1. Class Mammalia

2. Evolution of Mammals
Mammals did not come to dominate until the CENOZOIC ERA, after the dinosaurs became extinct
Early mammals were probably “rodent like”

3. Fig 3

4. Synapsids 4

5. Pelycosaurs Synapsid reptiles from Pennsylvanian and Permian
MYA
Body close to ground
Legs away from body
Canine like teeth
Dimetron

6. Therapsids Body raised off the ground Limbs more under the body
Teeth differentiated into 3 types
Secondary palate developing
Lystosaurus 6

7. Cynodonts Lumbar ribs reduced or absent
Well developed secondary palate
Lower jaw reduced to one bone
Thrinaxodon 7
Cynognathus

8. Transitional Fossil Cynognathus8

9. Early Mammals Triassic 220 MYA Small Hair Mammary glands Skin glands
Molar teeth
Megazostrodon 9

10. Repenomamus robustus Ate Dinosaurs10

11. Cladogram of Synapsids
Cynodonts
Mammals
Therapsids
Molars, hair, glands
Pelycosaurs
Reduced ribs, 1 jaw bone
Limbs under body
Canine like teeth
Synapsid reptiles 11

12. Characteristics
Hair – composed of keratin for insulation, sensation, appearance, and protection. (other keratinized structures – horns, antlers, etc.)
Mammary Glands – modified sweat gland that, in females, produce milk to nourish their offspring.
3 Middle Ear Bones – malleus, incus, and stapes (hammer, anvil, and stirrup); the first two derived from the ancestral jaw.

13. Characteristics Highly differentiated teeth Single lower jaw bone
Secondary palate
Highly developed brain
Separate sexes (XX or XY)
Internal fertilization

14. General Skeleton

15. same bones, different stance

16. Teeth Diastema – toothless gap Carnassial apparatus
Incisors chisel shaped for gnawing and nipping (1 root)
Canines long conical for catching, killing, and tearing (1 root)
Premolars and Molars broad for chewing (1-2 or 2-3 roots)

18. Mammalian Glands
Glands are an epidermal tissue that secrete substances.
Sudoriferous – sweat for evaporative cooling and elimination of waste.
Sebaceous – secrete oil for waterproofing of hair.
Scent – secrete pheromones for defense, sex recognition, and territorial behavior.

19. Mammal Heat Regulation
Endothermy – the generation of internal heat
Homeothermy – the maintenance of constant temperature
Torpor – the organism is less active, alert, and easily aroused (Bears and raccoons)
Hibernation – the organism slows metabolism, and heart and respiratory rates (monotremes, and some insectivora, rodentia, and chiroptera)

21. 3 Types of Mammals Prototheria (Monotremes): oviparous (egg-laying).
Metatheria (Marsupials): viviparous with a short gestation, further development occurring in a pouch.
Eutheria (Placentals): viviparous with a long gestation.

22. Monotremes Lay eggs Incubate 12 days Lick milk from mothers fur
Monotremes
Lay eggs
Incubate 12 days
Lick milk from mothers fur
Transitional species
echidna
platypus

23. Marsupials Pouched mammals Birth to tiny embryo
Marsupials
Pouched mammals
Birth to tiny embryo
Embryo attaches to mother’s nipple to complete development
opossum
kangaroo

24. Placentals Placenta nourishes embryo Long gestation period
22 months for elephant
Most successful group of mammals
Competitive advantage over monotremes and marsupials
Better nutrition from placenta
Less vulnerable to predators
More advanced at birth

25. Evolution of Placenta from Amniotic Egg
Reptile
Chorion
Oxygen from air
Amnion
Provides private pond
Yolk Sac
Food for embryo
Allantois
Store urinary waste
Mammal
Chorion
Form placenta to get oxygen & food from mothers blood
Amnion
Provides private pond
Yolk sac
Temporarily make RBCs
Allantois
Form umbilical cord