Diversity Mollusca

about 80% of known mollusc species gastropods (snails , slugs), including cowry (a sea snail).

estimates of accepted described living species of molluscs vary 50,000 maximum of 120,000 species. in 1969 david nicol estimated probable total number of living molluscs @ 107,000 of 12,000 fresh-water gastropods , 35,000 terrestrial. bivalvia comprise 14% of total , other 5 classes less 2% of living molluscs. in 2009, chapman estimated number of described living species @ 85,000. haszprunar in 2001 estimated 93,000 named species, include 23% of named marine organisms. molluscs second arthropods in numbers of living animal species—far behind arthropods 1,113,000 ahead of chordates 52,000. 200,000 living species in total estimated, , 70,000 fossil species, although total number of mollusc species ever have existed, whether or not preserved, must many times greater number alive today.

molluscs have more varied forms other animal phylum. include snails, slugs , other gastropods; clams , other bivalves; squids , other cephalopods; , other lesser-known distinctive subgroups. majority of species still live in oceans, seashores abyssal zone, form significant part of freshwater fauna , terrestrial ecosystems. molluscs extremely diverse in tropical , temperate regions, can found @ latitudes. 80% of known mollusc species gastropods. cephalopoda such squid, cuttlefish, , octopuses among neurologically advanced of invertebrates. giant squid, until had not been observed alive in adult form, 1 of largest invertebrates, caught specimen of colossal squid, 10 m (33 ft) long , weighing 500 kg (1,100 lb), may have overtaken it.

freshwater , terrestrial molluscs appear exceptionally vulnerable extinction. estimates of numbers of nonmarine molluscs vary widely, partly because many regions have not been thoroughly surveyed. there shortage of specialists can identify animals in 1 area species. however, in 2004 iucn red list of threatened species included 2,000 endangered nonmarine molluscs. comparison, great majority of mollusc species marine, 41 of these appeared on 2004 red list. 42% of recorded extinctions since year 1500 of molluscs, consisting entirely of nonmarine species.