Morphological changes in pedal phalanges through ornithopod dinosaur evolution: a biomechanical approach.

Area of Science:

• Paleontology
• Biomechanics
• Evolutionary Biology

Background:

• Ornithopod dinosaurs exhibit a significant evolutionary transition in foot morphology, moving from digitigrady to subunguligrady.
• This transition involved drastic changes from ancestral dinosaurian pedal structures to a more derived state, contrasting with the general conservatism in dinosaur feet.

Purpose of the Study:

• To investigate the functional consequences of the morphological changes during the ornithopod foot evolution.
• To understand how the shift from digitigrady to subunguligrady affected digit mobility, flexibility, and load-bearing capacity.

Main Methods:

• Analysis of external pedal morphology in four non-avian dinosaurs and two birds.
• Application of two-dimensional Finite Element Analysis (FEA) models.
• Examination of internal bone structure.

Main Results:

• The evolutionary shift to subunguligrady in ornithopods resulted in reduced digit mobility and flexibility.
• Pedal posture was modified to align the foot with the ground reaction force, enhancing load support.
• Morphological changes included alterations in unguals, phalanges, joint surfaces, and ligamentous structures.

Conclusions:

• The transition to subunguligrady provided functional advantages for load-bearing in ornithopods.
• These findings offer insights into parallel evolutionary adaptations in other dinosaur groups and mammals.
• The study highlights the interplay between morphology, function, and evolutionary pressures in vertebrate locomotion.