Evolution of Flight in Birds

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Evolution of Flight in Birds

• Emily Steinmetz

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Indroduction

• Archaeopteryx
• Ancestry of birds
• Evolution of flight
• Feathers

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Archaeopteryx

• First recognized in 1861
• Appeared to be a reptile/bird intermediate
• Believed to be an offshoot of the early avian line

www.aerospaceweb.org/ question/nature/q0201.shtml
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Ancestry

• Two hypotheses
• Theropod
• Thecodont

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Ancestry Theropod

• Theropods are bipedal, carnivorous dinosaurs
• Archaeopteryx has very similar skeletal structure
  to some smaller theropods
• Three fingered forelimb
• Reversed toe
• Bipedalism

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Ancestry Thecodont

• Thecodonts are ancestors of crocodilians,
  dinosaurs and pterosaurs
• Ancestor of birds a quadruped
• Long forelimbs better for wings
• Bipedalism a result of flight

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Flight

• Two hypothesis
• Cursorial (ground up)
• Arboreal (trees down)

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Flight Cursoreal

• Theropod running and jumping on the ground
• Use outstretched limbs for stabilizers
• Fringe allowed for longer jumps
• Lead to gliding and then powered flight

www.biology.eku.edu/ RITCHISO/554notes1.html
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Flight Arboreal

• Small theropod or thecodont jumping from tree to
  tree or to ground
• Fringe would slow fall
• Lead to gliding and then powered flight

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Feathers

• Initial function
• Temperature regulation
• Flight
• How developed
• Elongated scales
• Hollow tubes

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Feathers function (temperature)

• Theropod covered in downy feathers
• As moved from jumping to flying, down developed
  into flight feathers

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Feathers function (flight)

• Elongated scales developed along edges of limbs
• Scales evolved into flight feathers
• Feathers spread to streamline body

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Feathers development (scales)

• Scales elongated and began to be layered along a
  central vein
• Layer became the more complex interlocking barbs
  of modern feathers

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Feathers development (tubes)

• Evolved similarly to stages in embryos
• Hollow tubes gain barbs to form down feathers

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Hypotheses (authors opinion)

• Theropod
• Arboreal
• Thermoregulatory feathers
• Tube feathers

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References

• Alaxander, D.E. Natures Flyers Birds, Insects,
  and the Biomechanics of Flight. Baltimore
  Johns Hopkins University Press, 2002.
• Chatterjee, S. The Rise of Birds 225 Million
  Years of Evolution. Baltimore Johhs Hopkins
  University Press, 1997.
• Feduccia, A. The Origin and Evolution of Birds.
  New Haven Yale University Press,1996.
• Shipman, P. Taking Wing Archaeopteryx and the
  Evolution of Bird Flight. New York Simon and
  Schuster, 1998.
• Zimmer, C. 2005. Dinosaurs Why do we have so
  many questions about the most successful animals
  that ever lived. Discover. 2632-39.