The Mesozoic Era When Dinosaurs Ruled the Earth

The Mesozoic Era §Began approximately 245 million years ago after a major mass extinction. §Is subdivided into 3 periods: l Triassic l Jurassic l Cretaceous §Ends about 66 million years ago with a major mass extinction

Mesozoic Reptiles §Turtles §Crocodiles/Alligators §Lizards §Ichthyosaurs (large marine reptiles) §Pterosaurs (large flying reptiles) §Dinosaurs (land dinosaurs)

Dinosaurs Myths §All dinosaurs are the same §Everything that is big and extinct is a dinosaur §All dinosaurs lived at the same time §All ‘dinosaurs’ are extinct…...you’ll see!

The Triassic Period million years ago §Immediately after the Permian Mass Extinction §Lots of new area is open for animals to live §Three general types of animals: l holdovers from before the extinction l new groups that lasted only a short time l new groups that lasted a long time

The Triassic World

Triassic Plant Life §Mosses §Scale Trees (like palm trees) §Ginkos (my favorite)

Two Groups of Dinosaurs §Ornithischian l Hips were similar to modern bird hips l Carnivorous short-necked l Herbivorous, long-necked §Saurischian l Hips were similar to reptile hips l Herbivorous with grinding-teeth l Herbivorous without grinding-teeth

Earliest Dinosaurs (Triassic) Eoraptor: Length:3 feet Height:1 feet Weight:20 pounds Pisanosaurus Length:3 feet Height:1 foot Weight:15 pounds Lesothsaurus: Length:3 feet Height:1 foot Weight:15 pounds

The Jurassic Period Million Years Ago §Giant plant-eating dinosaurs §Vicious carnivore dinosaurs §Oceans full of fish, squid, sharks, etc. §Ichthyosaurs and Plesiosaurs §Pterosaurs §Birds

The Jurassic World

Jurassic Plant Eating Dinosaurs §Many different forms §Many had ‘armor’ to protect themselves l Triceratops l Ankylosaurus §Many very large (larger than a Rhino/Hippo) §Some were extremely large (as long as a city block): Diplodocus Triceratops

Diplodocus Ankyloasaurus

Jurassic Carnivorous Dinosaurs §Many different forms §Some were very large: l Tyrannosaurus Rex l Allasaurus §Some were smaller: l Raptors, and many more §All had sharp teeth, claws, and speed

Jurassic Marine Dinosaurs §Most with similar shapes as a dolphins or sharks §Ate fish and other marine animals §Some were VERY large §All could swim VERY fast Ichthyosaurus

Jurassic Pterosaurs §Pterodactyls and Pterosaurs §Most had trouble ‘walking’ §Were very good flyers §Had hollow bones §Small (~ 1 foot) and very large (~ 16 feet)

More Pterodactyls

Jurassic Birds(?) - Archaeopteryx §Not a Pterosaur §Jaws and bone structure like dinosaurs §Bones are hollow, like birds §Feathers §Was this an evolutionary link between dinosaurs and birds?

The Cretaceous Period million years ago §The last period when Dinosaurs lived §Ends with a mass extinction around 66 million years ago §First flowering plants!

The Cretaceous World

Cretaceous Plants §First plants with flowers l Their appearance was very rapid l They appeared at the same time as the number of insects increased… §Could insects have helped the flowering plants evolve?

The Cretaceous Mass Extinction §Approximately 60% of all species went extinct. §Affected many land animals/plants §Affected fewer marine animals

What organisms went extinct? §All dinosaurs §All pterosaurs §All ichthyosaurs §Many terrestrial plants §Many marine animals

What organisms survived? §MAMMALS (!) §Birds §Many plants (ferns were the most successful plant for a while) §Trees with flowers §Small lizards/crocodiles/alligators/turtles §Fish, squids, sharks, etc.

What caused the extinction? §Meteorite impact theory l 66 million years ago, a ~10 km wide meteorite struck the Earth near what is now Mexico.

Meteorite Impact §This is an EXAGGERATED view of a meteorite impact

How could a meteorite impact cause a mass extinction? §The impact caused shock waves, tidal waves, and sent a tremendous amount of dust into the atmosphere §As the dust re-entered the Earth’s atmosphere, it would have instantly heated the atmosphere causing tremendous forest fires §The dust could have caused the Earth’s climate to cool in the long-run by blocking sunlight §Plants, animals, etc went extinct due to the climate changes and competition between organisms

Meteorite Impact Evidence #1 §Unique Quartz Crystals l Very commonly formed under high pressure/temperature l This quarts was only found in meteorite craters and nuclear testing sites

Meteorite Impact Evidence #2 §Iridium l An element that is very rare in Earth rocks and very common in meteorites l The layer of rocks above the last dinosaur bones contains ~160 times ‘normal’ levels of iridium

Problems with the Meteorite Impact Hypothesis §Why were some animals affected, while others were not? l Why did birds survive, and dinosaurs (a very close relative) not? l Why did small reptiles survive when small dinosaurs didn’t? l Why did mammals survive?

Out-dated Hypotheses §Hay Fever - caused by flowering plants §Dinosaurs were so big, that they crushed themselves §Mammals out-competed the dinosaurs §Mammals ate all the dinosaur eggs §Cosmic rays killed the dinosaurs