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Mesozoic bird primary feather length and flight styles



From: Ben Creisler
bcreisler@gmail.com


A new online paper:


Nicholas R. Chan, Gareth J. Dyke & Michael J. Benton (2012)
Primary feather lengths may not be important for inferring the flight
styles of Mesozoic birds.
Lethaia (advance online publication)
DOI: 10.1111/j.1502-3931.2012.00325.x
http://onlinelibrary.wiley.com/doi/10.1111/j.1502-3931.2012.00325.x/abstract


Although many Mesozoic fossil birds have been found with primary
feathers preserved, these structures have rarely been included in
morphometric analyses. This is surprising because the flight feathers
of modern birds can contribute approximately 50% of the total wing
length, and so it would be assumed that their inclusion or exclusion
would modify functional interpretations. Here we show, contrary to
earlier work, that this may not be the case. Using forelimb
measurements and primary feather lengths from Mesozoic birds, we
constructed morphospaces for different clades, which we then compared
with morphospaces constructed for extant taxa classified according to
flight mode. Consistent with older work, our results indicate that
among extant birds some functional flight groups can be distinguished
on the basis of their body sizes and that variation in the relative
proportions of the wing elements is conservative. Mesozoic birds, on
the other hand, show variable proportions of wing bones, with primary
feather length contribution to the wing reduced in the earlier
diverging groups. We show that the diverse Mesozoic avian clade
Enantiornithes overlaps substantially with extant taxa in both size
and limb element proportions, confirming previous morphometric results
based on skeletal elements alone. However, these measurements cannot
be used to distinguish flight modes in extant birds, and so cannot be
used to infer flight mode in fossil forms. Our analyses suggest that
more data from fossil birds, combined with accurate functional
determination of the flight styles of living forms is required if we
are to be able to predict the flight modes of extinct birds.