How are corals related to cnidarians?

Corals are classified as invertebrate marine animals belonging to the phylum Cnidaria. Specifically, they are members of the class Anthozoa, which is one of the four major groups within the cnidarian phylum.12

Corals share the defining characteristics of all cnidarians, most notably the possession of nematocysts—specialized stinging structures used to paralyze prey—and a simple body organization centered around a gastrovascular cavity known as the coelenteron. Like other cnidarians, the basic body unit of a coral is the polyp, a hollow, cylindrical structure with a mouth surrounded by tentacles.12

While many cnidarians are soft-bodied, corals are distinguished by their ability to secrete skeletons of varying consistency, including stonelike, horny, or leathery materials. These skeletons may be internal or external, providing the structural framework for coral reefs and atolls. Through these shared biological traits and evolutionary origins, corals represent a specialized group within the broader, diverse phylum of cnidarians.231