, Volume 49, Issue 2, pp 89–99 | Cite as

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

  • Miyuki Kagaya
  • Naomichi Ogihara
  • Masato Nakatsukasa
Original Article


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.


Anthropoid Hominoid Rib curvature Scaling Thoracic cage 



This work was supported by JSPS-HOPE, a Grant for the Biodiversity Research of the 21st Century COE (A14), a Grant-in-Aid for Scientific Research on Priority Areas “Emergence of Adaptive Motor Function through Interaction between Body, Brain and Environment” and by the Cooperation Research Program of the Primate Research Institute, Kyoto University. We are grateful to Dr. Kunimatsu Yutaka, Primate Research Institute, Kyoto University, Japan; Dr. Takano Tomo, Japan Monkey Centre; Dr. Richard Kraft, The Bavarian State Collection of Zoology, München, Germany; and Professor Dr. Christoph P.E. Zollikofer and Dr. Marcia S. Ponce de León, University of Zürich, Switzerland, for their courtesy in allowing access to specimens.


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Copyright information

© Japan Monkey Centre and Springer 2007

Authors and Affiliations

  • Miyuki Kagaya
    • 1
  • Naomichi Ogihara
    • 1
  • Masato Nakatsukasa
    • 1
  1. 1.Laboratory of Physical Anthropology, Department of Zoology, Graduate School of ScienceKyoto UniversitySakyo, KyotoJapan

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