L'influence de la variabilité intraspécifique sur la taxinomie, la biostratigraphie et l'évolution des ammonites : une approche paléobiologique : exemples pris dans le Jurassique supérieur et le Crétacé inférieur

Abstract : The issue of this work involves concrete case of application of the palaeobiological approach in ammonites. Special attention was given to intraspecific variability and its taxonomic consequences and the study of evolutionary processes and patterns of the groups studied, in order to draw generalizations. Paleobiological studies on a variety of examples show that the degree of variability and its consideration by the authors has a particular influence on taxonomic concepts, and consequently on the biostratigraphy and the understanding of evolutionary mechanisms. Westermann laws seem to be dominant to explain intraspecific variability of a large number of ammonites groups, but they are not the only source of covariation and their influence must be relativized against other factors usually not taken into account. Factors of intraspecific variability recognized are: (1) dimorphism, (2) a dipolar variability in the strict application of the first Westermann’s law, (3) changes compared to the general statement of the law, (4) tripolar variability, (5) heterochronic relationships morphological dependent or independent, (6) an attenuation factor of ornamentation, and (7) various coiling factors related or not to other morphological and ornamental characters in heteromorphic ammonites.
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Didier Bert. L'influence de la variabilité intraspécifique sur la taxinomie, la biostratigraphie et l'évolution des ammonites : une approche paléobiologique : exemples pris dans le Jurassique supérieur et le Crétacé inférieur. Sciences de la Terre. Universite Rennes 1, 2014. Français. ⟨tel-01138094⟩

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