Ichthyornis
Encyclopedia
Ichthyornis is a genus of toothed seabird
s from the Late Cretaceous
of North America
. Its fossil
remains are known from the chalk
s of Alberta
, Alabama
, Kansas
, New Mexico
, Saskatchewan
, and Texas
, in strata that were laid down in the Western Interior Seaway
during the Turonian
-Campanian
ages, about 95-85 mya). Ichthyornis is a common component of the Niobrara Formation
fauna, and numerous specimens of both adult and immature individuals have been found.
Ichthyornis has been historically important in shedding light on bird evolution. It was the first discovered prehistoric bird preserved with teeth, and Charles Darwin
noted its significance during the early years of the theory of evolution
. Ichthyornis remains important today as it is one of the few Mesozoic era birds known from more than a few specimens.
s, petrel
s, and skimmer
s. It was the size of a pigeon, 24 centimetres (9.4 in) long, with a skeletal wingspan (not taking feathers into account) of around 43 centimetres (16.9 in).
Ichthyornis is notable primarily for its combination of vertebrae which are concave both in front and back (similar to some fish, which is where the bird gets its name) and several more subtle features of its skeleton which set it apart from its close relatives. Ichthyornis is perhaps most well known for its teeth. The teeth were present only in the middle portion of the upper and lower jaws. The jaw tips had no teeth and were covered in a beak. The beak of Ichthyornis, like the hesperornithids and other primitive birds, was compound and made up of several distinct plates, similar to the beak of an albatross
, rather than a single sheet of keratin
as in most modern birds. The teeth were more flattened than the rounded teeth found in crocodilia
ns, though they became wider towards the base of the crown. The tips of the teeth were curved backward and lacked any serrations.
Although the wings and breastbone were very modern in appearance (suggesting strong flight ability and placing it with modern birds
in the advanced group Carinatae
), the jaws had numerous small, sharp teeth. Unlike earlier birds such as the enantiornithines
, it appears to have matured to adulthood in a rather short, continuous process.
age (about 89 million years ago) to the Campanian
age (about 85 million years ago). Even earlier remains attributed to Ichthyornis have been found in the Greenhorn Formation of Kansas, dating to the early Turonian
age (about 93 million years ago), and the Cenomanian
of Saskatchewan
, dating to about 95 million years ago.
, a professor from Kansas State Agricultural College who recovered the initial fossils from the North Fork of the Solomon River
in Kansas
, USA. Mudge was a prolific fossil collector who shipped his discoveries to prominent scientists for study. Mudge had previously had a close partnership with paleontologist Edward Drinker Cope
of the Academy of Natural Sciences
in Philadelphia. However, as described by S.W. Williston in 1898, Mudge was soon contacted by Othniel Charles Marsh
, Cope's rival in the so-called Bone Wars
, a rush to collect and identify fossils in the American West. Marsh wrote to Mudge in 1872 and offered to identify any important fossils free of charge, and to give Mudge sole credit for their discovery. Marsh had been a friend of Mudge when they were younger, so when Mudge learned of Marsh's request, he changed the address on the shipping crate containing the Ichthyornis specimen (which had already been addressed to Cope and was ready to be sent), and shipped it to Marsh instead. Marsh had narrowly won the prestige of studying and naming the important fossil at the expense of his rival.
However, Marsh did not initially recognize the true importance of the fossil. Soon after receiving it, he reported back to Mudge his opinion that the chalk slab contained the bones of two distinct animals: a small bird, and the toothed jaws of some unknown reptile. Marsh considered the unusual vertebrae of the bird to resemble those of a fish, so he named it Ichthyornis, or "fish bird." Later in 1872, Marsh described the toothed jaws as a new species of marine reptile, named Colonosaurus mudgei after their discoverer.
By early in 1873, Marsh had recognized his error. Through further preparation and exposure of skull bones from the rock, he found that the toothed jaws must have come from the bird itself and not a marine reptile. Due to the previously unknown features of Ichthyornis (vertebrae concave on either side and teeth), Marsh chose to classify the bird in an entirely new sub-class of birds he called the Odontornithes (or "toothed birds"), and in the new order Ichthyornithes (later Ichthyornithiformes). The only other bird Marsh included in these groups was the newly named Apatornis
, which he had previously named as a species of Ichthyornis, I. celer. Mudge later noted the rare and unique quality of these toothed birds (including Hesperornis, which was found to also have teeth by 1877), and the irony of their association with the remains of toothless pterosaur
s, flying reptiles which were only known to have had teeth in other regions of the world at that time.
Soon after these discoveries, Ichthyornis was recognized for its significance to the theory of evolution recently published by Charles Darwin. Darwin himself told Marsh in an 1880 letter that Ichthyornis and Hesperornis
offered "the best support for the theory of evolution" since he had first published On the Origin of Species in 1859. (While Archaeopteryx
was the first known Mesozoic bird and is now known to have also had teeth, the first specimen with a skull was not described until 1884). Others at the time also recognized the implications of a nearly modern bird with reptilian teeth, and feared the controversy it caused. One Yale student described various men and women urging Marsh to conceal Ichthyornis from the public because it lent too much support to evolutionary theory. Many accused Marsh of having tampered with the fossils or intentionally created a hoax by associating reptilian jaws with the body of a bird, accusations that continued to surface even as late as 1967. However, an overwhelming majority of researchers have demonstrated that Marsh's interpretation of the fossils was correct, and he was fully vindicated by later finds.
At the turn of the 20th Century, the Peabody Museum of Natural History at Yale University
, where most Ichthyornis specimens were housed, began placing many of its most interesting or important specimens on display in the museum's Great Hall. Two panel mounts (that is, pieces where the skeleton is arranged and set into a plaster slab) were created for Ichthyornis; one for I. dispar, and one for I. victor. Both were created by Hugh Gibb, who prepared many of Marsh's fossils for study and display. The I. dispar mount contained only the holotype
fossils, while the I victor mount was a composite incorporating a variety of different specimens to make the piece appear more complete (it did not, however, contain any part of the actual I. victor holotype specimen).
At some point before 1937, the specimen of the actual I. victor type specimen was re-assigned to the panel mount. Later reports of the specimen, even by the Peabody Museum's staff, therefore mistakenly stated that the original I. dispar specimen comprised most of the skeleton, when it was in fact only three bones. By 1997, the situation had become so confused that Jacques Gauthier
, the current curator of the museum's vertebrate paleontology collection, authorized the dismantling of both panel mounts. This allowed the bones to be properly sorted out and studied in three dimensions, which had been impossible previously when they were embedded in plaster. A full re-description of these specimens was published by paleontologist Julia Clarke in 2004.
, Apatornis
, Iaceornis
and Guildavis — but these seem to be closer to the ancestors of modern birds than to Ichthyornis dispar. New data on the radiation of the latter, which is now known to have started already in the Cretaceous (see Vegavis
), could shed more light on the exact relationship of these taxa. In Clarke's 2004 review, the former order
Ichthyornithiformes and the family
Ichthyornithidae are now superseded by the subclass Ichthyornithes, which in the paper was also defined according to phylogenetic taxonomy as all descendants of the most recent common ancestor of Ichthyornis dispar and modern birds.
Of the several described species, only one, Ichthyornis dispar, is currently recognized, following the seminal review by Julia Clarke. Marsh had previously named a specimen now attributed to I. dispar as Graculavus anceps. Clarke argued that because the rules for naming animals laid out by the ICZN
state that a type species for a genus must have originally been included in that genus, Ichthyornis anceps is ineligible to replace I. dispar as the type species and so must be considered a junior synonym even though it was named first. However, Michael Mortimer pointed out that this is incorrect; while I. anceps cannot become the type species of Ichthyornis, the ICZN does not preclude it from becoming the senior synonym of the type species I. dispar. Therefore, I. ancesps should have been considered the correct name for the only recognized Ichthyornis species.
There has been considerable confusion about the attribution of the fossil material. The similarity of the lower jaw and teeth to those of mosasaur
s (fish
-eating marine lizard
s) is so great that as late as 1952, it was argued that it really belonged to a diminutive species or young individual of or related to the genus Clidastes
.
The presumed "Ichthyornis" lentus actually belongs into the early galliform
genus Austinornis. "Ichthyornis" minusculus from the Bissekty Formation
(Late Cretaceous) of Kyzyl Kum
, Uzbekistan
, is probably an enantiornithine.
Genus-level
Species-level
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 from the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. Its fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
remains are known from the chalk
Chalk
Chalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates shed from micro-organisms called coccolithophores....
s of Alberta
Alberta
Alberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...
, Alabama
Alabama
Alabama is a state located in the southeastern region of the United States. It is bordered by Tennessee to the north, Georgia to the east, Florida and the Gulf of Mexico to the south, and Mississippi to the west. Alabama ranks 30th in total land area and ranks second in the size of its inland...
, Kansas
Kansas
Kansas is a US state located in the Midwestern United States. It is named after the Kansas River which flows through it, which in turn was named after the Kansa Native American tribe, which inhabited the area. The tribe's name is often said to mean "people of the wind" or "people of the south...
, New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
, Saskatchewan
Saskatchewan
Saskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....
, and Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
, in strata that were laid down in the Western Interior Seaway
Western Interior Seaway
The Western Interior Seaway, also called the Cretaceous Seaway, the Niobraran Sea, and the North American Inland Sea, was a huge inland sea that split the continent of North America into two halves, Laramidia and Appalachia, during most of the mid- and late-Cretaceous Period...
during the Turonian
Turonian
The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous epoch, or a stage in the Upper Cretaceous series. It spans the time between 93.5 ± 0.8 Ma and 89.3 ± 1 Ma...
-Campanian
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...
ages, about 95-85 mya). Ichthyornis is a common component of the Niobrara Formation
Niobrara Formation
The Niobrara Formation, also called the Niobrara Chalk , is a geologic formation in North America that was laid down between 87 and 82 million years ago during the Coniacian, Santonian, and Campanian ages of the Late Cretaceous. It is composed of two structural units, the Smoky Hill Chalk Member...
fauna, and numerous specimens of both adult and immature individuals have been found.
Ichthyornis has been historically important in shedding light on bird evolution. It was the first discovered prehistoric bird preserved with teeth, and Charles Darwin
Charles Darwin
Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...
noted its significance during the early years of the theory of evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
. Ichthyornis remains important today as it is one of the few Mesozoic era birds known from more than a few specimens.
Description
It is thought that Ichthyornis was the Cretaceous ecological equivalent of modern seabirds such as gullGull
Gulls are birds in the family Laridae. They are most closely related to the terns and only distantly related to auks, skimmers, and more distantly to the waders...
s, 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 skimmer
Skimmer
The Skimmers, Rynchopidae, are a small family of tern-like birds in the order Charadriiformes, which also includes the waders, gulls and auks. The family comprises three species found in South Asia, Africa, and the Americas....
s. It was the size of a pigeon, 24 centimetres (9.4 in) long, with a skeletal wingspan (not taking feathers into account) of around 43 centimetres (16.9 in).
Ichthyornis is notable primarily for its combination of vertebrae which are concave both in front and back (similar to some fish, which is where the bird gets its name) and several more subtle features of its skeleton which set it apart from its close relatives. Ichthyornis is perhaps most well known for its teeth. The teeth were present only in the middle portion of the upper and lower jaws. The jaw tips had no teeth and were covered in a beak. The beak of Ichthyornis, like the hesperornithids and other primitive birds, was compound and made up of several distinct plates, similar to the beak of an 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...
, rather than a single sheet of keratin
Keratin
Keratin refers to a family of fibrous structural proteins. Keratin is the key of structural material making up the outer layer of human skin. It is also the key structural component of hair and nails...
as in most modern birds. The teeth were more flattened than the rounded teeth found in crocodilia
Crocodilia
Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria...
ns, though they became wider towards the base of the crown. The tips of the teeth were curved backward and lacked any serrations.
Although the wings and breastbone were very modern in appearance (suggesting strong flight ability and placing it with modern birds
Modern birds
Modern birds are the most recent common ancestor of all living birds and all its descendants.Modern birds are characterised by feathers, a beak with no teeth , the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a lightweight but strong skeleton...
in the advanced group Carinatae
Carinatae
This article is about bird taxonomy; for the topic in pottery and glassware design, see Carinate.The Carinatae are, in phylogenetic taxonomy, the last common ancestor of the Neornithes and Ichthyornis , and all its descendants...
), the jaws had numerous small, sharp teeth. Unlike earlier birds such as the enantiornithines
Enantiornithes
Enantiornithes is an extinct group of primitive birds. They were the most abundant and diverse avialans of the Mesozoic. Almost all retained teeth and clawed fingers on each wing, but otherwise looked much like modern birds externally. Over 50 species of Enantiornithines have been named, but some...
, it appears to have matured to adulthood in a rather short, continuous process.
Timespan and evolution
Ichthyornis fossils have been found in almost all levels of the Niobrara Chalk, from beds dating to the late ConiacianConiacian
The Coniacian is an age or stage in the geologic timescale. It is a subdivision of the Late Cretaceous epoch or Upper Cretaceous series and spans the time between 89.3 ± 1 Ma and 85.8 ± 0.7 Ma...
age (about 89 million years ago) to the Campanian
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...
age (about 85 million years ago). Even earlier remains attributed to Ichthyornis have been found in the Greenhorn Formation of Kansas, dating to the early Turonian
Turonian
The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous epoch, or a stage in the Upper Cretaceous series. It spans the time between 93.5 ± 0.8 Ma and 89.3 ± 1 Ma...
age (about 93 million years ago), and the Cenomanian
Cenomanian
The Cenomanian is, in the ICS' geological timescale the oldest or earliest age of the Late Cretaceous epoch or the lowest stage of the Upper Cretaceous series. An age is a unit of geochronology: it is a unit of time; the stage is a unit in the stratigraphic column deposited during the corresponding...
of Saskatchewan
Saskatchewan
Saskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....
, dating to about 95 million years ago.
History of study
Ichthyornis was first discovered in 1870 by Benjamin Franklin MudgeBenjamin Franklin Mudge
Benjamin Franklin Mudge was an American lawyer, geologist and teacher. Briefly the mayor of Lynn, Massachusetts, he later moved to Kansas where he was appointed the first State Geologist. He led the first geological survey of the state in 1864, and published the first book on the geology of Kansas...
, a professor from Kansas State Agricultural College who recovered the initial fossils from the North Fork of the Solomon River
Solomon River
The Solomon River, often referred to as the "Solomon Fork", is a river in the central Great Plains of North America. The entire length of the river lies in the U.S. state of Kansas. It is a tributary of the Smoky Hill River.-Names:...
in Kansas
Kansas
Kansas is a US state located in the Midwestern United States. It is named after the Kansas River which flows through it, which in turn was named after the Kansa Native American tribe, which inhabited the area. The tribe's name is often said to mean "people of the wind" or "people of the south...
, USA. Mudge was a prolific fossil collector who shipped his discoveries to prominent scientists for study. Mudge had previously had a close partnership with paleontologist Edward Drinker Cope
Edward Drinker Cope
Edward Drinker Cope was an American paleontologist and comparative anatomist, as well as a noted herpetologist and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested in science; he published his first scientific paper at the age of nineteen...
of the Academy of Natural Sciences
Academy of Natural Sciences
The Academy of Natural Sciences of Drexel University, formerly Academy of Natural Sciences of Philadelphia, is the oldest natural science research institution and museum in the New World...
in Philadelphia. However, as described by S.W. Williston in 1898, Mudge was soon contacted by Othniel Charles Marsh
Othniel Charles Marsh
Othniel Charles Marsh was an American paleontologist. Marsh was one of the preeminent scientists in the field; the discovery or description of dozens of news species and theories on the origins of birds are among his legacies.Born into a modest family, Marsh was able to afford higher education...
, Cope's rival in the so-called Bone Wars
Bone Wars
The Bone Wars, also known as the "Great Dinosaur Rush", refers to a period of intense fossil speculation and discovery during the Gilded Age of American history, marked by a heated rivalry between Edward Drinker Cope and Othniel Charles Marsh...
, a rush to collect and identify fossils in the American West. Marsh wrote to Mudge in 1872 and offered to identify any important fossils free of charge, and to give Mudge sole credit for their discovery. Marsh had been a friend of Mudge when they were younger, so when Mudge learned of Marsh's request, he changed the address on the shipping crate containing the Ichthyornis specimen (which had already been addressed to Cope and was ready to be sent), and shipped it to Marsh instead. Marsh had narrowly won the prestige of studying and naming the important fossil at the expense of his rival.
However, Marsh did not initially recognize the true importance of the fossil. Soon after receiving it, he reported back to Mudge his opinion that the chalk slab contained the bones of two distinct animals: a small bird, and the toothed jaws of some unknown reptile. Marsh considered the unusual vertebrae of the bird to resemble those of a fish, so he named it Ichthyornis, or "fish bird." Later in 1872, Marsh described the toothed jaws as a new species of marine reptile, named Colonosaurus mudgei after their discoverer.
Apatornis
Apatornis is a prehistoric terrestrial bird genus endemic to North America during the Late Cretaceous living about 83.5 mya. It is known from a single fossil specimen: a synsacrum, the fused series of vertebrae over the hips.-Taxonomy:...
, which he had previously named as a species of Ichthyornis, I. celer. Mudge later noted the rare and unique quality of these toothed birds (including Hesperornis, which was found to also have teeth by 1877), and the irony of their association with the remains of toothless pterosaur
Pterosaur
Pterosaurs were flying reptiles of the clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period . Pterosaurs are the earliest vertebrates known to have evolved powered flight...
s, flying reptiles which were only known to have had teeth in other regions of the world at that time.
Soon after these discoveries, Ichthyornis was recognized for its significance to the theory of evolution recently published by Charles Darwin. Darwin himself told Marsh in an 1880 letter that Ichthyornis and Hesperornis
Hesperornis
Hesperornis is a genus of flightless aquatic birds that spanned the first half of the Campanian age of the Late Cretaceous period . One of the lesser-known discoveries of the paleontologist O. C. Marsh in the late 19th century Bone Wars, it was an important early find in the history of avian...
offered "the best support for the theory of evolution" since he had first published On the Origin of Species in 1859. (While Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...
was the first known Mesozoic bird and is now known to have also had teeth, the first specimen with a skull was not described until 1884). Others at the time also recognized the implications of a nearly modern bird with reptilian teeth, and feared the controversy it caused. One Yale student described various men and women urging Marsh to conceal Ichthyornis from the public because it lent too much support to evolutionary theory. Many accused Marsh of having tampered with the fossils or intentionally created a hoax by associating reptilian jaws with the body of a bird, accusations that continued to surface even as late as 1967. However, an overwhelming majority of researchers have demonstrated that Marsh's interpretation of the fossils was correct, and he was fully vindicated by later finds.
Mounted specimens
Yale University
Yale University is a private, Ivy League university located in New Haven, Connecticut, United States. Founded in 1701 in the Colony of Connecticut, the university is the third-oldest institution of higher education in the United States...
, where most Ichthyornis specimens were housed, began placing many of its most interesting or important specimens on display in the museum's Great Hall. Two panel mounts (that is, pieces where the skeleton is arranged and set into a plaster slab) were created for Ichthyornis; one for I. dispar, and one for I. victor. Both were created by Hugh Gibb, who prepared many of Marsh's fossils for study and display. The I. dispar mount contained only the holotype
Holotype
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...
fossils, while the I victor mount was a composite incorporating a variety of different specimens to make the piece appear more complete (it did not, however, contain any part of the actual I. victor holotype specimen).
At some point before 1937, the specimen of the actual I. victor type specimen was re-assigned to the panel mount. Later reports of the specimen, even by the Peabody Museum's staff, therefore mistakenly stated that the original I. dispar specimen comprised most of the skeleton, when it was in fact only three bones. By 1997, the situation had become so confused that Jacques Gauthier
Jacques Gauthier
Jacques Armand Gauthier is a vertebrate paleontologist, comparative morphologist, and systematist, and one of the founders of the use of cladistics in biology....
, the current curator of the museum's vertebrate paleontology collection, authorized the dismantling of both panel mounts. This allowed the bones to be properly sorted out and studied in three dimensions, which had been impossible previously when they were embedded in plaster. A full re-description of these specimens was published by paleontologist Julia Clarke in 2004.
Classification
Ichthyornis is close to the ancestry of modern birds, the Neornithes, but represents an independent lineage. It was long believed that it was closely related to some other Cretaceous taxa known from very fragmentary remains — AmbiortusAmbiortus
Ambiortus is a prehistoric bird genus. The only known species, Ambiortus dementjevi, lived about 130 million years ago during the Early Cretaceous in today's Mongolia....
, Apatornis
Apatornis
Apatornis is a prehistoric terrestrial bird genus endemic to North America during the Late Cretaceous living about 83.5 mya. It is known from a single fossil specimen: a synsacrum, the fused series of vertebrae over the hips.-Taxonomy:...
, Iaceornis
Iaceornis
Iaceornis is a prehistoric marine bird genus endemic to North America during the Late Cretaceous living about 83.5 mya. It is known from a single fossil specimen consisting of a partial skeleton lacking a skull. Since it was first discovered by Othniel Charles Marsh in 1877, the specimen was long...
and Guildavis — but these seem to be closer to the ancestors of modern birds than to Ichthyornis dispar. New data on the radiation of the latter, which is now known to have started already in the Cretaceous (see Vegavis
Vegavis
Vegavis is a genus of extinct bird that lived during the Late Cretaceous of Antarctica, some 65 mya. It belonged to the clade Anseriformes...
), could shed more light on the exact relationship of these taxa. In Clarke's 2004 review, the former 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...
Ichthyornithiformes and the 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...
Ichthyornithidae are now superseded by the subclass Ichthyornithes, which in the paper was also defined according to phylogenetic taxonomy as all descendants of the most recent common ancestor of Ichthyornis dispar and modern birds.
Of the several described species, only one, Ichthyornis dispar, is currently recognized, following the seminal review by Julia Clarke. Marsh had previously named a specimen now attributed to I. dispar as Graculavus anceps. Clarke argued that because the rules for naming animals laid out by the ICZN
International Code of Zoological Nomenclature
The International Code of Zoological Nomenclature is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals...
state that a type species for a genus must have originally been included in that genus, Ichthyornis anceps is ineligible to replace I. dispar as the type species and so must be considered a junior synonym even though it was named first. However, Michael Mortimer pointed out that this is incorrect; while I. anceps cannot become the type species of Ichthyornis, the ICZN does not preclude it from becoming the senior synonym of the type species I. dispar. Therefore, I. ancesps should have been considered the correct name for the only recognized Ichthyornis species.
There has been considerable confusion about the attribution of the fossil material. The similarity of the lower jaw and teeth to those of mosasaur
Mosasaur
Mosasaurs are large extinct marine lizards. The first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764...
s (fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
-eating marine lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...
s) is so great that as late as 1952, it was argued that it really belonged to a diminutive species or young individual of or related to the genus Clidastes
Clidastes
Clidastes is an extinct genus of mosasaur lizard from marine environments of the Late Cretaceous.Clidastes was an agile and fast swimmer that cruised the surface or shallow waters hunting for fish, flying reptiles and anything that got too close.- Appearance :Clidastes was the smallest of the...
.
The presumed "Ichthyornis" lentus actually belongs into the early galliform
Galliformes
Galliformes are an order of heavy-bodied ground-feeding domestic or game bird, containing turkey, grouse, chicken, New and Old World Quail, ptarmigan, partridge, pheasant, and the Cracidae. Common names are gamefowl or gamebirds, landfowl, gallinaceous birds or galliforms...
genus Austinornis. "Ichthyornis" minusculus from the Bissekty Formation
Bissekty Formation
The Bissekty Formation is situated in the Kyzyl Kum desert of Uzbekistan, and dates from the late Cretaceous Period. Laid down in the early the Turonian to Coniacian stages, it is dated to about 90-85 ma .The Bissekty Formation is characterised by a mix of marine, brackish, freshwater, and...
(Late Cretaceous) of Kyzyl Kum
Kyzyl Kum
The Kyzyl Kum , also called Qyzylqum, is the 11th largest desert in the world. Its name means Red Sand in Turkic languages. It is located in Central Asia in the doab between the rivers Amu Darya and Syr Darya, and is divided between Kazakhstan, Uzbekistan and Turkmenistan...
, Uzbekistan
Uzbekistan
Uzbekistan , officially the Republic of Uzbekistan is a doubly landlocked country in Central Asia and one of the six independent Turkic states. It shares borders with Kazakhstan to the west and to the north, Kyrgyzstan and Tajikistan to the east, and Afghanistan and Turkmenistan to the south....
, is probably an enantiornithine.
Synonyms
Subclass-level- Odontotormae Marsh, 1875
Genus-level
- Angelinornis Kashin 1972
- Colonosaurus Marsh, 1872c
- Plegadornis WetmoreAlexander WetmoreFrank Alexander Wetmore was an American ornithologist and avian paleontologist.-Life:Wetmore studied at the University of Kansas...
, 1962 (non C.L. BrehmChristian Ludwig BrehmChristian Ludwig Brehm was a German pastor and ornithologist. He was the father of Alfred Brehm.Brehm was born near Gotha, and studied at the University of Jena. In 1813 he became the minister at Renthendorf, a village sixty miles south of Leipzig, where he remained until his death...
, 1855 - preoccupied)
Species-level
- Angelinornis antecessor (Wetmore, 1962)
- Colonosaurus mudgei Marsh, 1872c
- GraculavusGraculavusGraculavus is a prehistoric bird genus that was described by O. C. Marsh. Its remains were found in the Late Cretaceous Austin Chalk of Texas and Lance Formation , and the controversial Hornerstown Formation which straddles the Cretaceous–Paleocene boundary, possibly dating to the Danian stage...
agilis Marsh, 1873b - Graculavus anceps Marsh, 1872a
- Ichthyornis antecessor (Wetmore, 1962) Olson, 1975
- Ichthyornis anceps (Marsh, 1872a) Marsh, 1880
- Ichthyornis agilis (Marsh, 1873b) Marsh, 1880
- Ichthyornis tener Marsh, 1880
- Ichthyornis validus Marsh, 1880
- Ichthyornis victor Marsh, 1876
- Plegadornis antecessor Wetmore, 1962
External links
- Ichthyornis dispar: A toothed, flying bird from the Late Cretaceous of Kansas by Mike Everhart, Oceans of Kansas website. Retrieved 2006-09-16.