The Kendall shape space is a representation of all kinds of forms with a number of landmarks and a given dimensionality (that is: coordinates measured in two or three dimensions, so that the distance between the points representing two different forms corresponds to the distance of procrusts between the different forms (Kendall 1984); Klein 1996; Dryden and Mardia 1998; Kendall et al. 1999). These shape spaces are complex, multidimensional analogues of curved surfaces and are therefore difficult to visualize for all but the simplest patterns of landmarks. One shape space that can be visualized relatively easily is that of two-dimensional triangles that turns out to be the surface of a sphere (fig. 5a).