Comparing endocranial surfaces: mesh superimposition and coherent point drift registration

Abstract

The endocranial cavity is a major source of information for the assessment of brain morphology in extinct species. Digital molds of the endocranium can be reconstructed from fossil remains. In paleoneurology, these so-called endocasts are examined using shape analysis and multivariate statistical methods to quantify differences among species and individuals. These surfaces are relatively smooth and offer few landmarks; as such, morphometric comparisons are not straightforward, and correspondence search algorithms are necessary to identify loci of equivalent anatomical variation. Many solutions to this so-called correspondence problem have been proposed, but these often require considerable manual input. Here, we present the application in paleoneurology of a correspondence search and symmetrization algorithm originally designed for facial and palatal scans. Homologous representations of surfaces were used to render a computed visualization of differences in shape between modern humans, Neanderthals, archaic humans, and chimpanzees.