Can skeletal surface area predict in vivo foot surface area?

Area of Science:

• Comparative anatomy
• Biomechanics
• Paleontology

Background:

• The surface area of the foot contacting the ground is crucial for animal locomotion, affecting underfoot pressures, stresses, and stability.
• Understanding the relationship between skeletal structure and soft tissue morphology is vital for interpreting locomotion and fossil evidence.

Purpose of the Study:

• To determine if the skeletal foot area can predict the in vivo soft tissue foot surface area across diverse tetrapods.
• To establish a quantitative relationship between skeletal and soft tissue foot dimensions.

Main Methods:

• Computed tomography (CT) scans of 29 extant tetrapod feet (mammals, reptiles, birds, amphibians) were used to create digital models of both bones and soft tissues.
• Two-dimensional silhouette areas of soft tissue and skeletal models were calculated using projected outlines and alpha shapes.
• Skeletal models were analyzed in both their CT pose and with bones aligned to a horizontal plane.

Main Results:

• The underfoot area of soft tissue was approximately 1.67 times larger than the skeletal tissue area.
• This ratio was around 2 times for the manus (forefoot) and 1.6 times for the pes (hindfoot).
• A variable but consistent relationship was observed between skeletal and soft tissue foot areas across studied taxa.

Conclusions:

• The skeletal foot area serves as a reliable predictor of soft tissue foot surface area in extant tetrapods.
• This relationship has significant implications for paleontology, aiding in the identification of fossil trackmakers and the reconstruction of extinct animal sizes.
• The findings support the use of skeletal measurements for biomechanical modeling and inferring soft tissue characteristics in fossil remains.