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Palaeos Metazoa: Mollusca: Gastropoda: Gastropoda |
 | | Gastropods, the group of mollusks that include the terrestrial snails and slugs and the marine limpets, periwinkles, abalones, whelks, and their relatives, are the largest and most varied class of mollusks, with more than 75,000 extant species in addition to 15,000 fossil forms that are known. |
 | | The bellerophontiform gastropods he considers to be bi-phyletic, with one group perhaps ancestral to, and another an off-shoot of, a very early paraphyletic assemblage called the Sinuopeidae (latest Cambrian to middle of the Early Ordovician). |
 | | Gastropod systematics and phylogenetic understanding has undergone radical revision in the last few decades, and the old three-fold classification of Prosobranchia, Opisthobranchia, and Pulmonata, with the Prosobranchia divided into Archaeogastropoda, Mesogastropoda, and Neogastropoda, is no longer accepted by recent workers in this field, who have adopted a cladistic perspective based on more thorough recent research. |
| www.palaeos.com /Invertebrates/Molluscs/Gastropoda/Gastropoda.html (1802 words) |
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