Mesozoic, Middle Jurassic Period, 150 million years ago

Origin of Planet Earth

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Mesozoic MIDDLE JURASSIC PERIOD 150 MILLION YEARS AGO MORE SCIENCE FACTS During the Jurassic flying reptiles like the pterosaurs dominated the skies. They were the first vertebrates to take to the air, although another group of feathered reptiles evolved later in the Jurassic. These we now believe to be the direct ancestors of modern birds. This scene might be typical of many areas that bordered the Tethys Ocean during the Middle Jurassic. Tethys has largely vanished with its sediments forming the Himalayas and other mountains and the Mediterranean Sea is one of the last remnants of this formerly vast ocean.

The Jurassic is the second period of the Mesozoic. At this time the land was occupied by dinosaurs while marine reptiles like ichthyosaurs and plesiosaurs lived in the oceans.

The Jurassic seas contained different fossils from those seen earlier in the geologic record. Trilobites that had been so successful in the Paleozoic had vanished. Instead the oceans of this time were dominated by ammonites (left), floaters and swimmers in the seas that are distantly related to modern octopus, squid and pearly Nautilus. Jurassic rocks are present elsewhere in Canada but were either not deposited or eroded from this area in the distant geologic past.

The Jurassic Period was named after the Jura Mountain region on the French-Swiss border where these rocks are particularily well exposed. The start of the Jurassic (200 million years ago) saw the opening of the present North Atlantic Ocean created by the breakup of the former supercontinent of Pangaea. The Jurassic saw the development of the first flying reptiles (a pterodactyl, top left) and the feathered dinosaurs (Archaeopteryx, top right). Tree ferns (bottom right) and the cycads that we see today, flourished at this time.

The GeoTime Trail Project has been brought to you by the generosity of Concept, text and illustrations: Dr. Alan V. Morgan