Re: Aussie therizinosaurids? [and other things...]

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

A belated reply:

Dann Pigdon provided the link to a new partial humerus of a purported 
therizinosaurid, compared to
*Erlikosaurus*. Tim Williams (tijawi@hotmail.com) wrote:

<Conspicuous by its absence is the lack of a sigmoidal shaft - courtesy of the 
distal "twist",
which is quite obvious in the humerus of _Erlikosaurus_.  Also in 
therizinosauroids, the humerus
has a pointed internal tuberosity on its proximal end.  This cannot be 
discerned in the Aussie
bone.>

  The internal tuberosity appears to be broken in the specimen, so this is 
moot. Similarly, I
doubt the shaft of the humerus is complete distally, so the cranial projection 
of the distal
articulation may not be preserved, and there is an evident caudal inflection of 
the glenoid
tuberosity.

<Based on the illustration, the humerus could come from a range of theropod 
taxa.>

  Based on the proximal end of the humerus, I feel a reference to 
therizinosaurids is a good bet,
the humerus is not neccessarily identical to *Erlikosaurus* but this is to be 
expected. There are
superficial similarities to oviraptorosaurs, but there are more so to 
therizinosauroids than even
carnosaurs, which have similar large deltopectoral crests, deep internal 
tuberosities, and the
absence of a strong "twist" in the shaft may be either autapomorphic or an 
example of the other
therizinosauroid similarities to being convergences. In the proposition that 
the form is a
carnosaur, it can be considered that the therizinosauroid similarities are more 
parsimonious.

<I think this goes back to Greg Paul's _Predatory Dinosaurs of the World_, and 
is based on the
similar proportions of the respective tibiae.  Like _Avimums_, the shin bones 
of _Kakuru_ were
very slender.  I think we'll need more _Kakuru_ bones before we can be certain 
what this theropod
was.>

  Long, in 1999, and Molnar and Pledge, in 1981, supported a possible
*Ingenia*/*Microvenator*/*Kakuru* link, as well, and the evidence supporting 
*Kakuru* as a basal
oviraptorosaur stems from this. The distal tibial morphology also supports a 
general Caudipteridae
+ *Microvenator* + Caenagnathidae + *Ingenia* + *Avimimus* connection to the 
absence of any oher
contenders. The only other similar theropod tibia is *Acrocanthosaurus*, and 
this is similar only
in the form of the medial malleolus of the distal tibia. No other features 
indicate relationship
with any other taxon.

<This has not been published (AFAIK), but seems to be a safe bet.>

  Hopefully this will be published soon. Let's all cross out fingers... Holtz 
axiom #1....

<_Austrosaurus_ might be a titanosauriform - though, again, this placement is 
precarious.>

  Very precarious. I have a strong suspicion that *Austrosaurus* may be a true 
Cetiosaur ... the
femur lacks the specialized wide-gauge (Carrano, 1999) hip of titanosauroids, 
and the caudals are
not pleurocoelous. However, the material is scrappy, and until a relatively 
complete skeleton with
caudals associated is found to match the type, then there will be no 
satisfaction of this problem.

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