Mammalogy Exam 2: through Locomotion

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dentine: inner soft layer of the tooth
enamel: -outer hard part of the tooth
parts of a thecodont tooth: -crown and root
pulp cavity: -innermost part of the tooth
-blood supply and nerve
brachydont: -low crowned
-blood supply is cut off, tooth stops growing
hypsodont: -teeth do not stop growing
-require occlusion to wear tooth
teeth on which part of mouth?: -incisors on the premaxilla
-canine and premolars/molars on maxilla
differences in eutherian and metatherian teeth: deciduity: - molars nondecidious, all others diphyodont in eutherians
- only last premolar deciduous, all others monophyodont in metatherians
carnassials made up of what teeth?: -fourth premolar on top
-first molar on bottom
primitive dental formula for metatherians: -5/4i, 1/1c, 3/3p, 4/4m
primitive dental formula for eutherians: -3/3i, 1/1c, 4/4p, 3/3m
tooth loss: -incisors - posterior are lost first
-premolars - anterior to posterior loss
-molars - posterior to anterior loss
what is the primitive molar of therians?>: -tribosphenic molars
lophodont: -molars slide forward and backward across each other
-ridges of tooth move horizontally
-Elephantidae
selenodont: -grind teeth from side to side
-ridges run vertically across tooth
-Cervidae
selenolophodont: -Bovidae and Equidae
-ridges run in all directions
Inner ear: -contains sensory cells for hearing and balance
-contained in cochlea, coiled in some mammals and embedded in brain case in petrosal bone
Middle ear: -houses 3 ear ossicles
-convert sound waves into vibrations in cochlea that fire sensory cells
-bounded by tympanum, supported by tympanic bone
outer ear: -tympanum outward
-includes canal and pinnae
Common features of evolution: -gradual process
-modification of existing structures
--novel structures, which bud off from existing structures (derivation of masseter)
-coadapted systems (imposes constraints)
functional morphology: -using physics principles to analyze biological structures
Force vectors: -convey directionality and strength
equilibrium: -all forces are opposed by offsetting forces
ancestral condition of ear: -early synapsids including Pelycosaurs
-small temporal fenestra
-many bones in mandible (angular and articular)
-quadrate/articular jaw joint
-no tympanic bone - angular bone instead on lower jaw
-very large stapes (connects inner ear to quadrate)
-lacked tympanum
ancestral auditory path: -dentary (rested on ground) --> articular -->[jaw joint]-->quadrate-->stapes-->inner ear
effect of bite resistance on early synapsid jaws: -simple jaw adductor (temporalis), low coronoid emminence
-bite resistance and force of adductor offset
-generates stress on lower jaw
-quadrate and articular constrained to be large and robust to withstand jaw stresses
-animal probably didn't hear well
jaws of cynodonts: -larger, more complex jaw adductors
-masseter (splits off from temporalis)
-gradual expansion of coronoid process
-temporalis now attaches back and up (vs. straight up)
forces involved in cynodont jaws: -all 4 force vectors intersect directly over the bite point
-horizontal and vertical components cancel
-no stress at the jaw joint
-quadrate and articular free to respond to selection favoring increased transmission of sound vibrations
more cynodont jaw/ear stuff: -first evidence of tympanum (begin to see evolution of laminar process of angular bone, which supports the tympanum)
-quadrate and articular become gradually smaller, d/s expand backwards to fill space left by q/a
-d/s eventially touch to form current jaw joint
-articular migrates off lower jaw = malleus
-quadrate migrates off upper jaw = incus
-angular bone migrates off lower jaw= tympanic bone
fossils which obtained both types of jaw joint: -Probainognathus and Diarthragnathous
Didelphis jaw/ear stuff: -can watch changes in ear/jaw during development
-malleus first ossifies on lower haw
-incus first ossifies on upper jaw
-angular first ossifies on lower jaw
-expansion of brain case pulls inner ear away from jaw, induces migration of ancestral jaw elements and generates the inner ear cavity
chain of transmission in cynodonts: -tympanum -> angular ->articular -> [jaw joint] -> quadrate -> stapes -> inner ear
chain of transmission in mammals: -tympanum -> malleus -> incus -> stapes -> inner ear
-articulation between malleus and incus homologous to ancestral jaw joint
flight: -airfoil is asymmetric (disstance from leading edge to trailing edge is longer over top surface than bottom)
-relies on presence of laminar flow (parallel movement of air streams)
-simultaneous arrival at trailing edge
-velocity across upper surface greater then velocity across lower surface
Bernoulli's theorem: P=C-.5(dv^2) where P is air pressure, d is density of air, v is velocity
-air moving over top of wing exerts less pressure than bottom
PL-PU = Lift
-when lift defeats force of gravity, flight is achieved
-ultimately relies on differential of velocity
Speed of flight in bats: -lift is greater at high speeds than low speeds
-bats are slow flyers
-Myotis lucifugus = 20 mph
-Eptesicus fuscus = 40 mph
-Tadarida brasiliensis = 60 mph
How to achieve lift at low flight speeds: -alter camber (curvature) of wings
-Increase angle of attack
-Wing loading and aspect ratio
-Leading edge flaps
alter camber of wings: -bats have a thin air foil that can be flexible
-increasing camber increases velocity differential at low speeds
wing loading: -body weight / surface area of wing
-lower wing loading =easuer achievement of flight
-bats have low wing loadings
--House wren = .24 g/cm^2
--Glossaphaga = .11 g/cm^2
--Myotis = .06 g/cm^2
aspect ratio: -length / width of wings
-short, wide wings = better for slow, maneuverable flight (low AR)
-long, narrow wings = fast flyer (high AR)
leading edge flaps: -detiorate tendency toward turbulence
-turbulence caused by low flight speeds when the pressure differential is lost
downstroke: -power stroke
-powered by 3 muscles:
--pectoralis
--subscapularis
--serratus
7 parts of a bat wing: -propatagium
-dactylopatagium brevis
-dactylopatagium minus
-dactylopatagium longus
-dactylopatagium lattus
-plagiopatagium
-uropatagium
dactylopatagium longus: -thrust generator
-not well-braced
-leading edge pulled down faster during downstroke, trailing edge lags behind leading edge
--this generates thrust by pushing air backward
dactylopatagium lattus: -may also assist with thrust
propatagium, d. brevis, and d. minus: -form leading edge flaps
plagiopatagium: -primary lift generator
-5th digit strong and well-braced, maintains angle of attack
-muscularized - allows camber to be adjusted during flight
uropatagium: -rudder
-catching insects
upstroke: -recovery stroke
-passive
-shoulder-locking mechanism - greater tuberosity (halts upstroke passively)
differences in greater tuberosity in species of bats: -Molossidae and Vespertilionidae = greater tuberosity very well-developed
-Phyllostomatidae = moderately developed greater tuberosity
-Craseonycterus = no shoulder locking mechanism
other adaptations for flight: -keeled manubrium
-stiffening of axial skeleton
keeled manubrium: -anchoring point for pectoralis attachment
-first segment of sternum
Natalidae: -funnel-eared bats
-well represented stiffening of axial skeleton
-thoracic vertebrae extremely compressed = no flexibility
-fusion of sacral and lumbar vertebrae = only one flexion point in spinal column
in-force: -force muscles can generate = resultant vector
out-force: -force limb can generate against ground
relationship between in-force and out-force mediated by..: -lever arms
-In-lever and out-lever
In-lever: -perpendicular distance between line of action of the in-force and the fulcrum
out-lever: -perpendicular distance between line of action of out-force and fulcrum
Torque: -turning force
-In-torque generated by In-lever
--product of In-force and In-lever
-Out-torque generated by out-lever
--product of Out-force and Out-lever
-at equilibrium, out-torque = in-torque
optimized limb for digging: -want to optimize the out-force
-long in-lever (elbow), short out-lever (ulna)
how to optimize the out-force?: -increase in-force (diameter of muscle fibers)
=limited means
-increase in-lever/out-lever
=long in-lever, short out-lever
why aren't all mammals optimized like the mammals optimized for digging?: -Vo = out velocity = velocity at end of Lo
-Vi = in velocity = velocity at end of Li
-at equilibrium, VoLi = ViLo
-Vo is the phenotype on whicih selection can operate
-optimizing Vo optimizes mammal for speed
how do you optimize for speed?: -optimize Vo
--increase Vi (proportional to rate at which muscles can contract - physiologically limited)
--increase gear ratio (Lo/Li) - make Lo long and Li short

-short olecranon processes and long limbs
types of in terrestrial mammals: -saltation (bipedal hopping)
-cursorial (running)
-volant (gliding)
-scansorial (climbing)
-swimming
saltatorial locomotion: -aka richochetal locomotion
-long hind limbs
-reduction of number of digits
-front limb generalized
-stiffened spinal column
-hind limb ligaments and tendons have elasticity
-tails usually long
long hind limbs in saltatorial locomotion: -optimizes Vo
-long distal portion of limb (Lo)
-short Li (calcanea)
-maximize Fi (as much muscle as possible)
front limb generalized in saltatorial mammals: -used in grooming
stiffened spinal column in saltatorial mammals: -cervical vertebrae fused
-lumbar vertebrae thick and robust
-sacrum strongly fused to pelvis
-ligaments between regions in spinal column for shock absorption
tails long in saltatorial mammals: -serve as counterbalance
-tufted in many --> great amount of mobility
adaptations in cursorial mammals that increase stride length: -elongated limb bones
-change in foot posture
-expansion of metapodials
-pectoral girdle adaptations
-increased dorso-ventral flexion of spine
pectoral girdle adaptations in cursorial mammals: -loss of clavicle
-scapula can rotate
-muscular sling for scapula
--trapezius
--rhomboideus
--serratus
--pectoralis
--also absorbs shock of front limb striking ground during gait
adaptations for increasing stride rate of cursorial mammals: -optimizing Vo (long Lo, short Li)
-increase in number of joints (wrist, ankle, scapula as joints)
-decrease in distal inertia of limb (concentrating muscles to proximal portion, loss of peripheral digits)
-range of motion in single plane (front to back)
loss of peripheral digits in ungulates: -Cetardiodactyls - only 3rd and 4th remain
-Perrisodactyls - 3rd digit remains
Astragalus: -range of motion in single plane well-developed
two ways cursorial mammals increase speed: -increase stride length
-increase stride rate
scansorial locomotion: -danger of falling increases with larger animals (terminal velocity greater in larger animals = sa/v ratio)
-increase friction between substrate and hands/limbs
-stiffened trunks to resist bending
-elongated forelimbs
increasing friction between subtrate and hands/limbs in scansorial mammals: -friction pads (Procyon, Primates, porcupines)
-well-developed claws (Sciurus)
-prehensile organs (opposable digits, prehensile tails)
-suction disks (Myzopodidae)
stiffening of trunks in scansorial mammals: -robust vertebral column
-ribs expanded and overlapping
-elongated thoracic region
-lumbar shortening - decreased movement between pelvis and ribs
gibbons: -brachiation - locomotion relying on arms with no assistance from legs
Gliding: -Petauridae, Rodentia (Sciuridae), Dermoptera
-stylar cartilage manipulates "flaps" that counter induced drag
Induced drag: -downward pressure on tips of wings by boundary layer
-more a problem for gliders than powered fliers
Glaucomys: -can glide up to 50m
Eupetaurus: -cat-sized glider
-lives in caves above tree line in Pakistan
pressure drag: -displacement of water
-proportional to cross-sectional area of animal
-long thin rod-shaped minimizes pressure drag
frictional drag: -property of laminar flow
-caused by friction of parallel streams in water
-proportional to total surface area
-sphere = minimizes friction drag
what shape optimizes the trade-off between pressure drag and frictional drag?: -spindle-shaped
-fusiform body
adaptations in semi-aquatic mammals and some examples: -webbing -> increases thrust
-water shrews, Lontra (otter), Castor, Hippopatamus
Adaptations in fully aquatic mammals: -limb modification
--front limbs modified into flippers
--hind limbs modified
-axial skeleton modifications
--reduction in cervical vertebrae (shortened, compressed, fused - atlas and axis fused)
--increase in size/robustness of vertebrae
-tail flukes
front limbs modified into flippers: -entirely syndactylous
-provide thrust (Otariidae)
-rudders for steering (Cetaceans, Sirenians)
hind limbs modified in aquatic mammals: -propulsion (Phocids)
-absent or extremely vestigial (pelvis floating in musculature)
Archaeocetes: -document gradual transition of aquatic mammals from terrestrial to aquatic
Pakicetus: -oldest Archaeocete found - 52 mya
-fully functional hind limbs
Ambulocetus: -49 mya
-around Pakistan
Basilosaurus: -40 mya
-60 feet long
-fully formed hind limb, but tiny

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