Where and When Did Dinosaurs Live The Mesozoic Era which means middle life when dinosaurs were the dominant vertebrate terrestrial animals occurred from 252 million to 65 million years ago During this time period the map of the world was very different than it is today At the beginning of this Age of Dinosaurs there was only one super continent which we call Pangea Over millions of years Pangea began to break apart into separate continents as seas and oceans flowed into the widening gaps between the separating land masses This process called continental drift continues today The Mesozoic Era is divided into three periods the Triassic 252 to 208 million years ago the Jurassic 208 to 145 million years ago and the Cretaceous 145 to 65 million years ago During the Triassic the early dinosaurs were able to travel across the whole of Pangea but after the continents began to drift apart the movements of later dinosaurs became more and more restricted This allowed for dinosaur diversity on each of the isolated continents and dinosaur fossils have been discovered on every continent 12 Triassic map Jurassic map Cretaceous map
Dinosaurs and Hips Dinosaurs share a common ancestor that probably looked much like the small Triassic thecodontian reptiles Ornithosuchus and Lagosuchus pelvic bones the ilium ischium and pubis radiate out from the hip socket as in reptiles with the pubis pointing forward The bones in the Ornithischian dinosaur pelvic structure on the other hand are parallel to the ischium and All dinosaurs are divided into two large orders based on the shape the pubis is rotated backwards as in birds The Saurischians are further of their hips These groups are the Saurischian lizard hipped and divided into two suborders the carnivorous theropods terror foot and the Ornithischian bird hipped In Saurischian dinosaurs the three the generally huge herbivorous sauropods lizard foot Ornithosuchus Lagosuchus 13
The Centrosaurus is hipped bird Bird hip The Saurischians include the smallest Mesozoic dinosaurs such as the feathered Microraptor about the size of a crow as well later in this book Ironically it was lizard hipped and not bird hipped dinosaurs who were the ancestors of modern birds as the largest land animals that ever lived like the tall story story six Brachiosaurus The theropod dinosaurs walked on their hind legs and were generally carnivores like Tyrannosaurus though some seem to have been omnivorous like Falcarius both shown Lizard hip The Gorgosaurus is hipped lizard 14
Dinosaur Colors and Patterns How do we know what colors dinosaurs were The short answer is We don’t For the long answer turn the page 15
