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Re: Re-Deinocheirus



At 10:19 AM 1/26/98 -0800, you wrote:
>I was in Mongolia last summer and had the chance to see and photograph the
>famous arms.

I, too, have seen the type material (when it was in England), and have
worked with Yale's casts of the same (hollow, thankfully: would have been
very hard to deal with otherwise).  I took a nice couple of photos once of
Deinocheirus claws next to the type Torvosaurus claws: just goes to show how
non-raptorial they are!!>

>The scapulae are fairly long and the body would
>have been pretty robust to stay in  proportion with them, and I was
>wondering whether the length of the arms correlated to the length of the
>neck + skull. Are there any Theropods where the shoulder-to-claw distance
>is greater than the shoulder-to-snout tip distance?

Interesting thought: never run those particular parameters.  The very long
arms might well argue for a small head and long neck, though, as in
ornithomimosaurs and (to a lesser degree) troodontids and oviraptorosaurs
and dromaeosaurs.  Big-headed theropods of large body size (tyrannosaurs,
Giganotosaurus, Acrocanthosaurus) have relatively shorter arms (although
these can still be quite large in absolute length, especially compared to us!).

>My impression was that, unless the arms were wildly out of
>proportion to the rest of the body,  they came from an animal that was
>larger than the Tarbosaurus on display,

Here's the danger: trying to fit long arms onto a taxon characterized by
highly reduced arms!!

If you look at it a different way, the combined length of the humerus and
ulna in ornithomimosaurs is subequal to or greater than the distance between
the shoulder and hip sockets (glenoacetabular length).  Don't have my
measurements on me, but the forelimb minus the hand is about 2 m long in the
beast (the whole forelimb is something like 2.8 m).  A 2 m glenoacetabular
length is about the length in the type or the AMNH specimen of T. rex.

Most people tend to forget how long armed non-tyrannosaurid maniraptoriforms
are!

>    Deinocheirus may be more closely related to the Ornithomimosaurs than to
>the Therinzinosaurs, but it's still just a set of arms and shoulder blades,
>which makes it tough to assign it a definitive classification.

But for size, nobody would have a problem classifying them as
ornithomimosaurs.  It's only because they are so huge that people have
thought otherwise.  It's claws ARE different from all ornithomimids (but
closer in structure to them than to Harpymimus), so it would definitely be
its own genus.

>I wonder,
>though, if it is different enough from anything known to be assigned to it's
>own family.

See above.

>Have any of the theropod guys on the list (Dr Holtz, perhaps?)
>re-examined the material recently and compared it with some of the more
>recent  finds, or we still relying on interpretations based on what was
>known when Deinocheirus was first described?

It was reported some years ago (in one of the first issues of the Dinosaur
Report) that Perle was examining some new giant ornithomimosaur material
from Mongolia, but I haven't heard any follow up on that.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661