SKELETAL CONSIDERATIONS & ADAPTATIONS FOR

LOCOMOTION

Mammalogy (Fall 2012 Althoff - reference FDVM Chapter 6)

LEC 05

Axial Skeleton• For terrestrial mammals: skeleton, muscles, and

their associated structures can be viewed as one unit

• The ____________________ represents the deck or girders of a bridge & the legs are the pillars.

• A major, distinguishing feature of mammals is that the “pillars” (legs) must move as ________, via muscle action, to provide locomotion

Fig. 8-3 p170 PJH

lumbar thoracic

A neck!

Generalized primitive tetrapod condition

Fig. 8-2 p169 PJH

• ___________________ (zygapophysis singular)

processes that interlock and resisttwisting (torsion) andbending

(compression) to support weight ofviserca on land

Better suspension…on land !!

RIB

post-

pre-

spinalcord

notocord

Vertebral Column

• Cervical, thoracic, lumbar, sacral, and caudal vertebrate. Exceptions (sloths and manatees don’t have cervical vertebrate)

• 12-15 ribs which articulate with thoracic vertebrae• 4-7 lumbar vertebrae (_______________)• In most mammals, sacral vertebrae are ______ to

form os sacrum to which pelvic girdle attaches

• Pelvic girdle: ____________________• Caudal = tail (varies with tail length)

Bobcat: male or female ????

Atlas & Axis Junction

• Relative to “lower” vertebrates, these two vertebrate (at junction of vertebral column and skull) allow for significantly increased _____________ of the skull

• Increased movement translates to better positions for __________________ …doesn’t require that ________ body be moved

Axial & Appendicular Join

• Attachment of forelimbs & hindlimbs to axial skeleton

• __________—PECTORAL GIRDLE (clavicle & scapula)

• __________—PELVIC GIRDLE (ilium, ishium, & pubis)

PERMITS ROTATION

Joints

Fig. 8-1b p168 PJH

• End of joint bones covered by a smooth layer or articular ____________. Result: reduced friction

• Bone within the joint is covered cancellous bone (i.e., not as dense)

• Entire joint enclosed in a joint capsule containing synovial fluid which serves as a lubricant

more FLEXIBILITY !!

Appendicular Skeleton• FORELIMBS—__________ bone (humerus), 2

middle elements (radius and ulna), and the carpals, metacarpals, and phalanges.

• HINDLIMBS—___________ bone (femur), lower leg bones (fibula & tibia), and the tarsals, metatarsals, and phalanges. In some species fibula & tibia are fused

Harbor Seal Bobcat

Modes of Locomotion• Walking & Running• Jumping & Ricocheting• Swimming• Flying & Gliding• Climbing• Digging & Burrowing

Terms...

• SALTATORIAL—leapinga) spring (jumping)—______ feet

involvedb) richochet—___________ only

• SEMI-FOSSORIAL• FOSSIORIAL• SEMIAQUATIC

more terms…con’t

• SCANSORIAL—vertical movements on hard surfaces ___________________

• BRACHIATING—swinging movements with forelimbs (? __________________?)

Walking & Running

• Most are QUADRUPEDS• Some are BIPEDAL• Humans only ones habitually __________• Ambulatory = locomote mostly by _________

vs.• Cursorial = locomote at least part of time

by __________

Note position of scapula A B

Most Mammals…well adapted for _________________ locomotion

• PLANTIGRADE—walk on soles of hands and feet (humans, opossums, etc.)

• DIGITIGRADE—walk on digits (phalanges) (not always “all” digits) (coyotes)

• UNGULIGRADE—hoofed animals, phalanges are elevated so that only hoofs (modified digital keratin) are in contact with the substrate (pronghorn)

Unguligrade(pig) Digigrade

(dog) Plantigrade(man)

SOURCE: Fishbeck and Sebastiani (2008) Fig. 5.20

Running SpeedsSpecies Speed (km/h) LocomotionCheetah 110 Pronghorn 98 Elk 72 Coyote 70 Europeon hare 65 Grizzly bear 50 Human 45 Tree squirrel 20 Three-toed sloth 1 “hang”

Patterns of Running

• Gait--see p110, Fig. 6.14 • Walking & Pacing & Trotting (different

forms of symmetrical gaits = equal spacing of feet and contact with ground at even time intervals

vs. • Galloping & Bounding (different forms of

asymmetrical gaits = contact with ground at uneven time intervals)

Jumping & Ricocheting

• Saltatorial locomotion• Jumping = lagomorphs• Richocheting = kangaroos (p111, Fig. 6.15),

kangaroo rats (p354, Fig. 18.10), and jumping mice a) most in _________ mode most of

timeb) hind limbs larger than

front c) ________ tail for balance

Swimming• ___________ mammals--split time between aquatic

& terrestrial:a) beavers and ottersb) _________ tail

c) _________ feet (hind only)d) oscillatory propulsion

• ____________ mammals--most time in water:a) seals, sea lions, walrusb) __________________c) __________________

Swimming…con’t• Marine mammals--all the time in water: a)

baleen & toothed whales b) no hind limbs c) no sacrum d) tails, in some, have horizontalfluke--used for propulsion e) again—____________ forelimbs

pilot whale blue whale right whale

human arm

WH

ALE

(mys

ticet

e)TE

RES

TRIA

Lm

amm

al

vs.

Gliding & Flying• Patagium - “the flight membrane” a)

gliders: hind limbs to forelimbs b) volant mammals (bats): from

forelimb digits (hand-wing) to the tail (p258, Fig. 11.1)

• Gliding: patagium is thicker, position controlled by limbs a) evolved in 3 groups: Rodents

(flying squirrels),Dermoptera (colugos), & marsupials (sugar/honey gliders) b)

increase speed--decrease surfacearea…and vice versa

Colugos =Flying lemurs

PhilippinesJavaBorneo

Oddity - Bats• Only TRUE flying mammal• FORELIMB: ______________ forearm (radius),

metacarpals, and fingers; __________ humerus (see lecture notes on Eutherian mammals)

• Radius __________ rotate• HINDLIMB reduced, and unique among

mammals, in being rotated 1800 so that the knees point backward—aids in flight maneuvers

Flying: 3 challenges

• LIFT--generate with air stream over wing surface. Understand __________________….

a) dorsal surface: curved upwardb) ventral surface: concave (camber)

• DRAG--anything that __________ forward motion (friction at the leading edge, friction along the body surface, turbulence

• POWER--moving the wings ___________ air

Lift, Aspect Ratio, & Maneuverability

• Increasing “angle of attack” results in greater lift…up to the point of stalling

• Bats generally have broad wings with a _______ aspect ratio--the surface area of the wing divided by its length

• ________ wings, allow high degree of maneuverability needed to avoid obstacles and respond to detection of prey….

• Bats are relatively ______ fliers

BIRD

BAT

Climbing - arboreal locomotion • Increased ______ & _______ of claws

a) squirrels: claws key to grasping& moving vertically

b) bears: must grasp tree aided by claws• Prehensile hands & feet (some primates)

a) some have ________ pads & increasesensory receptors in hands & feet

b) longer & stronger forelimbs• Prehensile tail--some

Digging & Burrowing--Using Teeth

• Enlarged heads with strong rostrum and ________ ________ for muscle attachment to involve ______ ________ soil

•• Examples: bamboo rats and

naked mole rats

Digging & Burrowing--Using Limbs

• ___________ typically reflect increased size and strength--relative to hindlimbs:

a) clawsb) structure of limb, including

pectoral girdlec) musculature of limb

• Hind limbs reduced…but help move loosened soil

• Examples: moles & pocket gophers