lect 3+4 - locomotion + feeding Flashcards
(26 cards)
quadrupedalism
movement of all four limbs
- speed limited by stride length
bipedalism
movement of only the hind limbs
- raises centre of gravity and is not limited by stride length
typical footfall sequence in tetrapods
LF > RH > RF > LH
each foot in contact with the ground 75% of the time
gait descriptors
- sequence
- amount of contact on the ground (duty factor)
increase stride length
increase flexibility of hind limbs
- tendon passes over the heel to connect leg and toes makes movement more efficient (40%)
long legs and feet
- provide more propulsion force
top speed 4-pedal
5mph
top speed 2-pedal
12mph
lizards switching between quadrupedal and bipedal
- scaloporus (fence lizard)
- callisaurus (zebra-tailed lizard)
- australian frilled lizard
- basiliscus (basilisk lizard)
lamellae
expanded scales stacked on the toes of lizards to help them stick to smooth surfaces
- increase surface area and support body weight
- each lamellae carry setae
- can be divided or undivided
limbless locomotion
- lateral undulation
- rectilinear creeping
- sidewinding
- concertina (normal + internal)
body composition determines form of locomotion
lateral undulation
serpentine movement
- in snakes, caecilians, lizards
- where the snake bends it pushes outwards from both sides, cancelling out and propelling forward
- speed related to number of curves produced by body
rectilinear creeping
only in snakes (heavy bodied)
- minimal lateral movement
- muscles lift the ventral scales and move them forward, they anchor to surface irregularities and pull the snake forward
- waves of contraction + extension
- not fast
- muscle action, no bone movement
sidewinding
only in snakes
- horizontal + vertical waves run head to tail offset from each other
horizontal: makes exaggerated loops
vertical: lifts part of the body off the ground
- rapidly change direction by changing phasing of the waves
concertina (normal + internal)
normal (in snakes + caecilians)
- anchor bottom and push forward, then anchor top and pull the rest up
- muscles push against surface creating resistance points
- useful in confined spaces and inclined surfaces
internal (only in caecilians)
- only bend internal vertebrae column
- thick species use more frequently
ventral scales
prevent snakes from slipping or getting dragged backwards
- grips irregularities
scale lipid layer
upper body scales = disordered lipid structure
ventral body scales = organized lipid structure to slip against surfaces and reduces wear on the scale
bipes locomotion
- nocturnal
- limbs used a anchor points during concertina
- as efficient as lateral undulation
snake feeding
- need to swallow prey whole at one time
- kill prey by stopping the heart
- pressure in the arteries from the heart stops fast when constriction is applied
- release pressure when heartbeat is no longer detected
hypokinesis
allow animal to use pincer movements to grab prey
streptostyly
allow movement of the quadrate bone
- move lower jaw backwards and forewards
metakinesis
allow whole upper skull to move relative to the braincase
mesokinesis / prokinesis
front snot moves up + down from the braincase
snakes = front of the eye (meso)
lizards = behind the eye (pro)
cranial length pro/cons
short =
- bite with less force + longer to chew prey
- can open/close jaw fast
long =
- bite with more force
lower jaw in snakes
- bound together at the front and to the rest of the skull by tendons
- modified skin to allow spreading
