Class Cephalopoda Cuvier, 1797

et: peajalgsed; sv: bläckfiskar; fi: pääjalkaiset; ru: головоногие;

Taxon overview

Cephalopoda  or cephalopods are extraordinary molluscs equipped with vertebrate-like intelligence and a unique buoyancy system for locomotion. Cephalopods evolved during the Cambrian where external shell was modified into a chambered buoyancy apparatus. During the mid-Palaeozoic cephalopods diverged into nautiloids and the presently dominant coleoids. Coleoids (i.e. squids, cuttlefish and octopods) internalised their shells which appears to be a unique evolutionary event. The general tendency of shell reduction reflects a trend towards active modes of life and much more complex behaviour.

Cephalopods are exclusively marine animals. They are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles (muscular hydrostats) modified from the primitive molluscan foot. Fishermen sometimes call them inkfish, referring to their common ability to squirt ink. About 800 living species of cephalopods have been identified. Two important extinct taxa are the Ammonoidea (ammonites) and Belemnoidea (belemnites).

Visual identification guide (Cephalopoda)


Selection of related publications

  • Kröger & Aubrechtová, 2017(2018). Cephalopods from reef limestone of the Vasalemma Formation, northern Estonia (latest Sandbian, Upper Ordovician) and the establishment of a local warm-water fauna [DOI]
  • Vinn et al., 2018d. Cryptic encrusting fauna inside invertebtate fossils from the Ordovician of Estonia [DOI]
  • Aubrechtová & Meidla, 2016. The oldest ascocerid cephalopod from the Silurian of Estonia and notes on the biogeography of the order Ascocerida (class Cephalopoda) [DOI]
  • Klug et al., 2015. Normal giants? Temporal and latitudinal shifts of Palaeozoic marine invertebrate gigantism and global change [DOI]
  • Kröger, 2013. The cephalopods of the Boda Limestone, Late Ordovician, of Dalarna, Sweden [DOI]
  • Kröger, 2012. The "Vaginaten": the dominant cephalopods of the Baltoscandian Mid Ordovician endocerid limestone [DOI]
  • Mutvei & Dunca, 2011. Siphuncular structure in the orders Tarphycerida and Barrandeocerida (Cephalopoda: Nautiloidea) [DOI]
  • Kröger et al., 2011. Mass concentration of Hirnantian cephalopods from the Siljan District, Sweden; palaeoecology and palaeobiogeographic relationships [DOI]
  • Kröger et al., 2009. Discosorids and Oncocerids (Cephalopoda) of the Middle Ordovician Kunda and Aseri Regional Stages of Baltoscandia and the early evolution of these groups [DOI]
  • Kröger, 2007. Concentrations of juvenile and small adult cephalopods in the Hirnantian cherts (Late Ordovician) of Porkuni, Estonia
  • Kröger & Isakar, 2006. Revision of annulated orthoceridan cephalopods of the Baltoscandic Ordovician [DOI]
  • Kröger et al., 2005. Soft−tissue attachments in orthocerid and bactritid cephalopods from the Earlyand Middle Devonian of Germany and Morocco
  • Kröger & Mutvei, 2005. Nautiloids with multiple paired muscle scars from Lower-Middle Ordovician of Baltoscandia [DOI]
  • Kröger, 2004. Revision of Middle Ordovician orthoceratacean nautiloids from Baltoscandia
  • Mutvei, 2002a. Connecting ring structure and its significance for classification of the orthoceratid cephalopods
  • Jacobson, 1999. Five new cephalopod species from the Silurian of Gotland
  • Mutvei, 1998. Siphuncular structure in a Silurian narthecoceratid nautiloid cephalopod from the Island of Gotland [DOI]
  • Mutvei, 1997. Siphuncular structure in Ordovician endocerid cephalopods
  • Stumbur, H., 1975. Biomertical characteristics of the shell of a living Nautilus
  • Mutvei & Stumbur, H., 1971. Remarks on the Genus Pictetoceras (Cephalopoda: Ellesmerocerida)
  • Stumbur, H., 1962. Distribution of nautiloids in the Ordovician of Estonia with a description of some new genera
  • Stumbur, H., 1960a. On some ... of nautiloids
  • Stumbur, H., 1960b. On different ways of evolution of nautiloids
  • Stumbur, H., 1959. On the embryonic shells of some Ordovician Tarphyceratida
  • Stumbur, H., 1956. On the nautiloids of Kohila Subseries (Upper Ordovician of East Baltic)