Chapter 4

Question 1

What is a sprawling stance? What kind of animals does this stance refer to

Answer 1

• animal’s humerus and femur project horizontally
• > elbows and knees are strongly bent

-lizards, turtles, crocodiles and salamanders all have sprawling stances

Question 2

What is an erect stance? What kind of animal has an erect stance

Answer 2

• mammals and birds have what is termed an erect stance
• > in an erect stance, an animal’s humerus and femur project vertically
• > the limbs point straight down from the girdle

Question 3

What are the advantages of an erect stance over a sprawling one

Answer 3

1) the limb bones are directly under the body
- >this allows the limb bones to passively support the body’s weight without muscles having to strain

• going in a push up positions changes us into a sprawling stance
• > with a sprawling stance, our muscles do a lot of work and it is difficult to maintain

2) Erect stance is more for active animals
- >sprawling stance is for animals that mainly rest on their bellies like lizards do

3) Erect stance allows for the limb bones to contribute to the length of a stride
- >this improves speed
- >because if every step you take is longer, you can potentially cover ground more quickly

Question 4

Do all modern tetrapods share an ancestor that has a sprawling stance?

Answer 4

-yes

Question 5

Did birds and mammals evolve their erect stances independently of each other

Answer 5

• yes

- note that dinosaurs had erect postures, not sprawling

Question 6

What are cursorial limbs?

Answer 6

• they are limbs specially adapted for fast locomotion
• > they are elongated to further increase stride length
• elongation is achieved by having very long lower leg bones
• > leg bones are below the elbows and the knees

Question 7

What are the two different types of postures associated with cursorial limbs

Answer 7

• digitigrade posture
• > this is when animals stand on their toes
• > eg; cheetahs and ostriches
• unguligrade posture
• > modified toenails
• > the modification results in hoof
• > eg; horses and antelopes

Question 8

Are humans cursorial?

Answer 8

• no
• > humans simultaneously stand on their toes, flat of their feet and heels
• > this posture is referred to as plantigrade posture

Question 9

What are graviportal limbs

Answer 9

• specially adapted for supporting extreme body weight
• > they are robust and heavy
• > thye tend to have large feet with large fleshy pads
• > these pads provide a solid support base and help to absorb impacts when walking

Question 10

Are graviportal limbs short or long

Answer 10

• they are short
• > tend to bend as little as possible whne walking
• > elephants have graviportal limbs

Question 11

What are obligate bipeds

Answer 11

• they are animals that always walk and run on two legs

- >eg; birds and adult humans

Question 12

What are obligate quadrupeds

Answer 12

• animals that almost always run and walk on four legs

- >eg; turtles and horses

Question 13

What are facultative bipeds

Answer 13

• animals that usually walk on all fours but rise to run on all twos
• > eg; basilisk lizards, primatesw, kangaroos

Question 14

Was the ancestor of all dinosaurs obligate biped

Answer 14

-yes

Question 15

Are prosauropods bipedal

Answer 15

• many were probably bipedal

- >but whether they are facultative bipeds are hard to determine

Question 16

How does the size of ceratopsians determine if they are obligate or facultative bipeds

Answer 16

• small ceratopsians were obligate and facultative bipeds

- larger ceratopsians were obligate quadrupeds

Question 17

What is the caudofemoralis

Answer 17

• it is a large muscle in birds and crocodiles
• > it pulls backward on the hind leg and is important for powering birds and crocodiles when they walk and run
• it is anchored to the under surface of the ilium, to the caudal vertebrae and to the chevrons
• > it attaches via a tendon to the femur

Question 18

What is the trochanter

Answer 18

• femora of crocodiles and birds have a prominence of bone called the a trochanter
• this is where the caudofemoralis muscle-ligament attaches
• note that dinosaurs had a trochanter
• > so they must have a caudofemoralis

Question 19

How does the trochanter compare on carnivorous dinosaurs to carnivorous ones

Answer 19

Carnivorous dinosaurs

• > trochanter is located high on the femur
• > this would allow for the caudofemoralis to repeatedly retract quickly
• > this is useful because carnivorous animals depend on their ability to swing their legs fast when sprinting for prey

Herbivore dinosaurs

• > trochanter is located low on the femur
• > this would have reduced the speed at which the caudofemoralis repeatedly retracts
• > but would have resulted in greater endurance, which is useful for herbivores

Question 20

What are ichnofossils

Answer 20

• they are fossils that record traces of biological activity

- >burrows are all examples of ichnofossils

Question 21

What are trackways

Answer 21

• this is an entire series of dinosaur footprints that are found
• > trackways helps our understanding of dinosaur posture and locomotion
• it can also tell us how fast dinosaurs moved
• > when we run, we tend tot ake longer steps and so do other animals
• note that trackways made it hard to get sprint speed
• > as dinosaurs would continuously need to sprint in mud for footprints to be made
• > therefore, it only tells us about dinosaur walking speeds and not usually dinosaur sprinting speeds

-lastly, it can sometimes provide insights into other aspects of locomotion

Question 22

Describe the evidence offered by the trackways of hadrosaurs and iguanodonts

Answer 22

• they have deep imprints left by their hind feet and show that they carried most of their weight on their hind legs
• they also have shallow tracks made up by their front feet
• therefore, it is safe to assume that hadrosaurs and iguanodonts were probably facultative bipeds that walked on all fours most of the time
• > but likely reared up on only their back legs to run

Question 23

What are ectotherms

Answer 23

• animals that adjust their internal body temperatures through behaviors that depend on temperature differences within their environment
• they are commonly referred to as cold-blooded animals

Question 24

What are endotherms

Answer 24

• animals that regulate temperature through their metabolic processes
• > they burn energy to generate internal heat, and to cool down they may sweat or pant

-they are commonly referred to as warm-blooded animals

Question 25

What is the cost of being an endotherms over being an ectoderm

Answer 25

• in order to maintain a constant optimal body temperature
• > endotherms must expend a large sums of energy
• > pound for pound endotherms must successfully consume a great deal more food than ectotherms

Question 26

What are the advantages of an endotherm over an ectotherm

Answer 26

• endotherms can survive in cold cimates
• > where finding a warm place to absorb heat is impossible
• endotherms are always ready for action
• ectotherms may waste more time doing stuff like sunbathing while endotherms are out and about

Question 27

Were dinosaurs more likely to be endotherms or ectotherms

Answer 27

• they were more likely to be endotherms

- supported by limbs, simple-hair like feathers and bones

Question 28

What is histology

Answer 28

• it is the technique of slicing samples of bones into very thin sections
• > such that the internal structure of the bone can be observed under magnification

Question 29

What are bone cells referred to as

Answer 29

-they are referred to as osteons

Question 30

Do endotherms grow their bones more quickly

Answer 30

• yes endotherms grow bones more quickly than ectotherms
• > they have their osteons arranged in a different pattern than ectotherms
• > this is more for modern animals

Question 31

Were large dinosaurs endotherms or gigantothermic

Answer 31

-large dinosaurs were gigantothermic

Question 32

Describe the cube square law and how it can be used to describe the increasing size of dinosaurs

Answer 32

• the cube square law states that surface area increases more slowly than its volume
• therefore, larger animals have relatively less surface area than of smaller animals