Ornithischia


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	Like all animals on Earth, dinosaurs evolved over a long, long time. All dinosaurs have things in common because they share the same ancestors. What makes a dinosaur a dinosaur? A dinosaur was a special kind of reptile. Dinosaurs had legs directly beneath their bodies instead of splayed out from the sides. Most dinosaurs hatched out of eggs, like reptiles. They also had an upright gait, or way of walking. Over millions of years, the dinosaurs adapted to their different environments. Some dinosaurs ate meat and some ate plants. Some walked on four legs while others walked on two legs. Scientists can figure out how the dinosaurs evolved and became different by looking at fossils. The chart below shows where our dinosaurs fit in the dinosaur family tree. Click the dinosaur names on the right side to learn more about your favorite dinosaur!
	Ornithischia "bird-hipped" Ornithischia is one of the two main types of dinosaurs. These dinosaurs all have birdlike pelves, or hipbones that point backward.
		Marginocephalia "fringed heads" These herbivorous, or plant-eating dinosaurs had a "frill" on the back of their heads.
			Ceratopsidae Ceratopsians had beak-like snouts and rows of teeth in their cheeks for grinding; this means that they ate tough plants that other dinosaurs could not break apart. Their frills could have been for defense, for getting rid of excess heat, or for communicating with other dinosaurs. These dinosaurs traveled in herds, as their bones have been found in large groups.
			→Microceratops →Triceratops →Styracosaurus
			Pachycephalosauria "bone-headed" These dinosaurs had very thick, dome-shaped skulls that were large for their body size. They were mainly found from the Cretaceous period in the Northern Hemisphere. Most were small and bipedal, meaning they walked on their two hind legs.
			→Stygimoloch

		Ornithopods All Ornithopods were herbivores, or plant-eaters, and most of them were bipedal, meaning they walked upright on their two hind legs.
			Hadrosaurs "duck-billed" These dinosaurs were common during the Late Cretaceous Period in Europe, Asia, and North America. Hadrosaurs had unusual feet; they were either webbed or padded like a camel's. They spent most of their time on land, eating tough plants. Hadrosaurs migrated, or traveled, to nesting grounds to reproduce. Some of the Hadrosaurs, like Parasaurolophus, used the crests on their heads to make deep, loud sounds to communicate with the rest of the herd.
			→Parasaurolophus
			Hypsilophodontidae These herbivores (plant-eaters) walked on their two hind legs. They had broad, chisel-shaped teeth, usually set in two rows.
			→Thescelosaurus →Tenontosaurus


		Thyreophora These dinosaurs were armored, herbivorous (plant-eating), quadrapeds (animals who walk on all four legs, rather than on two legs).
			Stegosauria Stegosauria had two rows of spikes or plates along their backs and tails. Fossils of these dinosaurs are found all over the world.
			→Stegosaurus
			Ankylosauria Ankylosauria had more armor than most other dinosaurs; their plating was fused to some of their other bones. Their heads were broader and had spikes on the back; they also had heavy tails that could be used like a club against predators.
			→Ankylosaurus


	Saurischia "lizard-hipped" Saurischia is one of the two main types of dinosaurs. These dinosaurs are distinguished by their lizard-like pelves, or hipbones, that point downward and forward. Most dinosaurs in this group had a grasping hand, asymmetrical fingers, and long, agile necks.
		Sauropods Sauropods were quadrapedal dinosaurs, meaning they walked on all four feet. Sauropod means "lizard-foot"; their feet had five toes. As herbivores, or plant-eaters, they grazed for food across the countryside, often in herds. These large dinosaurs are most recognized for their extremely long necks and tails. Also, their nostrils were way up near the top of their heads instead of at the end of their snouts. Their small heads were equipped with blunt teeth for grinding up plants such as conifers, gingkos, cycads, ferns, and horsetails. Some dinosaurs, such as Brachiosaurus, held their necks vertically, like giraffes. They used their necks to reach the leaves and plants high in the trees. Other dinosaurs held their neck horizontally, closer to the ground. These dinosaurs probably stood on dry land and reached their necks into the swampier areas for food. They could also reach into the thick vegetation of the forest, where their large bodies could not fit.
			Prosauropoda	Plateosaurids		→Plateosaurus
			Sauropoda
				Diplocidae "double beams" These very large Sauropods had flexible tails that could move like a whip. They had pencil-like teeth.
				→Apatosaurus →Seismosaurus
				Titanosaurs "titanic lizards" These large dinosaurs had armored skin. Their heads were wider than other Sauropods. Their teeth were peg-shaped.
				→Alamosaurus →Argentinosaurus
				Brachiosaurids "arm lizards" These dinosaurs held their necks high like giraffes. Their front legs were longer than their hind legs and their tails were shorter and thicker than other Sauropods. Brachiosaurids had chisel-shaped teeth.
				→Brachiosaurus


		Therapods Therapods were bipedal, meaning they walked on two legs. These legs were muscular and they had bird-like, clawed feet. Therapod means "beast-footed" in Greek. All Theropods have hollow, thin-walled bones. Fast legs meant Therapods could move quickly across the land in pursuit of prey. They were carnivorous predators, or meat-eaters. Sharp teeth or beaks and strong jaws helped them rip into the flesh of other dinosaurs. At the end of their short arms were three main fingers with claws used for subduing their enemies. Large eyes suggest that Theropods had good eyesight for spotting future meals from long distances.
			Ceratosaurs "horned reptiles" The Ceratosauria were the were earliest Theropods. These dinosaurs are bird-like; they have hollow bones and curved S-shaped necks.
			→Ceratosaurus →Coelophysis →Dilophosaurus
			Coelurosauria This group of dinosaurs is closely related to birds. In fact, this group includes birds! Coelurosaurs have long arms and hinge-like ankles that allow faster movement.

				Ornithomimidae "bird mimics" These dinosaurs were slender, with slim back legs, very long front limbs, and hands that were not as good for grasping as the Maniraptors. Their necks were flexible and their heads were small and beaked. Their brain cavities were fairly large, suggesting higher than usual intelligence compared to other dinosaurs.
				→Ornithomimus
				Other Coelurosaurs These Coelurosaurs are difficult to classify, or put into a group. These are the most birdlike dinosaurs. Archaeopteryx, for example, is often considered to be the first bird. All three of the animals included in this category had feathers but did not fly.
				→Archaeopteryx →Caudipteryx →Microraptor
				*Tyrannosaurs "tyrant lizard"* These enormous carnivores had short, deep jaws with huge sharp teeth, small eyes, and tiny forelimbs. Tyrannosaur fossils are common in North America, especially their teeth, which they often lost. Their teeth, unlike most carnivores, are more like big spikes than razor-sharp knives.
				→Daspletosaurus →Tyrannosaurus Rex
				Maniraptora "seizing hands" These were the dinosaurs most closely related to birds. They had an unusual wrist with an extra bone. This wrist is what makes flight movements possible in birds. Their hands were larger than their feet. Their tails were stiffer and shorter than many other dinosaurs.
					*Primitive Dromaeosaur* This category only includes Megaraptor; It may be an ancestor of the Dromaesaurs, or part of an entirely different group of dinosaurs. It differs from the Dromaeosaurs with its much larger size and longer, more slender feet.
					→Megaraptor
					*Dromaeosaurs* This is the "raptor" group of dinosaurs. They had a slashing talon on their second toe of their feet.
					→Deinonychus →Velociraptor
					*Oviraptors "egg sna*tchers" These Maniraptors are very rare fossil finds, but have been well-preserved. Oviraptors have unique head shapes; the skulls were short and deep with large nasal cavities like the Hadrosaurs, probably used to make sounds. Their jaws were toothless, but good for crushing hard objects like molluscs.
					→Oviraptor
					Therizinosaurs This is a strange group of dinosaurs that does not fit well in most categories. Therizinosaurs had backward-pointing hips like birds, and hollow bones like other Theropods; but they probably ate only plants, unlike the other Theropods. They were large and bulky. Like Sauropods, Therizinosaurs had four main toes on their feet, small heads, and leaf-shaped teeth. Unlike other dinosaurs, this group had extremely long claws on their hands.
					→Therizinosaurus


			Carnosauria "flesh lizards" As the name suggests, these dinosaurs were carnivorous, or meat-eaters. Carnosaurs have thigh bones (femurs) that are longer than their shin bones (tibia). They also have large eye sockets and long, narrow tails.
				→Cryolophosaurus →Spinosaurus
				Allosaurs "different lizards" Allosaurs had large, narrow jaws, strong forelimbs with huge claws, and large legs. They were ferocious hunters.
				→Allosaurus →Giganotosaurus

			Other Theropods This group includes Chindesaurus and Syntarsus (Megapnosaurus). Both of these Theropods were found in Arizona, and they may be some of the oldest dinosaurs. Scientists are not sure yet how to classify these two dinosaurs, because not many of their fossils have been found.
			→Chindesaurus →Syntarsus


	Pre-historic Animals
		*Pterosaurs* Flying Reptiles	→Cearadactylus →Pteranadon →Quetzalcoatl →Tapejara
		*Archosaurs* Ancient Reptiles	→Archelon →Postosuchus
		Mammals	→Doedicurus →Sabertooth Cat →Uintatherium →Wooly Mammoth →Coelodonta →Hyracotherium

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