Pteropus hypomelanus vs megabat

Pteropus hypomelanus and megabat both are nouns.

Word	Noun	Adjective	Verb	Adverb
Pteropus hypomelanus	Yes	No	No	No
megabat	Yes	No	No	No

As nouns, megabat is a hypernym of Pteropus hypomelanus; that is, megabat is a word with a broader meaning than Pteropus hypomelanus:

Pteropus hypomelanus: a variety of fruit bat, known as the small flying fox, island flying fox or variable flying fox (Pteropus hypomelanus)
megabat: large Old World bat of warm and tropical regions that feeds on fruit

Other hypernyms of Pteropus hypomelanus include fruit bat.

Pteropus hypomelanus (noun)	megabat (noun)
a variety of fruit bat, known as the small flying fox, island flying fox or variable flying fox (Pteropus hypomelanus)	large Old World bat of warm and tropical regions that feeds on fruit