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Environmental Consequences: The Palaeontological Evidence Relating to Mass-Extinctions |
Department of Palaeontology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
A continuous sequence of terrestrial sediments bracketing the Cretaceous-Tertiary (K-T) boundary is known only in the western interior of North America. Documentation of terrestrial faunal diversity, and patterns of survival and extinction, demonstrate that dinosaurs (i.e. non-avian dinosaurs) declined in the Late Maastrichtian and were the only major terrestrial vertebrate group, along with the pterosaurs, that became extinct at or near the K-T boundary. There was a varying degree of turnover but no mass extinction in other vertebrate groups. Both gradualist and catastrophe scenarios have been advocated as the main cause. There is much less evidence in other parts of the world that can be brought to bear on the timing and nature of dinosaur extinction. None the less, there are dinosaur remains from Maastrichtian horizons on every continent and none are recorded from overlying Paleocene strata. This supports the axiom that dinosaurs died out world-wide at the end of the Cretaceous although there is no means of determining whether the extinction pattern in western North America was a local or global phenomenon. The disruption of reproductive patterns in herbivorous dinosaurs by trace element contamination derived from an impact, volcanic activity or both events is one factor which might correlate with their global extinction.
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