I distinctly remember seeing this movie in theaters. I may have even seen it twice (this was when I was working at the theater so it was very easy to see movies, especially while working). The thing I most remember about this movie is that it states "based on a short story." You already lost me there, movie. Based on a short story? What's next "this movie is based on a sentence."
The movie is about the butterfly effects of literally killing a butterfly while visiting the past. That simple action has an enormous effect on the modern world. Waves of "evolution" start affecting society, bringing horrible prehistoric creatures back into existence. The worst thing about this movie is the special effects. It looks like something made for TV. Maybe those kinds of effects would look good in 'Krull,' but not in 2004.