MOLLUSCA Part 1 - City College of San Francisco · 2009-10-08 · MOLLUSCA Part 1 Polyphacophora Scaphopoda Gastropoda Phylum Mollusca zLarge group of aquatic & terrestrial invertebrates

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MOLLUSCA Part 1

PolyphacophoraScaphopodaGastropoda

Phylum Mollusca

Large group of aquatic & terrestrial invertebrates with bilateral symmetry and a body covering called the mantle, commonly with a calcareous shellMost well preserved (except slugs)Most Important group of Fossils (numbers)Organs include heart, stomach, nerve cord, musclesInferred evolution from the Hypothetical Ancestral Mollusc

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Taxonomy to know

Kingdom AnimaliaPhylum Mollusca

Class Polyplacophora- chitonsClass Scaphopoda-tusk shellsClass Gastropoda-snailsClass Bivalvia-clamsClass Cephalopoda-nautiloids

Class Polyplacophora

Shell with 8 dorsal platesHerbivores, rocky environmentsCambrian to recent

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Fossil Polyplacophora

Cambrian – disarticulated plates

Ordovician

Class Scaphopoda

Tusk shaped, hollow shell (boat foot)Sandy or silty bottom, shallow water marineOrdovician to RecentSometimes very abundant e.g. Pennsylvanian of Texas

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Class Scaphopoda

Fossil Scaphopods

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Class Gastropoda

Stomach footSnails, slugs, whelks, limpets, abaloneHead with eyes, tentacles, broad flat foot, gills or lungsTypically coiled, unchambered shell (some cap-shaped)

coiled around a columella (axial pillar)Apex, whorl, spire, lip (see p. 291)Operculum

Typically aragonite shells that disolve in acid – casts, molds, steinkernsCambrian to Recent

Class Gastropoda

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Class Gastropoda

Fossil Gastropods

Pliocene Turritella

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Fossil Gastropoda

Amphiscapha catilloides Penn. Texas

Fossil Gastropoda

Worthenia tabulataPenn. TexasGyrodes genti Cretaceous, England

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MOLLUSCA Part 2

BivalviaCephalopoda

Taxonomy to know

Kingdom AnimaliaPhylum Mollusca

Class Polyplacophora- chitonsClass Scaphopoda-tusk shellsClass Gastropoda-snailsClass Bivalvia-clamsClass Cephalopoda-nautiloids

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Class Bivalvia

Class Bivalvia aka Pelecypoda

Shell with two mirror image partsHinge with various designsNo headCambrian to recent

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Class Bivalvia

Class Bivalvia

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Class Bivalvia

Fossil Bivalves

Anadara, a bivalve with taxodontdentition from the Pliocene of

Cyprus.

an extinct bivalve from the of Wooster, Ohio (external mold).

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Class Cephalopoda

Class Cephalopoda

“Head Foot” eyes, tentacles, head well developedIntellegentStraight or coiled shell, usually planispiralOrdovician – Recent1st large group of predators

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Class Cephalopoda

Ammonites

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Fossil Cephalopod

Fossil Cephalopod