Ichthyornis (meaning "fish bird", after its fish-like vertebrae) was a genus of toothed seabird-like ornithuran from the late Cretaceous period of North America. Its fossil remains are known from the chalks of Alberta, Alabama, Kansas (Greenhorn Limestone), New Mexico, Saskatchewan, and Texas, in strata that were laid down in the Western Interior Seaway during the Turonian through Campanian ages, about 95–83.5 million years ago. Ichthyornis is a common component of the Niobrara Formation fauna, and numerous specimens have been found.
Ichthyornis has been historically important in shedding light on bird evolution. It was the first known prehistoric bird relative 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 ornithurans known from more than a few specimens.
|Cast skeleton, Rocky Mountain Dinosaur Resource Center|
It is thought that Ichthyornis was the Cretaceous ecological equivalent of modern seabirds such as gulls, petrels, and skimmers. An average specimen 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 (17 in), though there is considerable size variation among known specimens, with some smaller and some much larger than the type specimen of I. dispar.
Ichthyornis is notable primarily for its combination of vertebrae which are concave both in front and back (similar to some fish, which is where it 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, 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 crocodilians, though they became wider towards the base of the crown. The tips of the teeth were curved backward and lacked any serrations.
The wings and breastbone were very modern in appearance, suggesting strong flight ability and placing it with modern birds in the advanced group Carinatae. Unlike earlier avialans such as the enantiornithines, the species appears to have matured to adulthood in a rather short, continuous process.
Ichthyornis fossils have been found in almost all levels of the Niobrara Chalk, from beds dating to the late Coniacian age (about 89 million years ago) to the Campanian age (about 83.5 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). Older specimens of Ichthyornis were, on average, smaller than younger ones. The holotype specimen of Ichthyornis dispar, YPM 1450, had a humerus about 58 centimetres (23 in) long. In many geologically younger specimens like YPM 1742, the same wing bone was 73 centimetres (29 in) long. Both the older, smaller specimens, and the more recent, larger specimens show signs that they had reached skeletal maturity and were adults, and came from the same geographic area. It is likely that Ichthyornis dispar as a species increased in size over the several million years it inhabited the Western Interior Seaway ecosystem.
Ichthyornis was one of the first Mesozoic avialans ever found and the first one known to have had teeth, making it an important discovery in the early history of paleontology. It remains important today, as it represents one of the closest non-avian relatives of modern birds, and one of a handful of Mesozoic bird relatives represented by numerous specimens. Ichthyornis was discovered in 1870 by Benjamin Franklin Mudge, a professor from Kansas State Agricultural College who recovered the initial fossils from the North Fork of the Solomon River in Kansas, United States. 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 animal, 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. The similarity of the lower jaw and teeth to those of mosasaurs is so great that as late as 1952, J.T. Gregory argued that it really belonged to a diminutive species or young individual related to the genus Clidastes.
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 it 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 pterosaurs, 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 avialan 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 catalogue number of the actual "I. victor" type specimen was mistakenly reassigned to the panel mount. Later reports of the specimen, even by the Peabody Museum's staff, therefore mistakenly stated that the original "I. victor" 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.
Ichthyornis is close to the ancestry of modern birds, the Aves, but represents an independent lineage. It was long believed that it was closely related to some other Cretaceous taxa known from very fragmentary remains — Ambiortus, Apatornis, Iaceornis and Guildavis — but these seem to be closer to the ancestors of modern birds than to Ichthyornis dispar. In Clarke's 2004 review, the former order Ichthyornithiformes and the family Ichthyornithidae are now superseded by the clade 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. anceps should have been considered the correct name for the only recognized Ichthyornis species. All other supposed species of Ichthyornis have not been supported as valid. The presumed "Ichthyornis" lentos, for example, actually belongs into the early galliform genus Austinornis. "Ichthyornis" minusculus from the Bissekty Formation (Late Cretaceous) of Kyzyl Kum, Uzbekistan, is probably an enantiornithine. All other Ichthyornis species are synonymous with I. dispar.
The cladogram below is the result of a 2014 analysis by Michael Lee and colleagues that expanded on data from an earlier study by O’Connor & Zhou in 2012. The clade names are positioned based on their definitions.
Apatornis is a genus of prehistoric birds endemic to North America during the late Cretaceous. It currently contains a single species, Apatornis celer, which lived around the Santonian-Campanian boundary, dated to about 83.5 million years ago. The remains of this species were found in the Smoky Hill Chalk of the Niobrara Formation in Kansas, United States. It is known from a single fossil specimen: a synsacrum, the fused series of vertebrae over the hips.
While the known fossil remains are very incomplete, enough has been found to reasonably estimate that the body length of this bird was between 7–8 inches (18–20 cm).The type specimen of A. celer, YPM 1451, was reportedly discovered by Othniel Charles Marsh in October 1872 at Butte Creek in Logan County, Kansas. This location is now recognized as falling between Marker Units 15 and 19 of the Smoky Hill Chalk geological formation. An additional, more complete specimen had also been referred to Apatornis celer by Marsh. This more complete specimen had historically been the one used almost exclusively to form the basis of what was known about Apatornis. However, Julia Clarke noted in 2004 that because the second specimen did not preserve any of the same bones as the first, the two could not be scientifically compared. Clarke therefore reclassified the second specimen as its own genus and species, Iaceornis marshi.Benjamin Franklin Mudge
Benjamin Franklin Mudge (August 11, 1817 – November 21, 1879) 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. He lectured extensively, and was department chair at the Kansas State Agricultural College (KSAC, now Kansas State University).
He also avidly collected fossils, and was one of the first to systematically explore the Permian and Mesozoic biota in the geologic formations of Kansas and the American West, including the Niobrara Chalk, the Morrison Formation, and the Dakota Sandstone. While not formally trained in paleontology, he kept extensive and accurate field notes and sent most of his fossils East to be described by some of the most noted paleontologists of his time, including the rivals Othniel Charles Marsh and Edward Drinker Cope.
His discoveries included at least 80 new species of extinct animals and plants, and are found in the collections of some of the most prestigious U.S. institutions of natural history, including the Smithsonian and Yale's Peabody Museum of Natural History. One of his most notable finds is the holotype of the first recognized "bird with teeth", Ichthyornis. While working for Marsh, he also discovered the type species of the sauropod dinosaur Diplodocus, and the theropod dinosaur Allosaurus, with his protégé Samuel Wendell Williston.Gansus
Gansus is a genus of aquatic birds that lived during the Aptian age of the Early Cretaceous (Aptian-Albian) period in what are now Gansu and Liaoning provinces, western China. The rock layers from which their fossils have been recovered are dated to 120 million years ago. It was first described in 1984 on the basis of an isolated left leg. It is the oldest-known member of the Ornithurae, the group which includes modern birds (Neornithes) and extinct related groups, such as Ichthyornis and Hesperornithes.Graculavus
Graculavus is a prehistoric bird genus that was described in the 19th century by American paleontologist O. C. Marsh. Its remains were found in the Late Cretaceous Austin Chalk of Texas, USA, and Lance Formation (late Maastrichtian faunal stage, or Lancian land mammal age), and the controversial Hornerstown Formation which straddles the Cretaceous–Paleocene boundary, possibly dating to the Danian stage. These birds lived on the shores of the northwestern Atlantic and the Western Interior Seaway some 68 to 62 million years ago.Halimornis
Halimornis was an enantiornithine bird. It lived during the Late Cretaceous about 80 mya and is known from fossils found in the Mooreville Chalk Formation in Greene County, Alabama. It is known from a single fossil individual, including preserved vertebrae, leg bones and part of the humerus (upper arm bone).
At the time, the area where the Mooreville Chalk was deposited was situated on the southern coast of the Western Interior Seaway, and may have been the site of a large delta where several major rivers flowed into the shallow sea. The fossil bird was found at a location that would have been about 50 km off shore, indicating that it was an ocean-going species. The name Halimornis means "bird of the sea". It would have lived alongside the more advanced seabird Ichthyornis dispar. It is one of the only known enantiornithine birds to have lived in a marine environment, along with the Australian Nanantius eos and "Ichthyornis" minusculus, which was originally misidentified as Ichthyornis based on its presence in marine deposits.Hesperornis
Hesperornis (meaning "western bird") is a genus of penguin-like bird that spanned the first half of the Campanian age of the Late Cretaceous period (83.5–78 mya). One of the lesser-known discoveries of the paleontologist O. C. Marsh in the late 19th century Bone Wars, it was an early find in the history of avian paleontology. Locations for Hesperornis fossils include the Late Cretaceous marine limestones from Kansas and the marine shales from Canada. Nine species are recognised, eight of which have been recovered from rocks in North America and one from Russia.Hesperornithes
Hesperornithes is an extinct and highly specialized group of aquatic avialans closely related to the ancestors of modern birds. They inhabited both marine and freshwater habitats in the Northern Hemisphere, and include genera such as Hesperornis, Parahesperornis, Baptornis, Enaliornis, and Potamornis, all strong-swimming, predatory divers. Many of the species most specialized for swimming were completely flightless. The largest known hesperornithean, Canadaga arctica, may have reached a maximum adult length of over 1.5 metres (4.9 ft).
Hesperornitheans were the only Mesozoic avialans to colonize the oceans. They were wiped out in the Cretaceous–Paleogene extinction event, along with enantiornitheans and all other non-avian dinosaurs, as well as many other diverse plant and animal groups.Hollanda luceria
Hollanda is a genus of small ground birds known from fossils found in the Barun Goyot Formation of Mongolia. Found at Khermeen Tsav, it dates from the late Cretaceous period (Campanian stage), about 75 million years ago. Known only from partial hind limbs, Hollanda has long legs with an unusual configuration of the toes. These indicate that it was a fast-running ground bird, possibly similar to the modern Roadrunner. Its relationships are uncertain. Some studies have found that it was an relatively advanced bird, a member of the Ornithurae, related to birds like Ichthyornis. Other studies have recovered it as a member of the primitive family Songlingornithidae.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 found in Gove County, Kansas (USA), and consisting of a partial skeleton lacking a skull.
Since it was first discovered by Othniel Charles Marsh in 1877, the specimen (YPM 1734) was long considered to belong to the contemporary species Apatornis celer. Because it is relatively complete, most discussions of Apatornis actually focused on the Iaceornis fossil. In 2004, paleontologist Julia A. Clarke showed that the skeleton actually differed in important characteristics of the wing bones from the true, holotype specimen of Apatornis. Therefore, she assigned the more complete remains to a new genus and species, Iaceornis marshi, meaning "Marsh's neglected bird".In Clarke's phylogenetic analysis, she found that Iaceornis is more advanced than Ichthyornis but less advanced than modern birds.Ichthyornithes
Ichthyornithes is an extinct group of toothed avialans very closely related to the common ancestor of all modern birds. They are known from fossil remains found throughout the late Cretaceous period of North America, though only one species, Ichthyornis dispar, is represented by complete enough fossils to have been named. Ichthyornitheans became extinct at the Cretaceous–Paleogene boundary, along with enantiornitheans, all other non-avian dinosaurs, and many other animal and plant groups.Julia Clarke
Julia Clarke is an American paleontologist who is particularly interested in flying animals and those that were related to ancestors of birds today. She works at the University of Texas where she is the John A. Wilson Professor in Vertebrate Paleontology.Lenesornis
Lenesornis is a genus of enantiornithine birds which lived during the Late Cretaceous about 78 mya and is known from fossils found in the Bissekty Formation in the Kyzyl Kum, Uzbekistan.Limenavis
Limenavis is a prehistoric bird genus from the Late Cretaceous. It lived about 70 million years ago, around the Campanian-Maastrichtian boundary. Known from several broken bones, the remains of the only known species Limenavis patagonica were found in rocks of the "lower member" of the Allen Formation at Salitral Moreno, 20 km south of General Roca, Río Negro (Argentina).Of all the prehistoric birds known to date, this species is among those closest to the common ancestor of all living birds. Its generic name pays tribute to this fact: Limenavis, meaning "bird of the threshold" or "limit-bird", is derived from Latin limen ("threshold") + avis ("bird"). The specific name patagonica refers to the specimen's Patagonian provenance.Mooreville Chalk
The Mooreville Chalk is a geological formation in North America, within the U.S. states of Alabama and Mississippi, which were part of the subcontinent of Appalachia. The strata date back to the early Santonian to the early Campanian stage of the Late Cretaceous. The chalk was formed by pelagic sediments deposited along the eastern edge of the Mississippi embayment. It is a unit of the Selma Group and consists of the upper Arcola Limestone Member and an unnamed lower member. Dinosaur, mosasaur, and primitive bird remains are among the fossils that have been recovered from the Mooreville Chalk Formation.Odontornithes
Odontornithes is an obsolete and disused taxonomic term proposed by Othniel Charles Marsh for birds possessing teeth, notably the genera Hesperornis and Ichthyornis from the Cretaceous deposits of Kansas.In 1875 Marsh divided this "subclass" into Odontolcae, with the teeth standing in grooves, and Odontotormae, with the teeth in separate alveoles or sockets. In his 1880 work, Odontornithes: A monograph on the extinct toothed birds of North America, he added the Saururae, represented by Archaeopteryx, as a third order.The resulting classification was paraphyletic, not accurately resolving evolutionary relationships, and so it has been abandoned by most modern scientists, though at least one 21st century paper re-used the concept under the older name Odontoholomorphae (first coined by Stejneger, 1885).Étienne Geoffroy Saint-Hilaire stated in 1821 that he had found a considerable number of tooth buds in the upper and lower jaws of the Palaeornis torquatus (rose-ringed parakeet). Émile Blanchard felt justified in recognizing flakes of dentine. However, M. Braun and especially P. Fraisse showed later that the structures in question are of the same kind as the well-known serrated "teeth" of the bill of anserine birds. In fact the papillae observed in the embryonic birds are the soft cutaneous extensions into the surrounding horny sheath of the bill, comparable to the well-known nutritive papillae in a horse's hoof. They are easily exposed in the well-macerated under jaw of a parrot, after removal of the horny sheath. Occasionally calcification occurs in or around these papillae, as it does regularly in the egg tooth of the embryos of all birds.The best known of the "Odontornithes" are Hesperornis regalis, standing about 3 ft. high, the somewhat taller H. crassipes, and Ichthyornis dispar. Hesperornis looked somewhat similar to a loon, while Ichthyornis was quite similar to a gull or petrel. However, they were entirely distinct groups of birds and merely shared with modern birds some distant ancestry in the Early Cretaceous. The Hesperornis lineage may have derived even sooner or possibly independently from the ancestors of modern birds.Ornithurae
Ornithurae (meaning "bird tails" in Greek) is a natural group which includes the common ancestor of Ichthyornis, Hesperornis, and all modern birds as well as all other descendants of that common ancestor.Paleornithology
Paleornithology also known as Avian Paleontology is the scientific study of bird evolution and fossil birds. It is a mix of ornithology and paleontology. Paleornithology began with the discovery of Archaeopteryx. The reptilian relationship of birds and their ancestors, the theropod dinosaurs, are important aspects of paleornithological research. Other areas of interest to paleornithologists are the early sea-birds Ichthyornis, Hesperornis, and others. Notable paleornithologists are Storrs L. Olson, Alexander Wetmore, Alan Feduccia, Cécile Mourer-Chauviré, Philip Ashmole, Pierce Brodkorb, Trevor H. Worthy, Zhou Zhonghe, Yevgeny Kurochkin, Bradley C. Livezey, Gareth J. Dyke, Luis M. Chiappe, Gerald Mayr and David Steadman.Pangalliformes
Pangalliformes is the scientific name of a provisional clade of birds within the group Galloanserae. It is defined as all birds more closely related to chickens than to ducks, and includes all modern chickens, turkeys, pheasants, and megapodes, as well as extinct species that do not fall within the crown group Galliformes.
A few fragmentary fossils have been described as pangalliforms from the Late Cretaceous (85 million years ago), most notably those of Austinornis lentus. Formerly referred to as Ichthyornis lentus, Graculavus lentus, or Pedioecetes lentus, its partial left tarsometatarsus was found in the Late Cretaceous Austin Chalk near Fort McKinney, Texas. This bird was quite certainly closely related to Galliformes, but whether it was a part of these or belongs elsewhere in the little-known galliform branch of Galloanserae is not clear. In 2004, Clarke classified it within Pangalliformes rather than true Galliformes, pending further fossil finds. Another specimen, PVPH 237, from the Late Cretaceous Portezuelo Formation (Turonian-Coniacian, about 90 Ma) in the Sierra de Portezuelo (Argentina) has also been suggested to be an early relative of true galliformes. This is a partial coracoid of a neornithine bird, which in its general shape and particularly the wide and deep attachment for the muscle joining the coracoid and the humerus bone resembles the more basal lineages of galliforms.Additional galliform-like pangalliformes are represented by extinct families from the Paleogene, namely the Gallinuloididae, Paraortygidae and Quercymegapodiidae. In the early Cenozoic, some additional birds may or may not be early Galliformes, though even if they are, it is rather unlikely that these belong to extant families:
†Argillipes (London Clay Early Eocene of England)
†Coturnipes (Early Eocene of England, and Virginia, USA?)
†Paleophasianus (Willwood Early Eocene of Bighorn County, USA)
†Percolinus (London Clay Early Eocene of England)
†"Palaeorallus" alienus (middle Oligocene of Tatal-Gol, Mongolia)
†Anisolornis (Santa Cruz Middle Miocene of Karaihen, Argentina)More recently, it has been discovered that Sylviornis and its sister taxa, Megavitiornis, lay outside the Galliformes crown group. This same study also presents Dromornithidae as possibly closer to Galliformes than to Anseriformes as traditionally expected, though it acknowledges more work to be needed in this field.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 93.9 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded by the Cenomanian stage and underlies the Coniacian stage.At the beginning of the Turonian an anoxic event took place which is called the Cenomanian-Turonian boundary event or the "Bonarelli Event".