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View of the Choristodera “It is the struggle itself that is most important. We must strive to be more than we are. It does not matter that we will not reach our ultimate goal. The effort itself yields its own reward." - Gene Roddenberry University of Alberta The jaw adductor muscles in Champsosaurus and their implications for feeding mechanics by Michael Spencer Brian James A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science in Systematics and Evolution Biological Sciences ©Michael Spencer Brian James Fall 2010 Edmonton, Alberta Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission. Examining Committee Philip J. Currie, Biological Sciences Michael W. Caldwell, Biological Sciences Richard C. Fox, Biological Sciences John Acorn, Renewable Resources Abstract The jaw musculature of Champsosaurus has been enigmatic since the taxon was first described. The extant phylogenetic bracketing method is used to determine the morphology of the jaw adductor musculature. Rotational mathematics is used to calculate the muscle forces, torques, angular accelerations, and angular velocities generated by the jaw muscles. The mechanical strength of the skulls of neochoristoderes and crocodilians are investigated using finite element analysis. Finally, the hydrodynamic performance of the skulls of neochoristoderes and crocodilians is studied. The analysis is used to compare neochoristoderes to their extant ecological analogues, crocodilians, and determine the palaeoecological implications of the results. It was found that Champsosaurus rotates the lower jaw faster, the mechanical strength was lower, and shows better hydrodynamic performance than crocodilians. The results suggest that Champsosaurus was ideally suited to prey upon small or juvenile fish, and did not overlap its niche with sympatric crocodilians. Acknowledgements I would like to thank the following people for their contributions to the making of this thesis: Dr. Philip Currie for his supervision and guidance, Dr. Michael Caldwell, Dr. Richard Fox, and John Acorn for providing suggestions and feedback on my thesis, Eric Snively and Victoria Arbour for teaching me the basics of biomechanics and assistance in operating the computer programs used in this study, Dr. Don Henderson for devising the computer program used to calculate rotational inertia, Eva Koppelhus for her support over these past few years, Ken Soehn for finding UALVP 47243, the graduate students of the palaeontology lab, Rhian Russell for digitizing the specimen of Crocodylus and her support, and my parents Leanne and Anthony Bowen for the free meals and supporting my interest in palaeontology since childhood. Table of Contents CHAPTER 1: Introduction…………………………………………………… 1 CHAPTER 2: Jaw Adductor Muscles of the Neochoristodera………………. 14 CHAPTER 3: Biomechanics of the Jaw Adductor Muscles of Champsosaurus……………………........................................... 52 CHAPTER 4: Finite Element and Hydrodynamic Performance of Neochoristodere and Extant Crocodilian Skulls……………….. 104 CHAPTER 5: Conclusions and Palaeoecological Implications……………… 183 LITERATURE CITED ……………………………………………………… 193 Tables 2.1: Origins of the jaw muscles in neochoristoderes……………………… 45 2.2: Insertions of the jaw muscles in neochoristoderes…………………… 46 3.1: Skull length and width of the neochoristoderes and crocodilians……. 83 3.2: ASCA and adductor chamber forces in neochoristoderes (ST = 24)… 83 3.3: ASCA and adductor chamber forces in neochoristoderes (ST = 30)… 83 3.4: ASCA and adductor chamber forces in crocodilians (ST = 24)……… 84 3.5: ASCA and adductor chamber forces in crocodilians (ST = 30)……… 84 3.6: Jaw muscle forces of UALVP 33928………………………………… 84 3.7: Jaw muscle forces of UALVP 47243………………………………… 85 3.8: Jaw muscle forces of TMP 1984.3.9…………………………………. 85 3.9: Jaw muscle forces of Simoedosaurus dakotensis………………………. 85 3.10: Jaw muscle forces of Alligator mississippiensis………………………. 86 3.11: Jaw muscle forces of Crocodylus cataphractus…………………….. 86 3.12: Jaw muscle forces of Gavialis gangeticus…………………………... 86 3.13: Jaw muscle forces of Tomistoma schlegelii………………………… 87 3.14: Tangential force of the jaw muscles of UAVLP 33928…………….. 87 3.15: Tangential force of the jaw muscles of UAVLP 47243…………….. 87 3.16: Tangential force of the jaw muscles of TMP 1984.3.9……………... 88 3.17: Tangential force of the jaw muscles of Simoedosaurus dakotensis…. 88 3.18: Tangential force of the jaw muscles of Alligator mississippiensis..... 88 3.19: Tangential force of the jaw muscles of Crocodylus cataphractus….. 89 3.20: Tangential force of the jaw muscles of Gavialis gangeticus………... 89 3.21: Tangential force of the jaw muscles of Tomistoma schlegelii……… 89 3.22: Torque of the jaw muscles of UAVLP 33928………………………. 90 3.23: Torque of the jaw muscles of UAVLP 47243………………………. 90 3.24: Torque of the jaw muscles of TMP 1984.3.9……………………….. 90 3.25: Torque of the jaw muscles of Simoedosaurus dakotensis…………... 91 3.26: Torque of the jaw muscles of Alligator mississippiensis…………… 91 3.27: Torque of the jaw muscles of Crocodylus cataphractus……………. 91 3.28: Torque of the jaw muscles of Gavialis gangeticus…………………. 92 3.29: Torque of the jaw muscles of Tomistoma schlegelii………………... 92 3.30: Bite force in all specimens………………………………………….. 93 3.31: Angular acceleration in UALVP 33928…………………………….. 94 3.32: Angular acceleration in UALVP 47243…………………………….. 94 3.33: Angular acceleration in TMP 1984.3.9……………………………... 94 3.34: Angular acceleration in Simoedosaurus dakotensis………………… 95 3.35: Angular acceleration in Alligator mississippiensis…………………. 95 3.36: Angular acceleration in Crocodylus cataphractus………………….. 95 3.37: Angular acceleration in Gavialis gangeticus……………………….. 96 3.38: Angular acceleration in Tomistoma schlegelii……………………… 96 3.39: Tangential acceleration in all specimens……………………………. 97 3.40: Jaw closing time and angular velocity………………………………. 98 3.41: Tangential velocity in all specimens………………………………... 99 4.1: Peak fluid velocity in neochoristodere and crocodilian skull x.s…….. 138 4.2: Fluid pressure in neochoristodere and crocodilian skull x.s………...... 138 4.3: Cell Reynolds number in neochoristodere and crocodilian skull x.s… 138 Figures Figure 2.1: Extant Phylogenetic Brackets of the Choristodera …………... 47 Figure 2.2: Osteology of the skull of Champsosaurus……………………. 48 Figure 2.3: Jaw muscle reconstruction 1 (Sphenodon)……………………. 49 Figure 2.4: Jaw muscle reconstruction 2 (Sphenodon)……………………. 50 Figure 2.5: Jaw muscle reconstruction 3 (crocodilian)……………………. 51 Figure 3.1: ASCA measurements in neochoristoderes……………………. 100 Figure 3.2: ASCA measurements in crocodilians………………………… 101 Figure 3.3: Measurements used in jaw rotation calculations……………… 102 Figure 3.4: Rotational inertia model of UALVP 33928…………………... 103 Figure 4.1: CT scans of UALVP 47243…………………………………... 139 Figure 4.2: Digital model of UALVP 33928……………………………… 140 Figure 4.3: Digital model of Crocodylus cataphractus…………………… 141 Figure 4.4: Stress in UALVP 33928; grasping, orbit……………………... 142 Figure 4.5: Stress in UALVP 33928; grasping, terminus…………............. 143 Figure 4.6: Stress in UALVP 33928; striking, orbit…………..................... 144 Figure 4.7: Stress in UALVP 33928; striking, terminus………….............. 145 Figure 4.8: Stress in UALVP 47243; grasping, terminus…………............. 146 Figure 4.9: Stress in UALVP 47243; striking, terminus………….............. 147 Figure 4.10: Stress in TMP 1984.3.9; grasping, terminus………………… 148 Figure 4.11: Stress in TMP 1984.3.9; striking, terminus…………………. 149 Figure 4.12: Stress in Simoedosaurus dakotensis; grasping, terminus……. 150 Figure 4.13: Stress in Simoedosaurus dakotensis; striking, terminus…….. 151 Figure 4.14: Stress in Alligator mississippiensis; grasping, orbit………… 152 Figure 4.15: Stress in Alligator mississippiensis; grasping, terminus…….. 153 Figure 4.16: Stress in Alligator mississippiensis; striking, orbit………….. 154 Figure 4.17: Stress in Alligator mississippiensis; striking, terminus……… 155 Figure 4.18: Stress in Crocodylus cataphractus; grasping, terminus……... 156 Figure 4.19: Stress in Crocodylus cataphractus; striking, terminus……… 157 Figure 4.20: Stress in Gavialis gangeticus; grasping, terminus…………... 158 Figure 4.21: Stress in Gavialis gangeticus; striking, terminus……………. 159 Figure 4.22: Stress in Tomistoma schlegelii; grasping, terminus…………. 160 Figure 4.23: Stress in Tomistoma schlegelii; striking, terminus…………... 161 Figure 4.24: Fluid velocity in UALVP 33928…………………………….. 162 Figure 4.25: Fluid velocity in UALVP 47243…………………………….. 163 Figure 4.26: Fluid velocity in Simoedosaurus dakotensis………………… 164 Figure 4.27: Fluid velocity in Alligator mississippiensis…………………. 165 Figure 4.28: Fluid velocity in Crocodylus cataphractus………………….. 166 Figure 4.29: Fluid velocity in Gavialis gangeticus……………………….. 167 Figure 4.30: Fluid velocity in Tomistoma schlegelii………………………
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