RE: Yurgovuchia, new dromaeosaurid from Utah

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

> -----Original Message-----
> From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu] 
> On Behalf Of Mickey Mortimer
> Sent: Tuesday, May 15, 2012 11:03 PM
> To: dinosaur@usc.edu
> Subject: 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).  

[snip]

>  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...
> 
Indeed.

However, I would not characterize it as "pessimistic", but rather as 
optimisitic. From a certain mindset, the idea that we have to
get a good 100% match to the True Tree makes sense, and we'd all like to see 
that accomplished. But on the other hand, recognizing
that the fossil record is incomplete and that the initial stages of any 
divergence will not include well-resolved synapomorphies
(which would be established after divergences take place), finding basal taxa 
as incertae sedis may indicate that you are very close
to those divergence points. And thus you have have better established the 
morphological conditions (and possibly paleobiological
conditions) from which major branches originated. This is a Good Thing. 
Phylogenetics is useful, but not only for its own sake: it
is also important as giving us the map onto which we can understand all aspects 
of the history of life.

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