Triassic Time and Ammonoids: Problems and Proposals

摘要: Problems arising from the classification and dating of Triassic rocks ammonoids are reviewed. It is emphasized that all chronostratigraphic units must be based on stratotypes in order to achieve an unambiguous time scale. Explanations sought for anomalies encountered when comparing ammonoid age ranges determined North America with alleged European Asian occurrences. Most can resolved by taking into account recent research penecontemporaneous solution processes or invoking condensation. Both have resulted mixing natural faunas at localities. Review problems taxonomy indicates recognition a variable species only possible full range variation has been established population, i.e. series specimens one obtained place. For discriminating higher taxa evidence no single character, either inner outer whorl, overriding sig...