Members of the Echinodermata phylum include which of the following?

Echinodermata is a unique phylum known for its marine organisms that exhibit radial symmetry, a calcareous endoskeleton, and a water vascular system. Sea urchins are a prime example of this phylum, characterized by their spiny exterior and ability to move using tube feet, which are part of the water vascular system. They are part of a larger group that also includes starfish, sea cucumbers, and sand dollars, all of which share the key features that define Echinodermata.

In contrast, flatworms belong to the phylum Platyhelminthes, jellyfish are part of the phylum Cnidaria, and snails belong to the phylum Mollusca. Each of these groups has distinct anatomical and biological characteristics that differentiate them from echinoderms. For instance, flatworms lack a coelom (body cavity), jellyfish possess a simple body structure without a centralized brain, and snails have a soft body often protected by a hard shell, which are all characteristics that set them apart from members of Echinodermata.