Researchers recently discovered the skull of ichthyornis, the ancestor of modern birds. His study led to a new hypothesis about how birds managed to survive the mass extinction, unlike dinosaurs.

At the turn of the Cretaceous and Paleogene periods, all representatives of the dinosaur group disappeared from the face of the Earth, but not birds. So how did they do it? Previously, scientists believed that the determining factor that contributed to the survival of birds was their small size. However, the new study authors suggest that the evolution of the bird’s brain played a crucial role—namely, its increase in size and the development of the visual system. The results of the study are published in the journal Science Advances.

Scientists analyzed a recently found 70-million-year-old ichthyornis skull. This toothed seabird most closely resembled modern gulls and petrels. She lived in North America just before the mass extinction of the dinosaurs that occurred 66 million years ago.

A new study found that the ancestors of modern birds had brains that were very different in shape from other dinosaurs, including early birds. The location of the individual’s visual lobes strongly suggests that the brain of the extinct genus of seabirds resembled that of Archeopteryx. As you know, this is a feathered dinosaur that looks like a bird.

Researchers analyzed the details of the structure of the skull of more than 2 thousand modern and extinct birds and found that, compared to early individuals such as Archeoptecryx, ichthyornis had an enlarged brain with a displacement of the ventral-visual lobes. It was these features that were inherited by modern birds, from which they developed even more.

The authors suggest that shortly before the Cretaceous-Paleogene extinction, the bird’s brain took its current form, and the functions of the visual system also expanded. According to scientists, this was the decisive advantage that allowed the birds to outlive the rest of the dinosaur group.