Locomotion

What bones are in Chrondichthyes pectoral girdle?

Coracoid
Scapula
Suprascapula

What bones are in Osteichthyes pectoral girdle?

Ventral clavicle
Enlarged cleithrum
Supracleithrum
Post temporal
Small ossified coracoid and scapula
Suprascapula

What bones are in frogs pectoral girdle?

Coracoid
Scapula
Suprascapula

What bones are in early tetrapods pectoral girdle?

Clavicle
Cleithrum
Supracleithrum
Coracoid
Scapula
Suprascapula

Agnatha

Jawless fish
No girdles

Cartilaginous fish

Consists of only cartilage
Chondrichthyes

Pectoral girdle in amphibians

Ossified scapula and coracoid
No cleithra
Glenoid cavity appears for the first time (less easily dislocated, humerus fits into this)
No interclavicle

Pectoral girdle in reptiles

Coracoid and scapula generally preset
Clavicles and interclavicles present
No pectoral girdle in snakes

Pectoral girdle in birds

Clavicles fused in midline to form furcula (wish bone)
Coracoid and scapula are long and slender

Pectoral girdle in mammals

Monotremes
- reptilian like
Other mamals
- interclavicle and reptilian coracoid are missing
- clavicles sometimes reduced or absent (ungulates, rodents) or prominent (man)
- scapula always present usually divided by spine into supra and infraspinous fossa

Fins of Primitive Elasmobranchs (subclass of chrondichthyes)

Stiff, paired and triangular
Base and fin in same horizontal plane
Used as stabilisers to maintain fish in horizontal plane
Insignificant in locomotion

General structure of fins in modern fish

Usually occur singly (dorsal, anal, caudal)
In pairs (pectoral, pelvic)
Paired fins are phylogenetic source of tetrapod limbs

Structure of fins

Thick basals first
Longer and thinner radials perpendicular to basals
Even thinner dermal fin rays

Dermal fin rays

Slender rods
Keratinised in elasmobranchs
Ossified or chondrified in bony fish

...

...

General structure of lobed fins

Fleshy proximal lobe containing fin skeleton and muscles
Membranous distal portion stiffened by rays
Lungfishes
Cossopterygians (certain fin features that approach limb features in early tetrapods eg coelacanth)

General structure of fin fold fins (Cladoselache - extinct sharks)

Broad base

General structure of ray fins (perch)

Very flexible fins
Lost components of basal skeleton
Some have no pelvic fins

Spiny fins

All extinct

Function of Fins

Stability
- prevent roll, pitch and yaw
Breaking action
- paired fins
Steering
- control direction of movement

How is forward propulsion in fish achieved?

- lateral flexion of vertebrae caused by axial musculature results in lateral undulations
- caudal fin sweeps from side to side which exerts a backwards and lateral force against resistance of water
- forward component of resistance propels fish forward
-

What is the general acception of where tetrapod limbs developed?

From lobe finned crossopterygians

Structure of early tetrapod limbs

Short
First segment almost horizontal
Second segment perpendicular to first
Toes tended to point laterally

Bones of stylopodium in forelimb and hindlimb

Upper arm - humerus
Thigh - femur

Bones of zeugopodium in forelimb and hindlimb

Forearm - radius and ulna
Shank - tibia and fibula

Bones of autopodium in forelimb and hindlimb

Manus:
Wrist - carpals
Palm - metacarpals
Fingers - phalanges
Pes:
Ankle - tarsals
Sole - metatarsals
Toes - phalanges

Function of limbs

Locomotion
As a tool
Climbing
Interaction with environment (touch)
Digging
Flying
Swimming

How do fish move in the water?

Propulsion through lateral undulations
Horizontally held fins - LIFT
Vertically held fins - THRUST

How did fish progress to move on land?

Muscles of primitive crossopterygians were too weak to support body out of water
But peg like lobe fins could anchor on ground
Lateral undulations place fins as pivot points and body moved around the anchored fin
e.g. 'bottom walking' of today's lungfish

What do method of locomotion do urodeles, lizards and turtles use?

Lifting and planting feet, then vertebral column rotates around pivot point
Lifting of limb brought in axial torque of vertebral column
Gait used = trot (simultaneous placement of diagonally opposite feet on ground)

Why is a trot unstable?

Centre of gravity balanced on thin line between 2 diagonal supports

How do trotting tetrapods gain stability?

Buoyancy of water
Tail on ground
Belly walking (ventral surface remains in contact with ground)

How does placing tail on ground increase stability?

Produces triangle of support between 3 points rather than single line between 2

How does lateral sequence gait increase stability?

The centre of gravity is always within the triangle of support formed by 3 legs

How do urodeles and some reptiles employ inefficient locomotion?

Sprawled posture and perpendicular limbs
Body weight supported by adductor(inside thigh) muscles
Overarm swing needed for each step
e.g. spotted salamander

How was locomotion efficiency improved in bipedalism?

Front legs initially little modified
Hindlimbs lengthened and strengthened
Knees rotated anteriorly to a position beneath body
e.g. ostrich
-wings used for balance
-knee joint right underneath hip, ankle lower down underneath knee

How was locomotion efficiency improved in a four footed gait?

Knees rotated anteriorly
Elbow rotated posteriorly and brought closer to body

What are the advantages of changed limb posture?

Body weight is now supported by rigid bones = decreased energy expenditure
Increased efficiency of limb swing, limb movement is in sagittal plane = easy pendulum swing beneath body
Change in flexion of vertebral column from later flexion to vertical flexi

Cursorial locomotion

Fast running
e.g. antelope, horse, cheetah

Fossorial locomotion

Digging or burrowing
e.g. rabbits, sand snake, some rodents

Saltatorial locomotion

Hopping
e.g. kangaroo, frog, hare

Arboreal locmotion

life in tree

Types of arboreal locomotion

Scansorial - climbing with claws
e.g. squirrel
Brachiator - hand grips branch and body swings beneath
e.g. monkeys, chimpanzees

Modes of locomotion without limbs

Lateral undulation (serpentine)
Rectilinear
Concertina
Sidewinder

Lateral undulation

Side to side flexion (normal snake movement)
~~~~~~

Rectilinear

Body only flexes when turning
Muscles lift belly off the ground and place it further forward
Opposing muscles pull back once belly is placed on ground and propel snake forward

Concertina

Pushing pulling and anchoring
Each portion of the snakes body goes through cycles of static contact with the ground and movement

Sidewinder

Body of snake is curved like lateral undulation
Sidewinding accomplished by lifting all segments with same slope off the ground, head gets thrown forward and body follows
Body is always static when in contact with ground

Speeds reached by animals

Cheetah - 120kmh
Pronghorn deer - 98kmh
Ostrich - 80kmh
Red fox - 72kmh
Horse - 70kmh
Whippet - 55kmh
Human - 37kmh

Stride

full cycle of running or walking

Speed

length of stride x rate of stride

How does lengthening the leg increase stride?

Longer the leg, further it can reach, greater the stride
Radius and tibia usually longer than proximal segment - light and slim
Longer metacarpals and metatarsals

How many digits do rodents, rabbits, carnivores walk on?

4

How many digits do rhinos and tapirs have?

3

How many digits do pigs and sheep and camels have?

2

How many digits do horses have?

Primitive - 4
Modern - 1

Features of plantigrade foot posture

Carpus, metacarpus and digits on ground
Pentadactyl (5 fingered)
e.g. human, monkey, bear

Features of digitigrade foot posture

Reduced thumb
Walk on ends of metacarpals

Features of unguligrade foot posture

3 or fewer digits
Walk on tips of remaining digits

Mobile scapula - increasing length of stride

Mobile scapula positioned to side
Reoriented to side, not over back so rotates in same plane as limb
(more mobile in mammals, fixed in amphibians)

Flexion of spine - increasing length of stride

Lateral flexion in lizards and amphibians
Vertical flexion and extension in fast quadrupedal mammals = body longer when back extended, achieved when back feet on ground front feet reaching out = increased stride length
Increase in back flexion = increase

Unsupported intervals - increasing length of stride

All feet off the ground in period of suspension
Maximum flexion of spine
Maximum rotation of scapula
Maximum extension of spine

How to increase rate of stride

Lengthen distal end of limb
-reduced muscle mass
-reduced digits

What is proximal insertion of a muscle associated with?

Speed
If muscle shortens by same length, moving part swings through large distance

What is distal insertion for a muscle associated with?

Strength
If muscle shortens by same length, moving part swings through small distance

Walk

4 independent footfalls in diagonal sequence

Amble

4 independent footfalls in lateral sequence

Trot

2 joint footfalls in diagonal sequence
Left anterior, right posterior step at same time
e.g. horse

Pace

2 joint footfalls in lateral sequence
Left anterior and posterior step at same time, then right anterior and posterior
Unstable in shorter legged animals
e.g. camel, giraffe

Gallop

Period of suspension when
-legs gathered under animal (horse)
-legs stretched out fore and hind (deer)
both (cheetah)

Pronk

All four feet on ground simultaneously
Then period of suspension

Role of tail in bipedal reptiles and ricochetal mammals

Counterbalance forepart of body (CofG over hind feet)
Used as a prop (3rd point of support)
Used to change direction (lash in air)

Why is a tail not necessary in humans?

Upright posture

Why is upright posture fundamentally unstable?

Only two supports
Large part of body weight above centre of gravity

What are the 3 changes to achieve upright position?

Front of body lifted 30degrees
Upper part of pelvis tilted back, rotating vertebral column another 30degrees
Lumbar region of vertebral column curves the last 30degrees