Nautilus

All around the edges of West Ard- namurchan are rocks which were formed long before the area's great volcanoes became active. Some of these were laid down as muds and oozes in a warm, shallow sea during the Jurassic, the time when dinosaurs ruled the land. This sea teemed with life, and the hard remains of some of these creatures are still visible in the rocks that now form our indented coastline.

The fossil shown here is well worth some attention. The set of house keys to its left gives a sense of scale, but the shell, when complete, was considerably bigger, over 50cm (20") across. Its a nautilus, an animal related to the cuttlefish and squids, but a particularly interesting fossil as it's a rare example of a group which, instead of evolving like most, has hardly changed in design over hundreds of millions of years.

A careful study of the fossil shows that it has almost identical features to this cut-away shell of a nautilus from the Pacific, photo taken by Chris_73 - except it is much bigger. The internal divisions of the shell, the septa, are clearly visible in the fossil, as is the long tube that enabled it to fill some of the chambers with water, allowing it to sink into the depths for safety during the day. In other words, it looks very much as if the ecological niche which the nautilus occupies has been so successful it has never felt the need to evolve.

This photo, taken in the Berlin Zoo by Fantagu, shows a living nautilus with it's highly efficient eyes, necessary for hunting small fish at night, and squid-like tentacles. Below the tentacles it has a tube like the squids, which enables it to squirt water as a means of propulsion.

Many visitors, geologists in particular, come to West Ardnamurchan to study one of Britain's last active volcanoes, but few realise that the local rocks hide these magnificent nautiluses - and many other fossils.