章节大纲

    • Cephalopods belong to the phylum Mollusca. They originated during the Cambrian period (541-485 million years ago (mya)). The early cephalopods were very small, with slightly curved shells, and occurred only in shallow seas, but they expanded their distribution during the Great Ordovician Biodiversity Event (485-443 mya). Today, there are about 790 species in two sub-classes: Coleoidea and Nautiloidea. The Coleoidea comprise two superorders: Octopodiformes and Decapodiformes.