The Western Interior Seaway, was a large inland sea that started to expand in the early Cretaceous period, though geological evidence suggests it started to expand in the late Jurassic period. It existed at its fullest extent from the mid-late Cretaceous period. At its greatest extent it was 600 miles (970 km) wide, 2,000 miles (3,200 km) long, and had a depth maximum depth of 2,500 feet (700 m). Various different species of fish existed in the Western Interior Seaway, throughout its 30 million time frame. Examples of which