A tardigrade

Well a facsimile. the most resilient beast on the planet. They have survived at least five extinction events. Toughest little creatures you will find, Freeze them to absolute zero, boil them to 150 degrees c, radiation 150 times that will be fatal to humans.....when we have fucked up the planet good and proper they will be all that is left. Party on you little tardigrade dudes.