A team of scientists constructs the three-dimensional skull of the Ichthyornis dispar, the bird that holds a clue to the evolution of dinosaurs to birds with beaks.
The researchers said their findings could trace how the skulls of modern-day birds evolved from their reptilian predecessor until they finally developed their beaks.
The three-dimensional piece showed that the Ichthyornis dispar has a brain similar to birds of today but still has a jaw with muscle configuration to that of the dinosaurs. This suggests that the brain evolved first while the skull remained more primitive, like the dinosaurs during that period when they are still transitioning to their avian descendants.
The First Beak
The most striking takeaway from the three-dimensional construction is that it shows how the very first bird beak looked when it finally developed, explains Bhart-Anjan Bhullar, principal investigator of the study and a paleontologist from Yale University.
"The first beak was a horn-covered pincer tip at the end of the jaw," Bhullar said. The study was published in the journal Nature.
The rest of the jaw was filled with teeth. In the beginning, the birds used their beaks as a precision grasping mechanism, as the hands continue to evolve into wings, explains Bhullar.
Ichthyornis dispar would have looked similar with seabirds, a gull or tern, if the bird species continue to exist today. As for their teeth, they probably would be hidden by a liplike structure or extra-oral tissue inside of their mouths, explains Michael Hanson from Yale and co-lead author of the study.
There have been modern-day studies that aimed to distinguish the birds' participation in the evolutionary history of dinosaurs. However, these studies had only made use of fragmentary remains found in the 1870s.
The current study is the first to conduct their analysis of the Ichthyornis dispar using CT-scan technology and several other specimens from major museums in the United States. Their model included one example of a complete skull and two cranial elements of the original specimen, which has been in the possession of the Yale University all this time.
With all these specimens as their materials, the reconstructed fossil became the only direct evidence of how modern-day birds undergo evolutionary transformations, explains Daniel Field from the Milner Center for Evolution at the University of Bath, also co-lead author of the study.
The Ichthyornis dispar lived for about 100 million years ago in North America. The bird species had already obtained the interest of Othniel Charles Marsh and Charles Darwin. Marsh was a paleontologist and one of the preeminent scientists who started theories on the origins of birds.