Cymatoceras are nautiloids that lived from the Jurassic to the Oligocene. Its shell is made of two layers--the innermost being iridescent and the outer layer providing protection. The interior have partitions that divide the shell into compartments, which help the animal maintain buoyancy.
Species: Cymatoceras sakalavuz
Class: Phylum Mollusca, Class Cephalopoda
Subclass: Nautiloidea, Order Nautilida
Age: Middle Cretaceous, Albian Stage (112 million years ago)
Formation: Alpian Formation
Locality: Mahajanga, Madagascar
Size: 5.38 x 4.44 x .5 inches
Weight: 10.7 oz.