Abstract

Results are presented of preliminary morphometric analyses on hadrosaurs using the landmark shape analysis method Resistant-Fit Theta-Rho-Analysis (RFTRA). The analyses were performed on both cranial and postcranial material. They show this approach to be useful for the analysis of hadrosaur morphology and provide insight into how this morphology varies within the context of the phylogenetic structure of the family. Further, the patterns are related to two other groups of Euornithopods, the iguanodontids and camptosaurids. The results highlight the distinct morphology of the lambeosaurine hadrosaurs, confirm that most of the significant morphological variation in hadrosaur crania is concentrated in the muzzle and narial regions, and indicate that pelvic element shape should be useful for taxonomic identification and discrimination. In general cranial shape, the lambeosaurines are shown to be most closely related to the hadrosaurines, supporting a monophyletic Hadrosauridae.

Introduction

Hadrosaurs have one of the most complex taxonomic histories of all the dinosaurs; over 100 species representing 44 genera have been named. This unusually high taxonomic diversity is a consequence of the interplay between the taxonomic philosophies of the many researchers studying hadrosaurs, the high level of real taxonomic diversity, the unusually abundant material available, and the high degree of morphological variability within populations and between age groups. The latter is the result of allometric and ontogenetic effects over a wide range of sizes (see Dodson 1975; Hopson 1975; Molnar 1977).