The ancestors of dinosaurs walked upright before they evolved into true dinosaurs. The earliest known dinosaur, Eoraptor, walked with upright legs underneath its body.
Dinosaurs that walk on two legs are called "bipeds". The term applies to all animals that walk on two legs.
No carnivorous dinosaurs walked on four legs. Some famous carnivorous reptiles that predate dinosaurs are often mistakenly called dinosaurs. An example is the Dimetrodon.
No, not all carnivorous dinosaurs walked on two legs. Some carnivorous dinosaurs, like the theropods, were bipedal, walking on two legs. However, others, such as the ceratosaurs, were quadrupedal, walking on four legs.
Animals walk on four legs because it is more stable than walking on two legs. Dinosaurs were very large, and it would have taken a lot of energy for them to walk on two legs. The ones who did walk on two legs were usually predators (like Tyrannosaurus rex or velociraptor) because they could get more energy from eating other animals than from eating plants.
All dinosaurs had four limbs. Some dinosaurs, like Tyrannosaurus and Allosaurus, were bipeds, which means that they only walked using their two hind limbs. Other dinosaurs, like Stegosaurus, Ankylosaurus, and Diplodocus, always walked on all four limbs, making them quadrupeds. And some dinosaurs walked on all fours, but ran on their two hind legs. Examples of such dinosaurs include Igaunodon and Parasaurolophus.
Theropods were the main bipedal dinosaurs. However, some small ornithopods, like Orodromeus, were bipeds, and hadrosaurs could walk on two or four legs.
No, it possessed two massive legs and two small arms.
Any animal that walks on four legs is called quadrupedal. Quadrupedal dinosaurs include sauropods, stegosaurs, ceratopsians, and ankylosaurs. Hadrosaurs could were usually quadrupedal, but could walk, stand, or run on two legs.
Dinosaurs were a subset of reptiles but they were different from any modern reptile. Modern reptiles are cold-blooded animals with a fairly slow metabolism. They walk with their legs stuck out to the side except for snakes and some lizards which have no legs. They are covered in scales. By contrast dinosaurs walked with their legs erect directly beneath them. There is evidence that many dinosaurs were warm blooded and had active lifestyles. Some are now known to have been covered in feathers rather than scales. A number of dinosaurs such as velociraptor were much more like birds than like modern reptiles.
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Triceratops are very large dinosaurs that had trouble lifting their body weight. Because of natural selection the dinosaur adapted to walking on four of it's legs instead of two.