The theory that dinosaurs starved because of the apparition of flowering plants is not supported anymore because it happened long before the KT boundary. The fossil record shows no large extinction related to the apparition of flowers.
The impact theory in which a large meteor falls to the earth and blows large clouds of dust in the sky, thus creating a nuclear winter effect, has serious shortcomings. Firstly, many impacts have occured during the time of the dinosaurs with barely any visible effect in the fossil record. Dinosaurs didn’t seem to care. Secondly, the orthodox impact theory fails to explain how the dust could have stayed suspended long enough in the atmosphere to produce widespread ecological mayhem.
The issue is complicated. The extinction at the end of the Mesozoic era was not restricted to dinosaurs. Many marine life forms in the sea disappeared too. These include giant molluscs, and all species of large reptiles that roamed the sea at the time (ichtyosaurs, plesiosaurs, mososaurs(sp?), etc, which are only distantly related to dinosaurs). It also seems that mammals did not have an easy time of it either. As for birds, they might be counted as dinosaurs, but even in such a case, they represented only a small fraction of dinosaurian life forms. The pterosaurs, true flying reptiles, did not survive that great extinction either.
A modified version of the impact theory is that the Yucatan Impact was different in one respect. It is possible that the impact site contained a large pocket of sulfur. Sulfur is much lighter than the usual mix of rock that would get thrown in the atmosphere. It could have floated much longer and created a nuclear winter effect. Additionaly, the sulfur would have combined to form sulfuric acid, that would have returned to the earth in the form of acid rain. The effect on the plant life would have been terrific.
Whatever killed the dinosaurs, it seems to have affected most life forms. Maybe dinosaurs died because they were the most sophisticated animals of their time.
At the end the of the Mesozoic era something that endangered the whole food chain occured. The most advanced animals of the time, the dinosaurs at the top levels of the food chain, would have been the first threatened since their survival depended on all the other life forms below them. Mammals were generalists at the time, and that might have been the key to their survival.
I’d like suggest one more theory (to muddy things up). Continental drift might have contributed significantly to whatever stressed the food chain at the time. Most of the continents were touching at the time of the dinosaurs and had been moving away since the beginning of the Mesozoic. When the continents separated they opened new water ways. It’s known now that the currents in the ocean have a very significant role as convection belts that carry heat from one region to the other and affect the environment greatly a la El Nino. These new water ways could have drastically changed the long established water currents and radically transformed the climate.
Of course, it’s just a theory.
I don’t know about the extinction at the end of the Pleistocene being just a blip. It may well be an ongoing process. The present rate of extinction is rather frightening. To our human perception, a few hundred species disappearing every generation might not seem like much, but it’s beginning to compare with the extinction of the dinosaurs.
If you don’t know what I’m talking about, you should know that the East Coast is experiencing serious fish depletion and that many large animals such as tigers and some species of rhinoceros might not survive beyond this generation. There is ample record of animals being already extinct because of us. We are experiencing one of the major extinctions of the earth, and we are the cause.
Only humans commit inhuman acts.
