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any "Dino-skunks"?

Jaime,
    I will certainly keep classifying Deinocheirus in Family
Ornithomimidae, but the similarities in "gross" body shape between
Ornithomimes and Therizinosaurs seriously make me wonder if one group (or
subgroups thereof) was mimicking the appearance of the other for some
reason.
    Such mimicry could very well have been enhanced by similarities in
color and patterns in the coat of feathery dinofuzz.  After all, I can
immediately tell a monarch from a viceroy butterfly with a mere glance, but
the similarities in patterns of colored wing-scales has been fooling some
rather "intelligent" bird predators for millions of years.
    I don't think the gross similarities of ornithomimes and therizinosaurs
is just coincidence.  The question is whether such similarities are due to
similar ways of life (and some degree of relatedness) or if this could be
mimicry.  If the latter, which was mimicking which?  Perhaps Ornithomimes
were in reality "Therizinomimes"?
     What would be the reason for such mimicry (that would be even more
difficult to test)?  But one group may have been better at defending
themselves against predators (e.g., maybe they were dino-skunks) and the
other relatively defenseless group would therefore benefit by mimicking
their general appearance.
     I now like the idea of a dino-skunk better than the monarch butterfly
example (I doubt that there would be any bad-tasting dinosaurs).  But really
bad-smelling ones that could spray predators like a skunk---now that is what
I would call a strong deterent (and mimicking them a good predator evasion
strategy).  But how would one ever prove that a dinosaur was a dino-skunk?
I have no idea, but I think it is any interesting possibility.  Has anyone
like Bakker ever proposed anything that might be referred to as a Dino-Skunk
Hypothesis for any group of dinosaurs?  I guess I really need to buy myself
some dinosaur books.
         ----In a brainstorming mood,    Ken
********************************************************

From: "Jaime A. Headden" <qilongia@yahoo.com>
Reply-To: qilongia@yahoo.com
To: dinosaur@usc.edu
CC: kinman@hotmail.com
Subject: Deinocheirus Again
Date: Sun, 1 Jul 2001 15:48:21 -0700 (PDT)

Ken Kinman (kinman@hotmail.com) wrote:

<Therefore Deinocheirus could be closest to ornithomimids and
yet still be fairly close to therizinosaurs as well. The
similarities between Deinocheirus and Therizinosaurus could be a
form of "parallelism" (convergence in two fairly closely-related
lineages). I would think that this "convergence" was probably
due to similar feeding strategies, but one could perhaps
speculate that one of these forms was mimicking the other form
for some reason (maybe similar to viceroy butterflies mimicking
monarchs---which is a predator evasion strategy). But mimicking
doesn't seem terribly likely, and would be extremely difficult
to test (but fun to think about). Who knows.>

  It would be easy to test, actually, using some forms of
phylogenetic analysis, including cladistics. However, in gross
anatomy, there is no relative similarity between *Deinocheirus*
and *Therizinosaurus*. Barsbold proposed in 1976 the name
Deinocheirosauria to include *Deinocheirus* and
*Therizinosaurus* (or to be exact, their "families", but they
were both monotypic, as Segnosauria was held separately.
Barsbold's diagnosis was related to three characteristics of the
taxa: gigantic size; unreduced shoulder region; and large claws.

  It is clear the first is not useful phylogenetically; the
second is true for both ornithomimids, whereas *Pelecanimimus*
and *Anserimimus* have more maniraptoran-like shoulders, and
therizinosauroides, though they too are basally
maniraptoran-like, both groups trending from shallow
supraglenoid scapulae with cranially oriented acromion
processes, rectangular coracoids, and moderately lateroventrally
facing glenoids to ventrally facing glenoids,
triangular/dorsally elongate rectangular coracoids, acromion
process reduced and facing dorsally or absent, tall triangular
scapulocoracoid contact, and elongated scapular shaft.

  It is also more likely that *Deinocheirus* is an
ornithomimosaur more closely related to *Ornithomimus* than even
*Pelecanimimus* is, based on features of the shoulder that Pele
lacks and the lack of complete appression of all metacarpals to
each other, and that *Therizinosaurus* in comparison with
*Segnosaurus* and *Erlikosaurus* in the forelimb, is more
closely related to them, thus synonymizing Segnosauridae with
Therizinosauridae.

  There is no real way these two are any more closely related
than *Ornithomimus* and *Oviraptor* or birds are, which forms
the distinction between Maniraptora and Maniraptoriformes.

=====
Jaime A. Headden

  Aaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhr-gen-ti-na
  Where the Wind Comes Sweeping Down the Pampas!!!!

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