<P> Nautiluses are found in only the Indo - Pacific, from 30 ° N to 30 ° S latitude and 90 ° E to 175 ° E longitude . They inhabit the deep slopes of coral reefs . </P> <P> Nautiluses usually inhabit depths of several hundred metres . It has long been believed that nautiluses rise at night to feed, mate and lay eggs, but it appears that, in at least some populations, the vertical movement patterns of these animals are far more complex . The greatest depth at which a nautilus has been sighted is 703 m (2,306 ft) (N. pompilius). Implosion depth for nautilus shells is thought to be around 800 m (2,600 ft). Only in New Caledonia, the Loyalty Islands, and Vanuatu can nautiluses be observed in very shallow water, at depths of as little as 5 m (15 ft). This is due to the cooler surface waters found in these southern hemisphere habitats as compared to the many equatorial habitats of other nautilus populations--these usually being restricted to depths greater than 100 m (300 ft). Nautiluses generally avoid water temperatures above 25 ° C (75 ° F). </P> <P> Nautiluses are scavengers and opportunistic predators . They eat molts of lobsters, hermit crabs, and carrion of any kind . </P> <P> Fossil records indicate that nautiloids have not evolved much during the last 500 million years . Many were initially straight - shelled, as in the extinct genus Lituites . They developed in the Late Cambrian period and became a significant group of sea predators during the Ordovician period . Certain species reached over 2.5 m (8 ft) in size . The other cephalopod subclass, Coleoidea, diverged from the nautiloids long ago and the nautilus has remained relatively unchanged since . Nautiloids were much more extensive and varied 200 million years ago . Extinct relatives of the nautilus include ammonites, such as the baculites and goniatites . </P>

At the beginning of the chambered nautilus the shell