The Age of Reptiles began with the evolution of amphibians in the Carboniferous Period and extended until the End Cretaceous Extinction. Mammal ancestors ruled the Permian. Beginning with the Triassic, archosaurs ruled the earth during the Mesozoic Era. Scientists classify archosaurs into two groups: archosaurs closer to crocodiles, and archosaurs closer to birds. The reason is that birds and crocodiles are the only archosaurs that survived the End Cretaceous extinction.
During the Devonian, lobe-finned lungfish began to evolve legs in shallow waters and eventually walked on land.[1] They moved to shallow waters to avoid predators. Their fins evolved the capability to pull themselves along through the shallow waters, which eventually became legs. They also developed the ability to breathe in air. Finally, they evolved skin and eggs that allowed them to live on dry land.
The archosaurs ruled the world after the Great Permian extinction (251 Ma). Scientists divide the archosaurs into two groups, archosaurs closer to dinosaurs and birds, and archosaurs closer to crocodiles. This section describes the evolution of the birds (Orthnithodira) within the Dinosauromorpha clade of the Archosauria.
The Colorado Plateau provides a record of animal and plant evolution during the Paleozoic and Mesozoic eras. It stretches across four states (Figure 10‑31). During the Paleozoic and Mesozoic, the Colorado Plateau (Figure 10‑31) region was near or below sea level and included coastal plains, swamps, large river valleys, tidal flats, deserts, and shallow seas. Sediment deposition formed over ten thousand feet of geologic strata over 500 million years and a record of invertebrate, fish, plant, archosaur, and early mammal evolution.
Animals that looked like crocodiles formed one of the two branches of the archosaurs. Because the Colorado Plateau region was a lowland with low-lying plains and swamps in the Triassic, crocodile-like animals lived there. The ancestors of modern crocodiles evolved in the Early Cretaceous, and this group survived the End Cretaceous extinction.
The Morrison Formation contains many Late Jurassic dinosaurs, such those in Jurassic Park movies. The greatest fossil deposit in the Morrison formation is at Dinosaur National Monument (DNM) in the far northern part of the Colorado Plateau. Uneven uplift has exposed geologic strata at the Carnegie Quarry, which is at a high elevation at the west end of Dinosaur National Monument (DNM). The Cedar Mountain formation overlies the Morrison Formation and documents dinosaur evolution during the Cretaceous Period. The Hell Creek Formation in North Dakota has Tyrannosaurus Rex and other End Cretaceous dinosaur fossils.
Moses stated that God's blessed the animals of the fifth age, which included birds and insects on land, and all of the animals in the sea, which would include crocodiles, fish, and aquatic invertebrates. The Hebrew word for sea includes rivers, lakes, and oceans.
Figure 10‑28. The Dromeosaurs of the Cretaceous: Microraptor, Velociraptor mongolensis, Austroraptor cabazai, Dromeaosaurus albertensis, Utahraptor ostrommaysorum, and Deinonychus antirrhopus. Credit: Fred Wierum. Used here per CC BY-SA 4.0.