What main body parts does feather stars have?

- Central disc: This is the body of the feather star, and it contains the digestive system, reproductive organs, and other internal organs.

- Arms: Feather stars have multiple arms that are used for feeding and locomotion. The arms are covered in small, hair-like structures called cirri, which help the feather star to grip surfaces.

- Pinnules: These are small, branching appendages that are located on the arms of the feather star. The pinnules are covered in cilia, which help the feather star to filter food from the water.

- Madreporite: This is a small, sieve-like structure that is located on the upper side of the central disc. The madreporite is used to filter water into the water vascular system, which is a network of canals that circulates water throughout the feather star's body.

- Calcareous ossicles: These are small, calcium-carbonate plates that form the skeleton of the feather star. The calcareous ossicles are connected by muscles and ligaments, which allow the feather star to move its arms and body.