Dinosaurs diverged from their archosaur ancestors approximately 230 million years ago during the Middle to Late Triassic period, roughly 20 million years after the Permian–Triassic extinction event wiped out an estimated 95% of all life on Earth. Archosaurs ( Greek for 'ruling lizards' are a group of Diapsid Reptiles represented by Modern birds and Crocodilians This group also The Triassic is a geologic period and system that extends from about 251 to 199 Ma (million years ago The Permian–Triassic (P–Tr extinction event, informally known as the Great Dying, was an Extinction event that occurred, and 70 percent of terrestrial Radiometric dating of the rock formation that contained fossils from the early dinosaur genus Eoraptor establishes its presence in the fossil record at this time. Radiometric dating (often called radioactive dating) is a technique used to date materials usually based on a comparison between the observed abundance of a naturally occurring This is a List of rock formations meaning isolated scenic or spectacular surface rock outcrops Eoraptor was one of the world's earliest Dinosaurs It was a two-legged meat-eater that lived between 230 and 225 Million years ago Paleontologists believe Eoraptor resembles the common ancestor of all dinosaurs; if this is true, its traits suggest that the first dinosaurs were small, bipedal predators. Bipedalism is a form of Terrestrial locomotion where an organism moves by means of its two rear limbs A carnivore (ˈkɑrnɪvɔər meaning 'meat eater' ( Latin carne meaning 'flesh' and vorare meaning 'to devour' is any animal with a diet consisting The discovery of primitive, dinosaur-like ornithodirans such as Marasuchus and Lagerpeton in Argentinian Middle Triassic strata supports this view; analysis of recovered fossils suggests that these animals were indeed small, bipedal predators. Ornithodira is a Clade within the larger group Archosauria In 1986 Jacques Gauthier coined the name for a node clade containing the last common Marasuchus is a genus of Dinosaur -like Ornithodiran from the middle Triassic Period of Argentina. Lagerpeton is the name given to a genus of basal dinosauromorph from the Ladinian (Middle Triassic) The Middle Triassic (also known as Muschelkalk) is the second of three epochs of the Triassic period.
The first few lines of primitive dinosaurs diversified rapidly through the rest of the Triassic period; dinosaur species quickly evolved the specialized features and range of sizes needed to exploit nearly every terrestrial ecological niche. In Ecology, a niche (pronounced nich nēsh or nish A shorthand definition of niche is how an organism makes a living During the period of dinosaur predominance, which encompassed the ensuing Jurassic and Cretaceous periods, nearly every known land animal larger than 1 meter in length was a dinosaur. The Jurassic is a geologic period and system that extends from about Ma (million years ago to Ma that is from the end of the Triassic to the beginning The Cretaceous (kriːˈteɪʃəs, usually abbreviated 'K' for its German translation "Kreide" is a geologic period and system, reaching from the end of
The Cretaceous–Tertiary extinction event, which occurred 65. The Cretaceous–Tertiary extinction event, which occurred approximately ( Ma) was a large-scale mass extinction of animal and plant species in a geologically 5 million years ago at the end of the Cretaceous period, caused the extinction of all dinosaurs except for the line that had already given rise to the first birds. Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. Other diapsid species related to the dinosaurs also survived the event. Diapsids ("two arches" are a group of Reptiles that developed two holes ( Temporal fenestra) in each side of their Skulls about 300 Million