Dinosaurs

The dinosaurs originated from diapside reptiles which survived the mass-extinction at the end of the Permian as swimming archosaurs. From those emerged bipedal archosaurs, among others two groups of bipedal herbivores, the short-necked ancestors of the ornitischian dinosaurs, and long-necked ancestors of the saurischian sauropods. Later emerged the short-necked meat-eaters, ancestors of the carnosaur dinosaurs. From a lineage of small bipedal, tree-mounting bird-ancestors the various groups of bird-like, coelurosaurs branched off. The dinosaurs disappeared as …

…sea decreased which upset the ecological balance of the sea too: The algae were food for other sea-organisms, which were food for fishes and other see-animals, which also decreased, why the lope-finned fishes and the see-reptiles, ichthyosaurs, plesiosaurs, mesosaurs ect. consequently disappeared. These factors, and surely many others, brought the world of the dinosaurs to an end, leaving a world covered with foliated forests, and the possibility for the small, warm-blooded mammals to evolve.