named species, Osteodontornis orri , which was described quite exactly one century after the first species of the Pelagornithidae was. O...
, Palaeochenoides, Pelagornis and perhaps the smaller Tympanoneisiotes appear to be very closely related and are probably part of a monophyletic lineage of (usually) giant pseudotooth birds. As at the time of its description no adequarte comparaticve material was known, it was explicitly cautioned that P. mioceanus might include Pseudodontornis – which may actually be synonymous with Pelagornis.