RE: Alamosaurus as biggest North American sauropod

[Jaime Headden <qi_leong@hotmail.com>]

  How do you assess that without comparison to the holotype? As it stands, the 
best data that helps characterize referral to *Alamosaurus sanjuanensis* is the 
ischium, not the scapula, and while the two are associated, this doesn't mean 
that the material from the North Horn in Utah, Big Bend in Texas are the same 
taxon as that in the Kirtland Formation in New Mexico. This is especially 
significant when you consider that very closely related taxa can co-occur, such 
as *Neuquensaurus australis* and *Saltasaurus loricatus* at El Brete in the 
Anacleto Formation (D'Emic & Wilson, 2011).

  Regardless of this, my reasoning is that morphology is and always will be the 
primary method by which material is assigned to species. DNA is an alternative, 
when present, but in this discussion it is simply not possible to use DNA 
comparison to measure relatedness or resolve the species question. This is 
also, of course, made more problematic by the absolute that _species are 
subjective categories_.

  The potential of closely related but distinct taxa in the same geographic 
region or stratigraphic horizon is validated simply by extension to extant taxa 
and the aforementioned co-occurrence of two saltasaurid titanosauroids. (In 
case anyone was interested, this just like most of the other things I say, is 
_opinion_. No one has to _believe_ a thing I say, but it surely is nice to have 
people engage on the level without telling someone a thing is _true_ simply by 
assertion [the argument from authority, in case it wasn't apparent, is a 
logical fallacy].)

  I cannot see how it is possible to qualify a reasoning that allows us to dump 
*Trachodon mirabilis*, then *Troodon formosus*, but not *Alamosaurus 
sanjuanensis* (despite that fact that D'Emic et al., 2011, affirm the 
diagnostic nature of the scapula).

D’emic, M. D. & Wilson, J. A. 2011. New remains attributable to the holotype of 
the sauropod dinosaur *Neuquensaurus australis*, with implications for 
saltasaurine systematics. _Acta Palaeontologica Polonica_ 56(1):61–73.
D’emic, M. D., Wilson, J. A. & Williamson, T. E. 2011. A sauropod dinosaur pes 
from the latest Cretaceous of North America and the validity of *Alamosaurus 
sanjuanensis* (Sauropoda, Titanosauria). _Journal of Vertebrate Paleontology_ 
31(5):1072-1079.

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)


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> Date: Fri, 9 Dec 2011 14:29:39 +1100
> From: tijawi@gmail.com
> To: dinosaur@usc.edu
> Subject: Re: Alamosaurus as biggest North American sauropod
>
> Jaime Headden <qi_leong@hotmail.com> wrote:
>
> >   The best strategy, in my opinion, is to simply do away with crap taxa.
>
>
> I think this is a bit harsh. If there is evidence for only one
> sauropod taxon in a given provenance (region/locality/horizon/bed),
> then that sauropod should be given the oldest available name. Names
> like _Astrodon_ and _Alamosaurus_ deserve to be kept around - and
> arguably _Titanosaurus_ does as well, IMHO. If the survival of "crap
> taxa" requires the designation of a neotype, then so be it.
>
>
> Sometimes it is necessary to do away with time-honored names that are
> based on crap type material. This has happened for _Deinodon_ and
> _Trachodon_, and I think this fate is inevitable for _Troodon_. But
> it shouldn't be the default setting for any and all names.
>
>
>
>
>
>
>
> Cheers
>
> Tim