Week 4 - moving around

Question 1

What is the difference between a sprawling stance and an erect stance?

Answer 1

Sprawling = humerus and femur project horizontally with elbow and knees strongly bent

Erect = humerus and femur projected vertically such that all the limbs point straight down

Question 2

What are the advantages of erect stances over sprawling stances?

Answer 2

1. passively support the body’s weight
   - allows the animal to be active
   - allows the animal to be larger
2. all limb bones contribute to the length of a stride
   - improves speed

Question 3

What stance did the common ancestor of all tetrapods have?

Answer 3

sprawling

Question 4

How do we know that dinos stood erect?

Answer 4

look at the limb joints and the articulation of limb girdles

Question 5

what is the difference between cursorial and graviportal limbs?

Answer 5

cursorial = limbs adapted for fast locomtion
graviportal = limbs adapted for supporting extreme body weight

Question 6

Describe characteristics of cursorial limbs

Answer 6

• very long lower leg bones –> elongated –> increase stride length
• often have a digitigrade or unguligrade posture

Question 7

Describe how onithomimid theropods show cursorial adaptations

Answer 7

digitigrade stance + long metatarsals

Question 8

Describe characterisitics of graviportal limbs

Answer 8

• bones are robust and heavy
• large feet with large fleshy pads –> solid support base + helps absorb impacts when walking
• short
• when walking, their joints bend as little as possible

Question 9

What are obligate bipeds?

Answer 9

animals that almost always walk on two legs

Question 10

what are obligate quadrapeds?

Answer 10

animals that almost always walk and run on two legs

Question 11

What are facultative bipeds?

Answer 11

some animals that walk on all fours but rise on two legs to run

Question 12

Was the ancestor of all dinos an obligate biped, obligate quadraped, or facultative biped?

Answer 12

obligate biped

Question 13

Where did most dinos carry a majority of their weight, what is the implication of this?

Answer 13

Carried most of their weight on their hind legs –> deeper footprints = hind legs, shallow footprints = front legs

Question 14

Were sauropods, stegosaurs, and ankylosaurs obligate bipeds (OB), obligate quadrapeds (OQ) or facultative bipeds (FB)?

Answer 14

obligate quadrapeds

Question 15

where prosauropods OB, OQ, or FB?

Answer 15

probably bipedal, but cannot tell if obligate or facultative

Question 16

were small ceratopsians, OB, OQ, or FB?

Answer 16

OB and FB

Question 17

were larger ceratopsians OB, OQ, or FB?

Answer 17

OQ

Question 18

were pachycephalosaurs and theropods OB, OQ or FB?

Answer 18

OB

Question 19

were small ornitopods OB, OQ, or FB?

Answer 19

OB

Question 20

were large ornithopods (including hadrosaurs and iguanodonts) OB, OQ, or FB?

Answer 20

strong hind limbs that are longer than front limbs –> bipedal

fossil footprints –> quadrapedal

Question 21

What tail muscle is important for powering dinos, birds, and crocs when they walk and run?

Answer 21

caudofemoralis muscle

Question 22

Describe how the caudofemoralis muscle powers dinos to walk and run

Answer 22

• anchored to the undreside of the ilium, to the caudal vertebrae and to the chevrons
• attatches to the femur
• pulls backwards on the hind leg

Question 23

What is the trochanter?

Answer 23

prominence of bone where the caudofemoralis muscle ligament attatches

Question 24

Describe the position of the trochanter on theropods vs hadrosaurs and what this implies

Answer 24

theropods:
- trocanter is located high on the femur –> caudofemoralis muscle can repeatedly contract quickly
- allows theropods to swing their legs fast when sprinting

hadrosaurs:
- trocanter is located further down the femur –> decreases the speed at which the caudofemoralis could have been repeatedly contracted
- better endurance because each retraction would have pulled with lots of leverage –> important of animal that needed to be constantly on the move and grazing from one patch of vegetation to the next

Question 25

What is an inchnofossil? Give examples/

Answer 25

ichnofossil = fossils that record traces of biologic activity e.g. footprints, tooth marks, and burrows

Question 26

How do footprints become fossilized?

Answer 26

1. footprint must be first made in soft mud 2. mud must dry out and harden 3. must be burried but eventually re-exposed

Question 27

How have dino trackways change our understanding of dino posture and locomotion?

Answer 27

- it was believed that bipedal dinos walked with their tails down --> would have seen tail marks in trackways - trackways of iguandonts and hadrosaurs --> deep imprints by their hind feet and shallow imprints by their front feet --> likely facultative bipeds - determined how fast dino moves - show theropod trackways preserve long claw marks --> swimming traces

Question 28

How do you determine how fast a dino moved?

Answer 28

1. measure the length of dino strides 2. estimate dino leg lengths from the proportions of their footprints 3. estimate the speed the dino was moving

Question 29

Why don't we usually see trackways that indicate running?

Answer 29

because it is difficult to run in mud which is where trackways are best preserved

Question 30

What is the difference between an ectotherm and an endotherm?

Answer 30

ectotherm = animal that adjusts their internal body temp via behaviours that depends on diff temperatures within their environment endotherm = animal that regulated their own body temp via metabolic processes

Question 31

Describe how ectotherms would warm up and cool down

Answer 31

warm up = sun bathing cool down = seek out shade or cool burrows

Question 32

Describe how endotherms would warm up and cool down

Answer 32

warm up = burn energy to generate heat cool down = sweat or pant

Question 33

What is a disadvantage of endothermy?

Answer 33

to maintain optimal body temp, must expend large sums of energy --> must consume more food

Question 34

What are three advantages of endothermy?

Answer 34

1. survive in cold climates 2. always ready for action --> ectotherms can be sluggosh --> easy prey or easy predator to avoid 3. do not have to waste time warming up or cooling down --> can maintain high activity levels

Question 35

What are the arguments that dinos were endotherm?

Answer 35

1. limbs of dinos are erect --> adopted for active lifestyle 2. some dinos had simple hair-like feathers --> insulating integument 3. overall pattern of ecological success --> endotherms tend to outcompete ectotherms 4. bone histology of dino osteons are arranged in an endotherm pattern (bones grew fast)

Question 36

What is bone histology?

Answer 36

techniques of slicing bones into very thin sections such that the internal structure of the bones can be observed under magnification

Question 37

Describe the theory that suggests that large dinos were gigantothermic

Answer 37

- cube square law --> larger animals have relatively less surface area than do smaller animals - even if big dinos were ectothermic, their low ration of surface are to volume --> prevent them from losing sig heat to the environment - could have lived active endothermic-like lives without actually needing to produce heat by burning energy