Saurischian dinosaurs

Seismosaurus
• The largest sauropod dinosaur ever found, so far…
• 50 m long, >100 tonnes
Theropods (carnivorous dinosaurs)
• A widespread and successful group of dinosaurs throughout the late
Triassic to the Cretaceous
• The only group of dinosaurs to survive past the Cretaceous, as the
specialized group known as birds
• All were bipedal, with a three-toed foot (1st and 5th digits
reduced)
• Characteristically, most had grasping forelimbs of three to four
digits (5th digit reduced), some had opposable thumbs
• Had sharp, recurved teeth for shearing flesh
• Most had hollow bones
• Improved structural integrity
• Decreased weight
Major Theropod Groups
• Coelophysids
• An early theropod group, includes the Triassic animal Coelophysis
• Coelurosaurs
• A advanced group, including largest theropods
• Many had long arms, legs, dextrous digits and large brains… smaller
animals that likely hunted medium-sized prey
• Tyrannosaurs
• Ornithomimids
• “Ostrich dinosaurs”
• Maniraptorans: smaller, agile carnivores
• Dromaeosaurs
• Highly specialized hunters, fast, agile, with slicing toe-claws
• Troodonts
• Large-brained, large-eyed hunters, some possibly nocturnal
• Birds
• Flying dinosaurs, only group to survive K-T extinction
Tyrannosaurs
• Includes Tyrannosaurus Rex
• Late Cretaceous (85 - 65 Ma)
• A group of similar species, T. Rex is the largest known
• Stood about 4 m (15’) high, about 12 m (40’) in length, ~6 tonnes
• Predator or Scavenger?
• Unclear, but large predators today rely on scavenging as much as
hunting… use intimidation to capture kills from other predators
• Nasal cavities are folded, high surface area… indicates acute sense of
smell, like modern dogs, bears… useful for seeking carrion
• Large olfactory lobes in the brain… area of the brain used to process
sense of smell
• Binocular vision… eyes positioned to give depth perception, acute
eyesight… large optic nerve tracks (carried optic nerve bundles to brain)