Fossil Information Sheet F011
Nautilus
There are many Nautilus preserved as fossils and these are found in various areas especially Madasgascar.
The Nautilus shell like the Ammonite is divided into compartments: about four in newly hatched specimens and up to thirty or so in mature individuals.
The animal only occupies the outer-most living chamber.
As it grows its body moves forwards in the enlarged shell and produces a wall to seal off the older chambers, which, filled with gas compensates for the weight of the the animals tissues and shell keeping the Nautilus neutrally buoyant so that it neither sinks nor floats and can move freely in the water.
Nautilus swim in a see-saw motion generated by jet propulsion.
They alternately pull water into the cavity within the shell and blow out the muscular syphon beneath the tentacles.
By directing the jet the Nautilus can swim forwards, sideways or backwards.
CLICK HERE to see a short video of a Nautilus swimming
Living Nautilus are now found only in the waters of the tropical western Pacific.
They live in poorly known marine environment, namely the deep slopes of coral reefs.
They are capable of migrating from depths of 1500 ft. (450 metres) to within 300 ft. (90m) or less of the surface, a depth range seen in few other marine organisms, and can tolerate dramatic changes in both temperature and pressure.
Like many creatures that live in open water or venture above the reef they show a form of camouflage called countershading.
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