Echinodermata is the exclusive marine phylum.

Echinodermata is a phylum of marine animals that includes familiar organisms such as starfish, sea urchins, sea cucumbers, and brittle stars. These animals are exclusively marine, meaning they are found only in the ocean. They exhibit a unique body plan and have a diverse range of characteristics.

Key characteristics of Echinodermata:

1. Radial symmetry: Echinoderms have a body plan characterized by radial symmetry, which means their body parts are arranged around a central axis. This allows them to move and feed in all directions.

2. Water vascular system: Echinoderms have a unique hydraulic system called the water vascular system. This system consists of a network of canals and tube feet that are used for locomotion, feeding, and respiration. The tube feet are filled with fluid and can be extended or retracted to grip surfaces or move.

3. Endoskeleton: Echinoderms have an internal skeleton made of calcareous plates or ossicles, which gives them structural support. These plates are often covered by a thin layer of skin or spines.

4. External gills or dermal branchiae: Some echinoderms have external gills or dermal branchiae, which are used for respiration. These structures allow them to extract oxygen directly from the water.

5. Regeneration: Echinoderms have a remarkable ability to regenerate lost or damaged body parts. This means that if a predator attacks them or they lose a limb, they can regrow the missing part.

6. Unique feeding strategies: Echinoderms have various feeding strategies. Some are filter feeders, using their tube feet or specialized appendages to capture small organisms from the water. Others are scavengers or predators, capturing prey with their tube feet or specialized feeding structures.

Overall, Echinodermata is an exclusive marine phylum characterized by radial symmetry, a water vascular system, an endoskeleton, and unique feeding strategies. Its members play important roles in marine ecosystems and exhibit fascinating adaptations to their environment.