Fossils & Minerals:  Mollusks
NautilusThe mollusca are one of the most diverse and largest of all the phyla of the animal kingdom. They are found in most of the earth's environments from the deepest ocean abysses to the dry deserts. Molluscs vary from slow, shelled Pelecypods to the quick, fleshy squids. The mollusca include Cephalopods, Gastropods (snails), Pelecypods (bivalves), Scaphopods (tusk shells), Chitons, the extinct Hyotithids, and Monoplacophora.

The Cephalopoda (meaning head-foot) first appeared in the Cambrian Period and then transformed and evolved throughout time. All Cephalopods are marine predators that compete with fish for food in the food chain. Cephalopoda include the ammonites (Paleozoic and Mesozoic), Nautiloids (Paleozoic through present), belemnites (Mesozoic mostly), squids (mostly Mesozoic through the recent), and octopus (Mesozoic through recent).


BaculiteGastropoda (meaning stomach footed) are the most various and wide ranging of all the molluscs. They are found paleontologically and through the present in fresh and marine waters, in the ground, on land, in trees, and on mountains. They vary from large, shelled whelks to small, fleshy slugs. Gastropods have existed since the Cambrian Period but they expanded greatly throughout the Mesozoic and Cenozoic Eras. Gastropods include snails, whelks, limpets, periwinkles, and slugs.

Pelecypoda, or Bivalves, are also found on land, in fresh water, and in marine environments. They contain two valves with the body in between. Bivalves, or Pelecypods, have been around since the Cambrian and include clams, oysters, scallops, and mussels.

Scaphopods, or tusk shells, are known since the Ordovician period. They are strictly marine bottom dwelling animals that have remained virtually unchanged since the Cretaceous.

The Chitons, or Polyplacoporas, have existed from the Cambrian through the recent, but fossils of them are very rare.

The Monoplacophoras have been known since the Cambrian. They consist of a single valve that often resembles a limpet.

There is another extinct class of Molluscs called Hyolitha which existed throughout the Paleozoic.

There is no other phyla of animals that assists geologists and paleontologist as much as the molluscs. Molluscs were abundant, wide spread, and evolved rapidly. They are used extensively to correlate and date geological horizons and formations

 - Ammonoids
 - Squid
 - Nautiloids


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