Re: Support for Enigmosauria

[Nick Longrich <longrich@alumni.princeton.edu>]

	Another part of the problem is, well, where else would they 
go? The thing is, no, I don't think the support for an 
oviraptorid-therizinosaur grouping is terribly strong, but it's 
better than for any other arrangement, considering that 
therizinosaurs are about as birdlike as the oviraptorids in most 
features of the anatomy and in some instances, moreso (e.g. 
posterodorsal process of the ischium, elongate digit IV of pes, 
tapered posterior iliac blade, terminal placement of the obturator 
process, opisthopuby), it seems like both groups may have lost (or 
convergently evolved) a number of derived features. The only times 
I've had therizinosaurs fall out anywhere besides with 
oviraptorosaurs (in some earlier versions of my analysis), they fell 
out *closer* to birds than did oviraptors, probably because of these 
characters.
	This is also where the consistency index thing is 
misunderstood. Some researchers seem to feel that it's a good thing 
to have a CI of .9 (for the non-cladists, CI is a measure of 
homoplasy, if a character either evolves twice or evolves once and is 
lost once, its CI becomes .5 e.g.). However, if you are looking at a 
group which has been evolving for a very long time (say, the whole 
Mesozoic), and has many members, your CI is going to be a lot lower- 
the longer these taxa evolve and the more taxa are included, the more 
convergence and reversal is going to up. Getting a CI anywhere near 
.9 for a large, diverse group of long-evolving animals is 
preposterous and indicates a fundamentally flawed method, possibly 
including problems in biased selection of OTUs, biased selection of 
characters, biased coding of characters, or most likely, all three. 
The point isn't to get a low CI, but rather the lowest CI relative to 
everything else out there. If .45 is the lowest CI you get out of 
several billion trees linking dozens of taxa, then that's the 
simplest answer. So therizinosaurs and oviraptorosaurs being related 
ain't simple- but no one has yet come up with a simpler possibility, 
given our current (poor) understanding of the anatomy of both groups.