The Mesozoic Age. By Daniel Maiuolo

The Mesozoic Era The age of when dinosaurs inhabited the earth was called the Mesozoic Era. During this time from 248 – 65 million years ago. The Mesozoic was a time of tectonic, climatic and evolutionary activity. The continents gradually shifted from a state of connectedness into their present configuration the drifting provided for speciation and other important evolutionary developments. The climate was exceptionally warm throughout the period, also playing an important role in the evolution and diversification of new animal species. By the end of the era, the basis of modern life was in place.

Triassic Period The Triassic Period (248 – 208) million years ago. The Triassic Period is a geologic period and system that extends from about 248 to 208 million years ago. As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events. The extinction event that closed the Triassic period has recently been more accurately dated, but as with most older geologic periods, the rock beds that define the start and end are well identified, but the exact dates of the start and end of the period are uncertain by a few million years. During the Triassic, both marine and continental life show an adaptive radiation beginning from the starkly impoverished biosphere that followed the Permian-Triassic - extinction. Corals of the hexacorallia group made their first appearance. The first flying vertebrates, the pterosaurs, evolved during the Triassic.

Jurassic Period The Jurassic Period(208-146 ) million years ago. At the start of the early Jurassic period, the giant continent Pangaea broke up, forming the beginning of the world that we now know. There were huge volcanoes with rivers of lava and clouds of poison gases. Land that had been part of the interior of the huge continent was now coastline of smaller continents, and the climate began to change accordingly. Forests of ferns, ginkgo trees, cycads and conifers grew. All these plants can still be seen today. Scuttling about at the bottom of these plants were the early mammals, all of them rat-sized. The dominant land animals were the huge dinosaurs, the largest land animals ever. They were the gigantic herbivore (plant-eaters) sauropods such as Diplodocus and Brachiosaurus. Other herbivores included Stegosaursaurus. Carnivorous (meat-eating) dinosaurs included Allosaurus and Dilophosaurus. The dinosaurs of the Jurassic were much more different from each other than in other periods: there was a greater variety. Because of the different climate, the forests grew, and the herbivores became huge in order to feed on the tall trees. The carnivores then had to become larger and more fierce to deal with such huge prey. The first birds appeared, such as Archaeopteryx. The seas were full of marine reptiles such as the plesiosaurs, crocodiles, ichthyosaurs, sharks and rays.  

Cretaceous Period The Cretaceous Period (146 – 65) million years ago . The Cretaceous period marks the end of The Age of the Dinosaurs. Big and small dinosaurs lived in great forests of cycads, conifers and ferns. There were great marine reptiles in the seas and great flying reptiles in the skies.  Some things happened in the Cretaceous period that were important to life on earth. One of these was the development of flowering plants. By the end of the period, there were many that we would recognise today, such as magnolias and waterlilies. The number of different insects increased during this period too. The beginnings of many modern insects were at this time: ants, grasshoppers, butterflies, aphids and termites among them. At the end of the Cretaceous period there was a great extinction of many species, including dinosaurs. Birds, small reptiles and mammals, many marine creatures and plants survived. Scientists believe a giant meteor hit the earth, causing massive destruction, tidal waves, acid rain, and huge clouds of dust that blocked the sun's rays from reaching the earth to light and warm it. The dinosaurs were among the many species that were wiped out. Following the great extinctions, there was a slow recovery and evolution of new species.

Plants of the Triassic Period The Triassic period (248 - 208 million years ago) followed the biggest mass extinction in the history of the Earth, the Permian extinction. This left the Earth relatively unpopulated (especially the seas) and ready for new life. During the Triassic period, the first dinosaurs and the first mammals appeared. Many plant families were culled; giant club mosses and horsetails also went extinct during the late Permian, and new forms evolved during the Triassic. The Triassic was the beginning of a boom in conifers and cycadophytes.

Plants of the Jurassic Period The Jurassic Period was the time when the enormous sauropods (like Brachiosaurus, Diplodocus, and Apatosaurus) lived, devouring tremendous amounts of foliage each day, probably mainly conifers. There probably weren't many of these gigantic plant-eaters in any one area since competition for food would have been a problem. These sauropods may have destroyed forests and trampled other plant habitats, forcing these dinosaurs to migrate occasionally in order to find new food sources.

Plants of the Cretaceous Period There was a tremendous boom in both plants and animals caused by the advent of flowering plants and the decline of less adaptable species (like conifers and seed ferns). This reshuffling of species led to the heyday of dinosaurs during the late Cretaceous period. Other Cretaceous period plants included: Podocarpus, Betulaceae (like Alnus), Araliaceae (like Aralia), conifers (like Araucarioxylon, Metasequoia, and Pinus), Corneaceae (like Cornus), Cycadeodias (like Cycadeoidea), Fagaceae (like Quercus - oak), Filincophyta (like Dryophyllum), Filincophyta (like Tetrastichia ), Ginkgophyta (like Ginkgo), Lauraceae (like Laurus and Sassafras), Magnoliaceae (like Magnolia), Moraceae (like Ficus), Palmae (Palmus), Pandanaceae (Pandanus), and Salicaceae (like Populus and Salicaceae).

Graph of the Habitat of the Dinosaurs

How The Dinosaurs Became Extinct Probably the most popular theory right now is the Asteroid Theory. According to this theory a large asteroid or comet collided with Earth about 65 million years ago. Scientists think that such a large collision would throw so much dust into the air that sunlight would not be able to shine and plants and animals would die. The dramatic changes in climate that resulted from this huge collision were too much for the dinosaurs. They were not able to survive. Another theory that could explain how the dinosaurs became extinct is volcanic activity. A huge increase in volcanic activity at around 65 millions years ago could have pumped so much ash into the air that it blocked out the sun killing the dinosaurs. Some scientists believe that there was a severe ice age. Throughout Earth's history there have been many ice ages. The last one ended about 10,000 years ago. A very severe ice age could have changed temperatures and frozen a lot of Earth's water. The dinosaurs would not be able live under such conditions and that is how the dinosaurs became extinct. It has also been suggested that disease killed off the dinosaurs. A very deadly and contagious desease may have circulated among the dinosaurs forcing them to become extinct. Still yet another theory is that the Earth just gradually changed in climate over a long time period and the dinosaurs were not able to adapt to the cooler, dryer climate.

Thankyou for watching my slide on the Mesozoic Age