Can skeletal surface area predictin vivofoot surface area?

Abstract

The surface area of feet in contact with the ground is a key morphological feature that influences animal locomotion. Underfoot pressures (and consequently stresses experienced by the foot), as well as stability of an animal during locomotion, depend on the size and shape of this area. Here we tested whether the area of a skeletal foot could predict in vivo soft tissue foot surface area. Computed tomography scans of 29 extant tetrapods (covering mammals, reptiles, birds and amphibians) were used to produce models of both the soft tissues and the bones of their feet. Soft tissue models were oriented to a horizontal plane, and their outlines projected onto a surface to produce two‐dimensional silhouettes. Silhouettes of skeletal models were generated either from bones in CT pose or with all autopodial bones aligned to the horizontal plane. Areas of these projections were calculated using alpha shapes (mathematical tight‐fitting outline). Underfoot area of soft tissue was approximately 1.67 times that of skeletal tissue area (~ 2 times for manus, ~ 1.6 times for pes, if analysed separately). This relationship between skeletal foot area and soft tissue area, while variable in some of our study taxa, could provide information about the size of the organisms responsible for fossil trackways, suggest what size of tracks might be expected from potential trackmakers known only from skeletal remains, and aid in soft tissue reconstruction of skeletal remains for biomechanical modelling.

Basal sauropodomorph locomotion: ichnological lessons from the Late Triassic trackways of bipeds and quadrupeds (Elliot Formation, main Karoo Basin)

“…Here, the pes and manus trace depth and associated soft-sediment deformation have been used as proxies for the distribution of weight and the final pressure distribution across the foot/manus ( Falkingham et al, 2011 ; Falkingham, Bates & Mannion, 2012 ; Strickson et al, 2020 ). We assume morphological variations caused by trackmaker speed are negligible because all estimated trackway speeds are walking gaits ( Table 1 ).…”

“…The pes: manus surface areas are more comparable than in Pseudotetrasauropus (low heteropody) with the manus trace reflecting a fleshier autopod. Tetrasauropus manual and pedal tracks provide evidence for fleshy feet that likely served to dispense the load away from individual digits and claws ( Strickson et al, 2020 ) and support a large animal.…”

Effects of Alpha Ketoacid Combined with Hybrid Blood Purification Treatment on Nutritional Status, Renal Function and Expressions of Serum Sclerostin, BMP-7, Irisin in Maintenance Hemodialysis Patients

“…The major elements of the biomechanics of locomotion are feet which are evolved due to severe adaptations. The stress factors increase foot sole pressure or force area in mammals despite greater foot areas (Strickson et al, 2020). In wild animals, the feet adaptive response to stress are on a very narrow margin, therefore, captive animals kept on walking areas having pressures higher than normal create increased incidences of mechanically induced pathologies (Panagiotopoulou et al, 2019;Regnault et al, 2017).…”

The evolutionary biomechanics of locomotor function in giant land animals

“…Importantly, stress (i.e. foot sole pressure or force/area) increases allometrically in mammals despite greater foot areas ( Michilsens et al, 2009 ; Chi and Louise Roth, 2010 ; Panagiotopoulou et al, 2012 , 2016 , 2019 ; Strickson et al, 2020 ). Giant mammals thus have repeatedly evolved adaptations to ameliorate increasing foot pressures, such as more upright osteological or functional (‘subunguligrade’) foot postures ( Wortman, 1893 ; Klaits, 1972 ; Carrano, 1997 ; Hutchinson et al, 2011a , b ; Kubo et al, 2019 ; Clemente et al, 2020 ), and foot pads that attenuate impact shocks ( Alexander et al, 1986 ; Warner et al, 2013 ).…”