EAGER: Digital Cranial Atlas of Pachycephalosaurid Dinosaurs

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

EAGER: A Digital Cranial Atlas of Pachycephalosaurid Dinosaurs Mark Goodwin University of California, Berkeley The Pachycephalosauria, or dome-headed dinosaurs, are characterized by a distinctive highly inflated dome with associated skull ornamentation. They are known primarily from the Upper Cretaceous (100-64 million years ago) Western Interior of North America and central Asia. Despite increasing sample sizes of domes, skulls and partial skulls in museum collections, considerable uncertainty and debate persist among students of pachycephalosaurs in regard to individual variation, ontogeny (growth and development), dome function, and systematic (how they are related to one another). Morphological or shape disparity between growth stages is increased by extended neoteny and late stage allometric growth in the Marginocephalia (pachycephalosaurids + ceratopsids), resulting in juveniles that look very different from adults of the same taxa. This pattern of extreme cranial growth trajectories potentially obscures evolutionary relationships, contributes to uncertain phylogenetic character selection, and may inflate dinosaur diversity estimates leading up to the terminal Cretaceous extinction event. Thus, it is critical to identify the relative growth stage of a pachycephalosaur cranium preceding any advanced analysis of comparative cranial morphology, variation, ontogeny and systematics. This project will begin to build a digital cranial atlas of North American pachycephalosaurid dinosaurs using non-destructive high-resolution X-ray computed tomography (HRCT) to: (1) confirm internal and external patterns of growth and development and determine the extent of cranial (skull) ontogenetic (growth) variation; (2) reevaluate and test opposing hypotheses and associated taxonomic, paleobiologic, and paleobiogeographic questions; (3) enhance recent histological studies and expand comparative cranial morphometric analyses; (4) advance evolutionary biology, paleontology, public education and outreach by serving the digital cranial atlas on www.ucmp.berkeley.edu. Proof of concept test scans and limited full scans of select pachycephalosaurid skulls were confirmed by the PI at the University of Texas High-Resolution X-ray CT Facility (UTCT). Skulls of nearly all pachycephalosaurid species in the Museum of the Rockies, Royal Ontario Museum, Royal Tyrrell Museum of Paleontology, and the UC Museum of Paleontology reflecting 100% of North American pachycephalosaur diversity will be accessed for this study. The PI will be using a NSF sponsored facility to do this work and will be developing the prototype of a larger geoinformatics project. Broader Impacts: This project will serve a broader audience in multiple ways. Students from the UC Berkeley undergraduate research apprentice program (URAP) will be engaged in building the digital atlas thus gaining new skills in digitization and engaging directly in scientific research from a paleobiological perspective. This project will serve to broaden their knowledge base and research experience as a UC Berkeley undergraduate. The PI will oversee the development of a user's guide to the atlas, which will allow the data to be used by students at both the high school and undergraduate levels and within a case study to be developed for UCMP's Understanding Science website.