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Re: Fwd: Aw: RE: Arboreal Theropods: The prize at the bottom of the cracker jack box
Ronald Orenstein <firstname.lastname@example.org> wrote:
> Take a look at photos of herons or storks in trees - usually they do not
> grasp, or curl their toes around, the
> branch but let them dangle on either side (see, e.g.,
The birds of today certainly make perching and roosting look easy.
Even many birds where the feet are not specialized for perching (=
grasping branches) can sit or roost in trees. Ron's stork is a good
example. Don's turkey can roost on a thick branch, without always
using its hind toe (hallux).
However, birds have re-worked their bauplan compared to their theropod
ancestors. When standing, a bird is in a permanently 'crouched'
position, with the thighs tucked under the body and the knees near to
the body's center of mass. This was quite a profound morphological
shift compared to the ancestral theropod condition, where the center
of mass was around the hips. If a non-avialan theropod adopted the
same posture as a perching/roosting bird, it might render the body
very unstable (especially considering the relative length of the
hindlimb). If not, and non-avialan theropods adopted an entirely
different stance when roosting, then extant birds offer a poor analog
for this hypothetical behavior in non-avialan theropods.
I don't know if the derived avialan bauplan/posture makes balancing on
a narrow substrate 'easier' or not. But either way, it makes it
challenging to extrapolate the arboreal locomotor abilities of birds
to those of non-avialan theropods.