DINOSAURS, EVOLVED?
Saurischians ("lizard-hips")
These long-necked dinosaurs contained many distinctive features. As well as their long necks, Saurischians had a grasping hand and asymmetrical fingers. However, it was their hip structure that distinguished the two suborders. The pelvis of Saurischians was arranged similarly to those found in the modern lizard, with the pubis bone pointing downward and forward at an angle toward the ischium(refer to diagram); thus them being referred to as "lizard-hipped". Saurischians consisted of both carnivores and herbivores. They are further divided into two suborders, theropoda and sauropodomorpha.
This order of dinosaurs roamed the Earth from the mid-Triassic period to the end of the Cretaceous period. Oddly enough, the only existing descendent of these lizard-hipped dinosaurs after their extinction is the modern bird.
Sauropodomorpha
Sauropodomorphs are long-necked, herbivorous dinosaurs. Its name translates to "lizard-footed forms", as these dinosaurs usually walked on four legs. Sauropodomorphs thrived during the late-Triassic period before declining towards the early Cretaceous.
They are the largest land animal to ever roam the Earth, having had a long neck, a relatively small head, and a tail. A common, well-know dinosaur of this suborder is the Apatosaurus(or once known as Brontosaurus).
Theropoda
Theropods include all the carnivorous dinosaurs. They are the largest carnivores that ever existed. These "beast-footed", or bipedal(meaning they walk on two legs) dinosaurs are very fast and agile, with strong, bird-like feet. Well-known theropods include the Tyrannosaurus rex and the Velociraptor.
Although dinosaurs have been extinct for a long time, birds are actually related to dinosaurs. More specifically, birds are descendants of small nonflying theropods.
Ornithischians ("bird-hips")
These dinosaurs are entirely made up of herbivores. They had a hip structure similar to that of a bird, with the pubis pointing downwards, parallel to the ischium.; thus, being named Ornithischians, meaning bird-hips. Modern birds, however, are not descendants of the Ornithischian suborder. As previously mentioned, birds are related to the Saurischians, "lizard-like", suborder ─more specifically, theropods.─rather than the Ornithischians. These bird-hipped dinosaurs also had a predentary bone, which is an extra bone in the lower jaw, forming a beak-like structure. This beak-like apparatus benefited the herbivorous lifestyle of Ornithischians, aiding in obtaining foliage and plant material.
Ornithischians are broken down into three suborders, thyreophora, marginocephalia, and ornithopoda.
Ornithopoda
Ornithopods are medium to large dinosaurs. As their name, which means bird feet, suggests, these dinosaurs were mainly bipedal, with three-toed feet. Ornithopods also had stiff tails, aiding in balance as they moved. Many had primitive, horny beaks; however, there were numerous who possessed a duck-bill feature.
A famous Ornithopod would be the Iguanodon, which was one of the very first dinosaurs to ever to be discovered, and the second to be named.
Marginocephalia
Marginocephalians are characterized by their distinctive skull structure. Their name, meaning "fringed heads", refers to the bony ridge on the back of their skull. Marginocephalians had either horns or a thick skull.
A well-known dinosaur of this suborder is the Triceratops.
Thyreophora
Thyreophorans range from small to fairly large dinosaurs. Their name means "shield bearers", as they are distinguished by the armour plates on their body and elaborate spikes.
Most familiar dinosaurs of this suborder are the Stegosaurus and Ankylosaurus.
Stegosaurus
Iguanadon
Tyrannosaurus Rex