Now comes the important question. What caused all these extinctions at one particular point in time, approximately 65 million years ago? Dozens of reasons have been suggested, some serious and sensible, others quite crazy, and yet others merely as a joke. Every year people come up with new theories on this thorny problem. The trouble is that if we are to find just one reason to account for them all, it would have to explain the deaths, all at the same time, of animals living on land and of animals living in the sea: but, in both cases, of only some of those animals, for many of the land-dwellers and many of the sea-dwellers went on living quite happily into the following period. Alas, no such one explanation exists.
Alan Charig, A New Look At The Dinosaurs, Facts on File, N.Y., March 1983, p.150-1.
Alan Charig was a leading paleontologist at the Natural Histoty Museum, London