Coprolites-Taxonomy Continued

   Another criterion used by some authors is based solely on chemical composition. Fossilized feces are usually enriched in calcium phosphate (due to phosphatization of the soft and/or hard parts of the fossil) and sometimes more rarely organic matter.

   Alternatively, some authors have used morphology as a classification system. For example, Neumayer in 1904 and Williams in 1972, described spiral coprolites as amphipolar and heteropolar. Amphipolar coprolites show closely spaced coils concentrated at one end only, while heteropolar coprolites show more evenly spaced coils along the entire length of the specimen.

   Nevertheless even these systems are not perfect when trying to classify coprolites. Form and composition can be severely altered during diagenetic processes (the biological, physical, and mechanical changes made to the host rock and fossil assemblage), thus making identification very difficult, if not impossible.