Growth curve of Psittacosaurus mongoliensis Osborn (Ceratopsia : Psittacosauridae) inferred from long bone histology

The skeleton undergoes substantial histological modification during ontogen y in association with longitudinal growth, shape changes, reproductive acti vity, and fatigue repair. This variation can hinder attempts to reconstruct life history attributes for individuals, particularly when only fossil mat erials are availale for study. Histological examinations of multiple elemen ts throughout development provide a means to control for such variability a nd facilitate accurate life history assessments. In the present study, the microstructure of various major long bones of the ceratopsian Psittacosauru s monogoliensis Osborn were examined from a growth series spanning juvenile through adult developmental stages. The first reconstruction of a growth c urve (mass vs. age) for a dinosaur was made for this taxon using a new meth od called Developmental Mass Extrapolation. The results suggest P. mongolie nsis: (1) had an S-shaped growth curve characteristics of most extant verte brates, and (2) had maximal growth rates that exceeded extant reptiles and marsupials, but were slower than most avian and eutherian taxa. (C) 2000 Th e Linnean Society of London.