Calcaneal shape variation in humans, nonhuman primates, and early hominins

Comparing and combining sliding semilandmarks and weighted spherical harmonics for shape analysis

“…The calcaneus is an ideal bone to use for the comparison of these two methods because sliding semilandmark analyses have been successfully carried out on the bone (Harper et al, 2021a(Harper et al, , 2021bPolly, 2008) and because the calcaneus is a genus-zero shape and thus appropriate for a SPHARM analysis. As a product of the SPHARM analysis, surface models are produced for each specimen that is represented by the same number of vertices.…”

“…A three-dimensional geometric morphometric (3D GM) sliding semilandmark analysis with 1007 sliding semilandmarks (Figure 2) was carried out for quantifying external calcaneus shape following Harper et al (2021aHarper et al ( , 2021b to compare with the SPHARM results. The borders of the articular facets were represented by 91 curve semilandmarks that were hand placed on each specimen (31 posterior talar facet border semilandmarks; 30 anterior/middle talar facet border semilandmarks; 30 cuboid facet border semilandmarks).…”

“…Curve sliding semilandmarks are in light blue and surface semilandmarks are in grey. Adapted from Harper et al (2021aHarper et al ( , 2021b and the SPHARM-sliding analysis) and scaled (up) to centroid size.…”

A new early hominin calcaneus from Kromdraai (South Africa)

“…Skeletal elements of the foot and ankle have played a critical role in reconstructing the locomotor repertoires of early hominins (e.g., Day & Napier, 1964; Latimer et al, 1987; Kidd, 1999; Harcourt‐Smith & Aiello, 2004; Gebo & Schwartz, 2006; Prang, 2016a, 2016b; McNutt et al, 2018; DeSilva et al, 2019; Sorrentino et al, 2020a). Within the foot, the calcaneus is a particularly relevant element to study because of its role in weight‐bearing and proximate contact with the substrate during locomotion (e.g., Boyle et al, 2018; Gebo, 1992; Harper et al, 2021a, 2021b; Holowka & Lieberman, 2018; Latimer & Lovejoy, 1989; Prang, 2015; Schmitt & Larson, 1995; Webber & Raichlen, 2016; Zeininger et al, 2020). Heel strike, for example, represents the beginning of the modern human bipedal gait cycle and is utilized by nonhuman great apes during both arboreal and terrestrial locomotor bouts (Carrier & Cunningham, 2017; Gebo, 1992; Schmitt & Larson, 1995; Vereecke et al, 2003; Zeininger et al, 2020).…”

“…Surface models were flipped to represent right calcanei for ease of visual comparison. Adapted from Harper et al, 2021a…”