Cephalopod classification and taxonomy

• Main Authors: Venkatesan, V, Mohamed, K S
• Format: Course Material
• Language: English
• Published: CMFRI; Kochi 2015
• Subjects: Cephalopods; Taxonomy; Nautilus; Colossal Squid; Mesonychoteuthis hamiltoni
• Online Access: http://eprints.cmfri.org.in/10414/; http://eprints.cmfri.org.in/10414/1/09_V._Venkatesan1.pdf

Chambered nautilus, cuttlefishes, squids and octopus are the four major groups of cephalopods, which belong to the highly evolved class of phylum Mollusca. Cephalopods are the third largest molluscan class after bivalves and gastropods and consist of more than 800 species (Lindgren et al. 2004). The fossil record contains about 17,000 named species of cephalopods. Although the diversity of cephalopods is very much reduced in the modern era, cephalopods are found to occur in all the oceans of the world from the tropics to the polar seas and at all depths ranging from the surface to below 5000m. Cephalopods were dominant predators millions of years before fish appeared. The earliest cephalopods were primitive shelled nautiloids which evolved in the Late Cambrian period. The living cephalopods range in size from 25mm (Southern pygmy squid, Idiosepius notoides) to more than 12m (Colossal squid, Mesonychoteuthis hamiltoni) in length.