The first true dinosaurs first appeared about 230 million years ago. The first dinosaur fossils are distinguished from those of their reptile ancestors by their more upright stance, with legs directly beneath the body instead of splayed to the side, as with other reptiles. The earliest dinosaur fossils were found in South America, although a December 2012 fossil discovery in southern Africa casts some doubt on a South American origin.
The first dinosaurs were a group of species known as theropods. They walked on two legs and varied in size from the 20-pound Eoraptor to the 400-pound Herrerasaurus. The group spread relatively quickly from South America to North America, and then further to Africa and Eurasia. Many famous types of dinosaur, including tyrannosaurs and allosaurs, were later species of theropod.
Dinosaurs with four legs evolved from theropods, but they are not considered theropods themselves. These species, which were mostly herbivores, were split into two groups by their hip structures. Lizard-hipped species included the giant sauropods. Bird-hipped groups included the armored anklyosaurs and the horned ceratopsians. Scientists think that all bird-hipped dinosaurs descend from a species called Eocursor, a species from South Africa, which, in turn, was probably descended from Eoraptor.Learn More
As of 2014, most palaeontologists believe that the Argentinosaurus was the largest dinosaur to have ever lived. It may have been the largest land animal to have ever existed.Full Answer >
The Cenozoic Era is known as the "Age of Mammals." This era is broken down into time periods according to the life forms that lived during that time. In the Paleogene Period, rodents, small horses were common and rhinoceroses and elephants first appeared. By the end, dogs, cats, and pigs became common mammals. The Neogene Period gave rise to early primates, which included early humans.Full Answer >
There is evidence that dinosaurs did not have a single, uniform and universal diet but rather a wide variety of dietary habits, with evidence supporting the idea that carnivorous, herbivorous and omnivorous species all existed. Different feeding styles were also likely, with some carnivorous species hunting prey such as mammals and small reptiles, while other carnivores may have been opportunistic carrion scavengers. There was likely even a good range of dietary variety amongst the herbivorous dinosaurs, which may have made up the majority of all dinosaur species.Full Answer >
Dinosaurs are hatched from eggs, therefore new baby dinosaurs are called hatchlings, just like their reptile cousins the turtles and crocodiles. Young dinosaurs, beyond the hatchling stage, are referred to as juveniles.Full Answer >