378 FOSSIL INVERTEBRATES/Gastropods exploiting the more specialist boring and cementing habit has continued to grow and there has been a further taxonomic explosion of the shallow burrowers at lower taxonomic levels See Also Biological Radiations and Speciation Fossil Invertebrates: Molluscs Overview; Gastropods; Cephalopods (Other Than Ammonites); Ammonites Mesozoic: End Cretaceous Extinctions Palaeoecology Further Reading Beesley PL, Ross GJB, and Wells A (1998) Mollusca: the Southern Synthesis, vol A Collingwood, Australia: CSIRO Publishing Harper EM (1998) The fossil record of bivalve molluscs In: Donovan SK and Paul CRC (eds.) The Adequacy of the Fossil Record, pp 243 267 Chichester: John Wiley and Sons Harper EM and Skelton PW (1993) The Mesozoic Marine Revolution and epifaunal bivalves Scripta Geologica, Special Issue 2: 127 153 Harper EM, Taylor JD, and Crame JA (2000) The Evolu tionary Biology of the Bivalvia Geological Society of London Special Publication 177 London: Geological Society of London Johnston PA and Haggart JW (1998) Bivalves: an Eon of Evolution Paleobiological Studies Honoring Norman D Newell Calgary: Calgary University Press Skelton PW, Crame JA, Morris NJ, and Harper EM (1990) Adaptive divergence and taxonomic radiation in post Palaeozoic bivalves In: Taylor PD and Larwood GP (eds.) Major Evolutionary Radiations The Systematics Association Special Volume 42, pp 91 117 Oxford: Clarendon Press Stanley SM (1970) Relation of shell form to life habits of the Bivalvia Geological Society of America Memoir 125: 296 Taylor JD (1996) Origin and Evolutionary Radiation of the Mollusca Oxford: Oxford University Press Vermeij GJ (1987) Evolution and Escalation An Ecological History of Life Princeton, NJ: Princeton University Press Vermeij GJ (1993) A Natural History of Shells Princeton, NJ: Princeton University Press Gastropods J Fry´da, Czech Geological Survey, Prague, Czech Republic ß 2005, Elsevier Ltd All Rights Reserved Introduction Gastropods are well-known animals which have been associated with humans since the dawn of civilization Their bodies were gathered for food and their shells were used as tools, ornaments, and later as money Their widespread occurrence is clear evidence of their successful adaptation to different environments During a long evolution, they are the only molluscan class to have colonized the majority of marine, freshwater, and terrestrial environments Marine gastropods occur mostly in shallow-water benthic communities; however, some gastropod species have also lived in the deep sea (e.g., faunas associated with hydrothermal vents), and others, such as holoplanktic animals, have spent their whole lives as freeswimming gastropods The terrestrial gastropods colonized most land environments, ranging from lowlands to high mountains, and including humid to arid biotopes of tropical to subarctic areas Such adaptive radiation is quite exceptional amongst all animal phyla and is linked to the extraordinary morphological and functional diversity of their bodies and shells The gastropods comprise one of the most diverse groups of living animals (the second after Insecta) All these facts, together with their long and rich fossil record, make gastropods a unique animal group for evolutionary, ecological, and biogeographical investigations There follows a brief review of gastropod anatomy, shell morphology, classification, and more than 500 million years of evolution Definition and General Description The Gastropoda forms one of eight molluscan classes, and is defined by several unique anatomical features which support its interpretation as a molluscan group derived from the same ancestor (i.e., monophyly) The most characteristic feature of gastropods is torsion of their soft bodies during early larval stages, producing a crossing of their nerve connectives, bending of the intestine, and twisting of the mantle cavity (together with associated structures, including the ctenidia, anus, kidney openings, etc.) anteriorly over the gastropod head Anatomical Features The exceptional morphological and functional diversity of gastropod bodies is also reflected in their anatomy Generally, the body consists of a large foot, a