class Merostomata vs arthropod

class Merostomata and arthropod both are nouns.

Word	Noun	Adjective	Verb	Adverb
class Merostomata	Yes	No	No	No
arthropod	Yes	No	No	No

As nouns, arthropod is a hypernym of class Merostomata; that is, arthropod is a word with a broader meaning than class Merostomata:

class Merostomata: used in some classifications; includes the orders Xiphosura and Eurypterida
arthropod: invertebrate having jointed limbs and a segmented body with an exoskeleton made of chitin

class Merostomata (noun)	arthropod (noun)
used in some classifications; includes the orders Xiphosura and Eurypterida	invertebrate having jointed limbs and a segmented body with an exoskeleton made of chitin