Interclavicle

An interclavicle is a special bone found in many four-legged animals, including amphibians, reptiles, and some birds. It sits between two other bones called clavicles, which help support the front part of the body. Most mammals, like marsupials and placentals, do not have an interclavicle. Instead, they have a bone called the sternum that does a similar job. The sternum grows from cartilage, while the interclavicle grows from skin tissue.

Scientists have found the interclavicle in many four-legged animals, but it is very rare in fish. When it does appear in fish, it is usually quite small. This bone helps scientists understand how different animals are related and how their bodies have changed over time.