RE: Abydosaurus mcintoshi, a new sauropod from the Albian of Utah

[Jaime Headden <qi_leong@hotmail.com>]

  Furthermore, Chure et al produced a phylogeny that further complicated this 
issue by failing to separate the taxa. At this point, the number taxa now 
referred to the Brachiosauridae are done so based on the false assumption that 
both species should be codified as a single entity. This is a major problem 
arising from refusal to code from specimens explicitly (as OTUs) or to use 
explicit specimens as the basis for species level OTUs.

  No few of us on this list have argued in the past that phylogenetic matrices 
should be produced using explicit specimens, in order to test the complex of 
species as has been argued by some. I would actually like to think that this 
debate resolves in someone, _anyone_ actually including the specimen-based otus 
for each species or at least just species based solely on type material and so 
forth as the only viable matrix to test from. This should be the best sauropod 
phylogenetic study to be produced to date. It should be done from scratch, and 
it should _NOT_ include characters that occur only in a single "species" or 
specimen, as this does not test the hypothesis of shared characteristics (an 
autapomorphy is great for typology, but bad for phylogeny).

Cheers,

Jaime A. Headden

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


"Human beings, who are almost unique in having the ability to learn
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Backs)





----------------------------------------
> Date: Wed, 24 Feb 2010 15:19:21 -0800
> From: tijawi@yahoo.com
> To: dinosaur@usc.edu
> CC: tijawi@yahoo.com
> Subject: Re: Abydosaurus mcintoshi, a new sauropod from the Albian of Utah
>
> Mike Taylor  wrote:
>
>
>> But I do think it's enough evidence to have shifted the null hypothesis
>> -- so that anyone who wants to challenge it really ought to make the
>> effort to dig out some actual evidence themselves. What Chure et al.
>> wrote -- "the identified differences have not been defended as
>> separating genera, rather than species, populations, or individuals"
>> -- really doesn't advance the discussion at all. It's an argument from
>> laziness, and all it does is muddy the waters (and perpetuate the
>> discredited notion that the Morrison and Tendaguru formations shared a
>> fauna).
>
>
> The discovery of _Abydosaurus_ might actually have provided a good 
> opportunity to test the monophyly of _altithorax_+_brancai_. Instead, this 
> monophyly was simply assumed by Chure &c, and _altithorax_+_brancai_ were 
> therefore treated as a single OTU (_Brachiosaurus_) in the phylogenetic 
> analysis.
>
>
> Also, as mentioned by Mike, _altithorax_ is from the Morrison, and _brancai_ 
> is from the Tendaguru. Thus, I would have thought that lumping the two into a 
> single genus would require compelling morphological evidence. This isn't the 
> case. IMHO, Taylor (2009) established a strong case for treating _brancai_ as 
> a separate genus (_Giraffatitan_). It's only historical tradition that's 
> holding the two together. If Janensch had *not* referred _brancai_ to 
> _Brachiosaurus_, but had instead erected a separate genus, we wouldn't be 
> having this discussion.
>
>
> Cheers
>
> Tim
>
>
>
>
>
                                          
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