2 - Shape analysis in the study of dinosaur morphology

Summary

Abstract

Morphometric and shape analysis methods can provide important information on the paleoecology, functional morphology, evolution, ontogeny, sexual dimorphism, phylogeny, taphonomy, and reconstruction of dinosaurs. The capabilities of one method, Resistant-Fit Theta-Rho-Analysis (RFTRA), a form of landmark shape analysis, are demonstrated using examples of cranial differences in the carnosaurs Allosaurus and Tyrannosaurus, ontogenetic development in the protoceratopsid Bagaceratops, sexual dimorphism in Protoceratops, cranial asymmetry in the prosauropod Plateosaurus, and pachycephalosaurian cranial morphology and phylogeny. The analyses show RFTRA to be a powerful method for elucidating shape differences within a variety of contexts and, in conjunction with standard phylogenetic methods, for providing information on taxonomic relationships.

Introduction

The dinosaur paleontologist interested in the quantitative analysis of his specimens' morphology is faced with a difficult paradox. The general rarity of specimens makes it all the more important to obtain the most information possible from the specimens, but this rarity prevents many of the more powerful techniques from being applied. Dinosaur researchers, or any paleontologists studying groups with limited fossil records (e.g., therapsids), must be pragmatic in their studies, framing questions to fit those techniques that can provide useful information. Within the proper context, those techniques adapted for answering these questions can provide a powerful set of tools for the analysis of dinosaur function, growth, evolution, and taphonomy.

This paper reviews in detail the types of questions accessible to dinosaur paleobiologists given the proper equipment and programs, but concentrates on one major method, Resistant-Fit Theta-Rho-Analysis.