Ichthyornis is a genus of toothed
seabirdSeabirds 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 CretaceousThe 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 AmericaNorth 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
fossilFossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
remains are known from the
chalkChalk 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
AlbertaAlberta 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...
,
AlabamaAlabama 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...
,
KansasKansas 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 MexicoNew 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...
,
SaskatchewanSaskatchewan 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
TexasTexas 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 SeawayThe 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
TuronianThe 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...
-
CampanianThe 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 FormationThe 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 DarwinCharles 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
evolutionEvolution 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
gullGulls 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,
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
skimmerThe 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
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...
, rather than a single sheet of
keratinKeratin 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
crocodiliaCrocodilia 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 birdsModern 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
CarinataeThis 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
enantiornithinesEnantiornithes 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
ConiacianThe 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
CampanianThe 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
TuronianThe 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
CenomanianThe 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
SaskatchewanSaskatchewan 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 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 RiverThe 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
KansasKansas 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 CopeEdward 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 SciencesThe 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 MarshOthniel 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 WarsThe 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.
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
ApatornisApatornis 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
pterosaurPterosaurs 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
HesperornisHesperornis 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
ArchaeopteryxArchaeopteryx , 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
At the turn of the 20th Century, the Peabody Museum of Natural History at
Yale UniversityYale 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
holotypeA 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 GauthierJacques 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 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....
,
ApatornisApatornis 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:...
,
IaceornisIaceornis 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
VegavisVegavis 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
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...
Ichthyornithiformes and the
familyIn 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
ICZNThe 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
mosasaurMosasaurs are large extinct marine lizards. The first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764...
s (
fishFish 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
lizardLizards 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
ClidastesClidastes 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
galliformGalliformes 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 FormationThe 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 KumThe 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...
,
UzbekistanUzbekistan , 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
Genus-level
- Angelinornis Kashin 1972
- Colonosaurus Marsh, 1872c
- Plegadornis Wetmore
Frank Alexander Wetmore was an American ornithologist and avian paleontologist.-Life:Wetmore studied at the University of Kansas...
, 1962 (non C.L. 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
- Graculavus
Graculavus 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