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RE: Last Dinosaur of 2011



Ah, crud, the typing goblin broke in again.

  What I meant to write was that the support for the nodes was relatively low, 
below 70% for most of the ceratosaurine clades, including those combining 
various species. Bremer values are low, while other strongly supported nodes 
are indicated with less than, say, 70% bootstrap values. These are, my 
understanding tells me, largely based on the amount of material involved. This 
is not necessarily a jab at *Spinops sternbergorum,* but rather at the apparent 
recognition of *Rubeosaurus* for *Styracosaurus ovatus,* qualified by an 
aberrant P2/P3 expression from other taxa; in *Spinops sternbergorum* at least 
the material poses more material and more interesting variation that is 
unlikely to belong a known *Styracosaurus* or *Centrosaurus* species, simply 
because material known for those taxa tend not to express the other's 
uniqueness (P1 hooks, or P2/P3 spikes, respectively)). If this condition has an 
unknown or unresolved homology, or is variable, this will enforce low support 
values, a result which is not aided by the lack of material.

  When I started typing "These analyses are based on weak me," I was actually 
trying to write two sentences and forgot to parse them separately. They are 
based on limited material, and that this results in weak support in 
bootstrapping (collapsing nodes) and material (which affects the Bremer numbers 
as well as the bootstrap results). But I think the issue with *Rubeosaurus 
ovatus* is worse, by far, than any other ceratopsian included in the analyses, 
because of the brevity of material and the shaky grounds (I think) which 
warrant "generic" justification.

  Anyways, hopefully this clears up what I should have written.

Cheers,

  Jaime A. Headden
  The Bite Stuff (site v2)
  http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)


________________________________
> Date: Sat, 31 Dec 2011 21:03:29 +0000 
> Subject: Re: Re: Last Dinosaur of 2011 
> From: afarke@gmail.com 
> To: Michael.OSullivan@port.ac.uk 
> CC: qi_leong@hotmail.com; dinosaur@usc.edu 
>  
> On , Michael OSullivan  wrote: 
>  > I'm still incredibly skeptical about the validity of Spinops as a 
>  > distinct taxon from Centrosaurus. 
>  
> How so? We have solid autapomorphies (as outlined in the paper), we  
> have two specimens from the same site with the same morphology (showing  
> that the autapomorphies aren't just an individual fluke), and we have  
> good growth series for Centrosaurus (and Styracosaurus) for comparison.  
> None of the growth series show anything Spinops-like at all at any  
> stage (or even a trend in that direction), so I think we can be  
> confident it's not just a very old or very young C. apertus. Or are you  
> referring to the issue of whether it should be in a separate genus? As  
> outlined in the paper and associated supplemental information (and as I  
> think Jaime was saying), Spinops could just as easily be closer to  
> Styracosaurus or C. apertus (the best resolution was achieved when C.  
> brinkmani was removed from the analysis - obviously, not the best  
> solution!). Shoehorning Spinops into Centrosaurus makes a hypothesis of  
> phylogeny that just isn't well-supported, and hence the new genus. I  
> suppose one could put the whole mess (C. apertus, C. brinkmani, S.  
> albertensis. S. sternbergorum) into Centrosaurus, but then this too is  
> yet another phylogenetic hypothesis that gets exploded again in the  
> next round of analysis by the next set of authors! 
>  
> Jaime - in your email I saw the sentence "These analyses are based on  
> weak me," - I suspect a few words are missing there. Did you mean to  
> say "weak characters"? I didn't want to put words in your mouth before  
> addressing your reply! 
>  
> Andy