Ichthyornis is a bird from the Late Cretaceous of the United States of America and Mexico. It was named in 1872 by Othniel Charles Marsh. It is one of the most important fossil discoveries, as it has allowed some insight into the evolution of birds; as well as this, it is one of the more taxonomically derived Mesozoic birds known from more than a few specimens.
Physiology[]
Ichthyornis likely resembled a tern with teeth. It had a small, sleek body, moderately long legs, a short, feathery tail, long wings, and a small head with a long, toothy beak. Most of its body (excluding its beak and legs) would have been covered in long, vaned feathers.
Diet[]
Ichthyornis was a predator, preying on small fish and cephalopods. Its teeth had knife-like serrations from back to back, and were used to cut prey into smaller chunks.
Ecology[]
Despite having teeth on its jaws, Ichthyornis's head was very similar to modern birds; its upper beak could rotate upwards as its mouth opened, allowing it to grab prey and preen itself. This shows that the avian feeding apparatus evolved earlier than expected, and predated the full transition into toothlessness. [1]Similarly to Hesperornis, another relatively derived, toothy marine bird from the Late Cretaceous, Ichthyornis exhibited continual tooth replacement that involved growing new teeth under its old ones (similarly to crocodilians); however, Hesperornis' teeth had small ridges from back to back and had firmer root attachment, meaning that it likely used its teeth to grab onto slippery prey before swallowing them whole, while Ichthyornis had sharp, knife-like serrations running down its teeth for cutting its prey into smaller, more digestible chunks of flesh before eating them.[2] Ichthyornis' brain had more in common with that of non-avian dinosaurs such as Velociraptor rather than that of modern birds, with a smaller cerebellum than that of a modern bird brain; it is hypothesized that a bigger cerebellum put the ancestor of modern birds at an advantage over more basal birds such as Ichthyornis, thus allowing the former to survive the extinction while the latter was not able to.[3]
References[]
- Field, D. J., Hanson, M., Burnham, D., Wilson, L. E., Super, K., Ehret, D., Ebersole, J. A., & Bhullar, B.-A. S. (2018). Assembly of the Avian Head. Nature Letters, 557.
- Dumont, M., Tafforeau, P., Bertin, T., Bhullar, B. A., Field, D., Schulp, A., Strilisky, B., Thivichon-Prince, B., Viriot, L., & Louchart, A. (2016). Synchrotron imaging of dentition provides insights into the biology of Hesperornis and Ichthyornis, the “last” toothed birds. BMC Evolutionary Biology, 16(1), 1–28. https://doi.org/10.1186/s12862-016-0753-6
- Torres, C. R., Norell, M. A., & Clarke, J. A. (2021). Bird neurocranial and body mass evolution across the end-Cretaceous mass extinction: The avian brain shape left other dinosaurs behind. Science Advances, 7(31), 1–10. https://doi.org/10.1126/sciadv.abg7099