Chambered Nautilus - Living Fossil

 Nautilus reminds us of the first submarine invented by French writer Jules Verne in his fiction novel, Twenty Thousand Leagues Under the Sea, more than two centuries ago.
Dr Abe V Rotor

Chambered Nautilus, the only surviving nautiloid today.

Fossils of ancient nautiloids

The mere mention of nautilus reminds us of the first submarine invented by French writer Jules Verne in his fiction novel, Twenty Thousand Leagues Under the Sea, more than two centuries ago. This fiction-come-true underwater steel monster which wrought havoc to battleships in the two world wars actually works on the principle of the only surviving member of a large phylum.

The nautiloids are relatives of the modern squid and octopus, but they have a hard shell. During the Paleozoic Era, there were many kinds of nautiloids, in many shapes and sizes. The largest was more than 20 feet long! Like the modern nautilus, Paleozoic nautiloids were probably predators. They most likely swam and floated in the sea, catching prey with their tentacles and cutting it up with their sharp, parrot-like beak.

The nautiloids were among the numerous multicellular animals that dominated the oceans at that time. They came with the Cambrian Explosion during that era - the sudden explosion of new, complex life forms which lasted from 550 to 240 million years ago. Then the first fossil bones - the oldest known traces of vertebrates - were found. For no sufficient evidences, the Paleozoic Era ended suddenly. (There is a new theory to explain this; it is attributed to super volcanoes simultaneously erupting along the cracks of the earth which we trace today as seismic or volcanic belt.)

After this cataclysm  a era of the vertebrates began, the Mesozoic Era, more popularly known as the age of the dinosaurs which flourished for as long as the Paleozoic Era did. Then 65 million years ago, a meteorite - or comet according to other scientists - struck the earth causing the extinction of the dinosaurs and a huge number of life forms, including the nautiloids. The present Cenozoic Era followed, the age to which the present living things, including humans, belong. ~

Ancient  nautiloids, collection of the Museum of Natural History, UPLB