Re: Another Alxasaurus query (was: thanks and ...)

["Thomas R. Holtz, Jr." <th81@umail.umd.edu>]

At 06:44 AM 2/2/99 -0800, you wrote:
>---"Jaime A. Headden" <qilongia@yahoo.com> wrote:
>
>>   Okay, I am operating on the assumption that segnosaurs are
>> theropods. 
>
>Aren't they considered to be?
>
>With all due respect to George (and I don't mean that sarcastically),
>is there real controversy among dinosaur paleontologists about the
>assignment of these dinosaurs ("therizinosaurs"/"segnosaurs")?

No.

>If so, has anyone published a critique of the Russell/Dong analysis in
>a (all together now) peer-reviewed scientific journal?

In a sense: a few papers currently out or in press reexamine the Russell &
Dong analyses (and additional data).  See Sues 1997 paper on _Chirostenotes_
(JVP 17:698-716) and Makovicky & Sues's _Microvenator_ paper in Am. Museum
Novitates for two explicit data matrices already published.

Now, to be fair, none of these studies currently *published* test what is
needed to refute Olshevsky's assertion: namely an analysis where
prosauropods and/or ornithischians are also included among the ingroups, so
that (in terms of the search mechanics) recovery of a
prosauropod-therizinosauorid clade is at least possible.

>The fourth toe is awfully odd, isn't it?

I assume you mean the first toe.  Both Russell & Currie have both suggested
(at least in talks) that we are looking at it the wrong way: digit I isn't
lenghtened, the rest of the metatarsus is shortened.  Yes, ad hoc and all
that, but given the rest of the character distribution that seems to be one
possible solution.

>Is there an analogy that can be drawn in, say, extant mammals?

Good question.  I'll see if someone else can call one up (i.e., a reduced
digit which recontacts the epipodial-metapodial joint and also recontacts
the ground).

I agree with George on therizinosauroids about one thing, though: it is
damned hard to make them the sister taxon to ornithomimosaurs (when so many
other maniraptoriforms share more features with them).

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