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Re: The poor unnamed Early Cretaceous Troodontid called GIN 100/44



Fam Jansma wrote-
 
> The material, at least as far as the text mentions it, comprimises: a quadrate, partial dentary and poorly > preserved postdentary section, a partial basioccipital, a poorly preserved series of 5 cervicals, a
> semilunate carpal, the complete metacarpus, several phalanges and unguals, fragments from the pelvis > and a partial left foot. Maybe more elements were discovered, but these are the elements mentioned.
 
The braincase section also includes fragmentary exoccipitals, the posterior basisphenoid and prootics.  No pelvic fragments are mentioned, but a distal femur is known.
 
> At a first glance at the age, I thought the material could be assigned to a specimen of Sinornithoides
> (Currie, P.J., Zhiming, D. 2001), but as a I started to look at details, some differences appeared.
 
Russell and Dong (1993) compared the two.  They merely stated the unnamed specimen was subadult, but still 20% larger than Sinornithoides.  Also, the second pedal ungual is relatively smaller and the distal phalanges of pedal digit III are much shorter.
 
> According to the text the preserved basioccipital portion of the braincase in specimen GIN 100/44 had > not developed the lateral depression, or at least it still lacked the basioccipital portion of that
> depression.
 
Which means we should compare it to Sinovenator, which also lacks the depression.  As the unnamed specimen is poorly preserved, and Sinovenator is sparingly illustrated, this is difficult.  Still, the less constricted third metatarsal of the latter suggests it may be more primitive.
 
> But my question is: what is it? Has it been more thourougly described recently and does someone
> have any additional pictures of this specimen that I could have? And what other info is available for > the specimen?
 
Who knows.  My guess is a troodontid phylogenetically intermediate between Sinovenator and Sinornithoides + other troodontids.  It has not been described since 1987 and no pictures are available outside those in the original description and The Dinosauria (what else would be illustrated anyway?  the dentary fragment, cervicals in lateral view, distal femur....).  I think it's pretty well described altogether.
 
Mickey Mortimer