The dinosaur exhibition at Cityplaza will showcase fossils from the Triassic, Jurassic and Cretaceous periods which together make up the Mesozoic era spanning 180 million years. The Triassic period lasted from about 245 to 208 million years ago when the world was very different from today. All of the earth's continents were joined together into one Pangaea and the central region was largely desert. Plants were drab and grass did not exist; ferns and mosses covered the ground instead. The earth had undergone a phase of extinction and over 90 per cent of plant and animal life had disappeared. It was not until the late Triassic period that dinosaurs such as the pterosaurs and marine reptiles began to appear The Jurassic period followed. It lasted from 205 to 144 million years ago, and the allosaurs and brachiosaurs existed during this time. Dinosaurs from the early Jurassic era were relatively small but, over time, they grew tremendously. The Mesozoic era was the age of giants when large dinosaurs ruled the land, oceans and skies. During the Cretaceous period, which lasted from 144 million to 65 million years ago, animal life became more abundant and familiar flowers and flowering plants began to appear but there were still no grasses. By the late Cretaceous period the earth had evolved into a more familiar form. The climate became humid and sub-tropical, and wet and dry seasons also appeared. About 65 million years ago the earth experienced the end of the Cretaceous era and dinosaurs began to go extinct. Some paleontologists think that climate change caused the dinosaurs' extinction, while others argue that an asteroid hit the earth. This debate is still going on, making the study of fossils a quest for the truth.