Dinosaurs

• When did they evolve?

  From Archosaurus in the Triassic, about 230 million years ago
• Dinosauria

  • Stands upright - not sprawling
  • straight knee joint
  • straight ankle joint
• First Dinosaurs

  Bipedal predators that were 1-2m long, both are from Argentina. Rare amongst other fossils
• Life of dinosaurs:

  • Pangaea created a large hot and dry env.
  • Archosaurus evolved in this environment so dinos also thrived
  • During the Jurassic, Pangaea broke however land bridges remained
  • Climate was warm and humid - Dinos evolved big
  • During the Cretaceous land bridges had gone so evolution went along separate lines
  • Climates cooled
  • Size of dino decreased - maybe due to change in diet as flowering plants increased or due to climate change
• Two types of Dinosaurs

  Ornithischians and Saurichians
• Saurischian Dinos

  “Reptile-Hipped” bones, pubis bone points towards their head
• Ornithischian Dinos


  “Bird-Hipped” bones, pubis bone points backwards
• What evolved into birds


  Saurischian
• Two types of Saurichians

  Sauropods and Theropods
• Theropods

  • Two-legged meat eaters
  • Evolved into birds
  • Only Carnivores
  • Range Of sizes
• Sauropods

  • Huge
  • 4-legged
  • Herbivores
• What is Rexy and example of?

  Saurischian Theropoda
• T-Rex as a Scavenger Vs. Predator

  • Small arms - hard to grasp preys (S)
  • Huge back leg - good for distances, slow (S)
  • Very good sense of smell (S)
  • Predators are also Scavengers (P)
  • Not all predators need to use arms (P)
  • Few trace fossils - cant Prove speed (P)
  • Large and Jagged teeth - meat eater
• What is Diplodocus an example of?

  Saurischia Sauropoda
• Diplodocus:

  • Herbivore
  • Long & Thin Skull - small brain compared to body
  • Very Long Neck - reach vegetation others couldnt
  • No Grinding teeth - swallowed veggies whole
  • Gastroliths - to aid in digestion
  • Extra bones under spine - support and mobility of neck and tail
  • Long tail - whip in defence, also helped in balance
• Ornithopods

  • “Bird-Hipped”
  • Move on 2 or 4 legs
  • Herbivore
• Ornithopods

  • Small or absent front teeth - replaced by a horny beak which became broader -> duck billed dinos
  • Armoured with bony plates - defence mechanism or for heat exchange
  • Some developed horns - protection
• What is Iguanadon an example of

  Ornithischia Orthropoda
• Iguanadon

  • Late Jurassic Onwards
  • Herbivore
  • Large skull w/ horse like snout ending in a toothless beak to chop veggies
  • minced food with leaf-shaped cheek teeth
  • hinged upper jaw could move side to side (like an Iguana)
  • 3 fingers with large thumb spike - either weapon or to obtain food
  • could be 4-legged or 2
• Uniformitarianism

  Using modern herbivores and carnivores and predatator/prey relationships to help infer the niches that dinos occupied in the Mesozoic ecosystems
• Evidence for Carnivores

  • Large brain: body mass ratio
  • Large, forward facing eyes - depth perception
  • Flexible base to tail to aid movement
  • Strong skull with powerful skull and sharp teeth
  • Sharp claws on forelimbs for slashing prey
  • covered in feathers to keep warm and maintain metabolic rate - possible warm blooded
  • Sharp claw on 2nd Toe or foot used for slashing at prey
• Evidence for Herbivores

  • Large body mass
  • 4 legs generally
  • Spikes, horns for defence
  • Short neck and small head - grazed bushes close to the ground
  • grazed in herds - like elephants today
  • Small brain
  • toothless beak and small cheek teeth
  • Sharp tail spikes to swing for protection
• Gastroliths

  Stones that are swallowed to help break down tough plants