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Hindlimb feathers in paravians + development of flight surfaces on avian wing

Ben Creisler

Two new papers in English. These were first published in Russian in 2014.

J. K. O’Connor &  H. Chang (2015)
Hindlimb feathers in paravians: Primarily “wings” or ornaments?
Biology Bulletin 42(7): 616-621
DOI: 10.1134/S1062359015070079

Recently a specimen of Sapeornis was described with feathers around
the ankle joint, the first basal bird with metatarsal feathers. The
discovery of several groups of paravians with feathered distal
hindlimbs has been used as evidence that flight in Aves evolved
through a tetrapteryx stage. However, most specimens of Sapeornis do
not preserve feathers around the feet, and these feathers are clearly
absent in at least one exceptional specimen preserving skin and
feather impressions. This suggests that the presence of ankle feathers
in Sapeornis may alternatively be interpreted as ornamentation. Basal
birds show more ornamental tail morphologies than aerodynamic ones
suggesting that sexual selection played a dominant role in shaping
tail plumage. Feathers on the forelimbs initially evolved for a
purpose other than flight and we propose aerodynamics was not the
driving force in hindlimb feather evolution. We suggest that feathers
as a means of visual communication played a very important role in the
evolution of paravian plumage.


G. Kaiser & G. Dyke (2105)
The development of flight surfaces on the avian wing.
Biology Bulletin 42(7): 607-615
DOI: 10.1134/S1062359015070067

The evolution of the feathering arrangements that comprise the modern
avian wing can be tracked using both physical evidence from the known
fossil record and by interpreting aerodynamic theory. Evidence from
both the fossil record and from living birds suggests that all
feathered wings reflect the same basic structural plan. Here we review
scenarios for the evolutionary history of the lifting surfaces of the
feathered wing, suggesting non-locomotory influences on their early
development and building on Pennycuick’s (2008) aerodynamic theories
for the eventual development of avian flight.