The Chambered Nautilus is one of the oldest animals on earth; it has inhabited the planet for over 500 million years. Unlike most of its contemporaries that florished during the Cambrian period (the first to harbor complex, multi-cellular life and large-scale predator-prey ecosystems), the Nautilus has adapted and thrived in spite of dramatic changes to the biosphere and ocean conditions.
Those early ancestral forms, called ammonites, evolved a coiled shell; as an ammonite grew it expanded its shell, closing off the smaller out-grown chamber, which because it was sealed was bouyant – and so the animal could, through controlling the amount of water in the sealed chambers, rise and sink at will. More remarkably, the nautilus has the ability to propel itself through its fluid home by expelling water efficiently through its mouth, in much the same way that a jet engine functions using air as the propellant. And the combination of these two traits gave it great mobility – with a little effort and a built-in bouyancy compensator, it could range over a large volume of ocean. Unlike most of its competetors, it could go where the conditions were advantageous.
So the Nautilus carries its past with it, but the past is sealed off; not a hinderance, but an aid to the present…