Marginocephalia is a group of Suborders Thyreophora Cerapoda    Ornithopoda    Marginocephalia Ornithischia is an order of beaked, herbivorous dinosaurs. They are known as the bird-hipped dinosaurs because of their hip structure, even though birds are actually descended from the lizard-hipped dinosaurs (the saurischians). They were also more numerous... ornithischian Orders Saurischia    Sauropodomorpha    Theropoda Ornithischia Dinosaurs are giant reptiles that dominated the terrestrial ecosystem for most of their 165-million year existence. They became extinct 65 million years ago (Ma) at the end of the Cretaceous period, and are known from fossilized bones, feces... dinosaurs that includes the thick-skulled pachycephalosaurids, and horned Groups Psittacosaurus Coronosauria Ceratopia (ser-a-TOP-ee-ah) or Ceratopsia is a group of ornithischian dinosaurs which evolved during the Cretaceous period in what is now North America and Asia. Early members such as Psittacosaurus were bipedal and had very small frills. This group later gave rise to a... ceratopsians. They were all In zoology, an herbivore is an animal that is adapted to eat primarily plants (rather than meat). Thus, while humans may choose not to eat meat, such individuals are vegetarians, not herbivores. A true herbivore, such as a cow, is unable to chew or digest meat. However, many herbivores will... herbivores, walking in two or four legs, and they all had some kind of crest or bump in their heads. The Greek clados = branch) or phylogenetic systematics is a branch of biology that determines the evolutionary relationships of living things based on derived similarities. It forms the basis for most modern systems of classification, which seek to group organisms by evolutionary relationships. In contrast, phenetics groups organisms based on their overall... clade evolved in the The Jurassic period is a major unit of the geologic timescale that extends from about 195 million years BP at the end of the Triassic to 135 million years BP at the beginning of the Cretaceous. As with other geologic periods, the rock beds that define the start and end... Jurassic period, and became common in the Upper The Cretaceous period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic period (about 135 mya) to the beginning of the Paleocene epoch of the Tertiary period (65 mya). The end of the Cretaceous also defines the boundary between the Mesozoic and... Cretaceous.