Dinosaur Evolution

How do we know when dinosaurs lived?

• Layers of sedimentary rock & absolute dating–Late Triassic (during Mesozoic)

through end of the Cretaceous

–Also see birds & flowers for the first time during the Mesozoic (you know this!)

Dinosaurs?• “Terrible Lizards” (1841)

– Sir Richard Owen

• Not all reptiles are dinosaurs!• Dinosaurs did not fly or swim!

– Pterodactyls were flying lizards (or at least winged lizards)

Ornithischia

• 1887- bird hipped (posterior pubis along ischium)

• Ceratopsia (Triceratops), Thyreophora (Stegosaurus), Ornithopoda (Iguanodon, Hadrosaurs)–Some may have been bipedal

Saurischia

• Lizard pelvis–Pubis anterior & downward

• Up to 75,000 kg

(over 165,000 lbs!)

*Brachiosaurus probably had a blood pressure that exceeded 630mmHg (yours is probably around 120mmHg)

• Sauropoda- herbivores(Diplodocus )

• Therapoda (bipedal meat eaters) T. rex, Maniraptora (Velociraptor), Dilophasaurus

Good bye…

• Cretaceous-Tertiary Extinction (K/T Extinction)–Active plate movement, mountain-

building, volcanism

–Lowering of global sea level

–Gentle global cooling

–Asteroid impact

K/T Extinction

• Chicxulub (devil’s tail) crater- Gulf of Mexico–Block sunlight–Short-term global warming–Global wildfires–Acid rain–Long term global cooling