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RE: Phylogeny of Maniraptora




Ralph Miller <dinoguyralph@sbcglobal.net> wrote:

_Microraptor gui_ may have held its "hind wings" underneath it in an
inverted "V" during active flapping, only unfolding them intermittently to
provide additional lift as it rests its outstretched "forewings" during
passive gliding.

This is a plausible scenario. However, my more conservative mindset tells me that passive gliding is the simplest explanation.


Certainly many birds glide between active flapping phases, just as bicyclists coast between active pedaling phases.

Yes, but birds and cyclists use only one pair of limbs during their respective behaviors.


And Gregory S. Paul has pointed out that _M. gui_ (as well as the juvenile
_Sinornithosaurus_) had hands and arms better configured for anchoring and
controlling long remiges than _Archaeopteryx_ had

But as I've noted in previous posts, the firmer attachment of the remiges to the manus has _nothing_ to do with the mechanics of powered flight. True, this feature presumably allowed the primaries to better resist the torsional stresses of flapping by providing a more secure attachment. But this does not mean this was the primordial function behind more firmly attached primaries. Maybe it was evolved in gliders or leapers; after all, the primaries still have to slice through the air, and may have been used in braking or orientational control (see Caple et al., 1983; Garner et al., 1999) prior to their use in powered flight.


Or maybe this feature was first evolved for a non-aerodynamic purpose - such as to prevent the primaries from detaching when the hands were used to grasp struggling prey. I would add that if the first birds, and their close relatives, used the hands to catch small terrestrial prey, then the primaries would be dragged through the dirt during the execution of the "predatory stroke". This seems like a good enough reason behind the selection of more firmly attached primaries. Its absence from _Archaeopteryx_ may be secondary.

Greg Paul has proposed one scenario for the inception of this character. But alternative scenarios should be considered.




Tim

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