Evolution and Mechanics of Unguligrady in Artiodactyls

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Overview

Title
Evolution and Mechanics of Unguligrady in Artiodactyls
Contributors
Clifford, Andrew Brant (creator)
Gatesy, Stephen (director)
Janis, Christine (reader)
Brainerd, Elizabeth (reader)
Roberts, Thomas (reader)
Swartz, Sharon (reader)
Brown University. Division of Biology and Medicine. Ecological and Evolutionary Biology (sponsor)
Doi
10.7301/Z0CN7266
Copyright Date
2009
Abstract
The derived didactyl limbs of most extant artiodactyls have traditionally been viewed as adaptations for fast locomotion. The most primitive condition for artiodactyls is a pentadactyl and digitigrade manus. The evolution of unguligrady took place at least three times in artiodactyls, between two morphological conditions of a tetradactyl manus, and is characterized by ginglymal digit joints and stiffened interosseus muscles. Application of a sophisticated bi-planar cinefluoroscopic 3-D analysis tests whether hinge-like morphologies of joints of the foot produce uni-axial motion. Minipigs show predominantly antero-posterior rotation during the stance phase of locomotion in forefeet during both level steps and downhill steps, although significant long-axis rotation also occurs. Joints of the forefoot in minipigs are anatomically and kinematically hinge-like, but the movements in non-antero-posterior axes make foot motions non-parasagittal. Minipigs use straighter leg postures during downhill steps than they do in level steps. Combining this kinematic analysis with kinetic forceplate data tests the mechanics of the metacarpophalangeal joint during locomotion. An ex vivo analysis of interosseus ligament function permits comparison with in vivo data and tests whether the ligaments produce a majority of joint torque at the metacarpophalangeal joint to resist torque resulting from ground reaction forces. Minipigs used interosseus ligaments to produce variable amounts of torque at the metacarpophalangeal joint, and the highest ligament contributions to total joint torque took place during slow walking and stationary standing. During downhill steps, the contribution from the interosseus ligaments to total joint torque decreased, primarily due to lower angles of extension at the metacarpophalangeal joint used during downhill steps compared to level steps. This suggests a braking function rather than a spring-like function of the interosseus ligaments. Finally, the evolution of unguligrade foot posture may not have been for fast locomotion but evolved for economical force production at the metacarpophalangeal joint at slow speed or during standing.
Keywords
unguligrady
artiodactyl
metacarpophalangeal joint
XROMM
interosseus ligament
Notes
Thesis (Ph.D.) -- Brown University (2010)
Extent
xxiii, 121 p.

Citation

Clifford, Andrew Brant, "Evolution and Mechanics of Unguligrady in Artiodactyls" (2009). Biology and Medicine Theses and Dissertations, Ecological and Evolutionary Biology Theses and Dissertations. Brown Digital Repository. Brown University Library. https://doi.org/10.7301/Z0CN7266

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