An attempt at biological interpretation of evolutionary changes in graptolite colonies
Adam Urbanek
Problems of morphological organization in graptolite colonies are discussed and suggestions made as to the supposed genetic mechanisms of their evolution. The regular astogenetic succession of thecae is interpreted as an effect of morphophysiological gradients. The spreading of new thecal types in forms constituting successive evolutionary stages of a lineage are believed to be manifestations of the penetrance and expressivity of respective genetic factors.
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