1. Mesozoic Era
Life

2. Mesozoic Life Known as “Age of Reptiles”
Mammals and angiosperms evolve

3. Marine Invertebrates Plankton
Coccolithophores
1st appeared (Jur)
Abundant (K)
Continue today
Diatoms (SiO2)
1st evolved (K)
Cold H2O
Dinoflagellates
Warm H2O
Foraminifera
Exploded
Most plankton extinct (end K)

4. Marine Invertebrates Corals & Echinoderms
Corals & Echinoderms proliferated
Scleractinians
Echinoderm

5. Mollusks Brachiopods & Gastropods
Significant invertebrate fauna
Brachiopods
Never fully recovered from Permian extinction
Minor invertebrate
Gastropods
Largest, most varied class
Marine, fresh H2O, terrestrial
Herbivore & carnivore

6. Mollusks Bivalves Burrowing organism Escaped predators
i.e., oysters, clams
Rudists significant
Formed large tropical reefs
Excellent guide fossils

7. Mollusks Cephalopods Important invertebrate group Ammonites
Nautilus
Important invertebrate group
Ammonites
Complex sutures
Abundant (Jr & K), extinct (end K)
Nautiloids and belemnoids survived

8. Mesozoic Life Fishes and Amphibians
Cartilaginous fish
↑ abundance
Amphibians
Frogs and salamanders appear
Greatest diversity (Permian)

9. Mesozoic Life Plants Primary producers – base of food chain
Gymnosperms
Gingkos
Conifers
Cycads
Modern cycads
Gymnosperms replaced by angiosperms
Gymnosperm
Angiosperm

10. Plants Angiosperms Adapted to nearly every terrestrial habitat
Factors to success:
Method of reproduction
Evolution of flowers
Pollinators
Evolution of enclosed seed
Seeds dispersed by wind, fruit, burr

11. Mesozoic Life Reptiles
Diversification began during Penn
Evolution of captorhinomorphs
1st to lay amniote egg
All other reptiles evolved
Thecodontian (L. Per-Tri)
Small, agile reptiles with long tails, short limbs
Teeth set in sockets
i.e. crocs, dinos, & mammal-like reptiles
Quadrupedal, ran bipedal
Herbivores & carnivores
Dinosaur ancestors

12. Warm-Blooded Dinosaurs
Ectotherm – “cold-blooded”
Animals whose body temp varies in response to outside temp
All reptiles ectothermic
Endotherm – “warm-blooded”
Capable of maintaining a constant body temp regardless of outside temp
Mammals & birds endothermic
Dinosaurs believed to be endothermic

13. Warm-Blooded Dinosaurs
Endotherm requirements
Dino bones numerous passageways = blood flow
Crocs, turtles have similar bone structure = ectotherm
High metabolic rates  need to eat more
Dinosaurs  3.5% prey pop’n
Similar to present-day mammals
Complex nervous system  large brain
Many dinos have small brains
Small carnivores = large brain
Active flight requires endothermy
Pterosaurs = hair-like feathers
Triceratops brain cavity

14. Mesozoic Life Dinosaurs Relationships
Two independent orders evolved
1. Saurischia “lizard-hipped”
Theropod & Sauropod
2. Ornithischia “bird-hipped”

15. Dinosaurs Saurischia Theropod
Theropods – “Carnivores”
Bipedal locomotion
Various sizes
60 cm to 15 m
2 kg to 8 tons
Tyrannosaurus (largest terrestrial carnivore)
Deinonychus – “terrible claw”

16. Dinosaurs Saurischia Sauropod
Sauropods – “Herbivores”
Quadruped locomotion
Largest land animals to ever exist
20 to 35 m in length
10 to 55 tons
Camasaurus “Brontosaur”
Brachiosaurus
Diplodocus

17. Mesozoic Life Dinosaurs Relationships
Two independent orders evolved
1. Saurischia
Theropod & Sauropod
2. Ornithischia

18. Dinosaurs Ornithischia
5 groups
1. Duck-billed dinos (K)
Colonial nesting, cared for young, herbivores, bipedal
2. Pachycephalosaurs
Dome-shaped skull, bipedal, butting
3. Ankylosaurs
Armored, quadrupeds, tail w/ club-like growth
4. Stegosaurs
Quadruped, herbivore with spike on tail
5. Certopsian
Triceratops, quadrupedal herbivores

19. Mesozoic Life Winged Dinosaurs
Pterosaurs
1st flying vertebrates
Flight adaptations
Winged membrane supported by elongated finger
Pteranodon (K)
Pterosaur
Could actively fly

20. Mesozoic Life Birds Few Meso birds Archaeopteryx Protoavis (Tri)
Jur strata, Germany
Protoavis (Tri)
Crow sized
Hollow bones

21. Mesozoic Life Early Mammals
1st mammals (Tri)
Small, rodent-like mammals
Evolved from Therapsids
Mammal-like reptiles
Cynodonts
Most abundant mammal-like reptile

22. Early Mammals Cynodonts
Monotremes
Egg-laying
i.e. today’s platypus & string anteater
Eupantotheres
Marsupials – pouched (E. K)
Placental mammals
All living mammals related to this branch

23. Mesozoic Life From Reptile to Mammal
Used skeletal structure to classify fossils
Skull
Middle ear
Lower jaw
Teeth
Mammal’s middle ear attached to dentary
Reptiles = 1 ear bone; mammals = 3
Reptile = several jaw bones; mammals = 1
Teeth = distinct types

24. Reptile vs. Mammal Comparison

25. Mesozoic Era Mass Extinction
Impact Theory
Huge asteroid or comet
Cloud of dust into atmosphere
Reduced sunlight
Plants die first
Herbivores followed
Then, carnivores starved

26. Mass Extinction Evidence
Large impact basin
Iridium-rich clay layers
Rare crustal rock
More in meterorites
Clay layers, New Mexico

27. Mass Extinction Problems
Selective extinction
Dinosaurs completely extinct
Corals, clams, snails – some extinction
Tropical plants, crocodiles, mammals, turtles, snakes, & birds unaffected
Why weren’t all organisms affected equally?