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 th
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 th
Ichthyornis