Article

Allometric shape vector projection: A new method for the identification of allometric shape characters and trajectories applied to the human astragalus (talus)

Research Department of Genetics, Evolution and Environment, Division of Biosciences, University College London, London, UK.
Journal of Theoretical Biology (Impact Factor: 2.3). 03/2011; 272(1):64-71. DOI: 10.1016/j.jtbi.2010.11.030
Source: PubMed

ABSTRACT The surface morphology of the human astragalus (talus) is difficult to represent accurately using landmarks as it is essentially globular in shape. Advances in laser scanning technology allow fast and accurate capture of bone surface morphology. However, methodologies to utilise these new accurate 3D data have not been fully developed. The present study uses canonical sampling of whole surface morphology attained through laser scanning and for the first time applies the technique to analysis of bone morphology. We introduce a new technique for identifying allometric shape characters in whole bone surface morphology. In a sample of adult human astragalus the new technique is successful in identifying and isolating intra-specific allometric shape characters in a bone which typically lacks landmarks and has, consequently, proved difficult to analyse using traditional 3D morphometric methods.

Download full-text

Full-text

Available from: William Parr, Aug 30, 2015
0 Followers
 · 
112 Views
  • Source
    • "The canonical sampling process (Douros et al. 2002; Buxton et al. 2003; Ruto et al. 2006; Ruto, 2009) gives an accurate representation of the whole talar surface morphology, and the resulting surface models were used in a PCA of whole talar shapes (following Parr et al. 2011a). The canonical sampling procedure used here is similar to the eigensurface method described by Polly & Macleod (2008) where the surface points per slice (50 slices) were obtained by projecting radii from the major axis at equally spaced angles (360 o /50). "
    [Show abstract] [Hide abstract]
    ABSTRACT: The hominoid foot is of particular interest to biological anthropologists, as changes in its anatomy through time reflect the adoption of terrestrial locomotion, particularly in species of Australopithecus and Homo. Understanding the osteological morphology associated with changes in whole foot function and the development of the plantar medial longitudinal foot arch are key to understanding the transition through habitual bipedalism in australopithecines to obligate bipedalism and long-distance running in Homo. The talus is ideal for studying relationships between morphology and function in this context, as it is a major contributor to the adduction–abduction, plantar–dorsal flexion and inversion–eversion of the foot, and transmits all forces encountered from the foot to the leg. The talar surface is predominantly covered by articular facets, which have different quantifiable morphological characters, including surface area, surface curvature and orientation. The talus also presents challenges to the investigator, as its globular shape is very difficult to quantify accurately and reproducibly. Here we apply a three-dimensional approach using type 3 landmarks (slid semilandmarks) that are geometrically homologous to determine overall talar shape variations in a range of living and fossil hominoid taxa. Additionally, we use novel approaches to quantify the relative orientations and curvatures of talar articular facets by determining the principal vectors of facet orientation and fitting spheres to articular facets. The resulting metrics are analysed using phylogenetic regressions and principal components analyses. Our results suggest that articular surface curvatures reflect locomotor specialisations with, in particular, orang-utans having more highly curved facets in all but the calcaneal facet. Similarly, our approach to quantifying articular facet orientation appears to be effective in discriminating between extant hominoid species, and may therefore provide a sound basis for the study of fossil taxa and evolution of bipedalism in Australopithecus and Homo.
    Journal of Anatomy 05/2014; 225(1). DOI:10.1111/joa.12195 · 2.23 Impact Factor
  • Source
    • "Non-landmark based three-dimensional methods offer a means to quantify hip joint size in fragmentary fossils that avoids the need for the preservation of a complete acetabulum or femoral head. Three-dimensional digital morphometric analysis using reconstructed surface or sectional scan data and automated design software has emerged as a tool for quantitative analysis (Tocheri et al., 2003, 2005, 2007; Harcourt-Smith et al., 2008; Parr et al., 2011; Garvin and Ruff, 2012). Due to the spherical shape of the femoral head and acetabulum, the hip joint is an excellent candidate for the application of least squares best-fit sphere-fitting techniques using automated design software to quantify joint size (Hammond et al., 2010b, 2012; Plavcan et al., 2012). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Hip joint diameter is highly correlated with body size in primates and so can potentially provide important information about the biology of fossil hominins. However, quantifying hip joint size has been difficult or impossible for many important but fragmentary specimens. New three-dimensional technologies can be used to digitally fit spheres to the acetabular lunate surface, potentially allowing hip joint diameter estimates for incomplete joint surfaces. Here we evaluate the reliability of sphere-fitting to incomplete lunate surfaces in silico using three-dimensional polygonal models of extant anthropoid hipbones. Measurement error in lunate sphere-fitting was assessed at the individual observer level, as well as between observers. Prediction error was also established for acetabular sphere size estimates for smaller divisions of the lunate surface. Sphere-fitting techniques were then applied to undistorted regions of lunate surface in Plio-Pleistocene hominin pelves, with a range of diameters constructed from extant error estimates. The results of this study indicate that digital sphere-fitting techniques are precise and that the lunate does not need to be completely preserved to accurately infer hip dimensions, although some aspects of joint size and morphology can influence sphere size estimates. Joint diameter is strongly predicted by spheres fit to the cranial and caudal halves of the lunate in all anthropoids. We present new hip joint size estimates for a number of fossil hominins, and outline additional applications for digital sphere-fitting as a morphometric technique. Am J Phys Anthropol, 2013. © 2013 Wiley Periodicals, Inc.
    American Journal of Physical Anthropology 04/2013; 150(4). DOI:10.1002/ajpa.22228 · 2.51 Impact Factor
  • Source
Show more