Archosauromorphs and birds

Question 1

What does evidence now suggest about the origins of birds?

Answer 1

Birds are deeply nested in the dinosaurian evolutionary tree + are specifically related to carnivorous dinosaurs

Question 2

Which animals make up Chelonia?

Answer 2

Turtles + tortoises

Question 3

What are the features of chelonia?

Answer 3

Carapace (top of shell) composed of rib cage + bones around the edge

Large, tough scales cover bone

Bottom of shell composed of gastralia

Arms, legs, tail + head retract inside shell

Question 4

What are the features of crocodilians?

Answer 4

Large bodied
Semiaquatic 
Predators
Cannibals 
Parental care

Question 5

How are crocodilians adapted to being semiaquatic?

Answer 5

• flattened tail for sculling
• massive bones help them sink to bottom
• eyes + nostrils on top of head

Question 6

What are the purposes of cannibalism in crocodilians?

Answer 6

Source of protein
Eliminates competitors for food
Eliminates offspring of others from gene pool

Question 7

When did crocodilians hit their peak?

What did they do?

Answer 7

Triassic

Radiated to take place of mammal-like reptiles

Question 8

What are the features of Aves (birds)?

Answer 8

> warm blood (41C)
> sophisticated respiratory system 
= air sacs + air-filled bones
> bipedal, upright limbs + digitigrade
> loss of teeth 
> elaborate parental care
> feathers = insulation 
> wings

Question 9

What are features of flight?

Answer 9

Fast
Energetically efficient 
Direct
Access any environment
Safe 

Power intensive

Question 10

How is flight in birds different to that in bats + pterosaurs?

Answer 10

Bird wings + legs are separate

Bats + pterosaurs have hindlimb bound into wings

Question 11

What are the 3 main lineages of birds?

Answer 11

Paleognaths
= ostrich 
Galloanseres
= chickens + ducks
Neoaves
= everything else

Question 12

What reptile-like features do birds have?

Answer 12

Scales

Lay eggs

Question 13

What mammal-like features do birds have?

Answer 13

Warm blooded
4-chambered heart 
Erect limbs
Parental care
Large brains

Question 14

What unique features do birds have?

Answer 14

Feathers 
Wishbone
Air-filled bones
Bipedalism 
Flight 
Highly reduced tail 
Beak

Question 15

Which is the transitional fossil for reptile to aves?

What advanced (bird) features does it have?

Which primitive (reptile) features does it have?

Answer 15

Archaeopteryx

Feathers
Wings
Wishbone

Clawed hands
Teeth
Long bony tail

Question 16

Which features suggest dinosaurs could be bird ancestors?

Answer 16

3 fingered hand
Foot structure - 3 weight-bearing toes + smaller inner toe
Wishbone 
Upright posture 
Nesting 
Rapid growth rate 
Feathers
Wings

Question 17

What are the 2 hypotheses for how dinosaurs evolved flight?

Which is the preferred hypothesis?

Answer 17

Trees-down (aboreal)
Ground-up (cursorial)

Aboreal

Question 18

Describe the trees-down (aboreal) hypothesis

Answer 18

1. Climber dinosaurs
   - reduces predation + opens up new niches
2. Parachuters
   - leaping
3. Gliders
4. Flyers

Question 19

Describe the ground-up (cursorial)

Answer 19

1. Terrestrial predator
2. Terrestrial leaper
3. Wing-assisted leaper
4. Powered flight

Question 20

What is the evidence to suggest birds originated from tree-dwelling animals?

Answer 20

Feathered hind-limbs for parachuting through trees

Curved claws for climbing

Question 21

How were birds affected by the K-T boundary?

Answer 21

• -> Mass extinction of archaic birds

- -> Cenozoic adaptive radiation