Most scientists believe that birds evolved from small therapod dinosaurs. The key step was the development of feathers, turning animals that could walk or climb into animals that could fly. In today’s post, Dr. Bakker discusses the evolution of a key feature of Archaeopteryx, the first dinosaur to be discovered with preserved feathers.
Lizard Paws to Chicken Fingers
320 million years ago – the first reptiles evolve, the earliest vertebrates that can lay air-breathing eggs on land. Legs are sprawling and flat-footed. The front paws have five fingers, all with claws.
250 million years ago – the first archosaurs evolve, the close kin of crocodiles and birds. Legs are more upright but still flat-footed. The hands have only three claws. The outer two fingers are thin and claw-less.
225 million years ago – the first dinosaurs evolve. Legs are upright and the heel held high, off the ground. The outer two fingers are weak.
160 million years ago – the earliest raptor-like dinosaurs evolve. The outer fingers are gone. Hind-legs are used for running and ankles are tall and thin. The three clawed fingers are long. And there’s a swivel joint on the wrist to let the hand move quickly side-to-side.
150 million years ago – Archaeopteryx evolves. Hind legs are like those of raptor-type dinosaurs. The hand is almost exactly like a raptor-dinosaur’s.
110 million years ago – the first modern-style birds evolve. Hind-legs have stiff ankle bones, all fused together. The wrist bones too are all fused together and no fingers have claws.
Interested in learning more about paleontology? Check out our past blogs.