Jurassic Period By: Sonia Kups Bio Project

Jurassic Period  Jurassic period began 208 million years ago and ended 144 million years ago.  The whole Jurassic period lasted million years.  The Jurassic period was part of the Mesozoic Era.  The Jurassic period was divided into three parts: early Jurassic- Lias, middle Jurassic- Dogger and late Jurassic- Malm.  The Jurassic period is the middle period of the Mesozoic era.  The Jurassic is known as “The Age of Dinosaurs.”  Most animals die out in the Triassic period, the dinosaurs survived  The armored placodonts and great Shastosaurs were all extinct because of the mid-Carnian and Rhaetic extinctions from the Triassic period.  This period was the height of the dinosaurs existence.  The word “Jurassic” came from the Jura Mountains in Europe.

Geography  In the beginning of the Jurassic Period most continents were joined together.  The Atlantic Ocean started to form and the Americas separated from Africa.  Arizona, Colorado and Utah were all deserts.  Italy, Greece Turkey and Iran were attached to the North African part of Gondwanaland.  Sandstone, limestone, shale and gypsum were deposited all over North America.  The Sierra Nevada, Klamaths, Cascades, Coast Ranges, Rocky Mountains and coastal mountains of Canada and Alaska were formed.  No glaciers were present.  The continents began to rotate and separate from each other.

Geography  There were three continents: North America, Eurasia and Gondwanaland  New sea floor formed along the South Atlantic.  The sea level rose in the Jurassic Period flooding large portions of continents.  The Sundance Sea formed in North America.  The land of the Jurassic period contained black organic mudstones with microcrystalline limestone.  Same group of dinosaurs and plants lived on all the continents.  Yorkshire, UK was actually a shallow sea or a lagoon during the Jurassic period.  What is now the Amazon and Congo forests were deserts in the Jurassic period.

Climate  Tropical climate  About 15 degrees F warmer then current temperature  The climate was warmer and moister then that of the Triassic period.  As time went on the climate became more humid.  Nowadays people classify the Jurassic terrestrial environments in different climate zones by looking at the leaf changes, geographic distribution and climate relationship.  As researchers find the original climate of the Jurassic they will see which plants lived on what parts of land.  In the early and middle Jurassic Pangea was very arid and hot.

Plants  Gymnosperm plants were present.  Cycads were the main dominant plant life.  There were two different types of cycads: the palm like ones and the short ones that looked like brushes.  Conifers, ginkoes, palms, horsetails and ferns were present.  Forests contained ferns and ginkos.  The ground was covered with ferns and cycads.  On the ocean floor different types of plankton were abundant.  There was no flowering plants.  The caytoniale plants later evolved into flowering plants.  The Petrified Forest National Park in Arizona has preserved trees from the Jurassic and Triassic periods.  Plants were the basis of the food web.

Cycads  This cycad was one of the palm like ones that bigger dinosaurs, like the brachiosaurus ate from.  There were also separate female and male cycad plants.

Animal Biology  1000 species of insects were present.  Some of these insects can be found on earth today  The reptiles were the dominant animal.  Dinosaurs ruled the land.  Crocodiles, ichthyosaurs and plesiosaurs ruled the sea  Pterosaurs ruled the sky  The first bird-like reptile appeared in the Jurassic Period known as Archaeopteryx.  Primitive mammals appear, but they are very small and not very important.  Invertebrates were plentiful: sponges, corals, bryzoa, gastropods, bivalves, ammonoid, belemnite and cephalopods  Clams, snails and branchiopods were also common  On land millipedes, scorpions, spiders and mites were present.  Modern shark groups appeared.

Animal Biology  During the late Jurassic some small carnivores developed feathers and learned how to fly.  The largest land animal was the sauropods.  The sauropods were plant eating.  The dinosaurs ruled land for 135 million years.  Some of the herbivores during the Jurassic were prosauropods, cynodont synapsids and other mostly small ornithischian dinosaurs.  Plant eating dinosaurs were the biggest dinosaurs around.  Dinosaurs like the Stegosaurus had brains the size of a walnut and yet grew up to be about 30 feet long.

Sauropods  These were the largest dinosaurs in the Jurassic period.  They were herbivores.  These dinosaurs were 46 feet long.

Early Jurassic  Also known as Lias.  The word Lias might of come from the local English spelling of the word layer.  There were four parts in the Early Jurassic: Toarcian, Pliensbachian, Sinemurian and Hettangian.  Lasted from 195 million years ago to 180 million years ago.  Ammonoids diversify.  The early Jurassic saw great disposition of limestone.  Evolution of dinosaurs and other animals stops in this period.

Early Jurassic Geographic Map

Middle Jurassic  The middle Jurassic was called Dogger.  There were four parts in the middle Jurassic: Callovian,Bathonina,Bajocian and Aalenian.  Lasted from million years ago.  Marine life like ammonities and bivalves dominated the earth.  New dinosaurs evolved like cetiosaurs, brachiosaurs, megalosaurs, and hypsilophodonts.  Ichthyosaurs reduce in diversity.  Cetiosaurids flourish.  Pangea starts to separate.  The cooling process of the earth is starting to take place.

Middle Jurassic Geographic Map

Late Jurassic  Also known as Malm.  The late Jurassic period had three parts: Tithonian,Kimmeridgian and Oxfordian.  Lasted from million years ago.  Central Atlantic Ocean was a narrow ocean that separated Africa from eastern North America.  Eastern Gondwana separates from western Gondwanaland.  Dinosaurs Sauropods, Camarasaurs, Brachiosaurs and Diplodocids flourished.  Smaller animals like reptiles, lizards, early mammals and early birds also were abundant.  As a result of Pangea breaking up the climate changed  The climate was less dry and snow and ice covered polar regions.

Late Jurassic Geographic Map

Fossils  Jurassic deposits can be found in the Rocky Mountains, England, western Europe and other parts of the world.  The Blue Nile Gorge in Ethiopia has some of the first dinosaur fossil.  In 1905 the Saurian Expedition in the West Humboldt Range in Nevada found Jurassic fossils of ichthyosaurs.  The Solnhofen Limestone in southern German has many detailed fossils from Jurassic deposits.  Many Solnhofen Limestone fossils are of fragile or soft bodied organisms which usually leave broken fossils but not these.  The Tendaguru Formation is filled with deposits from the Jurassic period.  About 225,000 kg of bones were uncovered at the Tendaguru Formation over 2 and a half years.  Lime stone and deposits are important in studying fossils because these stones contain the remains of ancient dinosaurs.

Interesting Facts  The name Lias was taken by a geologist from an english quarryman’s pronunciation of the word "layers".  The movie Jurassic Park by Steven Spielberg was actually somewhat inaccurate.  The dinosaurs, like Triceratops and Tyrannosaurus rex, did not evolve until the Jurassic period was over.  Most of the dinosaurs featured in the movie were from the Cretaceous period.

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