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Dinosaurs are a diverse group of reptiles [note 1] of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is a subject of active research.
Around 1880, dinosaurs were largely treated as a monophyletic group (i.e. having a last common ancestor not shared with other reptiles). However, Harry Seeley disagreed with this interpretation, and split the Dinosauria into two orders, the Saurischia ("lizard-hipped") and the Ornithischia ("bird-hipped"), which were seen as members of the Archosauria with no special relationship to each other.
Beginning of animal evolution. [54] [55] 720–630 Ma Possible global glaciation [56] [57] which increased the atmospheric oxygen and decreased carbon dioxide, and was either caused by land plant evolution [58] or resulted in it. [59] Opinion is divided on whether it increased or decreased biodiversity or the rate of evolution. [60] [61] [62 ...
The authors came up with five phases to explain dinosaurs’ ascendancy: Their ancestors were omnivorous, eating plants and animals. They evolved into the first carnivorous and plant-eating, or ...
From roughly 230-200 million years ago, during the Late Triassic and into the early Jurassic periods, dinosaurs emerged from just one of many reptilian species to become the dominant species on Earth.
The early dinosaurs were not very successful. They became the dominant animals at the beginning of the Jurassic period, which was marked by a mass extinction of many of their competitors. After covering this evolution, he discusses the speciation of dinosaurs in the Jurassic, with an especial focus on sauropods.
Darwin did not publish his ideas on evolution for 20 years. However, he did share them with certain other naturalists and friends, starting with Joseph Dalton Hooker, with whom he discussed his unpublished 1844 essay on natural selection. During this period he used the time he could spare from his other scientific work to slowly refine his ...
He suggested that dinosaurs, far from becoming extinct, had evolved into a wide variety of descendants in the form of birds. [1] [45] Ostrom's work led to a revolution in the classification of fossils and the understanding of dinosaur-bird lineages. [1] [2] Ostromia crassipes, previously known as the Haarlem Archaeopteryx