ZOO 4910 Lecture Notes - Lecture 12: Plantigrade, Digitigrade, Quadrupedalism
2 May 2018
School
Department
Course
Professor
Legged
•
Progressive loss of function in a limb
enhancer during snake evolution
○
Limbless
•
Rolling (ex. Pangolins)
•
Basic Forms of Locomotion:
Torso is 'slung' between legs
!
Large torsional loads
!
Support muscles exert constant force
!
Torso and limb muscles for
movement
!
Sprawling (salamanders, turtles, walking
frogs)
○
Torso is balanced on top of limbs
!
Fewer torsional loads
!
Require less robust skeletons
!
Movement is mostly derived from
limb muscles
!
Erect (mammals, birds, dinosaurs)
○
*see slide: erect vs. non-erect
○
Posture
•
Bipedal (birds, humans, hopping
mammals)
○
Quadrupedal (mammals, reptiles,
amphibians)
○
Number of legs
•
Plantigrade -walking on entire foot
(amphibians, reptiles, humans, bears,
squirrels)
○
Digitigrade -walking on toes (felids,
canines, birds)
○
Unguligrate -walking on 'tippy toes'
(horses, rhinos, deer, hippos, giraffes)
○
Functional structure of the foot (modified tibia
and fibula in length and structure)
•
Movement on Appendages:
Elongated distal limb
□
Loss/reduction of clavicle
allows scapula to pivot and
rotate with the limb
□
Foot posture
□
Stride length
!
Optimizing Vo: short "in-
levers" and long "out-levers"
□
Increase the number of joints
(VoTotal = sum of all Vo in
limb)
□
Decrease in limb inertia
□
Reallocation of muscle mass
from distal to proximal
□
Stride rate (Vo = velocity)
!
Can only run for short
distances due to
increasing prolactin
levels (very
energetically expensive)
!
Ex. Cheetah as a cursorial
champion (over short
distances)
□
Dorso-ventral flexion of the spine
!
Adaptations for running in both predator
and prey:
○
Cursorial (running)
•
See general functional
organization on slide
□
Stellate cells
□
Communication to cerebellum
□
Cerebellar complexity --> motor and
cognitive integration
!
Frictions
!
Claws
!
Prehensility
!
Suction
!
Adaptations:
○
Movement is a function of stability
and power, but also evolutionary
history
!
Vampire bats use primarily their
front limbs for running
!
Exceptions: vampire bats
○
Scansorial (climbing)
•
Gliding
•
Swimming
•
Bipedal hopping: typically pronounced in
prey species
○
Macropodids (kangaroos)
!
Primates (ring tailed lemurs)
!
Lagomoprhs
!
Rodents
!
Independently evolved in several groups:
○
Forelimbs and shortened, and
typically generalized (feeding,
grooming)
!
All have very long hind limbs to optimize
Vo
○
Cervical vertebrate is often
fused
□
Lumbar vertebrae robust
□
Sacrum and pelvic girdle are
fused
□
Ligaments run from thoracic-
cervical vertebrae and from
sacral-lumbar vertebrae
□
Stiffening of the spine to resist
whiplash
1.
Elasticity in hind limb ligaments
(elastic storage mechanisms)
2.
Long counter-balancing tail 3.
--> rapid acceleration, sudden
directional shifts
Other adaptations:
○
Enormous thigh muscles
!
Despite low BMR, high density of
mitochondria in thigh muscles
!
Evolution of Hopping:
○
Same habitat, predators, food source
and active hours
!
Different escape options based
on locomotion (ventures out
into the open)
□
Why? --> occupy different niches to
limit competition between species
!
Ex. Kangaroo Rats: Desert-dwelling Jeroba
(bipedal) vs. Gerbil (quadrupedal)
○
Like all jumpers --> elongated hind
limbs
!
Modified illium --> increased joints
(increased Vo)
!
Modified leg muscles --> enlarged
and specialized for jumping power
!
Frogs muscle have passive
flexibility (generate a ton of
mechanical energy during
jumps) --> cheating limits of
what muscles alone should be
capable of
□
Making muscles longer allows
(stretch) allows thrust to
increase (defying laws of
physics)
□
Contraction and relaxing muscles
over jump
!
Defying laws of physics (e.g. frogs) -->
increasing thrust (Vo):
○
Saltatorial (hopping)
•
Locomotory Specializations:
Distance moved increases with body mass
○
Different orders of mammals move
different distances (even with similar body
mass)
○
See daily distance moved vs. body mass
•
Significance:
Running, climbing, hopping
○
Many behavioural solutions to complex 3D space
•
Limbs, musculature, metabolic capacity
○
Diverse physiological adaptations
•
Driven by ecological niche
•
Ecological architecture driven by locomotion
•
Overall:
Locomotion on Land
Friday,*October*20,*2017
12:25*PM
Legged
•
Progressive loss of function in a limb
enhancer during snake evolution
○
Limbless
•
Rolling (ex. Pangolins)
•
Basic Forms of Locomotion:
Torso is 'slung' between legs
!
Large torsional loads
!
Support muscles exert constant force
!
Torso and limb muscles for
movement
!
Sprawling (salamanders, turtles, walking
frogs)
○
Torso is balanced on top of limbs
!
Fewer torsional loads
!
Require less robust skeletons
!
Movement is mostly derived from
limb muscles
!
Erect (mammals, birds, dinosaurs)
○
*see slide: erect vs. non-erect
○
Posture
•
Bipedal (birds, humans, hopping
mammals)
○
Quadrupedal (mammals, reptiles,
amphibians)
○
Number of legs
•
Plantigrade -walking on entire foot
(amphibians, reptiles, humans, bears,
squirrels)
○
Digitigrade -walking on toes (felids,
canines, birds)
○
Unguligrate -walking on 'tippy toes'
(horses, rhinos, deer, hippos, giraffes)
○
Functional structure of the foot (modified tibia
and fibula in length and structure)
•
Movement on Appendages:
Elongated distal limb
□
Loss/reduction of clavicle
allows scapula to pivot and
rotate with the limb
□
Foot posture
□
Stride length
!
Optimizing Vo: short "in-
levers" and long "out-levers"
□
Increase the number of joints
(VoTotal = sum of all Vo in
limb)
□
Decrease in limb inertia
□
Reallocation of muscle mass
from distal to proximal
□
Stride rate (Vo = velocity)
!
Can only run for short
distances due to
increasing prolactin
levels (very
energetically expensive)
!
Ex. Cheetah as a cursorial
champion (over short
distances)
□
Dorso-ventral flexion of the spine
!
Adaptations for running in both predator
and prey:
○
Cursorial (running)
•
See general functional
organization on slide
□
Stellate cells
□
Communication to cerebellum
□
Cerebellar complexity --> motor and
cognitive integration
!
Frictions
!
Claws
!
Prehensility
!
Suction
!
Adaptations:
○
Movement is a function of stability
and power, but also evolutionary
history
!
Vampire bats use primarily their
front limbs for running
!
Exceptions: vampire bats
○
Scansorial (climbing)
•
Gliding
•
Swimming
•
Bipedal hopping: typically pronounced in
prey species
○
Macropodids (kangaroos)
!
Primates (ring tailed lemurs)
!
Lagomoprhs
!
Rodents
!
Independently evolved in several groups:
○
Forelimbs and shortened, and
typically generalized (feeding,
grooming)
!
All have very long hind limbs to optimize
Vo
○
Cervical vertebrate is often
fused
□
Lumbar vertebrae robust
□
Sacrum and pelvic girdle are
fused
□
Ligaments run from thoracic-
cervical vertebrae and from
sacral-lumbar vertebrae
□
Stiffening of the spine to resist
whiplash
1.
Elasticity in hind limb ligaments
(elastic storage mechanisms)
2.
Long counter-balancing tail 3.
--> rapid acceleration, sudden
directional shifts
Other adaptations:
○
Enormous thigh muscles
!
Despite low BMR, high density of
mitochondria in thigh muscles
!
Evolution of Hopping:
○
Same habitat, predators, food source
and active hours
!
Different escape options based
on locomotion (ventures out
into the open)
□
Why? --> occupy different niches to
limit competition between species
!
Ex. Kangaroo Rats: Desert-dwelling Jeroba
(bipedal) vs. Gerbil (quadrupedal)
○
Like all jumpers --> elongated hind
limbs
!
Modified illium --> increased joints
(increased Vo)
!
Modified leg muscles --> enlarged
and specialized for jumping power
!
Frogs muscle have passive
flexibility (generate a ton of
mechanical energy during
jumps) --> cheating limits of
what muscles alone should be
capable of
□
Making muscles longer allows
(stretch) allows thrust to
increase (defying laws of
physics)
□
Contraction and relaxing muscles
over jump
!
Defying laws of physics (e.g. frogs) -->
increasing thrust (Vo):
○
Saltatorial (hopping)
•
Locomotory Specializations:
Distance moved increases with body mass
○
Different orders of mammals move
different distances (even with similar body
mass)
○
See daily distance moved vs. body mass
•
Significance:
Running, climbing, hopping
○
Many behavioural solutions to complex 3D space
•
Limbs, musculature, metabolic capacity
○
Diverse physiological adaptations
•
Driven by ecological niche
•
Ecological architecture driven by locomotion
•
Overall:
Locomotion on Land
Friday,*October*20,*2017 12:25*PM
