Zoanthids (order Zoantharia also called Zoanthidea or Zoanthiniaria) are an order of cnidarians commonly found on coral reefs.
They come in a variety of different colonizing formations and in numerous colors.
The term “zoanthid” refers to all animals within this Zoantharia order, and should not be confused with “Zoanthus”, which is a genus within Zoantharia.
Zoanthus have soft bodies covered with a leathery skin, called a cuticle, that gives them protection. Its polyps have fairly short stems surmounted by a small flat oral disc. Delicate tentacles radiate from the outside of the oral disc and generally expand day and night. The oral disc has a mouth, or syphonoglyph, in the center that leads into the stomach cavity. This cavity has vibrant cilia that help exchange water and feed.
Polyps of the genus Zoanthus are usually not larger than 1/2 “(1.25 cm) at the top. The polyps can connect to each other and grow primarily as mats.