Determination of a novel size proxy in comparative morphometrics

Abstract

Absolute size is a critical determinant of organismal biology, yet there exists no real consensus as to what particular metric of 'size' is empirically valid in assessments of extinct mammalian taxa. The methodological approach of JE Mosimann has found extensive favour in 'size correction' in comparative morphometrics, but not 'size prediction' in palaeontology and palaeobiology. Analyses of five distinct mammalian data sets confirm that a novel size variate (GMSize) derived from k=8 dimensions of the postcranial skeleton effectively satisfies all expectations of the Jolicoeur-Mosimann theorem of univariate and multivariate size. On the basis of strong parametric correlations between the k=8 variates and between scores derived from the first principal component and geometric mean size (GMSize) in all series, this novel size variable has considerable utility in comparative vertebrate morphometrics and palaeobiology as an appropriate descriptor of individual size in extant and extinct taxa.