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Types of Dinosaurs That Lived

Earth's fossil record shows that millions of years ago this planet was inhabited by massive dinosaurs. Many theories have been proposed trying to prove how and why these dinosaurs eventually became extinct. When they were alive, there were two main groups of dinosaurs. These groups were ornithischians, who had backward pointing pubic bones, and saurischians, who had forward-pointing pubic bones. These two groups have five categories, or types, of dinosaurs that have unique distinctions from each other.

Theropods
- These types of dinosaurs mostly hunted for their food and were carnivorous. The theropods walked on their hind legs and some had feathers with the ability to fly. Today's birds are ancestors of these flying feathered dinosaurs. Theropods were considered some of the smarter dinosaurs in history because of their large brains. Some of the more common dinosaurs in this group include albertosaurus, tyrannosaurus, velocirapture, allosaurus, megalosaurus, spinosaurus, sinosauropteryx and caudipteryx.
Sauropodomorphs
- The sauropodomorphs were very large dinosaurs. A large majority of these creatures walked on all four legs because they were so large. They were all plant eaters, or herbivores. These dinosaurs tended to have small heads and brains, long necks and massive stomachs for digesting the mass quantities of plants that they consumed. Some of the more common dinosaurs in this group include apatosaurus, diplodocus, brachiosaurus, omeisaurus, sauroposeidon and vulcanodon.
Thyreophorans
- The thyreophorans were dinosaurs that had defensive weapon-like and armor-like bodies. The protective characteristics and parts were very heavy-plated, armored bodies and flesh-piercing spines or spikes. These dinosaurs would walk on four legs, were large and relatively slow. Thyreophorans were herbivores and needed these defensive systems to fight off carnivorous dinosaurs that would try to eat them. Some of the more common dinosaurs in this group include stegosaurus, ankylosaurus, gargoyleosaurus and scelidosaurus.
Ornithopods
- The ornithopods were a type of dinosaur that thrived for many millions of years. These creatures were herbivores and because of the location of their pelvis, many of the ornithopods could walk on their hind legs. Some of the larger species of these dinosaurs walked on all of their legs. These dinosaurs had teeth meant for chewing and short beaks. Some of the more common dinosaurs in this group include iguanodon, callovosaurus, muttaburrasaurus and ouranosaurus.
Marginocephalians
- The marginocephalians were dinosaurs that also were herbivores and had horns attached to their heads. The horns were used for defensive measures, but many of the dinosaurs' horns were decorative or not used. These dinosaurs had extremely thick boney skulls and some of the largest skulls of all the dinosaurs. It's probable that these dinosaurs would ram their heads together in competition. Some of the more common dinosaurs in this group include triceratops, einosaurus, centrosaurus and styracosaurus.

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