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Temporal range: Ediacaran or Cambrian - Recent
|Caribbean Reef Squid, Sepioteuthis sepioidea|
Molluscs, or mollusks, are an important phylum of invertebrate animals. Most of them are marine. They have huge numbers in-shore, that is, in shallow waters near the shore. They are the largest marine phylum, with about 93,000 recognised species, 23% of all named marine organisms. They also occur in freshwater and on land.
Molluscs are extremely varied: they have great diversity. That may be why there is no word in English for the phylum as a whole. "In an evolutionary sense, molluscs are plastic material".
Most molluscs have shells, but some groups do not: octopods, slugs, and the gastropods known as sea slugs. There is great variety in the phylum, much more so than their ancient rivals, the brachiopods.
Classes of molluscs:
- Cephalopods: Squid, Octopus
- Gastropods: whelks, limpets, snails, slugs, Nudibranchs
- Bivalves: Most shellfish; clams, oysters, scallops, mussels
- Scaphopoda: the tusk shells
- Polyplacophora: Chitons
- Aplacophora: worm-like molluscs
- Helcionelloida: see below
It has become clear that the fossil taxon Helcionelloida does not belong to the class Gastropoda. It is now a separate class in the Mollusca. Parkhaev (2006, 2007) created the class Helcionelloida, whose members were previously treated as "Paleozoic molluscs of uncertain systematic position" by Bouchet & Rocroi.
- Many molluscs are eaten as food: clams, oysters, scallops, mussels, squid (calamari) and land snails (escargot)
- Oysters sometimes make pearls, which are valuable and used to make necklaces. Other shells are collected for their beauty and sometimes used to make jewellery.
|Wikispecies has information on: Mollusca.|
- Morton J.E. 1958. Molluscs. London: Hutchinson University Library, p11.
- Barnes, Robert D. 1982. Invertebrate zoology. Philadelphia PA: Holt-Saunders. ISBN 0-03-056747-5.
- P. Yu. Parkhaev (2006) "Adaptive radiation of the Cambrian helcionelloid mollusks (Gastropoda, Archaeobranchia)." In: S.V. Rozhnov (ed.) "Evolution of the biosphere and biodiversity. Towards the 70th anniversary of A. Y. Rozanov". 2006. Moscow, pp. 282-296.
- P. Yu. Parkhaev (2007). "The Cambrian 'basement' of gastropod evolution". Geological Society, London, Special Publications 286: 415–421. . . http://books.google.com/books?id=GA7-8JIh9IwC&pg=PA415.