, Volume 50, Issue 4, pp 305–310 | Cite as

Rib orientation and implications for orthograde positional behavior in nonhuman anthropoids

  • Miyuki Kagaya
  • Naomichi Ogihara
  • Masato Nakatsukasa
Original Article


Strong caudal obliquity of the lower ribs is one of the assumed characteristics of the thoracic region in hominoids and Ateles. Strong caudal obliquity keeps the scapula of the weight-bearing forelimb on the dorsal surface of the trunk via the serratus anterior muscles during propulsion (Stern et al. 1980). We examined the orientation of odd-numbered ribs in lateral view in remounted thoracic skeletons of fifteen nonhuman anthropoids. Hominoids exhibit pronounced caudal obliquity in the seventh and ninth ribs compared to Old and New World monkeys. The position of the maximum thoracic cage width, which approximates the attachment of the serratus anterior muscle, is more caudally located in Hylobates and Pongo. The overall pattern of rib obliquity is generally similar between New and Old World monkeys, including Ateles. Perhaps not only forelimb suspensory behavior but also various orthograde positional behaviors are related to the strong obliquity of the lower ribs; however, further investigation is necessary.


Rib obliquity Hominoids Functional adaptation Forelimb suspensory behavior 


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Copyright information

© Japan Monkey Centre and Springer 2009

Authors and Affiliations

  • Miyuki Kagaya
    • 1
    • 2
  • Naomichi Ogihara
    • 1
  • Masato Nakatsukasa
    • 1
  1. 1.Laboratory of Physical Anthropology, Department of Zoology, Graduate School of ScienceKyoto UniversityKyotoJapan
  2. 2.Département Histoire de la TerreMuséum National d’Histoire NaturelleParis Cedex 05France

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