Biomechanics of Animal Movement

Biomechanics of Animal Movement

• Biomechanics is the study of animal movement, often called "the mechanics of life."
• It examines how animals navigate and adapt to their environment.

Biomechanics of Extinct Animals

• Examining extinct animals provides insights into forms not currently observed.
• This aids in understanding the limitations of these extinct animals.
• Functional adaptations, such as terrestrial movement and flight, are studied.
• Examples include Quetzalcoatlus (pterosaur) and Patagotitan (sauropod).

Skeletal Adaptations to Size

• Small animals do not scale proportionally with larger animals.
• Small animals have thinner bones and crouched postures.
• Large animals have thicker, more robust bones and a straighter, column-like posture.
• Examples include the wood mouse and elephant.

Posture

• Sprawling posture was the ancestral form for tetrapods.
• Erect posture, seen in dinosaurs and mammals, necessitates special adaptations.
• An open hip socket in dinosaurs supported an erect posture.
• Examples include early tetrapod trackways and Seymouria, an early tetrapod.

Quadrupedalism

• Movement using all four limbs is ancestral for most tetrapods, promoting stability.
• Movement involves rotation of the chest and hips.

Bipedalism

• Walking on two hind limbs.
• Obligate bipedalism is seen in birds and humans, typically exhibiting erect postures.
• Bipedalism was ancestral to dinosaurs, enabling flight and increased manual dexterity in humans.
• Partial or occasional bipedalism is observed in other mammals.
• Examples include ostriches and dinosaurs like Tyrannosaurus.

Bipedalism—Further Innovations

• Bipedalism facilitated flight (birds) and increased manual dexterity and tool use (humans).

Bipedalism—Other Forms

• Occasional bipedalism is seen in some mammals and reptiles.
• Kangaroos use a tripodal stance, employing three limbs for support.

Postural Enigma

• Spinosaurus (Late Cretaceous theropod), inhabiting Egypt and Morocco, presents a postural challenge.
• Its wrists cannot pronate (rotate inwards) for hand support, unlike other theropods.
• Fossils of Spinosaurus hands and forearms are missing.

Speed Measurement

• Running speeds are measured from live animals.
• Stride length is analyzed using statistical tools.
• Dr. Robert McNeill Alexander, a biomechanist, determined relationships between speed, stride length, and body size in dinosaurs.

Alexander's Dinosaur Speed Calculator

• Predictions of running speeds were made using stride length and body size.
• These methods used empirical observations of modern animals, applied to dinosaur fossils.

Speed—Dinosaurs

• Smaller dinosaurs could reach speeds >35 km/hr.
• Large dinosaurs like Tyrannosaurus were slower.