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Re: Last Dinosaur of 2011



On Sat, Dec 31, 2011 at 9:58 PM, Jaime Headden <qi_leong@hotmail.com> wrote:
>
> 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.

Another part of the problem is that we're dealing with few characters
uniting even relatively well-known clades (pachyrhinosaurs, for
instance). Things were much more stable and better supported when we
had fewer taxa, even if it's paradoxical.

>   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.

OK, thanks for the clarification! In my own personal opinion, I'm
cautiously accepting of Rubeosaurus as a genus separate from
Styracosaurus, if only because there is little evidence for monophyly
of Rubeosaurus+Styracosaurus. But then this could change with more
data. . .

Andy