How are Birds Related to Reptiles?
Every living thing has a history and fits into a long line of relatives and ancestors. When it comes to birds, even though they look quite different than reptiles, they’re actually descended from prehistoric reptiles.
All birds and reptiles, along with mammals, amphibians, and fish, make up the class of animals known as tetrapods, which means “four limbs”. Tetrapods are the descendents of a large group of animals that emerged during the Devonian period, roughly 370 to 395 million years ago. Birds and reptiles share a common ancestor within these ancient vertebrates, so both birds and reptiles have a shared heritage that goes back many millions of years.
Birds and reptiles have three common physical characteristics that are a result of similar evolutionary development:
- Bones: Both birds and reptiles have hollow bones that are lightweight and enable both groups of animals to fly and move quickly.
- Scales: Birds and reptiles both have scales that are used for protection against predators and the environment.
- Fetal Development: Both birds and reptiles lay eggs, and while they differ in many ways, they both start out as a single cell that grows into a fetus.
Despite their many shared similarities, there are several characteristics that help to differentiate birds from reptiles.
- Wings: The main difference between birds and reptiles is that birds have wings and reptiles do not.
- Feathers: All birds have feathers, while reptiles do not. In addition, birds use their feathers to regulate their body temperature and stay warm, while reptiles rely entirely on the environment to keep their body temperature in an acceptable range.
- Lungs: While both birds and reptiles have lungs, birds use a system of air sacs to move oxygen around their bodies, while reptiles rely on their internal structures to distribute the oxygen.
Despite their quite different exterior appearances, birds and reptiles share a common ancestor from the ancient Devonian period. A number of physical characteristics that link the two, including hollow bones, scales, and egg-laying, are a result of similar evolutionary development. The main distinguishing feature between birds and reptiles is their wings and feathers; birds have both, while reptiles have neither.