Mollusc's evolution

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Simplified relationship diagram of mollusc's evolution:

					Caudofoveata (?)
					Aplacophora
hypothetical					Polyplacophora
ancestral					Monoplacophora
mollusk					Gastropoda
					Cephalopoda
					Bivalvia
					Scaphopoda

Cladogram shows hypothetical mollusc's evolution.

Vertical cladogram (modified from: EES 227: Paleobiology (Spring 2004) http://ethomas.web.wesleyan.edu/wescourses/2004s/ees227/01/227lect18.htm):

Polyplacophora   Gastropoda     Rostroconchia
Aplacophora  \Monoplacophora \  Cephalopoda  \  Scaphopoda  Bivalvia
\       \       \       \      /        \       \      /
\       \       \       \    /          \       \    /
\       \       \       \  /            \       \  /
\       \       \       \/              \       \/
\       \       \       * Cyrtosoma     \      /
\       \       \       \               \    /
\       \       \       \               \  /
\       \       \       \               \/
\       \       \       \              * Diasoma
\       \       \       \            /
\       \       \       \          /
\       \       \       \        /
\       \       \       \      /
\       \       \       \    /
\       \       \       \  /
\       \       \       \/
\       \       \      /
\       \       \    /
\       \       \  /
\       \       \/
\       \      * Conchifera
\       \    /
\       \  /
\       \/
\      * Testaria
\    /
\  /
\/
/
hypothetical ancestral mollusk

Horizontal cladogram (source: Zoology 250 Phylogenetic Trees (2006) http://www.biology.ualberta.ca/courses.hp/zool250/Clades/clade08-Mollusca.htm):

Mollusca molluscs
|
+-- Amphineura
|     |
|     +-- Aplacophora
|           |
|           +-- Solenogastres
|           +-- Caudofoeveata
|
+-- Testaria
|
+-- Polyplacophora - chitons
|     |
|     +-- Palaeoloricata
|     +-- Neoloricata
|
+-- Conchifera
|
+-- Monoplacophora
|
+--+
|
+--Cyrtosoma
|     |
|     +-- Gastropoda - gastropods
|     |
|     +-- Cephalopoda - cephalopods
+-- Diasoma
|
+-- Rostroconchia
|
+--+
|
+-- Scaphopoda - tusk shells
|
+-- Bivalvia - bivalves

References

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