WORLD OF SCIENCE
Jurassic invertebrates
DR. T. V. PADMA
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Scientists now say that dinosaurs did live in the Southern Hemisphere landmasses.
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CROCODILE BACK: Among the oldest fossils ever found. PHOTO: AP
Tom and Pat Rich, were among those who worked to increase our knowledge about dinosaurs in Australia and other Southern hemisphere landmasses. Many Jurassic invertebrates are known to have lived in Australia, but there is little evidence of large land animals. A few fossils exist : the large Sauropod called Rhoetosaurus, and fragments of theropods and aquatic reptiles called plesiosaurs. There is even one of the last known labyrinthodont amphibians, called Siderops. The biggest Australian dinosaur weighed as much as five African elephants, and stood two storeys tall. There was a small carnivorous Australian dinosaur, called Laellynasaurus which had large eyes to help it see during the long winters.
Fossils
The marine sediments of the shallow Cretaceous sea that covered Queensland, New South Wales and Southern Australia are the main source of dinosaur fossils, mostly of carcasses that were probably carried out to the sea after floods. Many of the fossils formed at this time were opalized. Because of the monetary value of opal, private collectors bought most of the opalized fossils and museums retained only a few.
Dinosaur fossils have also been found in the river sediments of the late Cretaceous. In Western Australia, Cretaceous reptiles were rare and only a few partial plesiosaurs and icthyosaurs have been found. Most known fossil vertebrates of New Zealand are from the late Cretaceous (65-72 Mya). Some scientists think that the Aussie and Kiwi dinos survived the major extinction event that killed off most of the Northern Hemisphere's Mesozoic reptiles. The end of the reptilian era was in sight, and these great beasts disappeared gradually, if not in one fell swoop, from every part of the globe.
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