A literature search for evidence of the evolution of the mollusk shell was completed. Little to no physical evidence exists of the theorized gradual transformation from some proposed common ancestor of mollusks. This is true in spite of the excellent preservation qualities of the shell and a fossil record exceeding most all other Phyla. This putative "simple" organism manifests complexity at such a high level that scientists have been unable to hypothesize its possible evolution. The mollusk shell is also an excellent example of an irreducibly complex structure. The shell is an exoskeleton that is integrated into the design of the entire animal.