Scapular Position in Primates

Chan, Ling-Yau

doi:10.1159/000095683

Cited by 32 publications

(67 citation statements)

References 37 publications

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“…The low degree of humeral torsion in these species is the consequence of several skeletal adaptations to quadrupedalism in the thorax and shoulder girdle. Cercopithecoids and platyrrhines that perform a high proportion of quadrupedalism have a narrower and deeper thorax and a more laterally positioned scapula than hominoids and Ateles (Erikson, 1963;Sarmiento, 1985;Chan, 2007). A laterally positioned scapula is part of a functional complex that is adaptive for the constricted forelimb movements in a parasagittal plane that characterize quadrupedal locomotion (Larson and Stern, 1989).…”

Section: Discussionmentioning

confidence: 99%

“…Scapular position has been shown to differ across anthropoid clades, with hominoids having the most dorsally positioned scapula, suspensory platyrrhines having a more laterally positioned scapula, and highly terrestrial cercopithecoids being characterized by the most laterally positioned scapula (Erikson, 1963;Sarmiento, 1985;Chan, 2007). In addition to scapular position, studies of captive versus wildshot orangutans (Sarmiento, 1985) and of human athletes in the sports medicine literature (Pieper, 1998;Osbahr et al, 2002) have suggested that humeral torsion is responsive to the mechanical activity performed over an individual's lifetime.…”

Section: Introductionmentioning

confidence: 99%

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Skeletal correlates of quadrupedalism and climbing in the anthropoid forelimb: Implications for inferring locomotion in Miocene catarrhines

Rein

Harrison

Zollikofer

2011

Journal of Human Evolution

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Several well-known Miocene catarrhines, including Proconsul heseloni, have been inferred to combine quadrupedal walking in an arboreal substrate with a significant amount of climbing during locomotion. The degree to which some of these species were adapted to perform these behaviors is not fully understood due to the mosaic of 'ape-like' and 'monkey-like' traits identified in the forelimb. Given these unique combinations of forelimb features in the fossils, we report on forelimb traits that should be emphasized when investigating skeletal adaptation to quadrupedalism (defined in this manuscript as symmetrical gait movement on horizontal supports, excluding knuckle-walking) and climbing (including both vertical climbing and clambering). We investigate the correspondence between: 1) quadrupedalism and two well-known forelimb traits, humeral torsion and olecranon process length, and 2) climbing and phalangeal curvature. We also test the degree of phylogenetic signal in these relationships using phylogenetic generalized least-squares and branch length transformation methods in order to determine the models of best-fit. We present models that can be used to predict proportions of quadrupedalism and climbing in extant and extinct anthropoid taxa. Each trait-behavior correlation is significant and characterized by an absence of phylogenetic signal. Thus, we employ models assuming a star phylogeny to predict locomotor proportions. The climbing model based on phalangeal curvature and a proxy for size provides the most accurate predictions of behavior across anthropoids. The two quadrupedalism models are less accurate, but distinguish highly quadrupedal species from those that are not. Predictive equations based on these traits support the inference that P. heseloni performed a high proportion of quadrupedalism with a significant climbing component. The degree of phalangeal curvature measured in Pliopithecus vindobonensis predicts that this Miocene catarrhine species performed a proportion of climbing similar to Proconsul, while humeral torsion and olecranon process length provide conflicting inferences of quadrupedal locomotion in this species. to combine quadrupedal walking in an arboreal substrate with a significant amount of climbing during locomotion. The degree to which some of these species were adapted to perform these behaviors is not fully understood due to the mosaic of "apelike" and "monkeylike" traits identified in the forelimb. Given these unique combinations of forelimb features in the fossils, we report on forelimb traits that should be emphasized when investigating skeletal adaptation to quadrupedalism (defined in this manuscript as symmetrical gait movement on horizontal supports excluding knuckle-walking) and climbing (including both vertical climbing and clambering). We investigate the correspondence between: 1) quadrupedalism and two wellknown forelimb traits, humeral torsion and olecranon process length, and 2) climbing and phalangeal curvature. We also test the degree of phylogenetic signa...

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Skeletal correlates of quadrupedalism and climbing in the anthropoid forelimb: Implications for inferring locomotion in Miocene catarrhines

Rein

Harrison

Zollikofer

2011

Journal of Human Evolution

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“…Data on scapular position [Chan, 2007] and, most importantly, empirical data on shoulder mobility in primates [Chan, in preparation] engaged in different locomotor behaviours are necessary for an evaluation of the brachiation and slow climbing theories of hominoid evolution.…”

Section: Implications For the Evolution Of Hominoid Evolution Specialmentioning

confidence: 99%

“…Separate measurements of clavicular length, scapular shape or even thoracic dimension do not indicate the true position of the scapula within the shoulder girdle complex. The position of the scapula is determined by the relative dimensions of these three components, about which data are only just emerging [Chan, 2007]. Furthermore, the relationship between glenohumeral morphology and mobility was incompletely understood.…”

Section: Introductionmentioning

confidence: 99%

Glenohumeral Mobility in Primates

Chan¹

2006

IJFP

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This study refutes the traditional idea that the glenohumeral joint of hominoids is more mobile than that of other primates, a belief that forms a basis for the two prominent theories of hominoid evolution. According to the brachiation theory, many anatomical features of the hominoid shoulder (including those of the glenohumeral joint) increase shoulder mobility and are interpreted as adaptations for brachiation. The slow climbing theory explains the same set of features as adaptations for slow climbing. The slow-climbing primates should therefore also possess these features, and their glenohumeral mobility should be the same as that of hominoids and be higher than that of other primates. This study presents three-dimensional glenohumeral mobility data, measured using a single video camera method on fresh specimens. The results show that the hominoid glenohumeral joint is actually less mobile than those of non-hominoid primates, including the habitually slow-climbing lorines, but it is characterized by a smooth excursion in the scapulocranial direction.

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“…However, comparatively fewer morphological studies have been undertaken on the living (Schultz 1956(Schultz , 1961Erikson 1963;Ohman 1986;Gebo 1996;Chan 1997;Preuschoft et al 2003) and fossil (Schultz 1960;Schmid 1983Schmid , 1991Jellema et al 1993;Moyà-Solà et al 2004;Sawyer and Maley 2005) hominoid thoracic region. Since morphology of the thoracic cage affects the functions of the forelimb during positional behavior (Ward 1993;Preuschoft et al 2003;Chan 2007), quantitative analysis of the thoracic features of living hominoids will enrich our understanding of the functional adaptation and evolution of the forelimb in living hominoids. Schultz (1956) compared the ratio of the transverse diameter to the dorsoventral diameter of the chest (chest index) at the level of the fourth rib in cadavers of 34 living primate genera and concluded that the thorax was relatively transversely wider in hominoids.…”

Section: Introductionmentioning

confidence: 99%

Morphological study of the anthropoid thoracic cage: scaling of thoracic width and an analysis of rib curvature

2007

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While a relatively broad thorax and strongly curved ribs are widely regarded as common features of living hominoids, few studies have quantitatively examined these traits by methods other than calculating the chest index. The present study aims to quantify variations in thoracic cage morphology for living anthropoids. The odd-numbered ribs (first to eleventh) were articulated with the corresponding vertebrae and the cranial and lateral views subsequently photographed. Rib profiles were digitized in both views and line-fitted by a Bézier curve to create a three-dimensional morphological data set. When thoracic cage width was scaled against body mass, Hylobates (and possibly Pongo) plotted above non-hominoid anthropoids at almost all rib levels, while Pan did not differ from non-hominoid anthropoids. The overall pattern of the normalized thoracic width differed between Hylobates and other hominoids. In Hylobates, an upward convex curve was seen between the first and seventh ribs while a more linear pattern was observed in Pan and Pongo. This result quantitatively confirmed that the barrel-shaped thoracic cage in Hylobates can be distinguished from the funnel-shaped form in other hominoids. Conversely, all hominoids shared two distinct features in the upper half-thorax: (1) a pronounced dorsal protrusion of the proximal part of the rib in accordance with ventral displacement of the thoracic spine and (2) a relatively medially projecting sternal end. Although these features are likely to provide some mechanical advantage in orthograde and/or suspensory positional behaviors, they were barely present in the suspensory Ateles.

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Scapular Position in Primates

Cited by 32 publications

References 37 publications

Skeletal correlates of quadrupedalism and climbing in the anthropoid forelimb: Implications for inferring locomotion in Miocene catarrhines

Skeletal correlates of quadrupedalism and climbing in the anthropoid forelimb: Implications for inferring locomotion in Miocene catarrhines

Glenohumeral Mobility in Primates

Morphological study of the anthropoid thoracic cage: scaling of thoracic width and an analysis of rib curvature

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