HOW DINOSAURS BECAME BIRDS

Dinosaurs were prehistoric egg-laying reptiles that went extinct millions of years ago, but their survivors still live among us

- By AILSA HARVEY

Over 66 million years ago, unfamiliar animals dominated the Earth, some growing to impressive heights of over 30 metres. The dinosaurs were captivating creatures, in part due to their size, power and strength. When you observe a robin gracefully flittering about your garden, it seems unlikely that they could be related. Palaeontologists are gathering information about the dinosaurs with every new fossil retrieved from the ground, and as more species are discovered, it becomes more apparent how diverse the dinosaurs were. All modern birds descended from a group of theropod dinosaurs called the maniraptoran theropods. These animals were relatively small, ranging from pigeon-sized to ten metres tall. Crucially, dinosaurs evolved into modern birds before the Cretaceous-Paleogene mass extinction event that wiped out the dinosaurs 66 million years ago. The earliest modern birds lived alongside the dinosaurs, and it was this less significant group of animals that outlived their mighty relatives.

One of the key evolutionary stages to the survival of some dinosaurs was when they learned to fly. This happened around 150 million years ago in the Jurassic period. The two main theories of how dinosaurs took to the air are the ‘ground-up’ theory and the ‘trees-down’ theory. The ground-up theory states that fast, ground-dwelling theropod dinosaurs with feathered arms flapped their wings while running at high speeds in order to lift themselves up into the air. Alternatively, the trees-down theory is that tree-dwelling dinosaurs used their wings for gliding. While they couldn't remain airborne for long periods, they could return to the ground and soar through the trees.