Mesogastropoda

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Mesogastropoda is a traditional order of prosobranch gastropods. This order was introduced by J. Thiele in his work from 1921. As Mesogastropoda is not a monophyletic taxon, it is no longer included in modern classifications, and instead rather used in a descriptive way.

The lower taxa traditionally contained in Mesogastropoda are now mostly covered by in the superorder Caenogastropoda. A more detailed account of the taxonomy is given in the articles on Gastropoda and Archaeogastropoda.

1 Description
2 Taxonomy
3 Families
4 References
5 External links

[edit] Description

There are about 30,000 species. Most are to be found in the sea, but there are also numerous species in freshwater and even a few occur on land. Their shells lack mother-of-pearl.

Most are herbivorous, but a few are parasites or predators. The radula have seven denticles (= teeth), sometimes reduced.

The Mesogastropoda are, in many ways, already more developed than the Archaeogastropoda. Through torsion of the intestinal mass and a spiral movement of the body, the gill, the kidney and the osphradium (= sensory receptor, olfactory organ) have disappeared on the right side. They all reside on the left side.

The heart consists of only one atrium and one ventricle. The nervous system is also progressively more developed. The ganglia are connected with different organs through nerve pathways. In the Mesogastropoda, the execretory and the reproductive ducts are separated (in contrast with the most primitive prosobranchs). Many members produce egg capsules, containing one to more than 1,000 eggs.