In other words, birds retain their original embryonic brain and skull configuration into adulthood.ĭr Abzhanov said: “The skulls and brains of birds are dramatically different from those of adult non-avian dinosaurs and other reptiles, and we can show that these differences reflect how birds evolved to become species of forever-young dinosaurs. The team discovered that in birds, this change in the brain-skull relation never occurs, and the roof of the skull continues to match brain shape throughout development. Later in development cranial muscles and other tissues also begin to affect skull shape. However, in the later stages of development in dinosaurs, crocodilians and other reptiles, the skull bones no longer mirror the brain growth as closely. Skull bones and brain shape of a chicken (top) and an American alligator (bottom)Īs the brain grows in an early embryo, the skull closely matches the shape of the brain – the new study shows that the boundary between the frontals and parietals perfectly matches the boundary between the forebrain and midbrain across most vertebrate groups. For example, the frontal bones cover the forebrain while parietal bones cover the midbrain. The skulls of vertebrate animals (those with backbones) are formed as a series of larger bones that correspond to particular regions of the brain. They studied how the two structures change relative to each other during embryonic development, in both modern birds and their reptile relatives. To better understand the origins of birds’ unique skulls during their evolution from more primitive reptiles, Dr Abzhanov and colleagues from Yale University have now analysed the relationship between brain and skull. It is known to play an important role in the evolution of some new species, as the ‘young’ creatures can adopt a different lifestyle compared to their more ‘mature’-looking relatives, avoiding competition for the same resources. ![]() Paedomorphism is caused by a change in timing of developmental events of an organism – for example growing certain body parts at later stages, slower, or not at all. ![]() This evolutionary phenomenon is known as ‘paedomorphism’ – where an adult retains features that are usually only seen at the young stages (embryo or baby) in its ancestors. Previously, Dr Arkhat Abzhanov, from the Department of Life Sciences at Imperial, and colleagues determined that the shape of the birds’ skulls most resemble those of young non-avian (non-birdlike) dinosaurs. However, birds have unique skeletons, particularly their beaked skulls, which have wider dome-shaped cranial bones to accommodate proportionally larger brains and eyes. Studying birds is a fascinating subject because they retain features of ‘young’ dinosaur ancestors, while also clearly adding their own adaptations, such as toothless beaks and wings.īirds are the only surviving members of a group of feathered dinosaurs, and are close cousins to modern crocodilians (alligators, crocodiles and gavials).
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