mantis crab vs mantis shrimp

mantis crab and mantis shrimp both are nouns.

Word	Noun	Adjective	Verb	Adverb
mantis crab	Yes	No	No	No
mantis shrimp	Yes	No	No	No

As nouns, mantis crab and mantis shrimp are synonyms defined as:

mantis crab and mantis shrimp: tropical marine burrowing crustaceans with large grasping appendages

mantis crab (noun)	mantis shrimp (noun)
tropical marine burrowing crustaceans with large grasping appendages	tropical marine burrowing crustaceans with large grasping appendages