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Published online 19 January 2009 | Nature | doi:10.1038/news.2009.40
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Dinosaur fossils suggest speedy extinction
Arctic find challenges the idea that the massive reptiles declined slowly.
Fossils uncovered recently in the Arctic support the idea that dinosaurs died off rapidly — perhaps as the result of a massive meteor hitting Earth. The finding contravenes the idea that dinosaurs were already declining by this time.
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With such recycling of hypotheses, some space can still be given to that one about the competitive exclusion of gymnosperms by angiosperms, causing some dinosaurs to loose food resources due to a bankrupt of the food chain.
Hm! I'm not an expert here, but regarding the decline of amphibians all over the world, I think there is one single, obvious cause: humans
The summary in the second-last paragraph suggests that there were likely multiple causes (or at least more than one) that led to the extinctions, so this could be interpreted to imply that some extinctions occurred due to a single event, some occurred due to multiple events; and either way, each class of extinctions could have occurred quickly or over a long period of time (i.e., both quick extinctions and slow extinctions occurred in overlapping timeframes). This can be seen in more contemporary extinctions. I think the key is to not think of dinosaurs as a single species. They certainly were not.
If you start from a neutral position, the catastrophe theory is by far the simplest explanation. Other theories need a lot of coincidences to explain why almost all higher species became extinct apparently at the same time. A sudden rise in volcanic activity is a likely RESULT of the impact, not a competing or coincidental cause. The land vertebrates which survived: rat-like mammals, vulture-like birds, crocodiles... were probably scavengers, a few of which survived by eating dead and maybe frozen vegetarians and carnivors.
One factor that puzzles me in regard to theories about the rapid decline of the dinosaurs is the consequence that results from the temperature dependance of sex determination. We see this "model" in crocodiles, turtles and other similar groups today. A few degrees in temperature elevation above an optimum value produces only males, a few degrees lower produces only females. The Upper Cretaceous period was a period of significantly higher temperatures than at present (perhaps 8-10 degrees, "super green house" period). If this progressively resulted in production of only one sex over the other around the world then that is a rapid route to extinction. Mammals on the other hand are self temperature regulated so this condition does not apply. Amphibians may have taken respite in water and are (as far as I know) not dependant upon temperature as a sex determinant. You do not need a "Holliwood" catastrophy to get rapid extinction, just natural and persistent climatic change (heating or cooling).