methanogen vs archaebacteria

methanogen and archaebacteria both are nouns.

Word	Noun	Adjective	Verb	Adverb
methanogen	Yes	No	No	No
archaebacteria	Yes	No	No	No

As nouns, archaebacteria is a hypernym of methanogen; that is, archaebacteria is a word with a broader meaning than methanogen:

methanogen: archaebacteria found in anaerobic environments such as animal intestinal tracts or sediments or sewage and capable of producing methane; a source of natural gas
archaebacteria: considered ancient life forms that evolved separately from bacteria and blue-green algae

Other hypernyms of methanogen include archaebacterium, archaeobacteria, archeobacteria.

methanogen (noun)	archaebacteria (noun)
archaebacteria found in anaerobic environments such as animal intestinal tracts or sediments or sewage and capable of producing methane; a source of natural gas	considered ancient life forms that evolved separately from bacteria and blue-green algae