Largest Creatures To Ever Exist On Earth: Monsters of the Ocean

This stunning mountain range stretching across North America is rightfully considered one of the most scenic places in the U.S. Hard to believe that at some point this area was covered by a sea, home to a vast number of underwater giants—true monsters for whom any marine predator alive today would have been easy prey.

That sea was named the Western Interior Seaway, and 80 million years ago, it divided what later became North America into two parts: Laramidia in the west and Appalachia in the east. At its greatest size, it was 2,500 feet (760 meters) deep, 600 miles (970 kilometers) wide, and over 2,000 miles (3,200 kilometers) long.

These ancient waters were ruled by giant reptiles up to 50 feet (15 meters) in length, the apex of the food chain of their time. Giant turtles, as large as modern SUVs, and colossal predatory fish up to 20 feet (6 meters) long, capable of swallowing human-sized prey whole. Some creatures were so powerful that they could easily crush a car with their jaws. But the most iconic figure of this ancient sea was the ultimate predator, the deadliest and most invincible underwater inhabitant of all time.

The Western Interior Seaway was home to everything terrifying and gigantic that you can, and cannot, imagine.