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Re: 11th specimen of Archaeopteryx



Habib, Michael <MHabib@chatham.edu> wrote:


> I suppose that's true enough, but at the same time I don't tend to have much 
> confidence in particularly specific behavior or lifestyle
> scenario building.  I know that paleontology has a long history of fun 
> scenario building.  I am not a fan, however.


Scenario building is more than just fun - I also think it's
scientifically valid to rule in or out certain lifestyles.  Observed
changes in morphology can be associated with inferred changes in
ecology.


> More general categories is probably all we can really ascribe.  So, for 
>example, any of terrestrial control-based models would seem to
>  fit the bill, even if they don't give a particularly specific scenario set.


I can appreciate that long, asymmetrical feathers along the forelimbs
could be useful as control surfaces in terrestrial-based locomotion.
However, the purpose of such feathers along the tail, and (especially)
the metatarsus seems hard to reconcile with terrestrial-based
locomotion.  Xu et al. (2003) even used the presence of long
metatarsal feathers in _Microraptor gui_ to refute a "ground-up
hypothesis" (their words), because they would be a hindrance to
cursoriality.  Although I think this is an exaggeration, the fact
remains that small feathered paravians (including microraptorines,
archaeopterygids, and confuciusornithids) were not exactly built for
speed on the ground.  I'm aware that control is more about
maneuverability than velocity.  But on that score it is difficult to
accord the hindwings and long feathered tail with increased agility on
the ground.


I apologize in advance if it seems like I'm putting words into Mike's
mouth here, and reading too much into "terrestrial control-based
models".  Nevertheless, as I said in a previous message, I think it is
noteworthy that those paravians which show aerodynamic plumage also
show certain modifications to the pes.  It is very tempting to tie all
these changes (elongate metatarsal feathers; more distal and/or
elongate hallux; longer penultimate phalanges, etc) toward a common,
non-terrestrial purpose.


It's also abundantly clear that no non-ornithothoracean theropod was a
specialist climber or percher.  There is nonetheless enough evidence
to suggest that critters such as _Microraptor_, _Archaeopteryx_ and
(other) basal birds represent a gray area in the so-called
arboreal/terrestrial divide.





Cheers

Tim