Re: Oppinions and questions

["Jaime A. Headden" <qilongia@yahoo.com>]

Renato Santos (dracontes@hotmail.com) wrote:


<Well after the Falcarius find (and even before that) I came to think that 
though therizinosaurs specially basal ones might have used the big claws to
bring branches to mouth's reach it seems too farfetched to be a very common
behaviour for one simple reason: the necks reach further than the claws.>

  My issue with any segnosaur using their claws for holding branches has a lot
to do with their extreme mediolateral compression and sharp ventral edges,
criteria used by workers to posit a raptorial function for the second pedal
ungual of dromaeosaurids and the trophic function of the "thumb" claw of
*Megaraptor* (and therefore possibly spinosaurids as well). Similarly, as in
other maniraptorans, the structure of the distal humerus inflected the forelimb
into a permanent flexure at the elbow, and thus one at the wrist: any extension
of the arm to grab branches would have been limited shortly in front of and
below the animal, not well in front or above.

<A strange mention of a parallelism at the same forum, between Falcarius and
Deinocheirus, makes me wonder: Is there any way the later can be a giant form
of basal therizinosauroid? Or is it still largely considered as an
indeterminate ornithomimosaur?>

  Not having access to their conclusions in _The Dinosauria, Second Edition_,
Kobayashi and others have suggested that *Deinocheirus* might not be an
ornithomimosaur at least as far as their work in the *Sinornithomimus* paper.
This conclusion was not supported by data, instead being left until _The
Dinosauria_, so I am not aware of their current conclusions regarding this
animal. However, responding to the implication, I have in the past listed a
suite of features that indicates an ornithomimosaurian nature for the animal,
though I haven't the time tonight to find the links. To summarize, however: 1)
elongated first metacarpal reaches the length of the second and third
metacarpals; 2) third metacarpal nearly as broad as second metacarpal; 3)
medial flange on first metacarpal extends as crest down over 50% of the its
length; 4) first metacarpal articulated to second metacarpal for most of its
length; 5) humerus with deltopectoral crest reduced to proximal 1/6th of
humeral length; 6) humeral distal end extremely narrow and mediolaterally less
than 150% midshaft width; 7) medial (dorsal) tuberosity of humerus small and
reduced in aspect compared to virtually ANY other theropod of considerable
size, including ALL segnosaurs; 8) humeral shaft relatively straight rather
than forming an S-shape in lateral view or with a proximal caudal orientation
of the humeral caput.

  There are other details of the scapula and ulna as well, but I will need to
get my refs out to remember them right now.

  Cheers,

Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


                
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