A Rare Extra Eye
Some animals have an unusual feature—a third eye. Unlike their primary eyes, this extra eye is often small and located on top of the head. It is scientifically called the parietal eye and is found in certain reptiles, amphibians, and fish.
Reptiles with Hidden Vision
Many lizards, such as iguanas and tuataras, have a third eye. The tuatara, a reptile from New Zealand, has one of the most developed parietal eyes. This eye can detect light and dark, helping it regulate its body functions.
Sensing Light in Unexpected Places
Some frogs, fish, and sharks also have a parietal eye. The spotted salamander uses it to sense seasonal changes, while lampreys, jawless fish, rely on theirs to respond to light even in deep water.
A Window to Evolution
Though it does not function like normal eyes, the parietal eye connects directly to the brain. Over millions of years, it has disappeared in most animals, but those that retain it still use it to sense the environment in unique ways.
Some animals have an unusual feature—a third eye. Unlike their primary eyes, this extra eye is often small and located on top of the head. It is scientifically called the parietal eye and is found in certain reptiles, amphibians, and fish. 🧵👇 pic.twitter.com/l6tmK9PExr
— Detective Tiger's Stories (@TigerDetective) February 16, 2025