Mental gland

A mental gland is a part of the body of amphibians and reptiles. Mental glands make chemicals that animals use to talk to each other.
Place.
There are two mental glands, one on each side of the head. They are behind the jawbone.
Function.
Mental glands make chemicals that come out through the skin. These chemicals help the animal tell when another animal is the same or a different species from them. These chemicals also helps them choose mates.
Scientists have seen turtles bob their heads up and down when they see another turtle. Scientists believe bobbing the head up and down helps the chemicals from the mental glands go through the air to the other turtle. Scientists have seen salamanders move when they see another salamander. For example, they snap their jaws. Only salamanders that have mental glands do this, so scientists believe they also spread the chemicals through the air.
Origins and evolution.
Not all reptiles and amphibians have mental glands. Some species in the same family have mental glands and others do not.
In 2021, one team of scientists found that most turtles that have mental glands live in the water. They wanted to know if different turtles got mental glands separately or if one ancestor turtle got mental glands. They found that mental glands happened just once in turtles, in the ancestor of the family Testudinoidea. Then some of the species that came from this ancestor kept their glands and some lost them. They believe that all turtles that have mental glands develop them from the same tissue.