Savage Earth: Cold Moon
Dinosaurs are a diverse group of reptiles, active animals with elevated metabolisms and numerous adaptations for social interaction. They were the dominant terrestrial vertebrates in the Americas and Asia for over 200 million years, from the late Triassic period (about 230 million years ago) until the end of the Cretaceous period (about 25 million years ago). At that time the dinosaurs began to go into decline in many areas, allowing the rise of Mammals to fill the gaps they left behind. In the current age Dinosaurs are in decline but are far from endangered and remain numerous even if they have been overtaken by mammals.
In Africa and Europe their age ended 65 million years ago when the Cretaceous–Tertiary extinction event caused the extinction of most dinosaur species, except for some birds. This complete extinction allowed Mammals to evolve to far greater degrees on these continents and to evolve many more species.
At their height Dinosaurs boasted over 9,000 species, with over 500 distinct genera and more than 1,000 different species of non-avian dinosaurs – making theme the most diverse group of vertebrate besides perciform fish. Dinosaurs are represented on every continent by both extant species and fossil remains. Some dinosaurs are or were herbivorous, others carnivorous. Some have been bipedal, others quadrupedal, and others have been able to shift between these body postures. Although generally known for the large size of some species, most dinosaurs were human-sized or even smaller. Most groups of dinosaurs are known to have built nests and laid eggs.
In the modern age there are three distinct groups of dinosaurs, birds (Avian dinosaurs), the Saurians (Hominid dinosaurs) and the surviving true Dinosaurs. Saurian engineering and technology has led to a resurgence in some species of true Dinosaur and has resulted in many of them being present in non natural environments.