2. Intro: Diet, Habitats, Extinction

What dinosaur branch was the only one to retain carnivory?

• Theropods were the only ones to retain carnivory

• E.g. t.rex, velociraptor

What teeth identifiers did carnivores have?

• serrated teeth

• Laterally compressed

• Recurved teeth

What adaptations did herbivory require?

• horn-y beaks

• gastric mills with stomach stones to break down plant materials

• Dental occlusion - contact between teeth

• Complex jaw mechanisms

• Elongated gastrointestinal tract

• fleshy cheeks and leaf-like teeth

When did herbivory become dominant?

Early middle jurassic until end of cretaceous

What percentage roughly were herbivores? Which clades were known to be herbivores?

• over half of non-avian dinosaurs were herbivores

• including ornithomimosaurs, sauropodmorphs and coelurosaurian theropod clades

What is a sauropodmorph?

• Large clade of mostly long-necked and large-sized plant eating saurischian dinosaurs

• Potentially the largest terrestrial animals to ever walk the earth.

What were the 2 life strategies that Mesozoic plants could sustain? Which strategy was more energy efficient?

• small individuals with larger populations

• Larger individuals with smaller populations - this was more energy efficient as the large size could support a specialised digestive system, have better conservations of heat and allow body temp and processes to be better regulated

Why does Asia’s environment contribute to the variety of dinosaurs?

• can be tropical further south but cold to freezing in the north allowing for many environments for different life to exist.

What is the order of the geological time scale?

1. Palaeozoic - ancient life

2. Mesozoic period, middle life - Triassic → Jurassic → Cretaceous, started 250mya

3. Cenozoic - recent life

What time scale does each portion of the Mesozoic period cover?

1. Triassic - 250 - 200 mya

2. Jurassic - 200 - 145mya

3. Cretaceous - 145 - 65mya (focus on last 15mil cretaceous in course)

How did the continents change throughout the Mesozoic era?

• Beginning Triassic - Pangea, all one continent

• Throughout the Triassic Laurasia and Gondwana supercontinents were formed

• By the end of the Mesozoic/cretaceous, the world was similar to how it is now

What caused the mass extinction? How do we know when it was?

• 10km wide asteroid caused latest cretaceous extinction of non-avion dinos

• Chicxulub crater, Yucatan peninsula, Mexico

• Evidence of the impact in a 65myo clay layer that’s deposited across the globe

• 2 coal boundaries (the K-T boundary) show the before and after - lower coal layer has large plant materials (tree logs) that were coalified and still identifiable, then the coal above is typical coal deposit that is from fires, volcanic eruptions, earthquakes etc that took weeks to months to settle as the fallout from all of these disasters. This upper coal layer contains deposits from everything that died as a result of extinction

• K-T boundary also has iridium between layers, know that this is extra-terrestrial deposit

What else could have contributed to extinction that was triggered by the chixculub impact?

• Deccan Trap volcanism

• Deccan traps in India’s deccan plateau are largest volcanic features on earth

• Associated with a deep mantle plume

• Impacts can set off large igneous areas and erupt them

• Deccan trap would have released SO2 causing acid rain and cooling but there would also be lower oxygen conditions due to more carbon in atmosphere

• Due to the size, Deccan traps would have greatly contributed to extinction after the initial impact.