QUANTIFYING MORPHOLOGICAL VARIABILITY THROUGH THE LATEST ONTOGENY OF HOPLOSCAPHITES (JELETZKYTES) FROM THE LATE CRETACEOUS WESTERN INTERIOR USING GEOGRAPHIC INFORMATION SYSTEMS AS A MORPHOMETRIC TOOL Mathew J. Knauss A Thesis Submitted to the Graduate College of Bowling Green State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE August 2013 Committee: Margaret M. Yacobucci, Advisor Enrique Gomezdelcampo Sheila Roberts © 2013 Mathew J. Knauss All Rights Reserved iii ABSTRACT Margaret M. Yacobucci, Advisor Ammonoids are known for their intraspecific and interspecific morphological variation through ontogeny, particularly in shell shape and ornamentation. Many shell features covary and individual shell elements (e.g., tubercles, ribs, etc.) are difficult to homologize, which make qualitative descriptions and widely-used morphometric tools inappropriate for quantifying these complex morphologies. However, spatial analyses such as those applied in geographic information systems (GIS) allow for quantification and visualization of global shell form. Here, I present a GIS-based methodology in which the variability of complex shell features is assessed in order to evaluate evolutionary patterns in a Cretaceous ammonoid clade. I applied GIS-based techniques to sister species from the Late Cretaceous Western Interior Seaway: the ancestral and more variable Hoploscaphites spedeni, and descendant and less variable H. nebrascensis. I created digital models exhibiting the shells’ lateral surfaces using photogrammetric software and imported the reconstructions into a GIS environment. I used the number of discrete aspect patches and the 3D to 2D area ratios of the lateral surface as terrain roughness indices. These 3D analyses exposed the overlapping morphological ranges of H. spedeni and H. nebrascensis, with H. nebrascensis specimens exhibiting similar ornamentation to the most ornate H. spedeni. In order to assess more specific shell characters, I digitized the tubercles (points), ribs (polylines) and shell shape (polygons) of select specimens from photographs for 2D analyses. These 2D analyses revealed that the distribution of ribs and the shape of the body chambers are fairly constrained in at least H. spedeni, and the distribution of tubercles is the most variable feature through ontogeny between both Hoploscaphites species. iv The results of the GIS-based spatial analyses demonstrated that the target for evolutionary change in this clade resides in the macroconch body chamber. Additionally, the results support the hypothesis that H. nebrascensis is a paedomorphic descendant of H. spedeni, derived by means of prolonged tubercle expression through later ontogenetic stages. H. nebrascensis microconchs retain developmental flexibility, and the macroconchs are more constrained. These geospatial analyses not only successfully quantified variability in complex morphologies, but also demonstrated the versatility of this method to address questions related to ontogeny and phylogeny. v ACKNOWLEDGMENTS I thank P. Gorsevski (Department of Geology, Bowling Green State University) and J. Haug (the Yale Peabody Museum of Natural History) for technical advice, D. Pavuk (Department of Biology, Bowling Green State University) for advice on the thesis proposal, S. Butts (the Yale Peabody Museum of Natural History) for access to specimens, and N. Landman (the American Museum of Natural History) for advice on Hoploscaphites morphology. I would also like to thank E. Gomezdelcampo and S. Roberts (Department of Geology, Bowling Green State University) for being on my thesis committee and providing guidance for both this research project and the final manuscript. I especially thank my advisor, M.M. Yacobucci, for all her advice and help in obtaining external funding, in conducting this research, and in writing and editing this manuscript. Funding for this research was provided by the Geological Society of America, the Paleontological Society, and the Department of Geology at Bowling Green State University. vi TABLE OF CONTENTS Page CHAPTER I. INTRODUCTION ........................................................................................... 1 Ammonoid Intraspecific Variation ............................................................................ 1 Quantifying Intraspecific Variability ......................................................................... 4 Heteromorphic Ammonoids and Scaphites ............................................................... 7 Hoploscaphites (Jeletzkytes) spedeni ......................................................................... 9 Hoploscaphites (Jeletzkytes) nebrascensis ................................................................ 9 Biostratigraphy ........................................................................................................... 10 Research Objectives ................................................................................................... 12 CHAPTER II. METHODOLOGY......................................................................................... 14 Acquisition of Digital Models ................................................................................... 14 Digital Models Imported into a GIS Environment .................................................... 17 3D GIS Methodology ................................................................................................. 18 Orientation Patch Count ................................................................................. 18 Surface-to-Planimetric Area Ratio ................................................................. 19 Generating Coordinate Systems for 2D Methodology............................................... 20 2D GIS Methodology ................................................................................................. 21 Rib and Tubercle Spacing .............................................................................. 21 Rib Density .................................................................................................... 22 Tubercle-Rib Spatial Correlation ................................................................... 22 Shell Coiling .................................................................................................. 23 Body Chamber Shape Distribution ................................................................ 24 vii Statistical Analyses .................................................................................................... 24 Sample Size for Statistical Analyses.......................................................................... 25 CHAPTER III. RESULTS ..................................................................................................... 26 3D GIS Analyses........................................................................................................ 26 Results of OPC Analysis ................................................................................ 26 Results of Surface-to-Planimetric Area Ratio Analysis................................. 28 2D GIS Analyses........................................................................................................ 30 Results of Rib and Tubercle Spacing Analysis .............................................. 30 Results of Rib Density Analysis .................................................................... 30 Results of Tubercle-Rib Spatial Correlation Analysis ................................... 31 Results of Shell Coiling Analysis .................................................................. 32 Results of Body Chamber Shape Distribution Analysis ................................ 33 CHAPTER IV. DISCUSSION............................................................................................... 35 3D GIS Discussion ..................................................................................................... 35 Interpretation of OPC Analysis ...................................................................... 35 Interpretation of Surface-to-Planimetric Area Ratio Analysis ....................... 39 2D GIS Discussion ..................................................................................................... 42 Interpretation of Rib and Tubercle Spacing Analysis .................................... 42 Interpretation of Rib Density Analysis .......................................................... 44 Interpretation of Tubercle-Rib Spatial Correlation Analysis ......................... 46 Interpretation of Shell Coiling Analysis ........................................................ 47 Interpretation of Body Chamber Shape Distribution Analysis ...................... 48 Evolutionary Implications .......................................................................................... 50 viii GIS as a Morphometric Tool ..................................................................................... 53 CHAPTER V. CONCLUSIONS ........................................................................................... 57 CHAPTER VI. FIGURES AND TABLES ............................................................................ 59 REFERENCES……... ........................................................................................................... 98 APPENDIX A. RAW DATA TABLES ................................................................................ 105 APPENDIX B. ADDITIONAL FIGURES ...........................................................................