By Dr Sandy Kawano, Royal Veterinary College

The invasion of land by stem tetrapods was a key evolutionary event that introduced a new suite of selective pressures, leading to functional innovations of the musculoskeletal system. One of the most intriguing transformations in this context was the evolution from fins to digit-bearing limbs. Although terrestrial locomotion is often thought to have resulted from the evolution of limbs, paleontological examinations indicate that the earliest tetrapods were aquatic and that the ability to move on land involved a series of morphological changes to accommodate the locomotor forces imposed by body support and propulsion. In the following talk, I will describe how biomechanical analyses of extant taxa that serve as modern analogs to early stem tetrapods have provided additional insights into the evolution of locomotor function in vertebrates. Specifically, semi-aquatic fishes and salamanders have been used as biological models to compare the functional capabilities of fins and limbs for terrestrial locomotion, and estimate how stressful walking on land would be on the limb bones of a generalized tetrapod Bauplan. The talk will then conclude with a summary of on-going work to apply laboratory experiments of extant taxa towards modeling the locomotor capabilities of early stem tetrapods. The integration of biomechanical evaluations with morphological analyses of fossil stem tetrapods will contribute additional insights into the physical constraints of moving onto land in the body plans of early stem tetrapods and, consequently, the locomotor behaviours that were likely unrealistic as incipient stages for terrestrial locomotion in vertebrates.

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