The eoraptor was one of the earliest known dinosaurs. They were here 231 to 228 million years ago. When first described in 1993, it was considered to be one of the earliest, if not the earliest known dinosaur. Eoraptor has heterodont dentition, suggesting that it was omnivorous, and that this feeding strategy had evolved early on in dinosaurs.
Troodon is a genus of relatively small, bird-like dinosaurs known definitively from the Campanian age of the Cretaceous period. Discovered in 1855, T. formosus was among the first dinosaurs found in North America, although it was thought to be a lizard until 1877. Troodon were small dinosaurs, up to 0.9 meters 3.0 ft in height, 2.4 meters 7.9 ft in length. Troodon had some of the largest known brains of any dinosaur group.
Dilophosaurus was one of the largest carnivorous dinosaurs of the early Jurassic period. Dilophosaurus gets its name from the two thin crests of bone on the top of its head. Dilophosaurus has been found in both the U.S. and China, which, although part of the same huge landmass, were still quite a long distance from each other. Dilophosaurus was discovered by a Native American. In 1942 Navajo Jesse Williams led fossil-hunters Bill Rush, Ed Kott, and Sam Welles to the site where he’d happened upon the first known Dilophosaurus remains two years earlier.
The T-Rex is twelve meters long. More than 30 specimens of T.rex have now been identified. Tyrannosaurus/ T-Rex is a genus of tyrannosaurid theropod dinosaur. The species Tyrannosaurus rex, is one of the most well-represented of the large theropods.