Tyrannosaurus rex and Stegosaurus

Tyrannosaurus Rex

Western North America

67,000,000-65,500,000

Now who doesn't like Tyrannosaurus Rex (ty-ran-O-saur-us rex)? The T. Rex is one of the most famous of dinosaurs, and one of the biggest meet eaters that has ever lived. Their is still debate on the T. Rex being a hunter or a scavenger, since it was so top-heavy and "slow" it would be a scavenger but it might have lived in packs making  it a better hunter. But we just don't know, it might have been both. 

There is speculation that the Tyrannosaurus Rex had feathers. They have found fossils of T. Rex chicks having feathers but it is unknown if adults did, scientists speculate that as the chicks grew they would have molted their feathers. It is also theorized that Nanotyrannus (na-no-ti-ran-us) were actually baby T. Rex's in that the fossilized bone tissue is spongy which means that Nanotyrannus was a juvenile and not full grown, while as the T. Rex was full grown with dense bone tissue. The main difference was just that Nanotyrannus had 17 teeth while the T. Rex had 12. But we have found transitions between the Nanotyrannus and T. Rex with 15, 14, and 13 teeth meaning that the T. Rex lost teeth as it grew older and bigger. In other words Nanotyrannus never existed.

Fun fact:
The T, Rex's closest living relative is the chicken.

Stegosaurus

Western North America

155,000,000-150,000,000

Stegosaurus (stay-go-sore-us) was the biggest of the Stegosauria family despite its small brain that was the size of a walnut. Stegosaurus was a herbivore that could chew its food, most other dinosaurs had teeth and jaws that would just swallow all the vegetation and then the food would be grounded up by stones in the stomach, a lot like most birds. 

It is unknown why Stegosaurus had boney plates along its back, but the tail spikes are known to have been powerful weapons. The plates might have been used as a 'sail', not the kind of sail that's on boats, but the kind that heats up the animals body. Few animals are known to have sails along their backs, but its not entirely impossible to roll out, they might have been a warning sign to predators too, by flushing blood into the plates to make them flash red or a mating attraction too. The tail spikes were dangerous and deadly, their have been allosaurus fossils found with stegosaurus spike wounds in the legs, hips, chest, and even head.