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The Hermit Crab belongs to the Crustacean family...
It is also known as a "fake crab" because of it's shell. True Crabs got there name because they have flat broad shells.
They change shells often so...
Crabs are crustaceans, but animals can be classified into multiple categories. Crabs also fall in the category of delicious animals, treyf animals, and animals that will pinch you if you annoy them.
Using "types" as plural requires the plural "animals". You can also phrase this as singular, with a different context, for example " What type of animal...? What type of an animal...?