Molluscs - Cephalopods

The Molluscs compose the large group of invertebrate animals known as the Mollusca. Around 85,000 extents species of Molluscs are recognised. Molluscs not just in size and in anatomical structure, but also in behaviour and in habitat too are a very diverse group that includes Bivalves, Gastropods and Cephalopods. The soft body is rarely preserved, so Molluscs are classified by their shell structure.

An exclusively marine animals and characterised by bilateral body symmetry, a prominent head and a set of arms or tentacles.

Cephalopods became dominant during the Ordovician. 
Two important extinct groups are Ammonites and Belemnites.