An article published in the journal “Nature” describes a research on the skull structure of Ichthyornis dispar, an ancient bird that lived almost 100 million years ago in North America. A team of researchers led by Yale University examined a complete skull and two pieces that were part of the first specimen of this species discovered in 1870 thanks to new technologies concluding that its characteristics represent a crucial moment in the evolution from dinosaurs to modern birds.
The first specimen of Ichthyornis dispar was discovered in Kansas in 1870 by the fossil hunter Othniel Charles Marsh. It was comparable to seagulls for its size and because it was a seabird but it lived during the Cretaceous period, when dinosaurs were still the dominant animal group. Birds were still differentiating from their “cousins” and the discovery of this species raised the interest of famous scientists of the time, including Charles Darwin.
After the first specimen, cataloged as YPM 1450, others were discovered but all incomplete. Some of the many differences between the dinosaur and bird skulls were visible but it was impossible to assess accurately at what point of the transition between the first and second group was Ichthyornis dispar’s anatomy. The situation changed in 2014 thanks to a new discovery.
Again in Kansas, in the Niobrara Formation, also known as Niobrara Chalk, a new specimen of Ichthyornis dispar was found by Kristopher Super, one of the authors of the article. The skeleton was relatively complete, especially its skull, a discovery that quickly led to the involvement of various paleontologists. Most of the specimens of this species are part of the collection of the Peabody Museum of Natural History at University of Yale, which became the center of the new research on these birds, the first after almost a century and a half.
For this new analysis, the researchers could use modern technologies, in particular a high resolution CT scan to create an almost complete 3D reproduction of Ichthyornis dispar’s skull. To obtain this result, the skull of the first specimen discovered, YPM 1450, was also used, and during the operations two pieces of the skull that were overlooked were discovered. Other specimens were provided by the Peabody Museum of Natural History and other institutions that own them.
The reconstruction of Ichthyornis dispar’s skull shows the transition from dinosaur to modern bird with mixed characteristics and above all the oldest known beak, which was equipped with teeth. Its brain already shows modern bird characteristics while its jaws and their muscular structure were still similar to those of dinosaurs.
The actual beak was the final part of Ichthyornis dispar’s jaws. According to the researchers, this bird used it as a kind of pincer and was originally used to grasp accurately. This mechanism was a hand surrogate at a time when hands were evolving into wings.
In essence, these are important discoveries in the reconstruction of the evolution of birds and was aided by new studies on fossils found almost a century and a half ago. Once again, new technologies allowed to obtain new information from fossils that were neglected for a long time because it seemed that it was no longer possible to learn anything from them.
