I believe Echinoderms evolved first.
Cnidarians are true radially symmetrical animals. They include jellyfish. Echinoderms (like starfish) also display radial symmetry. It is important to note that the larvae of echinoderms are bilaterally symmetrical and that Echinoderms evolved from a bilaterally symmetrical group.
Sponges, Cnidarians, Mollusks, and Echinoderms are not Arthropods.
Cnidarians and echinoderms
Seahorses are a type of pipefish.
fish, mollusks, worms, crustaceans, echinoderms, sponges, tunicates and other cnidarians
Echinoderms can only be found in water, as they are aquatic. Some characteristics of Echinoderms are: Hard Skin, have arms or spines, have 5 body parts, organs found towards centre of body. Examples: Star Fish, Sea Cucumber, Sea Urchin
Echinoderms (ex: starfish), cnidarians (ex: jellyfish) and and some vermiforms have longitudinal radial symmetry.
By swimming using tentacles
No, cnidarians are not protists. Cnidarians are a diverse group of animals that include jellyfish, corals, and sea anemones. Protists are a separate group of eukaryotic organisms that are not classified as animals.
In total there are 8 groups of invertebrates:-Insects-Arachnids-Crustaceans-Millipedes-Worms-Molluscs with shells-Molluscs without shellsThe groups of Invertibrates are Coelenterates, Echinoderms, Mollusks, Arthropods, Annelids, Plathelminths, Poriferas and Nematodes.
Cnidarians