process. A study on an Ichthyornis endocast reveals that it had a relatively basal brain compared to modern birds, similar to that of Archaeopteryx and other non-avian theropods. Conversely, it had a palate remarkably convergent with that of modern neognaths. Timespan and evolution 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). Specimens of Ichthyornis from earlier eras were, on average, smaller than later ones. The holotype specimen of Ichthyornis dispar, YPM 1450, had a humerus about long. In many geologically younger specimens like YPM 1742, the same wing bone was 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. History of study 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