👉 Echinoids are a group of marine animals that belong to the family Echidnae. They have a flattened body with a narrow, concave shell, and they have a segmented body and a long, flexible tentacle that is attached to their posterior part. Echinoids are known for their ability to scuba dive deep into the ocean's depths, and they are also thought to be able to communicate with other echinoids using ultrasonic waves.
echinoid