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RE: Deinocheirus 2nd try



> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Mickey Mortimer
>
> Well, it was an ornithomimosaur, so I would expect the skull to be
> comparatively small (~670 mm) and toothless.  Of course, it's
> anyone's guess
> what ornithomimosaurs ate, but Hurum (2001) feels their beaks are
> closest to
> larids (seagulls) in shape, suggesting they were omnivorous.  Deinocheirus
> probably ate leaves hooked by its long arms, as well as smaller dinosaurs
> that the raptorial claws helped kill.

Quite so, except for the "raptorial claws".  Despite thirty years of
commentary to the contrary, there is very little raptorial in the claws of
Deinocheirus.  If you hold a Deinocheirus ungual (or cast) in one hand, and
the ungual (or cast) of Torvosaurus' in the other, you see that they are of
similar heft, but the Torvosaurus is clearly a raptorial ungual.  In fact,
in almost every way the Torvosaurus ungual is more similar in shape,
curvature, cross-section to modern raptorial birds than are the claws of
dromaeosaurs.

Comparing the Deinocheirus to the Torvosaurus ungual, the latter is tapered
to a point, highly curved, roundish cross-section, while the former has a
blunt tip, is much less curved, and has a flatter-bottomed cross-section.
You could substitute Allosaurus or spinosaurids or Dryptosaurus are most any
large carnivorous non-maniraptoriform, non-tyrannosaurid tetanurine for
Torvosaurus there, and find that their unguals are similar and all are
dissimilar to the claws of Deinocheirus in the same fashion.

However, while not particularly raptorial, the claws of Deinocheirus might
have been useful in killing and catching small dinosaurs like
pachycephalosaurs and protoceratopsians, as well as grabbing plant food.

> Ooooh... Don't let Tom Holtz hear you say theropods had an evolutionary
> trend to decrease forelimb size.  :-) Perhaps I'll save his time
> by pointing
> out such a trend doesn't exist.

Thank you.  For those who are wondering what Mickey is talking about, you
can search the dino-list archives for the word
"AAAAAAARRRRRRRGGGGGGGGHHHHHHHH!"  (I may have misspelled it... :-).

> It was fabricated back when coelurosaurs
> were thought to be the most basal theropods and tyrannosaurids the epitomy
> of carnivorous evolution.

As opposed to know, when we know that tyrannosaurids are the epitome of
evolution, full stop. :-)

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796