skeletal considerations & adaptations for locomotion
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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
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