Why were prehistoric era animals so gigantic in comparison to animals from the “modern era”

Question

Why were prehistoric era animals so gigantic in comparison to animals from the “modern era”

In: 1281

Answer 1

I remember watching some animal show about the Titanoboa, and in that show they mentioned that the hot water had some sort of impact on how large they grew. I think that there is some sort of theory that dinosaurs and sea animals near the equator are bigger because I guess the logic behind it is that heat makes things expand and grow. I could be completely wrong, but this just made me think of that.