Merostomata vs arthropod

Merostomata and arthropod both are nouns.

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

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

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

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