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Which extinct mollusks are commonly found as fossils?
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mollusk
Mollusk shell classification chart, c. 1861.
Many extinct mollusks are commonly found as fossils, particularly those that possessed hard shells, which are well-preserved in the fossil record.
Cephalopods
Extinct cephalopods are among the most significant fossils for dating marine rocks.
* Ammonoids: These shelled relatives of the modern nautilus are frequently found in marine rocks from the Devonian to the Cretaceous periods. Because of their rapid evolution and wide distribution, they serve as vital index fossils. Notable genera include Baculites, Ceratites, and Scaphites.12345
* Belemnoids: These were squidlike cephalopods with internal skeletons that are also common in Mesozoic deposits.32
Bivalves and Gastropods
- Bivalves: These mollusks have a long history dating back to the Cambrian Period. Extinct genera often found as fossils include Gryphaea, Inoceramus, and Exogyra.673
- Gastropods: Snails are well-represented in the fossil record, with extinct genera such as Bellerophon and Maclurites frequently appearing in geological strata.3