Figure 13.24   Gradualistic evolution of Cretaceous belemnites from North Germany. Summary of changes of the length from the apex to the protoconch (LAP), Birkelund index (BI), Schatzky distance (SD), fi ssure angle (FA) and alveolar angle (AA) of nine samples of Belemnitella. Successive mean values are different at the 5% level (one arrow), 1% level (two arrows) and 0.1% level (three arrows). (Courtesy of the late Walter Kegel Christensen.)

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