GRASPING PRESSURES AND PHALANGEAL CURVATURE IN PRIMATES: AN EXPERIMENTAL IN VIVO APPROACH A Dissertation presented to the Faculty of the Graduate School at the University of Missouri- Columbia In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy by KIMBERLY A. CONGDON Dr. Matthew J. Ravosa, Dissertation Supervisor May 2015 The undersigned, appointed by the dean of the Graduate School, have examined the thesis or dissertation entitled GRASPING PRESSURE AND PHALANGEAL CURVATURE IN PRIMATES: AN EXPERIMENTAL IN VIVO APPROACH presented by Kimberly A. Congdon a candidate for the degree of doctor of philosophy and hereby certify that, in their opinion, it is worthy of acceptance Professor Charlotte Phillips Professor Daniel Schmitt DEDICATION This work is dedicated to my family, for never asking when I was going to get a “real job”. and Elizabeth Harmon, who laughed when I said “I’m not really interested in function.” ACKNOWLEDGEMENTS Committee members: Chair Matthew J. Ravosa, Libby Cowgill, Pierre Lemelin, Charlotte Phillips, Daniel Schmitt, and Carol Ward, thank you for all your support, feedback and encouragement. Thanks for assistance with 1. experimental design and execution; Erin Ehmke, David Brewer and the staff at the Duke Lemur Center 2. analysis and R coding; Andrew Deane, Charles Roseman, Andrew Barr and Eva Garret, 3. proof- reading, issues of layout and intellectual dilemmas; Lauren Butaric, Dave Dufeau, Scott Maddux, Rachel Menegaz, Jeremiah Scott, David Strait, and 4. moral support; all of the above, as well as Chris Robinson, Gisselle Garcia, Pam Weis, Gabrielle Russo, Tressa Maddux, Judah Maddux, Sarah Hlubik, Juliet Brophy, Ilya Shmulenson, Thierra Nalley, Alex Woods, Tamara Woods, Colleen Young, John Hawks and Steve Churchill. ii TABLE OF CONTENTS ACKNOWLEDGEMENTS………………………………………………….….……….ii LIST OF FIGURES…………………………………………………………….……….viii LIST OF TABLES……………………………...………………………………..…...…xiv ABSTRACT.......................................................................................................................xx 1: INTRODUCTION………………………………………………………...……………1 1.1: The Study of Functional Morphology Functional Morphology and Fossil Reconstructions Functional Morphology and Experimental Techniques 1.2: The Study of Primate Grasping Morphology The Biofunctionality of Bone Curvature 1.3: The Study of Primate Grasping Behaviors Primate Grasping and Substrate Orientation 1.4: Lemurs and Studies of Grasping 1.5: Body Size 1.6: Substrate Diameter 1.7: Hypotheses Hypothesis 1: Grasping pressure increases with increasing substrate orientation Hypothesis 2: Transitional locomotor behaviors exert higher pressures than the stereotypical behaviors performed at the same substrate orientation Hypothesis 3: Phalangeal curvature is positively correlated with digital grasping pressures Hypothesis 4: Morphological patterns observed in the subjects from the experimental sample are reflected in homologs from wild-caught adult conspecifics iii 2: MATERIALS AND METHODS………………………………………….………..50 2.1: Materials Sample Equipment Experimental Set-Up 2.2: Methods Identifying and Classifying Footfalls and Handfalls Pressure Measures Anatomical Measures Data Transformation 2.3: Data Analysis H1: Grasping pressure increases with increasing substrate orientation. H2: Grasping pressures exerted during ‘transitional locomotion’ are higher than stereotypical locomotion at the same orientation. H3: Phalangeal curvature is positively correlated with high digital grasping pressures. H4: Morphological patterns observed in the experimental sample persist in wild caught populations. Descriptive Statistics The Relationship Between Pressure Magnitude and Size 3: TESTING THE HYPOTHESES………………………………………….…………..77 3.1: Grasping Pressures Increase with Substrate Orientation Within Individual Within Species Within Taxon iv 3.2: Transitional Behaviors Exert Higher Pressures than Stereotypic Motion Within Species Within Taxon 3.3: Phalangeal Curvature is Positively Correlated With The Highest Grasping Pressure Magnitudes Within Individual Within Species Within Taxon 3.4: Morphological Patterns in the Captive Sample are Present In the Wild Population Within Species 4: DESCRIPTIVE STATISTICS………………………………………………….….154 4.1: External Measurements 4.2: Hand and Foot Use Within Individual Within Species Across Species 4.3: Pressure Magnitudes Within Individual Across Individuals Within Species Across Species Within Taxon v 4.4: Digit Length Within Individual Within Species Within Taxon 4.5 Body Mass Within Taxon 5: DISCUSSION……………………………………………………………………204 5.1: Patterns of Hand and Foot Use Frequency of Use Within substrate variation in pressure magnitude Variation in pressure magnitude across substrate Transitional Behaviors Relative Substrate Size Hands vs Feet Pooling Digits 5.2: The Functional Morphology of Arboreal Grasping The role of body size in grasping Correlations of Phalangeal Curvature with Grasping Pressure The Biological Role of Phalangeal Curvature Comparing Morphological Patterns in Wild and Captive Samples Plasticity and Biofunctionality of Phalangeal Curvature vi 5.3: Evolution of Primate Grasping Divergence in Autopod Function Evolution of Bipedality Origins of Bipedalism 6: CONCLUSIONS………………………………………………………………....….243 6.1: Hypotheses Hypothesis 1: Grasping pressure increases with substrate orientation Hypothesis 2: Pressures exerted during transitional behaviors are higher than those exerted during stereotypical behaviors at the same substrate orientation Hypothesis 3: Phalangeal curvature is positively correlated with grasping pressure Hypothesis 4: Morphological patterns found in the experimental sample are consistent with those in the wild sample 6.2: Methodology 6.3: Future Work and Applications 6.4: Biological Roles 7: REFERENCES………………………………………………………………………255 8. VITA............................................................................................................................282 vii List of Figures FIGURE PAGE 1: Introduction Figure 1.1: Stress distribution patterns in loaded columns…………………………...20 Figure 1.2: Model of bending strains in a curved beam……………………………...21 Figure 1.3: Example of below-branch suspension....….…………………....………..23 Figure 1.4: Example of above-branch locomotion.......................................................26 Figure 1.5: Example of vertical-branch locomotion.....................................................31 Figure 1.6: The role of substrate diameter in arboreal posture.....................................34 Figure 1.7: The effect of substrate orientation on arboreal posture.............................36 Figure 1.8: Substrate diameter and grasping pressure..................................................43 2: Materials and Methods Figure 2.1: Tactilus Mat……………………………………………………………...53 Figure 2.2: Research Room……………………………………………..………...….56 Figure 2.3: Three Experimental Set-ups……………………………………………...56 Figure 2.4: Identifying Anatomical Regions on the Pressure Output………………..60 Figure 2.5: X-ray of Propithecus coquereli………………………………………….63 Figure 2.6: Approximate anatomical measurements…………………………………64 Figure 2.7: Transformation of x-ray for analysis…………………………………….66 Figure 2.8: Flow chart linking data sets to forms of analysis.......................................69 viii 3: Testing the Hypotheses Figure 3.1: Lemur catta pedal regional flipping pressures...........................................92 Figure 3.2: Lemur catta pedal digital flipping pressures..............................................92 Figure 3.3: Lemur catta manual regional above-branch jumping pressures................93 Figure 3.4: Lemur catta pedal regional above-branch jumping pressures...................93 Figure 3.5: Lemur catta pedal digital above-branch jumping pressures......................94 Figure 3.6: Lemur catta pedal regional vertical-branch jumping pressures.................94 Figure 3.7: Lemur catta pedal digital vertical-branch jumping pressures....................95 Figure 3.8: Lemur catta pedal regional above-branch landing pressures.....................95 Figure 3.9: Lemur catta manual regional running pressures........................................96 Figure 3.10: Lemur catta manual digital running pressures...........................................96 Figure 3.11: Lemur catta pedal regional running pressures...........................................97 Figure 3.12: Lemur catta pedal digital running pressures..............................................97 Figure 3.13: Lemur catta manual regional turning pressures.........................................99 Figure 3.14: Lemur catta pedal regional turning pressures ..........................................100 Figure 3.15: Propithecus coquereli manual regional above-branch jumping pressures.....................................................................................................................100 Figure 3.16: Propithecus coquereli pedal regional above-branch jumping pressures.101 Figure 3.17: Propithecus coquereli pedal digital above-branch jumping pressures....101 Figure 3.18: Propithecus coquereli manual regional vertical-branch jumping pressures...................................................................................................................102 Figure 3.19: Propithecus coquereli manual digital vertical-branch jumping pressures....................................................................................................................102 Figure 3.20: Propithecus coquereli pedal regional vertical-branch