There is a fascinating example in science of an “eternal” living animal: the Turritopsis nutricula.
It is a tiny jellyfish-like creature that reverts to a juvenile after maturing to older life stages (an so on and so forth). It is a cell development process called transdifferentiation (say that ten times fast).
It tops any list of animal lifespans (which can be 100-400 years, depending on the animal/creature) as simply “never-ending.”
You learn something new every day! I love this beautiful amazing world.
Check out the entire wikipedia article here.