And Type the TITLE of YOUR WORK in All Caps
Total Page：16
File Type：pdf, Size：1020Kb
TESTING THE ROLES OF EXTRATROPICAL ORIGINATION AND PREDATION ON IRREGULAR ECHINOID EVOLUTION by JUSTIN MATTHEW MILLER (Under the Direction of Sally E. Walker) ABSTRACT The number of extratropical vs. tropical originations and the predation frequency of fossil irregular echinoids were analyzed to gain a better understanding of their evolution. The latitudinal diversity gradient for irregular echinoids is atypical compared to other marine bivalves and current evolutionary models are not applicable. An out-of-the-extratropics (OTE) model is used to describe how marine organisms may originate in the extratropics and then migrate into tropical regions. Irregular echinoids from the Late Eocene Ocala Limestone were categorized into burrow tiers based on morphological characters so predation frequency at different burrow depths could be assessed. Predation frequency was highest for medium and deep burrow tiers, suggesting that burrowing does not reduce cassid predation. This may indicate that evolution towards infaunalism for irregular echinoids was not driven by increasing predation pressure in the Mesozoic. INDEX WORDS: Evolution, Echinoid, Diversity, Planktotrophic, Extratropical, Predation, Drill Hole, Burrow, Tier, Eocene, Ocala Limestone TESTING THE ROLES OF EXTRATROPICAL ORIGINATION AND PREDATION ON IRREGULAR ECHINOID EVOLUTION by JUSTIN MATTHEW MILLER B.S., Georgia Southwestern State University, 2006 A Thesis Submitted to the Graduate Faculty of The University of Georgia in Partial Fulfillment of the Requirements for the Degree MASTER OF SCIENCE ATHENS, GEORGIA 2011 © 2011 Justin Matthew Miller All Rights Reserved TESTING THE ROLES OF EXTRATROPICAL ORIGINATION AND PREDATION ON IRREGULAR ECHINOID EVOLUTION by JUSTIN MATTHEW MILLER Major Professor: Sally E. Walker Committee: Steven M. Holland Bruce L. Railsback Electronic Version Approved: Maureen Grasso Dean of the Graduate School The University of Georgia May 2011 iv ACKNOWLEDGEMENTS My deepest and most sincere thanks go to my major advisor Dr. Sally Walker. Without her seemingly unwavering patience and guidance this project would not have been possible. I showed up at her office needing a major advisor in geology and she happily took me in and transformed my understanding of educating and science. I thank Dr. Railsback for helping to alleviate some of my major early writing problems. Thanks to Dr. Steven Holland for showing me that statisitics can be enjoyable through the use of R. Dr. Burt Carter, whether intentinally or not, is responsible for my interest in working with echinoids. Many thanks go to him for our many discussions regarding southeastern echinoids as well as educating me more on echinoids with each conversation. Special thanks go to Roger Portell for giving me access to Ocala Limestone quarries that were normally inaccessible. Thanks to Eleanor Gradner for helpful editing and to my good friend and field partner Matt Jarrett I thank you for your generous “donation” of fossil echinoids that contributed to this project. My friend Benjamin Caulton I thank for late night discussions regarding echinoids and allowing me to hone my ideas. Lastly, many thanks must go to my girlfriend Jacquie whose constant support allowed me to overcome many obstacles during this journey. I simply could not have done this without her. Financial support for this work was graciously awarded by the Paleontological Society Stephen J. Gould Student Grant-in-Aid Program, University of Georgia Department of Geology Wheeler-Watts Fund, and the Southwest Florida Fossil Club. v TABLE OF CONTENTS Page ACKNOWLEDGEMENTS ............................................................................................... iv LIST OF TABLES ............................................................................................................ vii LIST OF FIGURES ......................................................................................................... viii CHAPTER 1 INTRODUCTION AND LITERATURE REVIEW .........................................1 Statement of Objectives ...............................................................................2 Thesis Structure ...........................................................................................3 References ....................................................................................................4 2 THE EXTRATROPICS AS A CENTER FOR EVOLUTIONARY DIVERSIFICATION ...................................................................................6 Abstract ........................................................................................................7 Introduction ..................................................................................................7 Results ........................................................................................................11 Out of the Extratropics Model for Evolutionary Diversification ...............14 Methods......................................................................................................17 Acknowledgments......................................................................................19 References ..................................................................................................20 vi 3 TESTING THE INFAUNAL-EVOLUTION HYPOTHESIS: DO DEEP BURROWING IRREGULAR ECHINOIDS HAVE REDUCED INCIDENCE OF DRILLING PREDATION ............................................31 Abstract ......................................................................................................32 Introduction ................................................................................................32 Methods......................................................................................................35 Results ........................................................................................................37 Discussion ..................................................................................................39 Conclusions ................................................................................................44 Acknowledgments......................................................................................45 References ..................................................................................................45 4 CONCLUSIONS..............................................................................................61 APPENDICES A LATITUDINAL DIVERSITY GRADIENT DATA FOR MODERN IRREGULAR ECHINOIDS ..................................................................................64 B IRREGULAR ECHINOID GENERA WITH A MODERN REPRESENTATIVE AND FOSSIL RECORD .......................................................................................66 C COLLECTIONS DATA FROM THE SMITHSONIAN AND PALEOBIOLOGY DATABASES ........................................................................................................69 D REGISTER OF FIELD SITES ............................................................................137 E FIELD AND MUSEUM SPECIMENS ANALYZED FOR PREDATION ........139 vii LIST OF TABLES Page Table 2.1: Number of irregular echinoid genera (includes subgenera) that originated in the Cretaceous to Plio-Pleistocene .........................................................................26 Table 3.1: Burrow tiers used and the morphological characters that define those tiers ....52 Table 3.2: Irregular echinoid species, their inferred burrow depth and number of individuals examined for cassid predation .............................................................53 Table 3.3: Predation frequency of each species within the four burrow tiers....................54 Table 3.4: General size metrics for the fourteen species of irregular echinoids from the Late Eocene Ocala Limestone ...............................................................................55 Table 3.5: Summary of bore hole analysis performed by Gibson and Watson on five species of Ocala Limestone irregular echinoids ....................................................56 viii LIST OF FIGURES Page Figure 2.1: Comparative latitudinal diversity gradients (LDG) for modern irregular echinoids, infaunal and epifaunal bivalves ............................................................27 Figure 2.2: Latitudinal differences in tropical and extratropical originations and present- day latitudinal limits of irregular echinoid genera that first occur in the tropics ...28 Figure 2.4: Number of irregular echinoid collections per latitudinal bin for Cenozoic time periods. ...................................................................................................................29 Figure 2.4: Theoretical schematic for the out of the extratropics (OTE) model ................30 Figure 3.1: Location of museum and field samples used in this study ..............................57 Figure 3.2: Generalized stratigraphic column of the Ocala Limestone .............................58 Figure 3.3: Number of species per burrow tier for irregular echinoids from the Late Eocene Ocala Limestone........................................................................................59 Figure 3.4: Predation frequency vs. size class of irregular echinoids from the Late Eocene Ocala Limestone ....................................................................................................60 1 CHAPTER 1 INTRODUCTION AND LITERATURE REVIEW 2 Statement of Objectives Irregular echinoids (heart urchins, sand dollars, sea biscuits) are a group of infaunal