In my opinion, all dinosaur "sudden extinction" hypothesi (sae?) contain at least one major flaw.
There was a huge variety of Dinosaurs - in all sizes, from tiny to huge, carnivorous, herbivorous, omnivorous, land-dwelling, water-dwelling and amphibious.
I understand that sudden climate change or development of poisonous alcaloids by grass could have killed the huge dinosaurs quick. But what about the small ones?
How come the same size mammals, reptiles, insects and other kinds survived in the same locations while the dinosaurs completely perished in a short period of time?
The only thing that seems to me capable of such quick and complete devastation is biological - some virulent virus or germ combined with some defect in their immune system or genetic suseptibility that did not affect mammals/insects the same way - or maybe even was spread and supported by them.
If that bug affected some major biological mechanism common to all dinosaurs that could not be evolved out and/or was stable in soil for a long time or spread by other species, all the dinosaurs would die. For all we know, it could have been measles or common cold.
Just imagine a bug affecting humans with spore stability of anthrax, water-bournness(?) of dysinthery, virulence of ebola and spreadability of common cold.
One could such bug would quickly kill all of its own carriers just like ebola and there would remain pockets of humanity not affected - but imagine it could be spread by mice, birds and moskitoes without killing them?
So far bugs evolved resistant to all the new drigs we could come up with. Of course our immine system is very advanced and second in complexity only to brain, but in a period of millions of years something is bound to come up that will find a chink...
miko
