恐龙的灭亡

Why did all of the remaining dinosaurs die out suddenly at the end of the Cretaceous period? There is a short answer and a long answer to this question.

2 Here is the short answer. No one knows for sure.

3 Here is the long answer. There are a number of theories. Some are scientific, and some are ridiculous. Most scientists believe in one or two main ones, but no one knows for sure.

4 The reason no one knows for sure is because the whole thing happened about 65 million years ago. No one was around to see or hear what was going on back then, and no one was around to keep records.

5 What we do know comes mainly from fossil records. Scientists study the fossils themselves, and they study the rock in which the fossils are found. Fossil records haven't given us definite proof for any one theory. This is because there are some problems with fossil records. For one thing, most fossil evidence of dinosaurs has been found in