•Korarchaeumcryptofilum, whose name means “the cryptic filament of youth”, is the only characterized species in this phylum.
•K. Cryptofilumis an obligate anaerobe growing at 85oC.
•Cells are long, thin (less than 0.2 μm diameter) filaments of variable length (10 –100 μm).
•Filaments contain tough paracrystallinelayer which maintains cell integrity in its extremely hot habitat.