Dinosaurs first appeared on earth 245 million years ago on a continent called Pangaea (this continent was actually made up of all of todays modern continents.).
By the end of the Paleozoic period, 245 million years ago, reptiles ruled on land and fish in the sea, but they almost all died out at the end of the Permian period. This ushered at the end of the Mesozoic period which started with a long period of recovery. Soon the old Paleozoic reptiles called mammal-like reptiles because they were the ancestors of mammals, began to get replaced by the dinosaurs. For the rest of the Mesozoic period - 170 million years - dinosaurs were the dominant animals on land .in seas other giant reptiles took over all the large predator niches. Mammals' evolved but remained restricted in numbers; birds appeared and plants transformed completely by evolving flowers - but the dinosaurs strode on. Finally, at the end of the Mesozoic period, 65 million years ago, the second ever mass extinction on our planet occurred which wiped out all living living things except birds and mammals. The modern Cenzoic era opened with a lot of smaller animals, such as mammals and birds these diversified and some returned to their water evolving into whales. Gradually, the rich variety of mammals with which we are familiar today appeared and finally, in the last blink of an eye on this vast time scale, humans evolved from the apes.
Most dinosaurs lived between 120-85 million years ago such as the Diplodocus, Brachiosaurus, Allosaurus, Tyranosaurus, Velociraptor, Deinochysaurus, Utahraptor, Orinthocheirus, Tapejara, Iberomersonis, Iguanodon, Anurognathus (this dinosaur was no larger than a human hand!) and Dwarf Allosaur.
Sometime between 95-75 million years a great flood occured leaving what was once the massive continent of Pangaea in tiny little islands.The Pangael ocean was split in too 3 huge ocans.The smallest one called the Tethy's, another called Boreal and since the name Pangeael still remained as the largest ocean.These 3 oceans are known as The Three First Oceans.It is during this time that sea dinosaurs such as Ophthalmosaurus(the dolphines of the mid jurrasic)Cryptoclidus,liopleurodon , Eustretosspondylus and another small Ptreosaur, Rhamphorhynchus.
60 million years ago the largest volcanic eruption in the entire southern hemisphere occured. This eruption is known as the Elcore eruption and it wiped out almost all the dinosaurs living in the southern hemisphere.
Most of the larger dinosaurs began to appear 90 million-65 million years ago such as Spinosaurus Egyptucus, Giganotosaurus (The largest predatory dinosaur ever), Triceratops, Barasaurus (Barasaurus was the largest dinosaur ever discovered), Koolasuchus, Anatotitan, Deinosuchus (This "dinosaur" was actually a crocodile which hunted the dinosaurs!), some of the animals from earlier times still lived on such as the Tyrannosaurus, Velociraptor, Iguanodon and other such dinosaurs. Some of the first birrds appeared during this time and these birds are the ancestor of modern predatory birds such as eagles, falcons and hawks.
65 million years ago the largest comet ever known to this planet struck the earth wiping out all the living things (plants and animals) at the time except mammals, birds and fish.
Walking With Dinosaurs (encyclopedia by Tim Haines BBC)
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