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Re: Ornithomimus had feathers and "display" winglike forelimbs
Brad McFeeters <email@example.com> wrote:
> I'm not 100% convinced that Ornithomimus had pennaceous feathers or
> pennibrachia, even though the distribution and orientation of the markings on
> the arm is suggestive of that.
> Zelenitsky et al. (2012) described the markings as evidence of "type 3
> feathers or higher," but since there are no barbs preserved, all that can
> really be said is that they do not
> resemble the type 2 feathers. The morphology of the individual markings on
> the adult Ornithomimus forearm also seems consistent with the non-pennaceous
> type 1/EBFF display
> feathers of the new Beipiaosaurus (Xu et al. 2009), for example.
> Beipiaosaurus is a basal maniraptoran yet has no evidence of pennaceous
> feathers, so perhaps this is the more
> conservative interpretation on phylogenetic grounds?
A straightforward phylogenetic interpretation is somewhat complicated
by ontogeny. Is STM31-1 (the _Beipiaosaurus_ specimen showing EBFF
feathers) fully grown? If not, then the apparent lack of pennaceous
feathers might be due to the immaturity of the specimen. (The
holotype of _Beipiaosaurus_ is from a subadult individual, and also
lacks pennaceous feathers).
Also, Sullivan &c's original definition of pennibrachium is "a
forelimb bearing long feathers that form a planar, wing-like surface
but are not necessarily used in aerial locomotion". So even if the
long forelimb feathers of _Ornithomimus_ are not pennaceous or "type 3
feathers or higher", the feathered forelimb could still qualify as a