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"Avian" characters which evolved in the theropod lineage


Feathers

Birds possess large flight feathers and smaller downy feathers for insulation. in the theropod lineage feathers would not have been used for flight, and more likely evolved for insulation, display or camouflage.

 

The Furcula

Also known as the wishbone, this acts as a biomechanical spring-spacer, which bends and recoils during flight. The pectoralis flight muscles are also partially attached to the furcula. These muscles power the downstroke of flight. A role in breathing has also been suggested for the furcula.

For diagram of the avian skeleton click here

 

The Elongated Forearm

This is a prerequisite for flight-worthy wings

 

Laterally Flexing Wrist

Lateral flexing of the wrist allows a thrust to generated which is essential for the wingbeat. In certain theropods, this action would have been for quick seizing of prey.

 

Lightly Constructed Bones

This is a weight-reducing strategy in birds. Marrow or marrow-like tissue in the cavities of bones is replaced by air, even in the skull.

 

Backwards-pointing Pubis

This may have been advantageous in the earliest tree-climbing birds. A reversed pubis would not be such a hindrance as a vertically-pointing one.

For diagram of the avian skeleton click here

 

Oviparous

All birds (and thir reptilian ancestors) lay eggs. There are no exceptions.

 


Author: Robert Davis
Last updated: 21/11/05

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