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Aussie alvarezsaur? (was Re: Gondwanan Dinosaurs)


Jaime A. Headden wrote:

  *Rapator ornitholestoides*:

  I'll not say too much on this bone, but it bears
similarities to some Asian taxa which suggests it's
not a mcI to begin with, but a dI-1, like mononykids,

This is a very good observation. In alvarezsaurids, phalanx I-1 (the one that bears the big hand-claw) is very long anteroposteriorly but compressed lateromedially, giving it a distinctive "hourglass-like" shape. So is the "metacarpal" of _Rapator_ (BMNH R3178).

Phalanx I-1 of alvarezsaurids also shows (1) an elongated posteromedial process (quite hook-like in _Patagonykus_, less so in mononykines); (2) bilobed proximal end, giving it a "B-shaped" articular surface; (3) deep extensor ligament pit; and (4) a symmetrical distal ginglymus. Judging from Huene's figures (reproduced in Glut), characters (1), (2) and possibly (3) are seen in _Rapator_. I'm not sure about (4).


Tim


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