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Re: Third claw for climbing was Re: Pro(to)avis



T. Michael Keesey wrote:

As Longrich (2003) noted, _Archaeopteryx_ also has long leg feathers, albeit not as long as those of _Pedopenna_ and _Microraptor_.

Also, the hindlimb feathers of _Archaeopteryx_ appear to be limited to the femur and tibia. _Microraptor_ and _Pedopenna_, by contrast, show very long feathers on the metatarsus, as well as shorter feathers further up the leg. In _Microraptor_, the hindlimb feathers appear to be arranged into a wing, wherereas the leg feathers of _Archaeopteryx_ were narrow and probably open-vaned. This is based on the study of Christiansen and Bone (2004). There is no evidence that _Archaeopteryx_ had a 'pelvic wing'.


Taking into consideration that long leg feathers are unknown outside of _Eumaniraptora_, it seems that the best assumption for now is that the immediate ancestors of _Eumaniraptora_ had somewhat long leg feathers, as in _Archaeopteryx_, but not the really long leg feathers
of the Liaoning deinonychosaurs.

...unless _Pedopenna_ represents a non-avian, non-deinonychosaurian eumaniraptoran and exemplifies the basal eumaniraptoran condition - in which case _Archaeopteryx_'s condition is a secondary reversal.


Of course, the sample size is pretty durn small, so the "best" assumption is not necessarily that much better than its competition....

You're durn right - there are several competing scenarios, all equally plausible.


Cheers

Tim