Also known as 'moss animals', bryozoan colonies are composed of many tiny interconnected individuals called zooids. Each zooid is encased in a skeleton that is often made of calcium carbonate, chitin, or another rigid material. Colonies can be encrusting — forming a flat sheet on rock, seaweed, or other substrates — or they may layer and grow upright, sometimes forming elaborately branched structures. There is often symmetry and patterns in the way they grow, and the forms they take can look deceptively like hydroids, sponges, seaweeds, or other marine organisms. Click here for more information on byrozoans.