what are the 5 main features of cnidarians
Cells bound by inter-cell connections and carpet-like basement membranes; muscles; nervous systems; and some have sensory organs.
Cnidaria
 Both cnidarians and ctenophores are more complex than sponges as they have: cells bound by inter-cell connections and carpet-like basement membranes; muscles; nervous systems; and some have sensory organs. 
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Cnidaria [SEP] Distinguishing features
Cnidarians form a phylum of animal that are more complex than sponges, about as complex as ctenophores (comb jellies), and less complex than bilaterians, which include almost all other animals. Both cnidarians and ctenophores are more complex than sponges as they have: cells bound by inter-cell connections and carpet-like basement membranes; muscles; nervous systems; and some have sensory organs. Cnidarians are distinguished from all other animals by having cnidocytes that fire harpoon like structures and are usually used mainly to capture prey. In some species, cnidocytes can also be used as anchors. Cnidarians are also distinguished by the fact that they have only one opening in their body for ingestion and excretion i.e.