Week 4 - moving around Flashcards
What is the difference between a sprawling stance and an erect stance?
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
What are the advantages of erect stances over sprawling stances?
- passively support the body’s weight
- allows the animal to be active
- allows the animal to be larger - all limb bones contribute to the length of a stride
- improves speed
What stance did the common ancestor of all tetrapods have?
sprawling
How do we know that dinos stood erect?
look at the limb joints and the articulation of limb girdles
what is the difference between cursorial and graviportal limbs?
cursorial = limbs adapted for fast locomtion
graviportal = limbs adapted for supporting extreme body weight
Describe characteristics of cursorial limbs
- very long lower leg bones –> elongated –> increase stride length
- often have a digitigrade or unguligrade posture
Describe how onithomimid theropods show cursorial adaptations
digitigrade stance + long metatarsals
Describe characterisitics of graviportal limbs
- 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
What are obligate bipeds?
animals that almost always walk on two legs
what are obligate quadrapeds?
animals that almost always walk and run on two legs
What are facultative bipeds?
some animals that walk on all fours but rise on two legs to run
Was the ancestor of all dinos an obligate biped, obligate quadraped, or facultative biped?
obligate biped
Where did most dinos carry a majority of their weight, what is the implication of this?
Carried most of their weight on their hind legs –> deeper footprints = hind legs, shallow footprints = front legs
Were sauropods, stegosaurs, and ankylosaurs obligate bipeds (OB), obligate quadrapeds (OQ) or facultative bipeds (FB)?
obligate quadrapeds
where prosauropods OB, OQ, or FB?
probably bipedal, but cannot tell if obligate or facultative
were small ceratopsians, OB, OQ, or FB?
OB and FB
were larger ceratopsians OB, OQ, or FB?
OQ
were pachycephalosaurs and theropods OB, OQ or FB?
OB
were small ornitopods OB, OQ, or FB?
OB
were large ornithopods (including hadrosaurs and iguanodonts) OB, OQ, or FB?
strong hind limbs that are longer than front limbs –> bipedal
fossil footprints –> quadrapedal
What tail muscle is important for powering dinos, birds, and crocs when they walk and run?
caudofemoralis muscle
Describe how the caudofemoralis muscle powers dinos to walk and run
- 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
What is the trochanter?
prominence of bone where the caudofemoralis muscle ligament attatches
Describe the position of the trochanter on theropods vs hadrosaurs and what this implies
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
What is an inchnofossil? Give examples/
ichnofossil = fossils that record traces of biologic activity
e.g. footprints, tooth marks, and burrows
How do footprints become fossilized?
- footprint must be first made in soft mud
- mud must dry out and harden
- must be burried but eventually re-exposed
How have dino trackways change our understanding of dino posture and locomotion?
- 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
How do you determine how fast a dino moved?
- measure the length of dino strides
- estimate dino leg lengths from the proportions of their footprints
- estimate the speed the dino was moving
Why don’t we usually see trackways that indicate running?
because it is difficult to run in mud which is where trackways are best preserved
What is the difference between an ectotherm and an endotherm?
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
Describe how ectotherms would warm up and cool down
warm up = sun bathing
cool down = seek out shade or cool burrows
Describe how endotherms would warm up and cool down
warm up = burn energy to generate heat
cool down = sweat or pant
What is a disadvantage of endothermy?
to maintain optimal body temp, must expend large sums of energy –> must consume more food
What are three advantages of endothermy?
- survive in cold climates
- always ready for action –> ectotherms can be sluggosh –> easy prey or easy predator to avoid
- do not have to waste time warming up or cooling down –> can maintain high activity levels
What are the arguments that dinos were endotherm?
- limbs of dinos are erect –> adopted for active lifestyle
- some dinos had simple hair-like feathers –> insulating integument
- overall pattern of ecological success –> endotherms tend to outcompete ectotherms
- bone histology of dino osteons are arranged in an endotherm pattern (bones grew fast)
What is bone histology?
techniques of slicing bones into very thin sections such that the internal structure of the bones can be observed under magnification
Describe the theory that suggests that large dinos were gigantothermic
- 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
