Paleontology and geology

Most of Saskatchewan was above sea level at the beginning of the Cretaceous, but shallow seas returned as the Western Interior Seaway spread across the continent. The Rocky Mountains were being uplifted in the west, and sediments eroding from the highlands filled the seas with sand and mud. The warm waters were home to ammonoids, bivalves, and snails, as well as bony fish, sharks, turtles, crocodiles, and marine reptiles like mosasaurs and plesiosaurs. Toward the end of the period, the land began to emerge, and lakes and rivers replaced the seas. In the mild climate, forests of palms, conifers, and early flowering plants developed. Many different kinds of dinosaurs lived in these forests, including various species of hadrosaurs (duck-billed dinosaurs), Ankylosaurus, Triceratops, and Thescelosaurus. They were hunted by carnivores like Tyrannosaurus rex, Dromaeosaurus, and Troodon. There were also salamanders, lizards, toothed birds, and early mammals. The marine and continental sandstones, limestones, and mudstones that preserve these fossils can be found over the southern part of the province. Some of these rocks also hold reservoirs of oil and natural gas.