cenarchaeum cenarchaeum in taxonomy, cenarchaeum is a genus of the cenarchaeaceae. the marine archaean cenarchaeum symbiosum lives within (it is an endosymbiont of) the sponge axinella mexicana. axinella polypoides in aquarium cinéaqua map: 48° 51' 44" n 2° 17' 27" e cenarchaeum scientific classification domain: archaea phylum: thermoproteota class: incertae sedis order: cenarchaeales family: cenarchaeaceae genus: "cenarchaeum"delong and preston 1996 type species "cenarchaeum symbiosum"delong and preston 1996 species "c. symbiosum"