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Genre/Form: | Thèses et écrits académiques |
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Material Type: | Document, Thesis/dissertation, Internet resource |
Document Type: | Internet Resource, Computer File |
All Authors / Contributors: |
Didier Bert; Didier Néraudeau; Philippe Courville; Université de Rennes 1.; École doctorale Vie-Agro-Santé (Rennes).; Université européenne de Bretagne.; Géosciences (Rennes). |
OCLC Number: | 895253849 |
Notes: | Titre provenant de l'écran-titre. |
Description: | 1 online resource |
Responsibility: | Didier Bert ; sous la direction de Didier Néraudeau et de Philippe Courville. |
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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