WHAT ARE DINOSAURS?

• There are many kinds, or species, of dinosaurs varying in shape and size.
  
• There are an estimated 300 different kinds throughout history.
  
• Bipedal and Quadrupedal
  • Bipedal - walked on their two rear legs
  • Quadrupedal - walked on all four legs
  
  
• Dinosaurs evolved from two distinct lines:
  The difference? The arrangement of their hipbones and of their teeth in their jaws.
  
• Two types of hipbone structures:
  • Saurischia - "Lizard-like hip"
  • Ornithiscia - "Bird-like hip"
  
  
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ORNITHISCHIA

1. Horned Dinosaur
   • Triceratops
2. Armored Dinosaur
   • Stegosaurus
   • Ankylosaurus
3. Small Bipedals
   • Heterodontosaurus
4. Hadrosaurs - or the "duck-billed" Dinosaur
   • Maiasaura
   • Edmontosaurus

SAURISCHIA

1. Prosauropoda
   • Largely herbivorous
   • Dominately quadrupedal
   • Ex. Plateosaurus
2. Sauropoda
   • Long-necked and long-tailed
   • Enormous herbivores
   • Ex. Apatosaurus, Brachiosaurus, Diplodocus
3. Theropoda
   • Some Extinct -- Some Still Living
   • Extinct - Tyrannosaurus Rex and Dilophosaurus
   • Still Living - Birds

• These reptiles lived during the Age of the Reptiles.
• Beginning in theTriassic Period and into the late Cretaceous.
• Dinosaurs existance totalled 165 million years .
• The first known bones found in 1822 in England are of the dinosaur called Iguanodon.
  • This fossil is now located at the British Museum of Natural History in London, England.

1. UNABLE TO ADAPT TO CHANGES
   • Scientists believe that it was warmer at the end of the Cretaceous than it is now.
2. ASTEROID THEORY
   • Object or event in the earth's solar system or beyond.
   • Great extinctions have occured at 26 million year intervals.
   • This theory was proposed in 1980 by Luis and Walter Alvarez.
   • This theory is based on unusually high concentrations of the rare metal, Iridium, near rock levels close to the level of last dinosaur remains.
     • Iridium is common in meteorites.
     • The collision caused a hugh cloud of dust that circled the earth.
     • The dust blocked the sunlight for as long as 5 years.
     • This killed many plants and the Dinosaurs died too.
3. SUPERNOVA THEORY
   • Exploding star showered the earth with a deadly radiation killing the dinosaurs.
4. NEMESIS THEORY
   • Unseen companion star to our sun called Death Star, or Nemesis, theoretically orbits around the earth.
   • Every 26 million years it comes very close and disturbs the gravitational balance of the solar system.
   • This imbalance causes showers of comets to crash into Earth.
5. PLANET K THEORY
   • Proposes a tenth planet.
   • This theory proposes the same outcome of comet showers as the Nemesis theory.
   • Dinosaurs died from Disease.
   • When land masses were rejoined, enabling the Dinosaurs to migrate again, a deadly disease was spread.