1. The origin and rise of mammals
1. Mammal-like reptiles - mammals
2. What is a mammal?
3. Mammal-like reptiles
4. Mammals and dinosaurs
5. Palaeogene radiation of mammals
6. Mammals on a cooling Earth

2. 1. Mammal-like reptiles - mammals
Marsupials
Mammals
Monotremes
Triassic MLR
Mammals
By end Triassic
Cynodonts
Permian MLR
Therapsids
Gradual
acquisition
of mammalian
characteristics
Pelycosaurs

3. 2. What characters make a mammal?
Suckle young,
but may still lay eggs
Furry
Ears with ear bones
Secondary palate
Specialised teeth -
usually grow once
Simple jaw, complex jaw muscles
Warm blooded
Diaphragm
Erect gait

4. 2b. What skull characters make a mammal?
Reptilian jaw
Simple teeth
Quadrate
Jaw hinge
Squamosal
Articular
Simple bite
Dentary
Mammalian jaw
Articular and
quadrate now
ear bones
Secondary palate
Squamosal
Jaw hinge
Complicated
bite
Dentary
Specialised teeth
Masseter muscle

5. 3. Mammal-like reptiles Thrinaxodon Some tooth specialisation
Secondary
palate
Rigid spine
Complex jaw,
no ear bones
?Fur
Chewing
muscle
Endotherm
?Diaphragm
Sprawling gait
Small size = small eggs, small hatchlings, much care,? suckling?

6. 4. Mammals and dinosaurs
Limited Mesozoic radiation, all animals under 15kg. Mainly
small scavengers and carnivores.
Mammals
Cretaceous
origin. Evolved
on Laurentia
Marsupials
Cretaceous origin,
evolved on Gondwana
Monotremes
probably evolved near
Jurassic/
Cretaceous boundary.
Precise
ancestry uncertain
Multituberculates
successful
Mesozoic clade,
known principally
from teeth
Morganucodon
Lower Jurassic
tiny, agile carnivore
with complicated teeth

7. 5. Palaeogene radiation of mammals
Large flightless birds
radiated to become top
terrestrial predators
Large crocodiles radiated
to become
top marine
predators
Mammals radiated
into a large range of other niches.
90% of mammalian groups
appeared within 10 Ma
of dinosaur extinction.
Initially herbivores, omnivores,
insectivores, scavengers.
Gradually replaced birds and reptiles

8. 6. Mammals on a cooling Earth
Palaeogene Earth
Warm,wet,low ice,
abundant forests
Many isolated continents
promote intense speciation
Neogene Earth
Cool, dry, large icecaps,
evolution of grass,
formation of widespread
savanna
Himalayas rise
Americas collide
Continental collision and climate
change precipitate major extinction
modern mammals survive and radiate

9. 6b. Dinosaurs arrive Illium Birds Early Jurassic Ischium and pubis
Sauropods
lizard-hipped.
Vegetarians
Evolved extremely large size,
often in excess of 20 m in length
and 50 tonness in weight.
Theropods
Late Triassic.
All theropods
were predators,
including
Tryannosaurus rex.
Ornithischians
bird hipped dinosaurs
All herbivores, including
armoured forms
Iguanadonts
and duck-billed dinosaurs.
Highly modified teeth and jaws
Illium
Pubis
Ischium
Archosaurs