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Gastropod Main
Glossary
References
Links
Hooper Main |
Evolution
The key to the success of the gastropods is their striking diversity, enabling them to survive in many environments. The first primitive shelled gastropods, like the 500,000,000+ year old Aldanella, Helsionella, Scenella, and Bellerophrons, were uniformly marine. They were probably herbivorous or detrital feeders and reproduction occurred from two sexes. Unlike other animals such as mammals, gastropods underwent dramatic adaptive radiation early on in their history, and have shown relatively little progressive evolution in the last fifty million years in comparison. Their adaptions have shown some marked trends. For instance, gastropods have generally evolved from being herbivorous to carnivorous (although the majority today remain plant eaters), there is a trend for a loss of shell in the higher forms, and a migration from marine to freshwater and terrestrial habitats.
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Figure 2: A Bellerophron . One of the oldest gastropod families, the bellerophrons appeared first in the Cambrian. |
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