Wednesday, December 23, 2015

Powered flight, flapping flight, gliding

Basal Euparaves could fly by flapping their wings, but they could not take off from the ground. In other words, they capable of "powered flight" but not able to takeoff from the ground.
.... the work of Xu et al. (2003), (2005) and Hu et al. (2009) provide examples of basal and early paravians with four wings,[11][12][13] adapted to an arboreal lifestyle who would only lose their hindwings when some adapted to a life on the ground and when avialans evolved powered flight.[14] Newer research also indicates that gliding, flapping and parachuting was another ancestral trait of Paraves, while true powered flight only evolved once, in the lineage leading to modern birds.[15]

"Out of all these flappers and gliders, only the birds seem to have been capable of powered flight," said co-author Mike Benton, Professor of Vertebrate Palaeontology at Bristol.

The lack of a morphologically derived SC [supracoracoideus] in Late Jurassic and Early Cretaceous birds precluded a high velocity recovery stroke which undoubtedly limited powered flight in these forms. Subsequent evolution of the derived SC capable of imparting a large rotational force to the humerus about its longitudinal axis was an important step in the evolution of the wing upstroke and in the ability to supinate (circumflex) the manus in early upstroke, a movement fundamental to reducing air resistance during the recovery stroke.
Euavialae (meaning "true winged birds") is a group of birds which includes all avialan species more closely related to modern birds, than to the primitive, long-tailed birds Archaeopteryx and Jeholornis.[1]
The dorsal elevators, principally the deltoideus major, can effect the recovery stroke by themselves, as they did in Archaeopteryx. The German anatomist Maxheinz J. Sy proved this when he cut the tendons of the supracoracoideus in living crows and pigeons (1936). Sy found that pigeons were capable of normal, sustained flight; the only capacity they lost was the ability to take off from level ground.

Concerning flapping flight, also see:

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