Evolution of anthropoid jaw loading and kinematic patterns Export

@article{citeulike:2618290, abstract = {Major transformations in the skull and masticatory system characterized the evolution of crown anthropoids. To offer further insight into the phylogenetic and arguably adaptive significance of specific primate mandibular loading and kinematic patterns, allometric analyses of metric parameters linked to masticatory function are performed within and between 47 strepsirhine and 45 recent anthropoid species. When possible, basal anthropoids are considered. These results are subsequently integrated with prior experimental and morphological work on primate skull form.As compared to strepsirhines, crown anthropoids have a vertically longer ascending ramus linked to a glenoid and condyle positioned relatively higher above the occlusal plane. Interestingly, anthropoids and strepsirhines do not exhibit different mean ratios of condylar to glenoid height, which suggests that both clades are similar in their ability to evenly distribute occlusal contacts and perhaps forces along the postcanine teeth. Thus, given the considerable suborder differences in the scaling of both glenoid and condylar height, we argue that much of this variation in jaw-joint height is linked to suborder differences in relative facial height due in turn to increased encephalization, basicranial flexion, and facial kyphosis in anthropoids.Due to a more elongate ascending ramus, anthropoids evince more vertically oriented masseters than like-sized strepsirhines. Having a relatively longer ramus and a more medially displaced lateral pterygoid plate, crown anthropoids exhibit medial pterygoids oriented similar to those of strepsirhines, but with a variably longer lever arm. As anthropoid masseters are less advantageously placed to effect transverse movements/forces, we argue that balancing-side deep-masseter activity underlying a wishboning loading regime serves to increase, or at least maintain, transverse levels of jaw movement and occlusal force at the end of the masticatory power stroke.Crown anthropoids are also more isognathic and isodontic than strepsirhines. A consideration of early anthropoids suggests that the crown anthropoid masticatory pattern, i.e., more vertical masseters due to a high condyle as well as greater isognathy and isodonty, occurred stepwise during stem anthropoid evolution. This appears to correspond to a more transverse, and perhaps progressively larger, power stroke across oligopithecids, parapithecids, and propliopithecids. Am J Phys Anthropol 112:493-516, 2000. {\copyright} 2000 Wiley-Liss, Inc.}, address = {Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611-3008; Department of Zoology, Division of Mammals, Field Museum of Natural History, Chicago, Illinois 60605-2496; Department of Biological Anthropology and Anatomy, Duke University Medical Center, Durham, North Carolina 27710; Department of Anthropology, University of Toronto, Toronto, Ontario, Canada M5S 1A1; DDS Program, Northwestern University Dental School, Chicago, Illinois 60611-3008}, author = {Ravosa, Matthew J. and Vinyard, Christopher J. and Gagnon, Mario and Islam, Samar A.}, citeulike-article-id = {2618290}, citeulike-linkout-0 = {http://dx.doi.org/10.1002/1096-8644(200008)112:4%3C493::AID-AJPA6%3E3.0.CO;2-P}, citeulike-linkout-1 = {http://www3.interscience.wiley.com/cgi-bin/abstract/72512826/ABSTRACT}, doi = {10.1002/1096-8644(200008)112:4%3C493::AID-AJPA6%3E3.0.CO;2-P}, journal = {American Journal of Physical Anthropology}, keywords = {adductors, allometry, biomechanics, functional, jaw, joint, kinematics, loading, masticatory, morphology, occlusion, regimes}, number = {4}, pages = {493--516}, posted-at = {2008-04-01 02:36:48}, priority = {2}, title = {Evolution of anthropoid jaw loading and kinematic patterns}, url = {http://dx.doi.org/10.1002/1096-8644(200008)112:4%3C493::AID-AJPA6%3E3.0.CO;2-P}, volume = {112}, year = {2000} }

TY - JOUR ID - citeulike:2618290 L3 - citeulike-article-id:2618290 N2 - Major transformations in the skull and masticatory system characterized the evolution of crown anthropoids. To offer further insight into the phylogenetic and arguably adaptive significance of specific primate mandibular loading and kinematic patterns, allometric analyses of metric parameters linked to masticatory function are performed within and between 47 strepsirhine and 45 recent anthropoid species. When possible, basal anthropoids are considered. These results are subsequently integrated with prior experimental and morphological work on primate skull form.As compared to strepsirhines, crown anthropoids have a vertically longer ascending ramus linked to a glenoid and condyle positioned relatively higher above the occlusal plane. Interestingly, anthropoids and strepsirhines do not exhibit different mean ratios of condylar to glenoid height, which suggests that both clades are similar in their ability to evenly distribute occlusal contacts and perhaps forces along the postcanine teeth. Thus, given the considerable suborder differences in the scaling of both glenoid and condylar height, we argue that much of this variation in jaw-joint height is linked to suborder differences in relative facial height due in turn to increased encephalization, basicranial flexion, and facial kyphosis in anthropoids.Due to a more elongate ascending ramus, anthropoids evince more vertically oriented masseters than like-sized strepsirhines. Having a relatively longer ramus and a more medially displaced lateral pterygoid plate, crown anthropoids exhibit medial pterygoids oriented similar to those of strepsirhines, but with a variably longer lever arm. As anthropoid masseters are less advantageously placed to effect transverse movements/forces, we argue that balancing-side deep-masseter activity underlying a wishboning loading regime serves to increase, or at least maintain, transverse levels of jaw movement and occlusal force at the end of the masticatory power stroke.Crown anthropoids are also more isognathic and isodontic than strepsirhines. A consideration of early anthropoids suggests that the crown anthropoid masticatory pattern, i.e., more vertical masseters due to a high condyle as well as greater isognathy and isodonty, occurred stepwise during stem anthropoid evolution. This appears to correspond to a more transverse, and perhaps progressively larger, power stroke across oligopithecids, parapithecids, and propliopithecids. Am J Phys Anthropol 112:493-516, 2000. © 2000 Wiley-Liss, Inc. IS - 4 JF - American Journal of Physical Anthropology AD - Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611-3008; Department of Zoology, Division of Mammals, Field Museum of Natural History, Chicago, Illinois 60605-2496; Department of Biological Anthropology and Anatomy, Duke University Medical Center, Durham, North Carolina 27710; Department of Anthropology, University of Toronto, Toronto, Ontario, Canada M5S 1A1; DDS Program, Northwestern University Dental School, Chicago, Illinois 60611-3008 EP - 516 TI - Evolution of anthropoid jaw loading and kinematic patterns VL - 112 SP - 493 KW - adductors KW - allometry KW - biomechanics KW - functional KW - jaw KW - joint KW - kinematics KW - loading KW - masticatory KW - morphology KW - occlusion KW - regimes AU - Ravosa, Matthew AU - Vinyard, Christopher AU - Gagnon, Mario AU - Islam, Samar PY - 2000/// UR - http://dx.doi.org/10.1002/1096-8644(200008)112:4%3C493::AID-AJPA6%3E3.0.CO;2-P ER -