Relative growth in a phylogenetic series and in an ontogenetic series of one of its members

Abstract

Relative growth curves of the type y = bx k are pre-sented for 24 spp. of ceratopsians and for an ontogenetic series of Protoceratops. A number of skull dimensions are compared phylogenetically and ontogenetically. The phylogeny revealed agrees with Lull''s arrangement of the family. Certain dimensions show different values for b and k in different phyletic lines while others do not. The former may be considered as having diagnostic taxonomic value for units of less than family rank, while the latter remain constant throughout the sub-order. One form [Styracosaurus) showed characteristics of 2 different phyletic lines depending upon whether the spines of the crest were included in the measurement of the crest or not. The highest value for k was found to be 1.96 for the distance between horn cores in relation to beak-orbit distance. Nasal horns show a negative value for k.