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Re: Aw: RE: Arboreal Theropods: The prize at the bottom of the cracker jack box



Jason Brougham <jaseb@amnh.org> wrote:

> Well, hey, you can always say my counterexamples don't count. Strictly
> speaking, they don't, because we are using derived animals to see what may
> have been possible for primitive ones.


Excellent point, IMHO.  There are a great many extant birds that show
rudimentary aerial behaviors, such as WAIR or CFD (by fully volant
species, including juveniles) or fluttering and short glides as
exhibited by some secondarily flightless birds (the kagu has been
mentioned, but there are others).


It is possible that one of these extant non-flight aerial behaviors
replicates the incipient flight behavior of the theropod ancestors of
birds.  But they might not.  We may never know which behavior(s)
engendered flight in theropods.  However, I don't think we should
assume that it was "trees-down", despite the intuitive attraction of
an arboreal origin of flight.


> My goal is to stop people in this forum from saying it is impossible that
> basal paravians utilized trees to some limited extent. I believe I have
> demonstrated that it is possible, and that categorically excluding it with
> the current evidence is not correct.


I don't recall anyone saying that it was impossible for basal
paravians to use trees.  Speaking solely for myself, I would say that
the evidence for arboreality (i.e., spending most or all of their time
in trees) in microraptorines and archaeopterygids is less than
compelling.  To me, there is nothing in the osteology to back up
arboreal ecologies in these taxa.


However, occasional/opportunistic tree-climbing seems entirely
plausible (such as _Microraptor_ grabbing a little birdie off a tree
branch).  But because this is still part of a fundamentally
terrestrial ecology, it perhaps would not seep through into the
anatomy.  So it's difficult to test for.


I'm certainly intrigued by GSP's data on _Microraptor_'s claw
curvature.  Might highly arced pedal claws be useful for gaining
purchase on soft terrain, such as a forest floor, or soft mud?






Cheers

Tim