Uncinate processes of ribs

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The uncinate processes of the ribs are extensions of bone that in birds project caudally from the vertical segment of each rib. (Uncinate means hooked from Latin uncinatus, from uncinus, barb, from uncus, hook.) These processes help to strengthen the rib cage of birds by overlapping with the rib behind them.[1] They are also shown to have a role in respiration by increasing the effectiveness of muscles involved in inspiration including the external intercostal muscles.[2] The processes are short in walking birds and long in diving species and are of intermediate length in non-specialist birds.[3] The process has also been noted in some Enantiornithines.[4] Although bony uncinate processes are unique to birds, cartilaginous uncinate processes are present in crocodiles. The uncinate process has also been reported in Sphenodon, Caudipteryx, oviraptorids, Confuciusornis and Chaoyangia however it does not occur in Archaeopteryx.[4]

[edit] References

  1. ^ Bonney, Rick & Rohrbaugh, Jr., Ronald (2004), Handbook of Bird Biology (Second ed.), Princeton, NJ: Princeton University Press, ISBN 0-938-02762-X 
  2. ^ Codd, J. R., D. F. Boggs, S. F. Perry, and D. R. Carrier. 2005. Activity of three muscles associated with the uncinate processes of the giant Canada Goose Branta canadensis maximus. Journal of Experimental Biology 208:849-857. Full text
  3. ^ Tickle, Peter G. , A. Roland Ennos, Laura E. Lennox, Steven F. Perry and Jonathan R. Codd 2007. Functional significance of the uncinate processes in birds. Journal of Experimental Biology 210:3955-3961 Abstract
  4. ^ a b Fucheng, Zhang, Zhou Zhoghe, Hou Lianhai & Gu Gang 2001. Early diversification of birds:Evidence from a new opposite bird. Chinese Science Bulletin. 46(11):945-949 PDF