Paleontology - Moving Around

Locomotion

• Movement from place to place.

• Driven by skeletal mechanics.

• Influenced by posture.

• Essential for survival.

Sprawling Stance

• Limbs extend sideways from body.

• Requires muscular effort to support weight.

• Inefficient for endurance.

• Seen in reptiles.

Semi-Erect Posture

• Limbs partially under body.

• Intermediate efficiency.

• Transitional evolutionary form.

• Seen in some early archosaurs.

Erect Stance

• Limbs directly beneath body.

• Bones support body weight.

• More energy efficient.

• Seen in dinosaurs and mammals.

Obligate Biped

• Always moves on two legs.

• Forelimbs free for other functions.

• Faster acceleration.

• Seen in theropods.

Facultative Biped

• Walks on four legs normally.

• Runs on two legs when fast.

• Flexible locomotion.

• Seen in hadrosaurs.

Obligate Quadruped

• Always on four limbs.

• Increased stability.

• Supports massive body size.

• Seen in sauropods.

Cursorial Adaptations

• Built for speed.

• Long distal limb bones.

• Reduced toes.

• Lightweight structure.

Graviportal Adaptations

• Built for heavy weight support.

• Thick pillar-like limbs.

• Shortened bones.

• Broad feet.

Limb Proportions

• Relative bone length ratios.

• Affect speed and stride.

• Reflect body mass.

• Used to infer locomotion.

Plantigrade

• Entire foot contacts ground.

• High stability.

• Lower speed.

• Example: humans.

Digitigrade

• Walk on toes only.

• Heel elevated.

• Longer stride length.

• Seen in dinosaurs.

Unguligrade

• Walk on hoof tips.

• Extreme speed specialization.

• Minimal ground contact.

• Seen in horses.

Caudofemoralis Muscle

• Major hindlimb retractor.

• Runs from tail to femur.

• Powers backward leg motion.

• Key for running force.

Muscle Lever Systems

• Bones act as levers.

• Muscles provide force.

• Joint placement affects motion.

• Determines speed vs strength.

Trochanter Position

• Femur muscle attachment point.

• Controls leverage efficiency.

• High = faster movement.

• Low = stronger slower motion.

Ichnofossils

• Fossilized activity traces.

• Include tracks and trails.

• Show behavior.

• Not body parts.

Trackways

• Series of footprints.

• Reveal gait and posture.

• Show group movement.

• Estimate speed.

Stride Length

• Distance between footprints.

• Longer = faster motion.

• Related to leg length.

• Used in velocity calculations.

Pace Length

• Distance between left and right steps.

• Indicates gait type.

• Shows walking vs running.

• Measured in trackways.

Tail Drag Marks

• Trails from tail contact.

• Common in sprawlers.

• Rare in dinosaurs.

• Indicates elevated tail.

Biomechanics

• Study of forces in movement.

• Applies physics to anatomy.

• Explains locomotion efficiency.

• Core analysis tool.

Center of Mass

• Balance point of body.

• Must align over feet.

• Influences posture.

• Affected by tail.

Weight Distribution

• How mass spreads across limbs.

• Vertical limbs reduce stress.

• Important for large animals.

• Supports erect posture.

Cube-Square Law

• Volume increases faster than surface area.

• Larger animals retain heat better.

• Limits diffusion.

• Affects physiology.

Surface Area-to-Volume Ratio

• High in small animals.

• Low in large animals.

• Controls heat loss.

• Influences metabolic strategy.

Endothermy

• Internal heat production.

• Stable body temperature.

• High energy demand.

• Seen in birds/mammals.

Ectothermy

• External heat dependence.

• Variable temperature.

• Low energy demand.

• Seen in reptiles.

Gigantothermy

• Heat retention by large size.

• Mimics warm-bloodedness.

• Based on low SA:V ratio.

• Proposed for dinosaurs.

Gigantothermy Limitations

• Works only for large species.

• Doesn’t explain fast growth.

• Doesn’t fit small dinosaurs.

• Weak evidence.

Bone Histology

• Microscopic bone structure.

• Shows growth speed.

• Indicates metabolism.

• Dinosaur bones grow fast.

Osteon Density

• Number of bone structural units.

• High in fast-growing animals.

• Linked to high metabolism.

• Seen in dinosaurs.

Energetic Efficiency

• Energy per distance traveled.

• Improved by erect posture.

• Enables endurance movement.

• Advantage in hunting.

Endurance Locomotion

• Long-distance sustained movement.

• Low muscle fatigue.

• High oxygen delivery.

• Enabled by posture.

Locomotor Evolution

• Shift from sprawl to erect.

• Increased efficiency.

• Allowed large body size.

• Supported active lifestyle.

Functional Morphology

• Structure explains function.

• Predicts movement ability.

• Core paleontology principle.

• Used for reconstruction.