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

High temperatures, and 02 rich atmosphere and subsequent abundant food made it an evolutionary arms race between predators and prey to become as large as possible since simply being big was a great defense. Eventually certain physical and practical limitations came in to play to pretty much limit further growth beyond a certain size.