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RE: *Microraptor* the biplane: published
Mickey Mortimer wrote:
Anyone notice Chatterjee and Templin assign Microraptor amd Pedopenna to
Dromaeosauria in the cladogram? Is this the first time the taxon has been
Like David, I'm guessing this is a mistake; "Dromaeosauria" may be a typo
for Deinonychosauria or Dromaeosauridae. Note, however, that Xu and Zhang
(2005) actually recovered _Pedopenna_ as lying outside both Aves and
Deinonychosauria. Thus, I'm not sure what the justification is for allying
_Pedopenna_ closer to _Microraptor_ than to birds (Aves).
Also, Chatterjee and Templin (2007) mention that _Caudipteryx_ shows
"contour feathers on the hindlimbs". But I wasn't aware that any
_Caudipteryx_ specimen shows pennaceous feathers of any variety associated
with the hindlimbs. The best _Caudipteryx_ specimens lack both metatarsal
and tibial feathers (NGMC 97-4-A, NGMC-9-A, IVPP V 12344), even though
feathers are clearly preserved elsewhere (e.g., forelimbs, tail).
This might seem like nit-picking on my part (and it is), but the authors do
raise _Caudipteryx_ in the context of supporting the hypothesis that a
four-winged 'biplane' configuration is primitive for Eumaniraptora, and
therefore ancestral to the two-winged 'monoplane' configuration of birds.
The alternative hypothesis is that the _Microraptor_-style biplane
represents a dead-end experiment in aerial locomotion, and (consequently)
that the direct ancestors of birds never passed through this 'biplane'
stage. However, given that metatarsal contour feathers are limited to
microraptorans and _Pedopenna_, I don't think either hypothesis could be
said to be superior to the other. No incontrovertible fossil bird shows the
'biplane' arrangement. Even though the Berlin specimen of _Archaeopteryx_
shows long hindlimb feathers (as does an unnamed enantiornithean IVPP V
13939), these are not attached to the metatarsus, only to the
tibia/tibiotarsus. Therefore, there is no 'biplane' arrangement, which
requires a ventral wing formed by metatarsal contour feathers.
Having said all that, the idea of biplane-style gliding in microraptorans is
compelling - although I don't think we have enough evidence to argue that
birds must have passed through this stage on the way to powered flight. In
fact, microraptorans and _Pedopenna_ may represent experiment(s) in theropod
flight (probably "trees-down") that were independent of the manner in which
birds (Aves) achieved flight ("trees-down", "ground-up", or a combination of
the two). But if we do find long metatarsal feathers in a basal bird, then
it would be a huge boost to the biplane hypothesis for the origin of bird
I liked how they didn't pretend Cryptovolans didn't exist. ;)
All we need is a review of the specimen, to see if it is a junior synonym of
_Microraptor_ or not.
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