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Re: Anzu wyliei, near-complete caenagnathid oviraptorosaurian

Jaime Headden <jaimeheadden@gmail.com> wrote:

> There is much to agree with what Tim said, but it's too early to
> suggest this. GM and statistical analyses of caenagnathid feetw ould
> be useful when assessing capability of the foot in tranducing forces
> while walking, running, etc. One notable thing is that length of pd-IV
> seems a greater predictor of cursorial ability in theropods and birds
> than length of pd-II. This is especially true when you consider that
> in some taxa, pd-II is lost, but never pd-IV.

Pedal digit III is the principal weight-bearing toe, and so more
reflective of the animal's locomotor habits.  This was the rationale
of Hopson's 2001 quantitative study, and it seems sound.

> The ungual in pd-IV is
> also quite small in *Macrophalangia canadensis* (CMN 8538), despite
> large size of md-I and its ungual. pd-II and IV are subequal,
> revealing likely absence of high predatory capability. If generalists
> then, regardless of distal position of pd-I and its large ungual, the
> foot suggests limited grasping ability.

In maniraptoran fashion, the hindtoe (pedal digit I) is quite distal
by theropod standards.  However, it was not reversed, so the foot was
not capable of grasping in an anisodactyl fashion.  Grasping along the
lines of what has been hypothesized for the feet of dromaeosaurids
(Fowler et al., 2011) might have been possible - as you suggest.  This
needs further study.

The relatively long penultimate phalanges might have nothing to do
with grasping - either for predation or climbing.  Instead, it may
have something to do with improving traction, especially in soft or
slippery conditions.  Again, this needs further study.