Origin of
Dinosaurs
How Diversity is studied
Phylogenetics
Hypthesizing
Relationships
A (vague)
evolutionary
tree
Something more precise
Cladogram
A cladogram for dinosaurs and relatives
A cladogram for
advanced theropod
dinosaurs
Cladogram for group of
North American
stream fishes
SMN’s ground-breaking
work on African
anabantid fishes
Supraorbital pores of the cephalic lateralis
Deep time – dinosaur ancestors
Tetrapods are terrestrial adapted vertebrates –
they have legs with feet
First dinosaurs
First tetrapods
Tetrapods come out of the fish world
† Eusthenopteron
Tetrapoda
Neotetrapoda
Temnospondyli
“Fishes”
Actinistia
(coelacanth)
Lissamphibia
Dipneusti
(lungfish)
*Diverse
Devonian
groups†
Diverse
tetrapod
groups†
Amniota
(see Fig. 26.2)
Anura
Gymnophiona
Urodela
Ichthyostegans†
Diverse
temnospondyl
groups†
Characteristics
of jaw, skull
Modifications of skull
bones (tentative)
Three-lobed
tail; ossified
swim bladder;
double jaw
articulation
Tetrapods
† Panderichthys
Tetrapod
Origins
Ray Troll
Towards terrestrial
tetrapods
aquatic
Semi-terrestrial
Early tetrapod (fish-like)
Later tetrapod (more terrestrial)
† Acanthostega
Early tetrapod trackway
Eusthenopteron
aquatic
Semi-terrestrial
aquatic
Semi-terrestrial
Panderichthys
aquatic
Semi-terrestrial
Tiktaalik
Acanthostega
aquatic
Semi-terrestrial
Ichthyostega
aquatic
Semi-terrestrial
Pederpes
Not a fish
Ichthyostega
Acanthostega
“Fishes”
(more or less)
Tiktaalik
Panderichthys
Eusthenopteron
Nelson (2006): Tetrapods are a “divergent
sideline within the fishes that ascends
onto land and into the air and secondarily
returns to water.”
Early terrestrial tetrapods
Very rich Paleozoic diversity of these creatures
Carboniferous Era
Great time to be an
early terrestrial
tetrapod
Carboniferous
360-300 mya
Very rich Paleozoic diversity of these creatures
Amniotes
Frogs and
toads
Anthracosauria
Amniota
Lepospondyli
Salamanders
Ichthyostega
Lissamphibians
Caecilians
Dipneusti
Diverse
Devonian groups
Sarcopterygian
ancestor
Diverse temnospondyl
groups (includes Eusthenopteron,
Tiktaalik, and Acanthostega)
Coelacanth
Devonian
Carboniferous
Permian
PALEOZOIC
395
Geologic time (MY ago)
MESOZOIC
252
CENOZOIC
66
Most gone – Two groups survived
Reptiles / Mammals
Amniotes
Frogs and
toads
Anthracosauria
Amniota
Lepospondyli
Amphibians
Salamanders
Ichthyostega
Lissamphibians
Caecilians
Dipneusti
Diverse
Devonian groups
Sarcopterygian
ancestor
Diverse temnospondyl
groups (includes Eusthenopteron,
Tiktaalik, and Acanthostega)
Coelacanth
Devonian
Carboniferous
Permian
PALEOZOIC
395
Geologic time (MY ago)
MESOZOIC
252
CENOZOIC
66
Very rich Paleozoic diversity of these creatures
Amniotes
Frogs and
toads
Anthracosauria
Amniota
Lepospondyli
Salamanders
Ichthyostega
Lissamphibians
Caecilians
Dipneusti
Diverse
Devonian groups
Sarcopterygian
ancestor
Diverse temnospondyl
groups (includes Eusthenopteron,
Tiktaalik, and Acanthostega)
Coelacanth
Devonian
Carboniferous
Permian
PALEOZOIC
395
Geologic time (MY ago)
MESOZOIC
252
CENOZOIC
66
on our way to
amphibians
Class Amphibia
Very rich Paleozoic diversity of these creatures
Amniotes
Frogs and
toads
Anthracosauria
Amniota
Lepospondyli
Salamanders
Ichthyostega
Lissamphibians
Caecilians
Dipneusti
Diverse
Devonian groups
Sarcopterygian
ancestor
Diverse temnospondyl
groups (includes Eusthenopteron,
Tiktaalik, and Acanthostega)
Coelacanth
Devonian
Carboniferous
Permian
PALEOZOIC
395
Geologic time (MY ago)
MESOZOIC
252
CENOZOIC
66
On our way to
mammals / reptiles
Amniotes
Reptiles
Mammals
Other
Most gone – Two groups survived
Reptiles / Mammals
Amniotes
Frogs and
toads
Anthracosauria
Amniota
Lepospondyli
Amphibians
Salamanders
Ichthyostega
Lissamphibians
Caecilians
Dipneusti
Diverse
Devonian groups
Sarcopterygian
ancestor
Diverse temnospondyl
groups (includes Eusthenopteron,
Tiktaalik, and Acanthostega)
Coelacanth
Devonian
Carboniferous
Permian
PALEOZOIC
395
Geologic time (MY ago)
MESOZOIC
252
CENOZOIC
66
Carboniferous
360-300 mya
Before we get to the
Mesozoic, we have to
survive the Permian
Permian
Carboniferous
Permian – it all almost ends
Permian – cooler and drier
A new, drier, world favors a new type of tetrapod
Amniotes
Amniotes
Amniotes
Frogs and
toads
Anthracosauria
Amniota
Lepospondyli
Salamanders
Ichthyostega
Lissamphibians
Caecilians
Dipneusti
Diverse
Devonian groups
Sarcopterygian
ancestor
Diverse temnospondyl
groups (includes Eusthenopteron,
Tiktaalik, and Acanthostega)
Coelacanth
Devonian
Carboniferous
Permian
PALEOZOIC
395
Geologic time (MY ago)
MESOZOIC
252
CENOZOIC
66
Amniota
Amnoita (living)
Deriving
Amniotes
Carboniferous
terrestrial habitats
Permian – cooler and drier
Post-Paleozoic
is the age of
amniotes
The Mesozoic
was really cool
AGE OF AMNIOTES
Adapting to the new conditions
Moving away
from water
Amniotes
Amnoites
Frogs and
toads
Anthracosauria
Amniota
Lepospondyli
Salamanders
Ichthyostega
Lissamphibians
Caecilians
Dipneusti
Diverse
Devonian groups
Sarcopterygian
ancestor
Diverse temnospondyl
groups (includes Eusthenopteron,
Tiktaalik, and Acanthostega)
Coelacanth
Devonian
Carboniferous
Permian
PALEOZOIC
395
Geologic time (MY ago)
MESOZOIC
252
CENOZOIC
66
Amniota
What’s going on
at the beginning?
Amniotic Egg
Amniotic Egg
Fish
Amphibian
Amniote
Internal
Fertilization
No more gill
breathing – even
in larvae
amphibian larvae
Body covering
Dry and dead
Respiration
Anamniotes – Positive
Pressure Breathing
Amniotes – negative pressure breathing
Patterns in Skull
Evolution
Pre-Amniote
Diadectes
Pre-Amniote
Skulls
Anapsid
Pre-Amniote
Synapsid
Diapsid
anapsid skull and jaw muscles
pre-amniote
anapsid skull and
jaw muscles
pre-amniote
foramen
pre-amniote
amniote
Skulls
Anapsid
Synapsid
Diapsid
No foramen
foramen present
Anapsid
Synapsid
Diapsid
Amniote ancestor
Anapsid
Diapsid
Synapsid
Mammals and
ancestors
Reptiles, birds,
dinosaurs, etc.
Anapsid
anamniotes,
stem amniotes
Synapsid
Synapsid
Dimetrodon
Synapsid
Modern mammal
Synapsid
fenestra joined with
orbit
Modern mammal
orbit
Diapsid
Diapsid
orbit
orbit
Diapsid
tuatara
orbit
Diapsid
Modern Lizard
Diapsid
Modern snake
Diapsid
Modern bird
orbit
Diapsid
orbit
Mesozoic reptiles
orbit
Turtles
Turtles
are diapsids with a (secondarily acquired)
anapsid skull
Fenestration
Clear proof of diapsids on Mars
NASA Photos
(Science Education is important)
Jaw
rearrangements
The big split
anapsid
anamniote
diapsid
synapsid
The big
split
The big split
Synapsid
lineage
Diapsid
radiation
The big split
Synapsids – only
mammals remain
All this is extinct
Diapsids – many fossil
groups, but many groups
remain
Some interesting
parallels in
evolution
Endothermy
warm-bloodedness
Living Amniotes
Synapsid
Diapsid
Endothermy
warm-bloodedness
Diapsids
Synapsids
Both groups
Greater Mobility
Greater Mobility
Higher metabolism
More heat generation
better respiration
better circulation
waste heat
elimination
diet / digestion
heat conservation /
utilization
What do we do
with the heat?
Diet
Respiration
ancestor
towards mammals
towards birds
Circulation
Some interesting
parallels in
evolution
Reptiles and Diapsids