The biomechanics of terrestrial locomotion

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Walking an running animals encompass terrific diversity and, in contrast to swimming, terrestrial locomotion involves the complex interaction of many moving parts whose identity and proportions vary across taxa, so we can only deal with walking superficially. In this lecture, we will address two borad themes:

Common requirements:

Support: The limbs must physically bear the load of the animal's weight. For this, they must be scaled and shaped appropriately.

Stability: The limbs that touch the ground form a base of support that encompasses the animal's center of mass when it is standing or walking.

Propulsion: Animals don't just stand there. The limb must be able to exert lateral force against the ground, causing the animal to move in reaction.

Maneuverability: The animal must be able to vary the size and direction of the locomotor force it exerts in order to accelerate, turn, and stop without excessively sacrificing stability. Note: A running animal is essentially always falling and catching itself. It is deliberately sacrificing support for speed and maneuverability.

These factors, together, give us.

Gait. Depending on the foregoing factors and the specific demands of the moment, animals choose between distinct gaits, repeated patterns of footfalls.

Sources of difference:

Posture: Major issues:

Ecology: Regardless of gait, we can divide all terrestrial locomotion into:

These characteristics easily enable us to predict the locomotor specialization of Uintatherium, a rhino-sized mammal from the Paleogene.

What about Terrestrisuchus, a small Triassic crocodylomorph?

A real challenge with Triceratops, large quadrupedal dinosaur of the Cretaceous? To interpret this animal, we may need to think about it ancestors.

Scaling effects: We have previously discussed the responses of organisms to the demands of increasing size:

Energy storage:

Many terrestrial animals conserve energy by storing it in some way. Two significant strategies: