THE HYDROSTATICS AND HYDRODYNAMICS OF PROMINENT HETEROMORPH AMMONOID MORPHOTYPES AND THE FUNCTIONAL MORPHOLOGY OF AMMONITIC SEPTA A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy By DAVID JOSEPH PETERMAN M.S., Wright State University, 2016 B.S., Wright State University, 2014 2020 Wright State University WRIGHT STATE UNIVERSITY GRADUATE SCHOOL April 17th, 2020 I HEREBY RECOMMEND THAT THE DISSERTATION PREPARED UNDER MY SUPERVISION BY David Joseph Peterman ENTITLED The hydrostatics and hydrodynamics of prominent heteromorph ammonoid morphotypes and the functional morphology of ammonitic septa BE ACCEPTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF Doctor of Philosophy Committee on Final Examination Christopher Barton, PhD Dissertation Director Charles Ciampaglio, PhD Don Cipollini, PhD Director, Environmental Sciences PhD program Margaret Yacobucci, PhD Barry Milligan, PhD Interim Dean of the Graduate School Sarah Tebbens, PhD Stephen Jacquemin, PhD ABSTRACT Peterman, David Joseph. PhD. Environmental Sciences PhD Program, Wright State University, 2020. The hydrostatics and hydrodynamics of prominent heteromorph ammonoid morphotypes and the functional morphology of ammonitic septa. Ammonoid cephalopods have chambered shells that regulated buoyancy. The morphology of their shells strongly influenced the physical properties acting on these animals during life. Heteromorph ammonoids, which undergo changes in coiling throughout ontogeny, are the focus of this dissertation. The biomechanics of these cephalopods are investigated in a framework involving functional morphology, paleoecology, and possible modes of life. Constructional constraints were investigated for the marginally-corrugated septal walls within the chambered ammonoid shell. These constraints governed the positive relationship between septal complexity and terminal size. Furthermore, increased septal complexity facilitated liquid retention via surface tension. More complex septa would have increased liquid retention at larger scales, which could have been used as liquid ballasts, reserves for buoyancy adjustment, or to prevent disruptive sloshing of cameral liquid. New methods for the virtual reconstruction of cephalopod shells are described. The shell constrains the volume and shape of each material of unique density that influenced organismal mass and its distribution. Therefore, these virtual models can be used to compute the conditions for neutral buoyancy, hydrostatic stability, syn vivo orientation, and the directional efficiency of movement. The rigid shell also constrains how the living ammonoid would have interacted with fluids in a dynamic setting. A new iii method for the construction of neutrally-buoyant, physical models is described, which can be used to compute hydrodynamic properties such as drag and swimming velocity. The biomechanics of three heteromorph ammonoid morphotypes from the North American Western Interior Seaway are discussed. These morphotypes represent the families Baculitidae, Nostoceratidae, and Scaphitidae. These investigations provide a better understanding of the hydrostatic and hydrodynamic properties that constrained the modes of life for the majority of prominent ammonoid taxa from the Late Cretaceous of the U.S. Western Interior. Novel modeling techniques provide data that suggests heteromorph ammonoids had selective pressures imposed on them for specific biological functions or life habits, rather than pointless morphological experimentation or liberation from such evolutionary pressures. These syn vivo physical properties also influenced the biogeographic dispersal and paleoecology for these enigmatic creatures that were once vital components of marine ecosystems. iv TABLE OF CONTENTS Page LIST OF FIGURES .............................................................................................. xi LIST OF TABLES .............................................................................................. xiv LIST OF INSTITUTIONAL ABBREVIATIONS .............................................. xvi PUBLICATION LIST OF THE DISSERTATION ........................................... xvii AUTHOR CONTRIBUTIONS ............................................................................ xix ACKNOWLEDGEMENTS ................................................................................. xxi 1.0 INTRODUCTION ...................................................................................................1 1.1 REFERENCES ............................................................................................8 2.0 Power scaling of ammonitic suture patterns from Cretaceous Ancyloceratina (Ammonoidea): constraints on septal/sutural complexity ......................................9 2.1 INTRODUCTION ....................................................................................10 2.1.1 Fractal geometry of ammonitic sutures .........................................12 2.1.2 Previous studies of the power scaling of ammonitic sutures ........14 2.2 METHODS ...............................................................................................16 2.2.1 Box-counting method of fractal analysis ......................................16 2.2.2 Box method as implemented by the fractal analysis software – Benoit 1.3 ......................................................................................16 2.2.3 Reconstruction of a baculite septum for capillary retention experiments ....................................................................................18 v 2.3 RESULTS ..................................................................................................19 2.3.1 Distribution in complexity and whorl height .................................19 2.3.2 Sutural ontogeny in Baculites compressus ....................................21 2.3.3 Sutural symmetry and asymmetry in heteromorphic ammonites ..22 2.3.4 Sutural complexity and whorl height .............................................23 2.3.5 Capillary retention simulated by 3D printed models .....................27 2.4 DISCUSSION ............................................................................................29 2.4.1 Septal asymmetry in 3D coiled heteromorphs and the scaling properties of their hemisutures .......................................................29 2.4.2 Sutural/septal scaling, shell size, and constructional constraints ...30 2.4.3 Functional constraints of septal frilling by capillary retention of cameral liquids ...............................................................................33 2.5 CONCLUSIONS........................................................................................36 2.6 ACKNOWLEDGEMENTS .......................................................................37 2.7 REFERENCES ..........................................................................................38 3.0 Mode of life and hydrostatic stability of orthoconic ectocochleate cephalopods: hydrodynamic analyses of restoring moments from 3D-printed, neutrally buoyant models ....................................................................................................................44 3.1 INTRODUCTION .....................................................................................45 3.1.1 Function of ectocochleate cephalopod shells and their hydrostatics ....................................................................................................................45 3.1.2 Previous studies of baculite hydrostatics and mode of life ............47 3.1.3 Three-dimensional modeling of ectocochleate cephalopods .........49 vi 3.2 METHODS ................................................................................................51 3.2.1 Modeled specimens ........................................................................51 3.2.2 Virtual model generation ...............................................................52 3.2.3 Hydrostatic calculations .................................................................56 3.2.4 Restoring moment experiments with 3D-printed models .............58 3.2.5 Experiments on active locomotion to overcome hydrostatic stability .........................................................................................62 3.3 RESULTS ..................................................................................................64 3.3.1 Virtual 3D models of Baculites compressus ..................................64 3.3.2 Restoring moments of Nautilus pompilius .....................................73 3.3.3 Restoring moment of Baculites compressus ..................................75 3.3.4 Thrust required to overcome the Baculites compressus restoring moment .........................................................................................79 3.4 DISCUSSION ............................................................................................81 3.4.1 Hydrostatic properties of Baculites compressus ............................81 3.4.2 Restoring moment of the stable, orthoconic morphotype ..............84 3.4.3 Were orthoconic cephalopods able to overcome their restoring moments? ......................................................................................84 3.4.4 Insights on the mode of life for highly-stable orthoconic cephalopods ..................................................................................86 3.5 CONCLUSIONS........................................................................................90