[dinosaur] Flight, symmetry and barb angle evolution in bird and dinosaur feathers

Ben Creisler
[email protected]

A new paper:

Xia Wang, Ho Kwan Tang and Julia A. Clarke (2019)
Flight, symmetry and barb angle evolution in the feathers of birds and
other dinosaurs.
Biology Letters 15(12): 20190622
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1098_rsbl.2019.0622&d=DwIBaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=N0gisLppmgK028sWHMMGG2RkXDYQgPgbjXCvvjRofwg&s=uuz_Et2wPknPWjd3v1WNqREcDA3J2EQvUjXY8u8XidI&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__royalsocietypublishing.org_doi_10.1098_rsbl.2019.0622&d=DwIBaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=N0gisLppmgK028sWHMMGG2RkXDYQgPgbjXCvvjRofwg&s=KX9Mjl8vY4smAaQs5Yaf6Elb87lCRbUOjduN0Rrd8o8&e= 


There has been much discussion over whether basal birds (e.g. Archaeopteryx
and Confuciusornis) exhibited active flight. A recent study of barb angles
has suggested they likely could not but instead may have exhibited a
gliding phase. Pennaceous primary flight feathers were proposed to show
significant shifts in barb angle values of relevance to the inference of
flight in these extinct taxa. However, evolutionary trends in the evolution
of these barb angle traits in extant volant taxa were not analysed in a
phylogenetic frame. Neither the ancestral crown avian condition nor the
condition in outgroup dinosaurs with symmetrical feathers were assessed.
Here, we expand the fossil sample and reanalyse these data in a
phylogenetic frame. We show that extant taxa, including strong flyers (e.g.
some songbirds), show convergence on trailing barb angles and barb angle
asymmetry observed in Mesozoic taxa that were proposed not to be active
fliers. Trailing barb angles in these Mesozoic taxa are similar to
symmetrical feathers in outgroup dinosaurs, indicating that selective
regimes acted to modify primarily the leading-edge barb angles. These
trends inform dynamics in feather shape evolution and challenge the notion
that barb angle and barb angle ratios in extant birds directly inform the
reconstruction of function in extinct stem taxa.

Footnotes

Electronic supplementary material is available online at
https://urldefense.proofpoint.com/v2/url?u=http-3A__dx.doi.org_10.6084_m9.figshare.c.4745939&d=DwIBaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=N0gisLppmgK028sWHMMGG2RkXDYQgPgbjXCvvjRofwg&s=NiEcyESVtDUt_Bgs7v2PwqAGMc605k0ZWjM_xUzpTfc&e= .