week 4

Question 1

what is the difference between sprawling and erect stance?

Answer 1

sprawling:
- humerus and femur project horizontally

erect:
- humerus and femur project vertically
- limbs point straight down from girdles

Question 2

what are the benefits and problems of erect stance?

Answer 2

+ as limb bones are positioned under the body, limb bones can passively support body weight
+ as limb bones are positioned under the body, limb bones contribute to stride length

Question 3

why do lizards like to lie on they bellies? why has this trait not been evo’d out?

Answer 3

sprawling stance - ‘standing’ is not passively supported

trait remains bc lizards live relatively sedentary lifestyles until they need to move, and so far it’s worked

Question 4

what are the characteristics of cursorial limbs?

Answer 4

elongated limbs w longer lower leg bones (below knee/elbow) which contributes to a longer stride

Question 5

what is ditigrade and unguligrade posture? is it cursorial or graviportal?

Answer 5

ditigrade: stand on toes (ex. cheetah, ostrich)

unguligrade: stand on hooves (horse, antelope)

both are cursorial

Question 6

humans are not cursorial. what are we, and what does this mean?

Answer 6

we are plantigrade, which means we stand on toes, flat of the feet, and heels at the same time (phalanges and metatarsals make contact w the ground)

Question 7

what are graviportal limbs good for?

Answer 7

short and stout, w heavy robust bones and large fleshy pads that absorb the impact shock of walking

Question 8

define obligate biped, obligate quadruped, and facultative biped

what are humans?

Answer 8

obligate biped: has to stay on two legs

obligate quadruped: has to stay on all fours

facultative biped: stays on all fours but can get on feet if it wants (ex. basilisk lizard)

the distinctions aren’t great: we are obligate bipeds, but we can crawl if necessary

Question 9

whtat was the ancestor of all dinosaurs in terms of biped/quadruped?

Answer 9

ancestor was a obligate biped, meaning dinosaurs were standing and then they went to all fours

Question 10

im gonna list a bunch of dinos. see if u can list of they’re biped or quadruped
- ankylosaurs
- ceratopsians
- pachycephalosaurs
- ornithopods
- prosauropods
- sauropods
- stegosaurus

Answer 10

ankylosaur: Q

ceratopsian: smaller were facultative B, larger were Q

pachycephalosaurs: B

ornitopods: we’ll get there :)

prosauropods: B

sauropods: Q

stegosaurs: Q

Question 11

what is the caudofemoralis?

Answer 11

important muscle in crocs, birds, and dinos for powering running

Question 12

how does the caudofemoralis attach to the vertebral column?

Answer 12

achored under the surface of the ilium, caudal vertebrae, and chevrons + attached to a tendon on femur

Question 13

how did theropods and hadrosaurs differ in their caudofemoralis’

Answer 13

theropods: trochanter (connection point) is higher on the femur - better for larger leg swinging, allowing for better running (more leg power)

hadrosaurs: trochanter is lower on the femur - not as dramatic swings, but tires less quickly

Question 14

what is an ichnofossil

Answer 14

ichnofossils are record traces of biological activity

includes things like footprints, tooth marks (BUT NOT TEETH), and burrows

Question 15

dinosaurs are not thought to have walked w their tails dragging. what evidence suggests this?

Answer 15

we have many trackways that tell us about posture and locomotion, and we rarely see tailmarks

Question 16

earlier we briefly touched on the movement style of iguanodonts (hadrosaurs). how do they move :)

Answer 16

trackways demonstrate deep imprints left by hindfeet, and shallow tracks made by front feet
–> were prob facultative bipeds

three toed footprints in hindlegs, crescent shaped prints for hands

Question 17

what is the difference between an ectotherm and an endotherm?

Answer 17

ectotherm: external heating, behav regulated

endotherm: internal heating, metabolism regulated

Question 18

what are some advantages of endotherm > ectotherm

Answer 18

+ endotherm can survive colder climates where ectotherms can’t just find a spot to heat up
+ while ectotherms save energy from not metabolizing, they need time to heat up
+ endotherms are always ready to go, whereas ectotherms gotta warm up a little

Question 19

were dinosaurs ectotherms or endotherms?

Answer 19

its thought they may have experienced gigantothermism. this is ectotherm, but due to the cube square law, their volume of heat is larger than the surface area that loses it –> functionally act as endotherms

Question 20

is graviportal and cursorial stances fixed in a species?

Answer 20

no! we demonstrate shifts when we’re just standing around (graviportal) vs running on our front feet (cursorial)

Question 21

are biped and quadruped fixed in a species?

Answer 21

no! we demonstrate this when we crawl as babies and walk as adults

Question 22

what is an advantage of switching from quadruped to biped?

Answer 22

use of arms

Question 23

what are insulating integumentary structures associated with?

Answer 23

endotherm!