Nautiloid Cephalopods Capitulo 21

FREY, R. C.,BERESI M.S., EVANS D., KING A. AND PERCIVAL I.G

The Great Ordovician Biodiversification Event

Columbia University Press, New York

Lugar: New York; Año: 2003; p. 209 - 213

24  Nautiloid Cephalopods R. C. Frey, S. M. Beresi, D. H. Evans, A. H. King, and I. G. Percival The Ordovician Period can be termed the “Age of Cephalopods” as it marks the time of the great radiation of nautiloids, which proliferated from a single order at the beginning of the Ordovician (489 m.y.) to a maximum of at least nine orders by the early Late Ordovician (455 m.y.). It is also in the Ordovician that the greatest diversity of shell form and structures occurs in these externally-shelled cephalopods (Flower 1976; Holland 1987; Teichert 1988). Most of these various shell architectures were new solutions to the problem of buoyancy control in these mobile molluscs (Crick 1988). Ordovician nautiloids are represented in strata exposed from the Arctic Circle to Tasmania, and have been identified from lithofacies indicative of diverse marine environments. In the Ordovician, however, nautiloids are most abundant, display maximum diversity, and reach their greatest size in shallow marine carbonate platform facies deposited under tropical or subtropical climatic conditions (Flower 1976).