Dinosauria uga wis disaranake bisa ditetepake babagan MRCA saka Megalosaurus lan Iguanodon, amarga iki minangka loro saka telung genera sing dikutip dening Richard Owen nalika dheweke ngakoni Dinosauria. Kaloro definisi kasebut ngasilake klompok kewan sing padha sing ditetepake minangka dinosaurus: "Dinosauria = Ornithischia + Saurischia", kalebu ankyloproposaurians (herbivore herbivore herbivore quadruped), stegoposaurians (herbivore quadruped platinum), ceratopsians (herbivore quadruped with horns and horns), utawa frognithopods (frognithopeds), utawa frognithopids (frognithopes), utawa frognithopids (frognithopes), kalebu dinosaurus lan dinosaurus sing dianggep minangka anggota saka klompok dinosaurus sing luwih gedhe tinimbang dinosaurus tradisional. Nanging, miturut analisis tradisional, para ahli taksonomi, kalebu Ornithis, Ornithis, Bird, lan Thermophthora, ora bisa ngatasi klompok dinosaurus sing diklasifikasikake minangka dinosaurus sing luwih cedhak karo dinosaurus tradisional
leluhur umum paling anyar (MRCA) saka Triceratops lan Neornithes, lan kabeh turune