primate vs prosimian

primate and prosimian both are nouns.

Word	Noun	Adjective	Verb	Adverb
primate	Yes	No	No	No
prosimian	Yes	No	No	No

As nouns, prosimian is a hyponym of primate; that is, prosimian is a word with a more specific, narrower meaning than primate:

primate: any placental mammal of the order Primates; has good eyesight and flexible hands and feet
prosimian: primitive primates having large ears and eyes and characterized by nocturnal habits

Other hyponyms of primate include simian, ape, anthropoid, hominoid, hominid, monkey, lemur, tarsier.

primate (noun)	prosimian (noun)
any placental mammal of the order Primates; has good eyesight and flexible hands and feet	primitive primates having large ears and eyes and characterized by nocturnal habits
a senior clergyman and dignitary