abstract: Despite the critical role that the vertebral column plays in postural and locomotor behaviors, the functional morphology of the cervical region (i.e., the bony neck) remains poorly understood, particularly in comparison to that of the thoracic and lumbar sections. This dissertation tests the hypothesis that morphological variation in cervical vertebrae reflects differences in positional behavior (i.e., suspensory vs. nonsuspensory and orthograde vs. pronograde locomotion and postures). Specifically, this project addresses two broad research questions: (1) how does the morphology of cervical vertebrae vary with positional behavior and cranial morphology among primates and (2) where does fossil hominoid morphology fall within the context of the extant primates. Three biomechanical models were developed for the primate cervical spine and their predictions were tested by conducting a comparative analysis using a taxonomically and behaviorally diverse sample of primates. The results of these analyses were used to evaluate fossil hominoid morphology. The two biomechanical models relating vertebral shape to positional behaviors are not supported. However, a number of features distinguish behavioral groups. For example, the angle of the transverse process in relation to the cranial surface of the vertebral body--a trait hypothesized to reflect the deep spinal muscles' ability to extend and stabilize the neck--tends to be greater in pronograde species; this difference is in the opposite of the direction predicted by the biomechanical models. Other traits distinguish behavioral groups (e.g., spinous process length and cross-sectional area), but only in certain parts of the cervical column. The correlation of several vertebral features, especially transverse process length and pedicle cross-sectional area, with anterior cranial length supports the predictions made by the third model that links cervical morphology with head stabilization (i.e., head balancing). Fossil hominoid cervical remains indicate that the morphological pattern that characterizes modern humans was not present in Homo erectus or earlier hominins. These hominins are generally similar to apes in having larger neural arch cross-sectional areas and longer spinous processes than modern humans, likely indicating the presence of comparatively large nuchal muscles. The functional significance of this morphology remains unclear. / Dissertation/Thesis / Ph.D. Anthropology 2013

Studies of comparative morphology clearly distinguish the shoulder morphology of Homo from that of the other hominoids. While the shoulder morphology of non-human hominoids is thought to signal adaptations to arboreal locomotion, human shoulder morphology is understood to have lost this adaptation during hominin evolution. Ideas how non-human hominoid shoulder morphology is advantageous in an arboreal context suggest that the specific shoulder morphological traits enhance the arm-raising mechanism. However, this idea has not been biomechanically tested. This thesis constitutes the first analysis of the biomechanical consequences of two distinct shoulder morphologies within Hominoidea by comparing the glenohumeral muscle capabilities of Gorilla to Homo. The biomechanical capabilities are evaluated by constructing a computational musculoskeletal model of a gorilla thorax, shoulder girdle and upper arm, which is used to predict relevant biomechanical metrics such as muscle moments and moment arms. Muscle moments and moment arms are predicted for two important mechanisms, arm-raising and arm-lowering. The predictions are compared to those of an already existing human musculoskeletal model in order to evaluate differences in arm-raising and arm-lowering capability based on the two distinct thorax and shoulder girdle morphologies. The results of the biomechanical analyses show that the arm-lowering mechanism is enhanced in Gorilla compared to Homo, instead of the arm-raising mechanism. The enhanced arm-lowering mechanism is evident by greater moment capacities of two important arm-lowering muscles, pectoralis major and teres major. The greater moments are the result of greater muscle force capacities and greater moment arms, due to the beneficial musculoskeletal geometry of Gorilla. The results highlight that a more distal muscle insertion along the humerus has the greatest enhancing effect on the arm-lowering moment arms of teres major and pectoralis major. Furthermore, thorax and shoulder girdle morphological traits that are well known to distinguish non-human apes from humans were found to contribute to the enhancement of the arm-lowering mechanism. The more cranially oriented glenoid, obliquely oriented scapular spine and cranial scapula position on the thorax enabled certain muscles to act as arm-lowering muscles in Gorilla, contrary to the arm-raising action capability that is predicted for Homo. The enhanced arm-lowering capability is likely advantageous for the arboreal locomotion of apes. During hoisting behaviours that are known to occur during suspension and vertical climbing, arm-lowering is used to lift the heavy body of the apes upward. The results of this thesis in conjunction with earlier EMG studies suggest those muscles which are highly activated during these hoisting behaviours also have enhanced arm-lowering capacities in Gorilla and potentially other non-human hominoids compared to Homo. As such, the results highlight shoulder morphological traits that are biomechanically important for the arboreal locomotor behaviour of apes. By this, the thesis demonstrates a link between the conformation of shoulder morphological traits and their biomechanical capability, which will aid future functional interpretations of extant and extinct species.:Acknowledgements Bibliographische Darstellung Summary Zusammenfassung Chapter 1: Exploring the functional morphology of the Gorilla shoulder through musculoskeletal modelling Chapter 2: Comparison of the arm-lowering performance between Gorilla and Homo through musculoskeletal modeling Conclusion Appendix A: Supplementary Information for Chapter 1 Appendix B: Supplementary Information for Chapter 2 Appendix C: Curriculum Vitae Appendix D: Author Contributions

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Everyday ecologically relevant tasks that affect organismal fitness, such as foraging, reproduction, predator avoidance, and escape responses, rely upon successful locomotion. The effectiveness of animal locomotion depends on many underlying factors, such as the morphology of the locomotor limbs, which evolved to fulfill specific locomotor tasks. Besides morphology, the material properties of the limbs also play a crucial role in locomotion. The skeletal structures of locomotor limbs must be able to withstand the repeated stresses that come with locomotion, either on land or underwater, as they use their limbs to generate propulsive forces. The natural environment animals move in is complex and dynamic, as various conditions crucial to locomotor performance can change unexpectedly. Perturbations to locomotor stability can take different forms, such as elevation changes, obstacles, substrate changes, and slipping. To maintain stable locomotor performance in these environments, animals rely on locomotor control mechanisms to counteract destabilizing effects of locomotor perturbations. In this Dissertation, I investigated the biomechanical control mechanisms and morphological adaptations during locomotion in challenging locomotor scenarios. Over the course of three chapters, the goals were to: 1) explore the effects of limb loss on a side-ways running sprint specialist, the Atlantic ghost crab, 2) determine the response and control mechanisms that allow ghost crabs overcome slip perturbations, and 3) to describe the pelvic morphology of bottom-walking Antarctic plunderfish and compare the pelvic morphologies among multiple species of nothenioids that do not bottom-walk. This study demonstrates the robustness of Atlantic ghost crabs to limb loss and slip perturbations. Paired limb removals resulted in a pattern of kinematic adjustments, which reduced locomotor performance by up to 25%, which was dependent on specific limbs being lost. I suggest that these limbs serve more important limb functions that can’t be replaced by the remaining limbs, however the loss of these particular limbs also results in re-patterning of limb relationships, which may reveal a neural component that may be the cause of decreased locomotor performance. Slip perturbations on the other hand were found to not have any significant effects on the locomotor performance of ghost crabs. Kinematics remained constant as ghost crabs traversed the slip surface, suggesting that ghost crabs may rely on feedforward control to overcome slip perturbations, however further studies measuring neural activity are required to confirm our finding. Most importantly though this chapter demonstrates and corroborates the role of momentum and how it allows animals to overcome perturbations. The last chapter investigated the pelvic morphology and material properties of fin rays in bottom walking fish. The Antarctic plunderfish was found to possess high flexural stiffness in its pelvic fin rays, which likely facilitate the bottom walking behavior in this species. Other, non-bottom walking notothenioids did not have fin rays of similar stiffness. Pelvic plate morphology was not different between species, however there were stark differences in mineralization. The bottom-walking fish had higher bone mineral density compared to the other species analyzed in this chapter. I also found mineralization patterns which seem to align with muscle fiber alignment of the major pelvic muscles, suggesting that these regionalized increases in stiffness provide stability while allowing for a lightweight pelvic plate. / Biology

Recent molecular evidence suggests staurozoans are medusozoans that diverged from Medusozoa before the medusa stage emerged. Morphological studies are needed to determine whether this framework can provide insight into medusa evolution. I studied the neuromuscular morphology of two staurozoans, Haliclystus ‘sanjuanensis’ and Manania handi using FMRFamide and α-tubulin antibodies to label neurons, and phalloidin to label muscles. Results indicate that similar to polyps, staurozoans possess one regionally differentiated FMRFamide and α-tubulin immunoreactive (IR) nerve net, and smooth muscles only. Comparisons with other cnidarians indicate that ancestral medusozoans had a marginal circular muscle and muscular manubrium, but lacked the parallel conducting nerve nets, striated muscle, and pacemaker required to coordinate medusa swimming. A possibly light-sensitive concentration of neurons at the base of the primary tentacles suggests that staurozoan primary tentacles are homologous to medusozoan rhopalia. The unique neuromusculature of nematocyst clusters suggests a defensive or predatory function for these staurozoan synapomorphies. / Graduate / 0287 / 0317

Performance is key to survival. From day-to-day foraging events, to reproductive activities, to life-or-death crises, how well an organism performs these tasks can determine success or failure. Selection, therefore, both natural and sexual, act upon performance, and performance demands on individuals shape a population’s morphological and physiological trait distributions. While studies of morphological adaptations to ecological pressures implicitly center on the idea that responses to selection improve performance via changes in morphology, the relationships between morphology, performance, and fitness are not always well understood. In this dissertation, I investigate these relationships explicitly, as well as determine the effects that different ecological and genetic contexts have on selection and how populations respond to performance pressures. Using a model of lizard locomotor performance, I address three issues that may impact selection on performance that are often overlooked in performance studies. First, performance is not a static trait. Rather, individuals possess a range of performance abilities or intensities that can be expressed as needed. Using a novel, individual-based, quantitative genetic simulation model, I demonstrate the effects of variable performance expression and genetic constraints on how a population experiences and responds to selection on sprint and endurance performance. Second, sex differences in performance are expected in sexually dimorphic species, but empirical evidence for this is lacking. To this end, I measured and analyzed multivariate morphology and performance in Anolis carolinensis to identify sex-specific patterns in functional morphology and functional trade-offs within a broad suite of performance traits. Third, intralocus sexual conflict should constrain the evolution of the multivariate performance phenotype in both sexes. By extending the simulation model to include correlated trait inheritance between sexes and sex-specific selection on certain performance traits, I demonstrate the extent to which this sexual conflict constrains performance evolution. In combining studies of natural populations with simulation studies of selection, this dissertation embraces the complexity of performance to address the multiple contributing factors and constraints on performance evolution, and demonstrates the importance of accounting for such complexity when studying animal performance.