[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

RE: Yurgovuchia, new dromaeosaurid from Utah

Lee and Worthy (2011) reanalyzed Xu et al.'s (2011) matrix using liklihood, 
which no other Mesozoic theropod analysis has done to my knowledge.  Not to say 
it's wrong or worse than parsimony, but keep in mind everything else we think 
we know about Mesozoic theropod phylogeny is based on using a different 
method.  Similarly, Lee and Worthy's tree has some unusual relationships, like 
Dilong+Eotyrannus being closer to birds than to tyrannosaurids, Haplocheirus as 
a basal ornithomimosaur, and scansoriopterygids sister to Shenzhouraptor.  
While these aren't necessarily wrong, I don't think anyone would say Lee and 
Worthy's analysis should be trusted over Xu et al.'s in these areas, and the 
same goes for the position of Archaeopteryx.

As for Holtz's comment, I'm not so pessimistic.  There's a ton wrong with the 
basic TWG data, and less but still a significant amount wrong with Senter's 
(that the Xu et al. analysis is based on, and Xu et al. changed some data to 
make it even less accurate).  It's possible that once these codings are 
corrected, taxa that shift around a lot now will actually have relatively 
stable placements.  In the same vein, differences between current analyses are 
at least partially due to different taxon- and character-sets.  The results of 
Senter et al. (2012, on Yurgovuchia) can be said to be better than those of 
Senter et al. (2010, on Geminiraptor plus his evo/creation paper) and Xu et al. 
(2011, on Xiaotingia), simply because the former includes all of the data from 
both of the latter, plus more.  So we don't have to say "well, some analyses 
place Archaeopteryx in Deinonychosauria and some place it in Avialae", we can 
say "the best version of each TWG variant has placed Archaeopteryx in Avialae, 
and the one placing it in Deinonychosauria was due to missing taxa and 
characters (and maybe Xu et al.'s wrong scansoriopterygid, basal bird and basal 
oviraptorosaur "corrections").  It's perfectly possible that simply 
incorporating all of the taxa and characters we know of now in one analysis 
will result in stable positions for Archaeopteryx and such, even when new taxa 
and characters are added in the future.  Or maybe Tom's right and things will 
stay uncertain.  Only one way to find out...

Mickey Mortimer

> Date: Tue, 15 May 2012 22:06:55 -0400
> From: tholtz@umd.edu
> To: schenck.rob@gmail.com
> CC: dinosaur@usc.edu
> Subject: Re: Yurgovuchia, new dromaeosaurid from Utah
> If anyone thinks the position of Archaeopteryx, Anchiornis, and Xiaotingia
> are settled relative to each other, to Avialae, and to Deinonychosauria,
> forget it.
> These taxa seem close enough morphologically to the actual divergence that
> they will remain in no certain position for long between new specimens and
> analyses.
> On Tue, May 15, 2012 9:48 pm, Robert Schenck wrote:
> > Didn't Lee 2011's "likelihood reinstates archaeopteryx as a primitive
> > bird", already er, reinstate archeaopteryx as a bird?
> >
> > On Tue, May 15, 2012 at 8:26 PM, Mickey Mortimer
> > <mickey_mortimer111@msn.com> wrote:
> >>
> >>See what I meant about waiting for other analyses to confirm Xu et al.'s
> >> finding before accepting >it?  Also contra Xu et al., Anchiornis and
> >> Xiaotingia aren't archaeopterygids and don't form a
> >>clade,
> > snip
> >>
> >> Mickey Mortimer
> >
> Thomas R. Holtz, Jr.
> Email: tholtz@umd.edu Phone: 301-405-4084
> Office: Centreville 1216
> Senior Lecturer, Vertebrate Paleontology
> Dept. of Geology, University of Maryland
> http://www.geol.umd.edu/~tholtz/
> Fax: 301-314-9661
> Faculty Director, Science & Global Change Program, College Park Scholars
> http://www.geol.umd.edu/sgc
> Fax: 301-314-9843
> Mailing Address: Thomas R. Holtz, Jr.
> Department of Geology
> Building 237, Room 1117
> University of Maryland
> College Park, MD 20742 USA